Here is a list of all the postings Pete has made in our forums. Click on a thread name to jump to the thread.
|Thread: when is a precision vice not a precision vice>?|
Sigh, here we go again. I thought I gave a proper example of "supposedly" precision milling vise's that clearly werent. And just like Fizzy's example both as I said looked very nice as well.Or aren't Kurt type vises now classified and defined as something precision? A common bench vise wouldn't fit that precision term, but a milling vise should and better be if you expect any precision and dependable results while machining parts held in them. And I wasn't as you call it slagging anything at all, I was stating exactly what could be possible even when not buying at the very bottom of the price ladder. And the full story was a little more complex than I thought would even need mentioning. Apparently that wasn't correct. Buying both those vises in person over 3,000 miles from where my home is happened to be very convienient for me at the time since getting them home cost me nothing. And no where were there any accuracy guarantees. I based my purchase on what I was told and was seeing at the time. And as I also said both vises were quite precisely ground and finished. My checks did show that. So my gut feeling while buying them wasn't wrong. But they only fit that precision term until you actualy put them under there working loads. I then went on to explain WHY that was so. Investing even more money to ship them back that 3,000 + miles would have been more costs. So it wasn't a just pop down a mile or two to the local dealer to return them type of situation.I simply decided to write the mistake off as the most cost effective way forward. Fizzy the OP's exact question was a bit more than "when is a precision vise not a precision vise" since you want to point back to the OP. It was also "should we have to". I gave some first hand examples and reasons that doing a lot more than simply machining the jaws and tightening some bolts as he did might be required. Even to the point where it might become impossible to fix some core issues if there serious enough. So should we have to as he first asked? Certainly not, but I thought I made it plain that if you don't do some checks yourself then how would you know if it's a precision vise or not. It should also be obvious that he did that checking and fixed what wasn't precise on his vise. I wasn't arguing for or against what some think of as RR quality. Others who seem to know a fair bit seemed to understand my points and didn't consider it going off on a tangent. Yet it still seems some took them as condensending and OT. I implied nor meant either and have already said as much before. It's quite apparent that's still not to be believed by some who chose to take it that way. You can take my posts as exactly what they say without any added and unsaid words or implications. Michael, Larry, Hopper and Nick's last posts were what I was responding to, or does doing that not make any sense to you either? Exactly as Nick pointed out had I not bought cheaper rubbish I wouldn't have needed to replace them. Both of what I bought were sold as Kurt style vises with the same working principals as the real Kurt's use. Using that in the sales description is a deceptive at best way to entice a buyer into thinking there a lot better than they were. Given the precision mine were made to where it could be seen and measured at home they could have easily passed some fairly impressive accuracy guarantee's had they even had them. And just static testing would have agreed with any half decent numbers as well. So simple testing to the numbers wouldn't have made them unfit as you say. Using them did. So is my post now understandable to you Brian or do you want to needlessly complicate the issues and argue some more?
Anyone here is of course free to form there own opinions. I'm certainly not arrogant enough to expect or think anyone will or even should to have the same opinions as mine. That however doesn't automaticaly make what I've tried to show as at least one hard learned lesson as being wrong now does it? Some of the guilty might be quite surprised in what a few of the most knowledable members here have to say in private messages about the style of personal sniping and argumentive posting that's becoming more and more common on this forum. And I can think of a few who were the very best and most knowledgable who suddenly left for those exact reasons. I can honestly say I don't blame them at all. To me this forum is much less than it once was because those people are now gone. If I really wanted to defend and explain every single one of my words then my ex wife and I would still be married. The need to constantly do so for a few total strangers seems tiresome, illogical and a waste of mine and others time imo. Some here seem to have an undiagnosed but fully developed Don Quixote complex. If my posts bother you that much then your also free to ignore them. I'm here for one reason only, to learn what I don't already know. If I can try to pass along a few bits of information at times that might help someone while doing that then that's a bonus to me that I can return just a small fraction of what others have done for me.
Possibly a proper example of the difference between cheap and something that works as intended might prevent some from misinterpreting what's meant. Deciding to jump up to a much larger mill some years ago was going to be at the far end of what I really wanted to spend. And tooling up that mill has turned out to be far more expensive than I'd thought. Shortly after buying that mill I then bought 2 Kurt "style" 4" capacity milling vises. They looked pretty good on the surface, nice smooth and mostly well finished castings. At least the painted and well ground surfaces lead me to think they should be fairly decent. In use I started seeing some inaccuracy's far outside what was wanted or that should have been there. The vise beds were checked and both were ground parrallel to the bottom surfaces, the jaws well finished and all looked fine. The rear fixed jaws on both vises were then checked with indicators as each was tightened. I was seeing .005" - about .007" deflection even under moderate tightening pressures and a workpiece would not stay tight to the parrallels no matter how much a dead blow was used. The rear jaw was lifting so I readjusted the set screw at the rear of the movable jaw that prevents that. Sometimes it then didn't lift, but it wasn't a very consistant condition.
