Here is a list of all the postings Martin of Wick has made in our forums. Click on a thread name to jump to the thread.
|Thread: Just bought an ML7, what should i do first?|
1 Just skimming the top of the bed is unlikely to recover a worn item to an adequate condition, you will need to address all 4 sides of the shears.
2 The chuck is really too big for the lathe and if it has been used extensively or for a long period on that machine it will have caused accelerated wear to the front spindle bearing. There is a reason why Myford recommend you stick to a lighter 4 inch chuck on the ML7 . The other more obvious reason is that the larger chuck can rarely accommodate larger workpieces without the risk of the jaws engaging the lathe (as the damage to your machine so convincingly reveals).
3 The spindle bearings are not trivial items to deal with if worn. Yes in theory all you need to do is rip off a shim layer and check the fit to spindle , giving a scrape or two if needed (metal is very soft, grind up an old hacksaw blade for your scraping tools). In reality, front at back bearing wear at different rates and usually into an oval condition. This may give you some issues when setting them to re-establish correct spindle alignment. Expect to spend a considerable amount of time when re-setting the old bearings.
From the pictures, the unit is in very poor shape and has obviously had some serious abuse. It will need a considerable sum of money spent on it to bring it to a usable condition. If you are prepared to do that and you enjoy restoring old machinery then crack on, at the moment, oilers are the least of your problem and suggest you don't waste any money on these until you have carried out the test below...
The first thing you need to do is wind up the saddle to 2 to 4 inches from the chuck and adjust the gibs to give smooth movement with no play at this position. slowly begin winding the saddle back towards the tailstock. If you notice the movement becoming progressively tighter and needing more effort, the then the bed is to badly worn for normal use and will need regrinding (together with the saddle and probably cross and top slides). Even if you can find a commercial operator willing to do it, these days it you are already talking north of 300 quid for a full job, plus transport.
If the bed and other sliding components are good, or money is no object and you want to cost up the other components from the Myford web site for restoration, from your description I would consider you will need to replace:
All olite bushings on the leadscrew and countershaft and carriage pinion drive assembly
possibly the counter shaft, if worn
All feed screws and feed screw nuts on top and cross slide
Leadscrew nut and possibly leadscrew, although you could get by turning the leadscrew around or if you want to convert it to metric, then all leadscrews and feedscew components can be replaced with the appropriate metric equivalent if available.
carriage drive pinion and possibly rack if worn
Spindle gear pinion and by the look of it some of the basic lead screw drive train
Headstock and back gear clusters
rear spindle thrust bearing
Check also the condition of the spindle nose and fit of spindle in the white metal bearings. If there is damage here, your only recourse will be to find a second hand spindle, most of which will be as bad as your specimen. you will need to check runout and deflection under load to assess headstock bearing condition
sundry nuts bolts grubs lock nuts, oilers, oil nipples, change gears etc to suit, plus bits I have forgotten
If all that is to your liking, there is a good 8 or 9 part vid on utube by someone from NZ that takes you through a comprehensive re-build that shows you the teardown and testing sequence ( where it definitely helps to have another lathe available in order to restore the one that is the basket case).
Enjoy, as they say.
Edited By Martin of Wick on 08/09/2019 10:29:56
Edited By Martin of Wick on 08/09/2019 10:31:41
|Thread: Help choosing a Chinese lathe please|
I sourced my CML from Amadeal and always had good service from Amadeal, ARC and Warco.
|Thread: Stripped the drive belt on my Chinese Mini lathe|
Guilty as charged of assuming all CMLs are the same. Should have read the OP more closely so treat all my previous comments as not applicable to the Seig flavour of mini lathe.
Interesting to know what the belt standard is. Certainly the T5 does not look like the OEMs belt that I had (kind of looks halfway between a T5 and an M5). As it fitted into the pulleys OK I used the T5 anyway.
So Jim, best stick to OEMs spares unless changing the drive system. Looking at the work you do, it seems to be biased towards low speed high torque end of lathe operations (tapping, knurling, drilling etc). Because of the lack of back gear arrangement on CMLs, I think it is fair to say the CML struggles in this region and will always put large loads on the belt.
In terms of mods there is not much to assist high torque operations with this type of lathe without totally remodelling it. Some designs of auxiliary counter shaft are available, but while these help match motor and controller for low speed operations, the torque loads on the final drive to the spindle remain the same.
