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Member postings for mgj

Here is a list of all the postings mgj has made in our forums. Click on a thread name to jump to the thread.

Thread: Precision Tailstock Alignment
23/04/2011 16:11:26
Well I did apologise in advance, but I hope you will allow me to suggest that there has been a lot of grabbing at fixes, without clearly identifying where the error lies.
 
May I ask a three questions?
 
1. What exactly is the error?
2. What is causing it.?
3 What steps have been taken to eliminate the effects of other factors which may influence that error?
 
For instance, its no good shimming anything(except under the feet of the lathe)if the bed isn't set straight. If as Les has suggested, there is a chunk of grot or a bit of paint under the headstock, you will always get an error. How do you identify Les suggestion without taking half the machine apart? I have heard nothing of the use of test bars or turning tests, yet you need these things to find these errors, never mind reassembling the machine after lapping/grinding bits off it. Do you have them?What tests did you do, and what were the results?
 

 
 
 

 
 
 
 

 

Thread: Technical and engineering drawing.
23/04/2011 15:44:41
Steve - you are dead right, and I think an important point has been missed.
 
A hell of a lot of drawings, both in industry and in the modelling worlds are still not just in old formats, but in old dimensions too and they are unlikely to be updated. (though I agree some have been cleaned up in CAD)
 
So its no good the young generation thowing a hissy fit - if they want to make something badly enough they will have to learn.
 
Sure one can (should) encourage, and one can (should)assist, but if they want to be (model) engineers, they HAVE to learn how to take a 2d drawing on paper, and in their mind turn it into a 3d hunk of finished metal. If they don't have that imagination or kind of brain, they might just as well go off and play golf, where, if they cannot hit a ball straight, and in their minds eye they have to put together stroke, distance wind etc .......
 
Perhaps we ought to accept that this is in general, possibly not a young mans hobby? We need kit which is expensive, we need patience on long projects, and we need expertise, and none of these come easily to the young?
 
There is IMO, a difference between a youngster and a beginner BTW.
 
 
 

 
 
 

 
 
 

Thread: Precision Tailstock Alignment
23/04/2011 12:44:25
Boring tool .
 
You need a pilot hole - I don't know how long this one has to be. If its short enough you could use jobbers drills.Or a set of blacksmiths drills - any cheap way of getting a near sized hole.
 
If its long, one is going to need a proper gun drill to make that first incision as it were. That will cost.
 
 
Next step is to get the hole to size - you just make up a big thick boring bar, or several if you are going up in steps. I did a TE piston rod guide with a 1.25" dia bar carrying a 1/4" bit inclined fwds at 45deg. I locked it in the 4 jaw since that gives a better grip than the 3 jaw. Best would be an MT and a drawbar I suppose.(and properly adjusted headstock bearings)
 
Bit has to be really really sharp and you just go backwards and fwds twice (I think) per size of cut to make sure all the spring gets taken out of the tool. Its not difficult, its just tedious.
 
The great thing about such holes is that they are always parallel (apart from the very first smidgen where the load is applied, and thats not going to affect us) If one has a sexy applier of the bit, then one can cut to size. Otherwise you get to a close size and make quill to fit. I'd finish size the quill with emery and oil to have a clearance of about .0005"
 
You do have a chicken and egg in that you need a quill to make a quill, and you have no accurate tailstock. So you have to make a plug for the Tstock bore to carry a centre, once you have a new aligned bore.
 
Or one finds a friend (if one has have any!(with machine tools) ), or you join the SMEE (plug for worthy cause ) if you live near London, and use their machinery.
 
----------------
Scrim - we have a problem.Several actually
 
You are talking about measuring with calipers. Calipers, even nice Mitutoyo ones are all well and good, but they only read to 1/2 a thou. They are nice quick and convenient. Accurate in the true sense of the word, they are not. We (Gray me and the others) are talking about measuring to 1/10 of a thou.
 
How  can you set up a lathe straight, and talk of bed adequate bed fitting, when it would appear that you cannot, with the equipment you have available, measure to within 100% of the limits required?
 
So that is one direction that you need to go in - because you cannot set your machine up to do the preliminary work with a pair of calipers.
 
The other is away from hand grinding which I think you mentioned. Perhaps we are talking of different hand grinding, in which case I apologise in advance.
 
At the moment you have merely a dodgy tailstock, and you could get round that temporarily using an offsettable boring head fitted with a centre, or shims. Start hand grinding and you will have a glossy bit of junk which you will never repair.
 