At that point I decided on a full disassembly. As they say don't judge a book by it's cover. The internal surfaces that you can't see even when judging how well somethings made in a display case were much much different than those exterior ones are. The wedge used on Kurt type vises were in the as cast condition. That design requires the half ball to smoothly slide down that angle and help pull the movable jaw down as the vise get's tightened. But here's where the real problems started showing up. The internal as cast surfaces were extremely rough with more than a few incompleted cast sections. I then took one of the vise body's down to the local radiator shop and paid them so I could use there sand blaster. Finding a blow hole ridden and bondo filled casting under that smooth paint meant that even though I could have fixed what some of the mechanical problems were I can't begin to fix faulty castings who's quality of cast iron was now more than a little suspect. Lot's of problems on some of the cheaper tooling can be fixed by the end user. Stefan Gotteswinter on Youtube shows doing exactly that on quite a bit from the far east and ending up with a far superior bit of tooling. You still have to start with something sound enough to make the effort worth while. Those 2 vises cost me approximately $400. At best they'd be ok for less than precision work on a drill press. I'm also sure anyone here would have reached the same conclusions as I did. So finding out I'd now wasted everything they cost was at best an expensive learning lesson for me. Are some of those cheaper (not the very cheapest) vises any good? Likely some are. Mine certainly weren't. I suppose a great deal depends on which factory is making them and there own quality control for the cast irons specifications and quality as well. I also learned that the less your prepared to spend then the more double checking you should be prepared to do to obtain the minimum of what's required to match your expectations and needs. Upgrading to 2 more 6" capacity vises then cost a bit more than 1k. However that money wasn't wasted and they do exactly what decent vises should. I also tested and checked there internals to be sure I did get what I was paying for. My lessons have been learned the hard way. I now take little I buy on faith including checking as best I can anything with well regarded brand names on them.
|Thread: Milling table regrind|
Anyone using a cup grinding wheel, flycutter etc powered by the mills spindle while trying to correct any faults in the tables surface simply hasn't thought through how the machine functions. For one part to move within another there HAS to be some clearance. A 1" or 25 mm shaft will not fit within a 1" or 25 mm hole no matter how straight and accurately made they are or how perfect the surface finish is on both parts. Even a brand new top of the line mill will have a few thou of clearance. It has to or the table couldn't move. And once that table does move past it's balance point enough, it's own weight is going to lower the heavy end and raise the lighter end until that clearance is taken up. It's easy enough to check for anyone who doesn't believe the above facts with an indicator. A normal vertical mill can not accurately resurface it's own table. Planers, bed mills, high precision surface or slideway grinders have a fully supported table and very accurately aligned table ways for this exact reason. And because there's a multiplcation factor involved even an extremely good 2 thou clearance would get multiplied to more than that at the tables surface so you'd be cutting the tables face in a bow shape. An older mill with some or a lot of wear the problem would be even larger.
Going by the quote I got to regrind my 9" x 32" table by a very experienced grinding shop who also did this type of work from time to time I'd expect the costs would be in the 150 - 250 quid range.
|Thread: Best edge finder for oldie|
What hasn't been stated is exactly why the cheap wigglers aren't worth using and why the better ones cost what they do. How repeatable and accurate they are is a function of how well the wigglers working faces have been heat treated, ground and then precision lapped. The best ones will have a dead flat mirror lapped finish on both faces so they kick off at a constant and repeatable point every time. They do need a gentle cleaning and a single drop of light machine oil applied from time to time. Russell's mention of cigarrette rolling papers is a very old machinist's trick and one I use quite often. If your careful that paper can do edge finding that no other tool can do. The Zig Zag brand I use are almost exactly .001" thick. Held with a pair of needle nose pliers to protect your fingers edges can be found with the cutting tool rotating in the exact tool holder your going to be using so even tool runout can be compensated for. X,Y and Z can also be found with that simple piece of paper. They can also be used to locate a tool tip on the part face or it's O.D. on the lathe, locating a drill point at a known location for tailstock drilling and do it all to less than 1/2 a thou if you take a bit of time and your careful. Thicker paper can't be as accurate since you have no idea how much the cutting tool is compressing the paper with a stationary tool or exactly at what position it tears the paper with a rotating tool or part. I've also got and use a Haimer 3D and there's no doubt it's far more accurate than any wiggler type I've used. They do need to be properly zeroed to the machines spindle C/L and kept in a dedicated end mill holder to get the very best from them.