One change I made to the leadscrew drive was to use a Ralph Paterson mod that places an extra change gear reduction step on the banjo. This then makes some very fine feeds available (down to .001 thou). I am not sure if the SC2 has the same banjo arrangement as the older style non brushless CML, but you could take a look.
Some people have fitted an ammeter to judge how much load they are putting on the machine.
If you are doing a lot of tapping, as an accessory I would recommend making a hand crank for the spindle rather than attempting to bully taps through the job using the motor, as that places the drive under a lot of strain.
I don't know what arrangements are available for adjusting the gibs on the carriage on your SC2. On my CML, this was a total pig, In the end I got fed up with having to partially dismantle the lathe to adjust and then having it loosen off a week later etc . I used a design from the internet and replaced the original arrangement with a tapered gib arrangement (forget who - google minilathe tapered gibs). There was nothing fundamentally difficult in the job, but you need access to a mill and another lathe (I had to reduce the shaft diameter of the carriage drive gear shaft). A great deal of faffing and fitting to and fro was required - but what joy to be able simply adjust carriage play without having to take off the apron.
..........I was attempting to part off and had the workpiece dislodge from the chuck
Aha! after remorse comes the confession... Don't worry we've all been there!
Thing is, given the nature of the belt, at the kind of RPM and torque load needed for parting, the 5T belt is right on the limit of its design parameter and close to tooth stripping territory and a lock up is the last straw.
Drilling larger holes is another activity that puts a large load on the belt and motor.
As above, switching to 5M system may help a bit, but the difference to T5 at low RPM is not huge.
Although it is a PITA, (particularly setting motor alignment and position) it is well worth ensuring all alignments and belt tension is appropriate to give the belt the best chance of survival. Loads of other DIY mods available on the net to suit any particular requirement.
Often you can hear the protest from the speed controller or see the RPM drop when the motor is struggling. Minimising strain on the machine comes with practice and experience and breaking a few tools is just part of the learning process.
Just crack on, and soon you will be lathing away like a pro!
always slightly worried when I read that replacement belts are hard to get... on both my Chinese specimens I have used a 5T replacement belt, readily obtainable from the usual belt and bearing factors. Maybe I have used the wrong belts...If the originals were not 5T then they must be very close as never had a problem with the 5T replacements.
HTD 5M is better for power transmission, (and belts are about half the price of synchroflex) but as pointed out, you have to change the pulleys.
The dodgy plastic motor pinion is a potential source of problems. From new, the supplied belt and replacement belts did not fit that well on my mini lathe (well the teeth fitted into the gaps, but not what I would call a precision fit). I have ignored the issue in the absence of any problems to date. May replace it one day with a metal pulley as I think could help reduce heat build up in the belt.
Ex factory, the supplied belts are not always of the highest quality. I have a C1 on which the first belt simply disintegrated as if attacked by some sort of contamination. Replaced with UK sourced T5 belt, not had a problem since.
Was the lack of drive due to motor stalling or the belt slipping?
I suspect that you need to look at alignment and tension in the first instance. Prolonged high speed running on tight belts can cause accelerated wear. Have some mechanical sympathy, avoid loading up the lathe by checking/reducing the RPM drop under cutting load. Oh, and avoid hard mechanical 'stops' (jus sayin!)
Easy to replace, unscrew the plastic plate on the end of the motor pulley, slip the old belt off and the new belt on, then check alignment of the motor with the lathe bed , that the motor pulley is in line with the countershaft pulley and a reasonable tension on the belt - say 1/2 an inch play
ex factory the motor on my CJ18 the back of the motor was an inch higher than the front ( how do they do it?). Detected by the slight whine as the pulley wheel tried to pull the over tensioned belt off the countershaft pulley. Had it been left in this condition, the belt would have failed quite quickly.
Ah the mini lathe - dontcha luve em!
Edited By Martin of Wick on 02/09/2019 11:24:20
|Thread: Backplate debacle|
When I started this game years ago, one of the first jobs I had to do was prepare a back plate for a new chuck. So I went to consult the professionals in the blacksmiths shop and someone recommended cutting the register to a 'grip fit' in the chuck body.