|Thread: 'Repairing' badly scored dovetail slide surfaces|
Ignore it? It's your machine so any decisions are up to you of course. But visualise how the machine works and it's required alignments. With scoring that deep it was run for a very long time without oil. The previous owner should have been able to hear at least some changes and investigated a bit and long before it got that bad. The lack of oil dripping off the front of the one dovetail should have been a good clue as well. The one side of the ram is now running at a large misalignment which in turn misaligns the good dovetail side. The ram weight and cutting forces are now being shifted to a couple of very narrow areas on both the male and female dovetail on the good side. That will greatly accelerate wear and the problem can only get far worse. Shapers and the surface finish and accuracy they can produce can be fairly close to surface grinding with a good condition machine and properly sharpened tools. Any excess wear and misalignment in the machines movements will directly show up as a measureable amount on whatever part is being machined.At the barest minimum milling to get all 4 of the dovetail surfaces correct would help a great deal over what it is now. Surface grinding is much more accurate obviously and would be much better. Most machines today are only surface ground with some oil flaking such as the Bridgeports use. It's usually a very expensive industrial CNC or tool room machine before hand or power scrapeing is done on any of them today.
Since machine tool slides ride on an oil wedge having that center oil groove may not have been thought to be needed by the factory. Adding one certainly couldn't hurt. But there is NO easy, cheap, or fast way of fixing all that wear without at least milling on a very accurate and good condition industrial quality machine. Having it ground by a really good and experienced machine tool rebuilder would be the way I'd go if it were mine. That still depends on just how important the machine is to you and what your willing to invest into it. Hand scrapeing that amount of wear while still maintaining it's 3 dimensional alignments would take a very long time and take a great deal of experience and skill. The investment in the correct test and alignment tools to do so would be far more than having every one of the machines slide surfaces ground.
|Thread: What sort and how big an end mill or other milling cutter?|
If your trimming that lump off your vise as shown in the other thread then bandsawing or even hacksawing off the majority of what needs to be removed first will make the job far faster and easier on the machine. With a flycutter in the lathe you will or should see the tool cutting on the backside of the cut once you get across the job far enough but it will be by a very small amount. That's quite normal and doesn't indicate a misalignment of the headstock. It's mostly caused by the cutter flexing and not taking 100% of the cut that was dialed in.
Before the influx of the much cheaper offshore benchtop mills started and with tough times for many in the UK even up into the 1960's due to the war few had the luxury of having any sort of a mill in a home shop. The very small BCA jig borers sold for almost 4 times what a then brand new Myford Super 7 was selling for. The old Model Engineer magazines show some extremely complex milling tasks all done on the only machine tool many had in the shop, there lathe. For anyone trying to do the same today I can't recommend the Workshop Practice book Milling in the Lathe highly enough.Even having a vertical mill it can still teach a lot. I have a Bridgeport clone yet still bought a large Palmgren milling attachment for the lathe. It's rare, but some jobs such as milling, drilling, boring or tapping the ends of long bars can still be done easier while using that milling attachment and the lathes headstock much like a horizontal mill. Boring between centers with the work on the lathes cross slide for work that fits is still a more accurate and better but slower method for through bores than a vertical mill is with a boring head.
|Thread: Reference bar ?|
If your wanting to use that test bar to check your lathes headstock alignment and I think you are, then there's a way around buying one if you've got a large faceplate for the lathe. Clean, adjust the lathes cross slide, nut and gib so everything is as it should be. Take a very fine clean up cut across the full width of that faceplate. Remove the compound slide, back the cross slide out towards you, set up a dial indicators tip just past the faceplates center at the 3 o'clock position and the magnetic indicators stand on the cross slide. Run the indicator away from you with the cross slide towards the backside of the faceplate. Your measurement changes between the center of the faceplate and it's outside edge will be DOUBLE what any misalignment is. On a good toolroom lathe in new condition the cross slide is biased inwards and machined, ground, and/or scraped so the lathe should face concave .001"-.003" over 12". IF? and it's fairly rare your headstock is out of alignment the above test should show that. With smaller lathes using a 10ths reading DTI for the measurements might be better than a .001" reading dial indicator. There's far too many on forums and Youtube avocating adjusting the headstocks alignment without properly testing that it is in fact the real problem and not something else. A very well made test bar can indicate problems, but the headstocks internal Morse Taper has to be spotless, in perfect concentricity and condition or it will show a misalignment that the headstock doesn't have.
If your wanting to check the tailstock then assumeing it's MT is concentric and in very good unmarked condition a test bar can help. But I'd start by extending it's quill fully out, locking the quill clamp, then run an indicator along the top and then along the side that's closest to you. The tailstocks bed clamp should also be used during that test. These tests will show more than using just a test bar will and especialy so if your Morse tapers aren't perfect. I do have some of those expensive test bars and I still do the above tests first. A seriously worn tailstocks base and spindle bore can show misalignments that have to be addressed first before any meaningful tests can be done.
Edited By Pete on 10/07/2017 00:51:12
|Thread: Milling in a pillar drill|
You've had your question well answered Nige and have made the more than correct decision not to try and force a machine no where close to being designed for it into something it just can't do with any accuracy or surface finish. So just for future referance since the subject is sure to come up again.
Most if not all consumer grade light duty pillar / drill presses sold today don't even make a good job of drilling holes if your willing to run a few simple tests. Set up an indicators magnetic base on the rear column with the tip of the indicator at the middle or outside edge of the table then just start adding some pressure to the table with your thumb. Then visualise driving a 1/4", 3/8", or 1/2" drill through steel and how much added pressure the table sees plus the vise and work piece weight. Tramming the table to the spindle is almost a waste of time because of that variable table flexing.The usual very light wall column and head castings also flex under those pressures if your willing to set up an indicator that's not attached to the machine but can indicate the head movement while drilling with a larger diameter drill. Those mill / drills only resemble a pillar drill with an added X,Y table. Check there weights and there far heavier than adding that X,Y table would add on it's own. The column and head casting are much heavier and far more rigid. Better bearings that are designed for the side loads, a drawbar, and much more rigid and accurate fine feed on the Z axis. With all that they still don't make the greatest milling machine, but they can be made to work.I own a mill but still tried milling just once on a 180 lb. 16 speed floor model drill press that had the drill chuck secured with a center bolt into the end of the jacobs taper and a 35 lb X,Y table bolted down to see how well it might work. It was a waste of time with very poor ragged edges on aluminum even while reducing the cut to .005" depth. I'm extremely doubtful adding a proper end mill holder or collet chuck would have made any noticable improvment.
Youtube has more than a few videos by people saying it works and trying to prove it. Read the comments and the ones most in favor of it seem to know the least. The ones against it all seem to have a large amount of experience and understand the requirements and forces involved. Then watch the video and take note of the depth of cut, vibration and surface finish quality.Yes you probably could rebuild and work around the light duty components with something far better, and after all that time and money still have something that only works semi well compared to even an X2 sized mini mill. They do make industrial floor model drills with a built in X,Y table that can do light milling and even proper boring with a boring head. Check the weights and what they cost and both numbers approach what an off shore Bridgeport clone would cost and weigh. A 2200 lb Bridgeport because of it's design is actualy a very flexable machine if it's pushed harder than it should be. There used so much simply because of how versitile they are than there absolute rigidity. Trying to make a 100 - 200 lb. light duty pillar drill do milling is a great way to test your frustration and patience limits in my opinion. I no longer even own any pillar / drill press for working with metal because of there limitations and poor accuracy. My knee mill will drill holes 10 times as well at least against any pillar drill I could afford.
|Thread: Bridgeport one shot lube repair, plus lubrication question|
If the machine is bolted down to the floor the cap the ram slides in can just have the 4 bolts loosened and the whole head and ram swung off to one side. Without it fastened down I'd not take the chance since the knee, saddle and table add up to a significant amount of the weight and the machine could easily go over sideways with all that weight off to one side. So if it's not bolted down I'd remove the motor then remove the head from the knuckel by supporting the end of the spindle first with a piece of plywood between the spindle end and the table. Raise the knee until it just takes the heads weight then remove the 4 head bolts that fasten it to the knuckel. Then remove the ram. If you remove the column cap be aware that some machines have nothing to support the internal spider inside the top of the column casting once the cap bolts are removed. But the spider can be held through the columns side access panel while the bolts are removed or replaced The head, table, ram and knee aren't light so it depends on what you have other than human power for lifting them. Remove the main one shot lube container after you've removed the table and saddle. With the table and saddle off and if there's no rear mounted electrical cabinet on the rear of the main column casting the machine can be laid over on its back. Bolt a 3'-4' long wooden 2"x4" to the underside of the columns base to keep the machine from rolling over sideways while it's postioned on it's back. Wind the knee up the dovetail with the knee crank until it's clear of the nut, remove the knee gib and locks and the knee can then be slid the rest of the way up the dovetail until it clears that dovetail. Assembly is done in reverse. I'd want to have an engine hoist at least for doing the heavy lifting or a good chain fall.