This I did using a cast iron backplate and hardly daring to breath during the operation. As the cast iron was quite soft and easy than expected to machine, I was able to shave dust off at the final stage and get the desired grip fit. Needless to say, the 3J chuck when so fitted still had about 1.5 TIR.
Until yesterday I was still clinging religiously to that original advice on register size. Until yesterday I hadn't had to machine a steel back plate... It was very hard steel too, in the end I had to resort to carbide to get a decent finish at a reasonable speed.
So two lessons learned,
The back plate register doesn't need to be a precise fit and it may be beneficial as 5 thou smaller (so why have a register at all I wonder).
And don't attempt to get a precise finish with carbide tools - switch to HSS for fine cuts because I think what happened is the tool just rubbed at a very light cut and as I increased the pressure to start the cut, it eventually bit and chewed off a thou rather than the dust I had intended. An yes, the plate was bloody hot too... piles of beautiful blue swarf, so will certainly bear that in mind if I need a close tolerance in future
So not only was the back plate prep not a debacle as I assumed, but thanks to the experience of all those that helped, I have been re-educated too!
Thanks to all.
Hmm, thanks gents, it seems that I have been labouring under a doctrinal delusion and have now suddenly become enlightened.
I was dimly aware that one dodge for an old or bad chuck was to shave a bit off the register to be able to offset it, but apparently the power of dogma has meant I never considered extending the concept as suitable method for the fitting of new chucks.
No reason in principle why it shouldn't be OK, so as suggested will leave the back plate as is and use slightly larger mounting holes with some sort of low strength adhesive just to assist the hold down bolts.
I guess this is what they mean by lifelong learning, so thanks to all of you for your help, not least because I can stop kicking myself now!
In cutting the register on a steel back plate for a new 5" chuck, the 'just shave off some dust' resulted in the inevitable - an undersize register. Discouraging words have been edited to avoid offence.
I was aiming for a firm push fit. What I have now is between about 1/4 to 1/2 thou undersize as measured with a clock while the chuck on the plate (but not bolted down).
Question is are there any way to remedy the back plate that may work, like dolloping some blobs of weld or cutting the register further and pressing or gluing on a thick shim? The register is very shallow at 3mm, but if I turn it all off and start again, the mandrel nose may foul the back of the chuck.
If the plate is now scrap, could I get away with slathering the register with Loctite 648, then tap up the chuck to give the minimum run out, before bolting down and hoping for the best...?
Apart from paying attention and being more careful, are there any tips that others may have to achieve a stress free perfect fit?
|Thread: 4 jaw chuck axial allignment|
This is a 4in chuck that I hadn't used for precision work until now because the 3 jaw that came with the minilathe was so good! On that basis I wasn't expecting problems. Come the day I needed an accurate set up there was a wailing and a gnashing of teeth.....Having not ever experienced problems with a 4 jaw chuck before, until someone pointed out it might be an issue with the chuck I had assumed it was some fundamental operator error!
Eventually checking the jaw mating surfaces alignment with the chuck body when tightened on a short round of silver steel, using a square off the back of the chuck shows the following.
'Go figure' as they say....
It would appear that the long surface of the jaws were not ground originally parallel and there has been some bodged attempt to correct the problem at the factory (possibly explaining why the clamping surfaces are much wider than expected).
The result is it is almost impossible to get an acceptable axial setting for longer work using the jaws with the long edge holding the work.
In other respects, the chuck is not to bad, useable with the jaws reversed, the axial surface of the jaws is true and the jaw fit in the slots good. with smooth movement.
The approach I would use based on a posting above is to lightly clamp up a washer in the gap between the rearmost two teeth. with the chuck stationary and spindle locked, grind all the forward teeth of the jaw to something resembling an even height and hopefully parallel to the lathe axis, repeat for other jaws.
Then go back in with the grinder to grind down the tooth that was behind the washer to below the level of the newly ground jaw surface so it will not impact clamping geometry. This may mean that the minimum stock size that is chuckable increases from 6mm to about 8mm, but I don't think that is going to be a particular issue.
I would like to think the vendor might offer to replace it, but it has been over 18 months since purchased - moral here is if you get some new stuff give it a good teardown and test the day you get it!
These are all really useful tips that I will keep in mind for the future, but for any of them to succeed, I think you need to have some degree of parallelism in the jaws to start with!