It's not a big or hard job but it does take some thought and planning. And cleaning out all the old congealed oil, swarf etc makes a large difference in the machines feel and accuracy. The feed screws and nuts should be washed down with a good solvent as well. All that black oil on every surface is because of wear particals and swarf.Neither is good for a machines life span. Make sure to readjust the feed nuts during reassembly and replace any suspect way wipers and felts. The machine will feel a lot nicer to use once all this is done. But on a well worn machine there's only so far you can go with the nut and gib adjustments before the screws and slides will get tight at the extremes of travel. Use a seperate container for each set of parts and lable where there from as there removed. I make sure parts like the tables bearing hangers that the X axis screw is supported on go back on the same ends of the table. The two bevel gears on the top of the knee screw are the only place I use a light grease unless your one shot oils that area as well. The rest of the machine gets way oil. And with the head off the machine be very careful how you set it down once removed from that knuckel. It's all too easy and common to break parts off like the small spindle direction feed knob. Don't ask how I now know that. Once back togeather remove the oil zerks from the area on the side or back of the head to check that there is in fact the proper spindle oil inside. It should take spindle oil and way oil is too thick. Bridgeports are a total loss head oiling system so it's not uncommon to get the odd drip once in awhile off the spindle area.
|Thread: Truing up chucks|
Fwiw, my named by Emco high precision "heavy duty" Compact 5 three jaw is very specific in the instructions that came with it about returning each scroll pinion back to the same location they came out of in the chuck body after cleaning a chuck. Especially the one marked with the 0 postion on these chucks since that was the one they used to grind both sets of chuck jaws. Maybe something to keep in mind when cleaning and servicing a chuck, or when regrinding the jaws back true to the chucks body. Suburban Tool on Youtube has a very good video about how to properly regrind the jaws in a scroll chuck with some impressive results for runout. If anyone needs good dependable and accurate chucks I'd think they would. The jaws are just slightly ground with a recessed area at the very rear and a ring is used at that location to load the jaws by tightening against that ring. That preloads the jaws in the normal working direction then there ground. Preloading the jaws on the outside tips will tilt them very slightly outwards due to the minute but still important slot to jaw clearance. But the video explains the how and why far better than I can. The last set of chuck jaws I ground I wasn't seeing the improvement I thought I should. Not using the method Suburban does may be why but I can't say for sure yet.
Neils 100% correct about how important it is for a chuck to be properly cleaned. But something a thou or two in size can be fairly tough to spot at times. I've found a lot of improvement can sometimes be made if a sharp scriber is used to loosen any swarf in the corners of the scroll and jaw teeth. It's surprising just how much will still come out of a chuck you thought was spotless. Through drilling and boring tends to be what causes the most swarf to enter a chuck through the jaw slots. Whenever I can on shorter work pieces that need that through drilling or boring I'll usualy wedge a paper towel or small rag into the chucks through hole and just behind where the work will sit before tightening the workpiece in the chuck. Chucks still need cleaning every so often and the paper or rag just prolongs that job for a bit longer.
Yes it's likely correct that cutting the backplates step 1/32nd undersize so set screws can be used as a cheap alternative to a Grip Tru would cause it to be less resistant to movement when hogging great amounts of material off. I'm doubtful many M.E.'s really push there lathes that hard. But the coefficent of friction with the backplates bolts torqued up properly has to be quite high so you'd really have to be working a machine hard before I'd worry too much about it. Prof. Chaddock and GHT were two who really knew and practiced what they were talking about. Out of everything GHT wrote about the only single thing I can think of that I disagreed with was him stamping the numerials into a replacement shop made dial while it was still screwed to the lathes spindle nose. I suspect that Super 7 may have had sleeve type bearings? But it's still not a practice I'd subject a good chuck to. He did know far more than I ever will so I'd not really want to argue he was totaly and absolutely wrong either.
|Thread: Accuracy of an old machine|
Center drill a steel or aluminum bar of whatever you have around. A couple of inches in diameter and 8"-12" long would work well. Center drill each end.Then take a lump of any steel you have handy 1"-2" in diameter and roughly 2" long. Turn half the length down by around 1/4" smaller in diameter and do a good facing job where that step is. Reverse that in the chuck jaws and turn a 60 degree point on it. (30 degrees per side as a normal fixed center would have) Now DO NOT remove that from the chuck until the next test is complete since the center tip is now as concentric as the lathes bearings will allow. That turned step goes against the face of the chuck jaws and prevents it from being pushed back in the chuck. Set your previously center drilled bar up between that headstock center and the tailstock center. Add a drive dog at the headstock end and let one of the chucks jaws drive it.Turn the length of the bar until it fully cleans up and measure each end with a good micrometer. This removes any chuck jaw holding inaccuracy and will produce a proper example of what the lathe can actualy do under cutting conditions. But only if your tailstocks side to side alignment is properly set to the headstocks center line.
You have to eliminate as many variables as possible or cutting tests are meaningless. As each part of the lathe is tested and verified as correct that's one less variable you can eliminate. By doing the proper tests you can then access exactly where and what any problems might be. Turning between centers is the most accurate way of holding and turning any shaft type work as long as it's diameter is large enough to prevent bending. As a bonus it allows work to be turned end for end put back in the lathe and still be accurately centered. If the tailstock is properly aligned and your turned test bar has less than the .003" taper your seeing then the faults lie elsewhere.
Given the age of your lathe I'd expect your tailstock is worn especially at the front where it slides on the ways. However it takes a great deal of wear to show very much change on the parts diameter. George Thomas and a few others have clearly showed that by simple math.
An impressive and extremely heavy duty lathe for there size. Anythings possible of course, but after seeing those pictures from KWIL's link (thank you) I'd be even less concerned about that crash shifting the headstock just as Hopper said. And I think much the same as he does about spending the money on those test bars. First they have to be made very well with as close to zero runout as possible. Getting that accuracy no matter where there made costs a great deal of money.Then the spindle taper has to be in perfect condition or the tests don't mean much. I have some and have learned that for what they cost the return wasn't worth it. They are handy for checking and aligning a tailstock not so much for a true C/L with the headstock, but for the tailstock being angled off side to side or pointing up or down hill. But even that can be done without having one.
Your Lang lathe certainly has the quality to justify a proper rebuild. If you ever decide to do so it's best not to chose to have the grinding done by price alone. The shops that do know what it takes to correctly align and regrind a lathe bed will charge accordingly. As Hopper said sorting out your headstock bearing clearance should be the next step. With that .003" clearance it's impossible to judge how much the bed wear is causing a taper in the workpiece and how much the excessive bearing clearance is. Logic and some guessing suggests it could be causing most of that .002" taper. It is a very heavily built lathe, but even so it's not impossible for the bed to twist and on an uneven floor, even more so if it's been bolted down without being sure it's level or not twisted in all directions. That could have happened at any time before you bought it. The lathe carriage then wears to the beds position and the bed can also take on a permanent twist over time. If so it needs to be shimmed and gently forced back into to being true.
I'm not familure with a Lang lathe, but they all work much the same. .003" seems high though. For the adjustable type preload you slowly tighten, run at top speed for 20 min. to 1/2 an hr and check the headstock temperatures with your hand. Keep adjusting until the headstock starts to warm.Proper preload is very close to being correct at quite warm but not so hot you can't leave your hand on it for some time. A bit subjective but that's what most of the recomendations I've read have to say. You might find ground shims at a good bearing supplier and add, subtract in various combinations until it's correct.
Likely that's a 4 1/2 to 3 morse taper. Fairly common on a lot of lathes in the 5 MT size and not usually too tough to find by contacting a few machine tool suppliers. Memory if it's right then the Colchester Chipmaster used it as well. It usually takes a fairly serious crash to move a headstock on a well built lathe, but possibly that was enough.
I'll try to shorten this as much as possible but..................
What type of tool was used to turn that 6" long piece down. To test like that you need to start with ultra sharp HSS since carbide takes a lot more pressure to make it cut unless it's one of the specialty tips meant for aluminum and has lapped edges. That pressure can change your results because it pushes the bar away instead of cleanly cutting it.With that very sharp HSS tool you then take a clean up cut with tailstock support. Remove the TS support then take a very light cut with that same very sharp HSS tool. .001" - .002" depth of cut. The general rule for cutting without tailstock support is 3-1 so your 2" diameter x 6" long just fits the rule.