Using a bump centre to attempt to address the issue was quite entertaining. With the jaws set semi tight the topslide and toolpost would flex and twist in the most alarming manner. Slackening off the jaws to allow the work piece to move would get the axis OK at the bump, but everywhere else on the bar would be out of true.
I am certainly not an uber-perfectionist (slipshod and cavalier would be a better description), so could have lived with 4 or 5 thou axial drift over 4 inches, but not 30 thou!
I had been using the 4 jaw in an attempt to be a little more rigorous in my approach and working on short pieces, all seemed to be going OK . The issues only became apparent when working on the spindle for the lathe handwheel, a longer piece that needed internal and external concentricity on re-chucking to drill, thread from both ends etc.
Same problems showed up when mounting 3 inches of 45mm steel bar to skim a piece for the clamp fitting - and even setting the working end to true, the chuck end would precess and it would go out of centre with the lightest skim.
Thing is, until you examine the jaws in detail, the chuck looks quite good - the jaws are a good fit in the slots and the movement is smooth. It is just that the jaw faces have not been ground properly. If the chuck had been second hand, I would have attributed the problem to someone having attempted a bit of casual, freehand jaw grinding for personal amusement. That is how bad the clamping surface of the jaws are. Strange as the 3 jaw chuck from the same manufacturer was outstandingly good.
I shall give the vendors a call on Monday to see if they can help.
Thanks for all the feedback and some very good advice.
I didn't want to blame the tools, so was kind of in denial about the possibility of the chuck being bad ( 4 jaw came with new machine and had been unused until recently so had assumed it would be as good as the 3 jaw).
Subsequent to MG's and other posts I had a bit of an investigation. Checking jaws 2 by 2 clamped on some silver steel showed beyond any shadow of a doubt the jaws were absolutely diabolical. Not only was the grip wobbly and insecure in the plane of the pair of jaws, but clocking the steel bar showed 20-25 thou off axis over 3 inches for one pair and the other pair could be set at almost any position you like, none of which gave a true axis.
Checking against a backlit straight edge was utterly disheartening - some jaws were convex, some hollowed, others had uneven teeth (serrated jaws). A new chuck!! If you wanted to make one as bad as this it would actually be quite hard work Doh!.
Other parameters like spindle TIR checked out at half a thou and half thou wobble on the spindle plate mounting which is bit disappointing but probably OK for a CML. Slightly concerned, for as I recall there was almost undetectable run out when I unboxed the new machine 18 months ago and it has been fitted with angular contact bearings.
So replaced what is now a large heavy paperweight with the original 3 jaw that I had recently spurned for having a totally outrageous 1.5 thou TIR and an axial drift of half a thou over 6 inches. Incidentally, both chucks are from the same 'no name' manufacturer (orbiting stars brand from the logo!).
A new chuck is called for I think. I quite like the idea of attempting to re-grind but is a bit of a scary prospect, although difficult to see how any remedial action could make this specimen any worse..
At the moment all I would like to do is throw the chuck at the head of person that QA'd it. Interestingly, the gaudy check sheet that came with the chuck gives expected parameters for run out on the various planes and axis, but has no data for a chucked test bar (like the 3 Jaw has). Why is that I wonder!!!
Thanks again to all for your help.
How is one supposed to set either stock for machining, or work undergoing second operations to run to a true axis within the 4 jaw chuck?
Radial setting - no problem I can set up to les than half a thou TIR, on a point but move the DTI out or back along the work and the run-out can quite literally go 'off the clock' especially when working with 4 or 5 inch stock.
There must be a way to set up for a true axis but I can find no reference to this problem in my meagre stock of literature. It is causing me some stress at the moment as no amount of nudging, thumping, hammering of the work piece or praying and swearing seems to be helping me set the work to run true down the axis. When I set zero TIR adjacent to the chuck the tailstock end goes out of true. If I clock in the tailstock end, I find the chuck end is now off centre. OOOF!
I thought that one of the great benefits of the 4 jaw was the ability to clock in a repeat setting - but how is that achieved without some reliable way to get the axis running true?