Another test is a long heavy bar 2" + in diameter and again a light HSS cut along the whole bar until it cleans up and using tailstock support. Carefully measure that with an accurate and trusted micrometer at the tailstock, middle, and headstock end. More places is even better. Both these tests will give you some starting numbers. And the tailstock may well be slightly off center from the headstocks C/L. But you'll have the start of a good test bar.
Bearing checks and adjustments as mentioned by someone else should be done. Once your confident there well adjusted and in good condition then the bed has to be checked for twist. Getting it leveled with a high precision machinists level is the easiest method. The actual level isn't really important but you need both ways in the same plane with no twist. Given the ratio between what's happening at the bed mounting feet and the tool tip .001" at the bed foot can make .003" or far more at the tool tip. Actual bed wear has a lot less effect. Visualise your tool tip moving up or down .003" - .004" on a large 2" diameter bar. The movement difference will create very little change to the cutting tips location on the material or a difference in the cutting size. A .004" thou up or down movement does not decrease or increase the finished diameter by that .004". Bed twist causes the tool tip to move in or out and that does change the cut diameter by the same amount. It rolls the tool tip in or away from the material depending on which way the bed is twisted.With the bed level then the tailstocks morse taper can be checked by swinging an indicator to the front and rear just inside the morse tapers bore. This DOES NOT work for checking the tailstocks alightment for up and down. Gravity can and will throw those results off. As much as .010" or more. Once the tailstock is aligned and with all of the above done I'd then take another light cut on the long bar with a good dead center and tailstock support.
The measurements taken then will have some meaning about what your lathe is capable of doing. The quick test you've already done isn't of much use because there's too many variables that can sway the measurements. If that cutting test on the long heavy bar with support shows some real improvement then it's time to repeat the test you've just done.
Flat bed lathes like most of the Myfords and some others are the cheapest to have reground. But it's not quite that simple. Doing so lowers the carriage by the amount that was ground off. That affects the half nuts position on the leadscrew. And the same if you have a seperate rod for power feeds. If the bed is worn enough to need that regrinding the bottom surfaces of the carriage will need it as well. So more material is then taken off. To regain the correct alignments material such as moglice is bonded to the bottom of the carriage to lift it back to the original position. The mounts for the leadscrew and possibly gearbox if equipped with one could be lowered to regain the alignment, but adding the moglice is much easier. There's a bit more than all this, but it should give you an idea of what's roughly involved and getting some numbers that can be trusted.
There seems to be more misinformation and lack of understanding about testing and aligning machines tools on every forum I can think of than there is correct information. I've also seen multiple posts on just about every forum about just jumping in and moving the headstocks position. That's the very last thing you do without properly tested and verified results that do show there's no doubt it's actually out of alignment.Googleing for the online PDF of what Dr. Georg Schlessinger wrote about machine tool testing is well worth the time to read it enough so it's understood what's being done and why. I've had to spend a great deal of time, research and hands on trial and error trying to learn the very little I do know about it. There is more than a few ways of doing this with some more complicated methods than others. But I know what I've mentioned does work.
|Thread: Another great youtube channel|
I've been watching Robin's channel ever since Tom Lipton mentioned him on his channel David. An extremely talented person who's demonstrating a lot of topics that haven't been covered by others. There is a lot of really decent machining content showing up on Youtube by people who know there subject very well. Stefan Gotteswinter, Clickspring, Tom Lipton, Abom, This Old Tony just to name a few. I'd still have to put Robin right at the top of the one's I know about today. That's just my own opinion and others may think differently.
|Thread: Slipping drill chuck|
Yep I'd certainly agree with you about Makita. Only thing I can come up with is even the very best can turn out a faulty product sometimes. Since I don't know the exact drill, nor can I compare it with another to see if they both perform the same, then it's just a best guess right now.But it could also be just a poor design. One wouldn't think so, but even Henry Ford produced some lemons. I do have an Albrecht and 3 Glacern machine tools integral shank keyless chucks for my lathe and mill. But for a hand drill, those Dewalt keyless are pretty damned good. No where near what that Albrecht is of course, but far better than I thought they would be. I wouldn't think twice about buying another one.
Edited By Pete on 15/08/2015 12:43:07
To answer your original question, some drill chucks are to be honest completely worthless. And those factory's are more than willing to sell us the worthless junk as long as we keep accepting it. There should be no need to buy drills with the 3 flats ground on them, or need to use any other methods to work around what is a manufactured fault in the OEM chuck you already have. I once owned a Black & Decker corded portable drill with a key type chuck. It was 100% impossible to get that chuck tight enough to prevent the drills from spinning and ruining the drills runout due to the scored shanks. Before I finally got fed up and binned the whole drill, I ruined far more in good drills than the whole machine was worth. Today I have an 18V Dewalt cordless with the keyless chuck, and a 12V Dewalt. They barely take any real effort to properly tighten either of there chucks, and I've yet to ever spin a drill in either of them. If your chuck won't hold a drill without spinning it, then it's a fault of the chuck. Don't waste your time and just replace the chuck or the whole drill with something decent. Good cutting tools aren't exactly cheap today, so it takes very few ruined drills before you could comfortably buy a very good quality drill chuck at the minimum.
If I were to buy any new corded or cordless drill now, and I knew I was properly tightening the drill chuck, and it spun any drill just once. It would be taken back for a full refund. I learned my lesson long ago and I'll not repeat the same mistake again.
|Thread: Tail alignment and gear handle play|
I can fully understand your frustration of having to rework what should have been correct right from the factory. With the almost universal use of CNC on production machine tools even in China, or at least the bare minimum of today's cheap Chinese built, but still fairly high accuracy DRO's on any manual machine's that might possibly still be used in a production environment, plus the standard world wide use of jigs and fixtures to speed up production. It is more than inexcusable today that even those cheap machine tools are still being made this inaccurate. Even a 5 second check with an in house shop built gauge would show when an adjustment or new tool tip is required. I honestly can't logically figure out how they can still make any of the cheap machine's that inaccurate today. With the volume there producing, then just add $5 to the price and start checking and using some gauges to show when and where there's a problem developing long before we start seeing what we have been as the end users.
But your certainly not alone with having problems with Seig machines. I spent over $4000 on a Sieg C6, there X2 mini mill, and a lot of accessories. My tailstock pointed uphill over .009" in 2" . Add on a drill chuck, plus the length of a standard drill, and that drill tip was about .025" high or higher with the tailstocks barrel extended. It was impossible to use any center drill because the drill tip was so high the tips would instantly get ripped off as soon as they touched a spinning work piece. Reaming from the tailstock was obviously not going to happen without a very tapered but reamed hole. The additional tee slotted milling table was severely warped enough to easily see it visually. And the cross slide's surface was incorrectly ground over .003" in both directions. So it was impossible to do any accurate milling or between centers boring with the work bolted to the cross slide the way the machine was originally machined, ground and built. So to again use some logic, Seig either has very poorly trained and incompetent employee's, or there management could care less about there customers. I certainly won't ever buy another Seig machine no matter how much they improve there quality control in the future. My comments here may or may not affect company's such as Arc Euro who I do think is a very good company, and who will stand behind what there selling. But I didn't buy from them, and I can only comment on what my personal experience has been with Seig machines.
And I'm certainly not expecting Schaublin quality or accuracy at that much cheaper price. I am expecting the basic machine alignment's to be at least much more correct than what I found so the machine was usable without having to correct the factory errors. You could hardly do worse even on purpose. But it was that machine that forced me into educating myself about what's really involved with the correct yet basic lathe alignments. I do think you don't see all that many complaints on these forums about those alignments because most think what they've bought has to be correct, so most probably won't check like you have.
Yes I do know about that uncertainty of measurement. So you are quite correct that there is no such thing as "100% positive" exact, or even perfection with anything while measuring. I did use an incorrect term I guess. But that NPL website does look interesting. Many thanks for that link.
Yes John I'd certainly agree that testing against the tail stocks OD would only be the first step. But if your metrology equipment is accurate enough? Then no lathe no matter how good or expensive they are including the worlds best that are available today including the temperature controlled spindle and bed machines that are designed for optical and/or laser equipment would be without fault. And yes you are 100% correct, the tail stocks OD is just a place to start. But I did have to shorten my post by over 2700 letters since the allowable limits on this forum don't like lengthly explanations of what are fairly complicated ideas that both Conolly and Schlesinger had. You do need to run multiple tests if possible on multiple areas just to start forming some ideas of where the problems might be.Then it will take some real thought and I think education before you can properly pinpoint where the those problems might be. To state the completely obvious, the cheaper your machine is, then the more knowledgeable you have to be to be able to wring the very best out of it. It's not impossible, but it does take a real desire to properly educate yourself. I've been learning about this for well over 30 years, and I never expect to ever know what I'd like to.
But..............to end up so that you are 100% positive of the exact issues and exactly where there located with any certainty can take a huge amount of time,testing, thought and energy. That's where your own personal understanding and education starts. I highly recommend NOT asking questions on forums like this first, but you should be doing your own research through Google, and then possibly start to ask some questions on these forums only after doing so.
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