I clearly have a major learning gap here, so would be very interested to learn what approach others have used.
|Thread: Myford Super7 Chuck and Tool Holder points|
If you feel the need to use He-Man insert style tooling on the 7, the easy way is to just determine the shim requirement and superglue the required thickness of material to the bottom of the 12mm tools so they can be directly off the top slide with the original clamp fitting. Simple and quick.
Get some 10mm tooling for use with a quick set tool post. No prizes for guessing which tools you will use most of the time!
If you are desperate to use 12mm tooling in a quick set format, then some people have adopted the expedient of milling down the top slide to suit. Wouldn't be my first choice ( neither would milling the bottom od the 12mm tool because, er, um, it wouldn't be a 12 mm tool any longer).
|Thread: Dam Solution?|
|On a similar thought can anyone explain how a hydraulic ram works ?
It is based on using the surge pressure or transient caused by the kinetic energy release delivered by the instantaneous stop of a moving body of water. Also known as water hammer to anyone with old plumbing who has fitted an instant cut off tap. The 'clunk' that you may hear or feel through the house on slamming the tap shut is a pressure transient that can be many times the ambient pressure in the system. If you are experiencing this frequently, I suggest you get it sorted before you find your compression fittings starting to leak. (or not find until too late as in my case)
T hydraulic pump functions as water under some sort of pressure flows out of the waste valve of the pump, the fluid drag then shuts the 'waste' valve triggering a positive transient that opens a non return valve (nrv) on the delivery pipe and moves a small quantity of water up the delivery pipe.
Milliseconds later, the reflected negative transient causes the delivery nrv to shut and the waste valve to open allowing flow through the 'power' section of the pump again. The process repeats ad infinitum.
At each pulse, only a small volume is moved, but the process can continue endlessly as long as the flow and pump internals are maintained so over time domestically useful volumes can be moved.
'Stonishingly low tech, but very effective, however in the complex and demanding world we live in they are of limited application these days.
If you have a stream at the bottom of your garden, and wanted to move water up hill to storage at the top of your garden at practically zero cost, this is the device for you.
Siphons are a practical solution for rapid drain down in situations where it is clear there are no valve arrangements to discharge water in quantity.
A company I used to work for employed just such a mechanism to supply the transmission pumps, for circumstances when the usual draw off valve arrangements were not available (usually due to statutory reservoir inspections). Volumes could be maintained at up to 80 million litres per day via an 18 inch diameter siphon - limited by pump capacity and need to maintain reasonable suction conditions to protect the pump impellers.
If the calculation above is correct, 500 gallons/s approximates to 190 million litres per day, factor in a few losses and say 150 Ml/d should be achievable.
Compare that to the current rate of pumping - approx. 96 million litres day according to BBC (not clear whether this was the rate of pumping or the net water removed).
I suppose there are practical issues with sourcing and handling large diameter pipe quickly, but I would have thought the water companies or their contractors would have material available.
After the Rotherham dam incident, we were all told by our political masters to determine the cost of remedials to emplace rapid drain-down arrangements in critical infrastructure that did not have appropriate facilities. When the great and the good saw the cost, they turned white at the gills and ran for the hills.
As I recall we did consider siphons, but these were not put forward on the grounds of aesthetics - serried ranks of blue plastic pipe snaking over the dam was the issue, so they said...
|Thread: Myford 7 Capacity Check|
For possible raiser, see **LINK** for myfordboys interpretation. Although his is designed for a ML10, you could try asking if he would be prepared to flog you a casting that you could adapt for a 7.
I would have imagined that T10 timing pulleys and belt would be preferable to gears for a smoother drive - and no need to run in reverse. Just as easy to gear down to suit your intended use.
|Thread: RENAULT DAUPHINE|
See also Skoda Rapide - a more recent version of said Renault.
If you attempted to corner the Skoda at the speed of a front engine car, you would find yourself being rapidly overtaken by the rear end! At motorway speeds, there was an uncomfortable hovercraft feeling caused by the front wheels were barely in contact with the road.
Thankfully got rid of it after only ten days ownership, much to my relief.
|Thread: Myford 7 Capacity Check|
7 in. swing over bed 9 in. in the gap
Barely 1 1/4 in. (31mm) horizontal in gap between faceplate and bed on a 7
Just over 1 1/2 in. on S7
Edited By Martin of Wick on 02/08/2019 17:04:28
Edited By Martin of Wick on 02/08/2019 17:06:35
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.