This has been a very intriguing post, - I have enjoyed it a lot - but my most earnest recomendation is that you take the time to get the machine back to the suppliers, and get them to sort it. You write the cheque of course, and it will possibly be quite a large one, but not though as large as the one you may have to write if some of your suggestions are adopted?
 
If genuinely you have the expertise to sort this problem, good luck to you, and all credit - but if you have that expertise, why  start this post? If you have doubts, then just throw money at the problem - its the quickest, cheapest and most painless way of making it go away.

 
 
 


Edited By mgj on 23/04/2011 12:45:39

Edited By mgj on 23/04/2011 13:13:47

Thread: Cutting speed theory
23/04/2011 12:20:11
Norman - it was the motto of the Royal Military College of Science at Shrivenham, where I did my MSc. (It is now all part of Creanfield)
 
They translated it as "To know the cause of things" which is the literal one. The more general one is "To know the reason why".
 
I've always hated the monkey see, monkey do approach.
23/04/2011 09:04:21
Thankyou all for that. I have really learned something very useful.
 
Rerum cognoscere causas.
Thread: Precision Tailstock Alignment
23/04/2011 08:59:33
I wonder we need to go lowering headstocks.
 
I imagine there is a serviceable tailstock base, - its the bit above which is the poblem.
 
Were I going that route, I would ask the suppliers to get me a blank casting for the tailstock upper and machine. Or I'd go to someone like College Engineering Supplies and buy a chunk of cast iron the right size and machine that up, to fit existing quills and the like. It would involve a fair bit of miling, but none of it would be complicated. That might be a lot easier than trying to take a headstock off and cutting vee bedways and the like.
 
First stop for me would be to check to see if fitting a new quill would do the job and is feasible. Work out the new diameter , set the lathe bed exactly and precisely, bodge up a tailstock puller off the carriage to permit power feed, and bore the tailstock to the new dia off the lathe. Once the "tube" is bored, I'd fit the new quill and fittings, and bore/ream the MT in the quill, again finishing in situ.
 
It might not have the funny angles,(it would be dead true) but then nor does my Myford, and that seems to work well enough!
Thread: Face cutter cutting width
21/04/2011 07:06:50
What alloy is it - if it's a cast LM4 job getting a really good finish may be interesting.
Thread: Stainless Steel
19/04/2011 21:32:12
I think you will need a former for each hand made out of hardwood. Anneal, clamp each end and then with a small stretching hammer tap it into final shape. If it wrinkles, use a contracting hammer and tin bash the wrinkles out. Make hte blank a bit oversize and finish to size. Its not nearly as difficult as one might think.


For the amateur a contracting hammer can be knocked up out of a file, and a nice well radiused face on a small hammer will do for stretching. Or a softface if oyu are putting marks in)


The only problem is that stainless is a sod for work hardening so you'll be annealing every few bashes.(taps) Prototypically they were iron/steel shares, so I'd be inclined to make them out of steel and polish them up on a buffing wheel. Lot easier. Give it a couple or three tries in ali just for learning how you can move metal around quite effectively with just those two hammers.


(Buy a book on tinbashing, preferably by an american author. The techniques are not rocket science. Thats how I taught myself because I had to tinbash bits of racers to a reasonable standard in both ali and steel.)
Thread: Technical and engineering drawing.
19/04/2011 21:12:59
It should be very welcome I think. Its thebasic language of what we do, and anyone who doesn't understand engineering drawings just doesn't "talk" engineering.
 
Theh problem is that many just don't want to put any effort into learning the tools of the trade, and somehow in this modern world of quick fix games, no one will say "You need to know this now (metaphorically) pin your ears back an listen, because if you can't do this, you are never going to make a model".
 
Its rahter like the feeble minded responses about beginners articles being too complicated. They aren't - mostly they are very good and well pitched, but in the same way that the authors are writing articles and not encyclopaedias, the beginner has to want to learn and has to take a magazine artircle as a basis for additional and personal research. Nowadays its all on the internet and easily googled anyway.
 
So I'd say go for it - illustrate it well with 1st 3rd and isometric drawings side by side. Those that want to learn will and will hopefully progress or join a model club and find help. Those who don't have that motivation wil fall by the wayside, where probably they were going to fall anyway.
 
As for putting it in Workshop - that is a shame when you have beginners series on making this or that in ME.
 
 

 
Thread: Precision Tailstock Alignment
19/04/2011 17:55:28
Gray - I don't think we disagree in principle..
 
My only point is that before we go slapping stuff onto, or chomping bits off a machine irreparably, we are very sure of hte error (if any).
 
Nobby had mentioned an MT socket that is out. The other classis is that if the lathe bed is not bolted true (set to turn true by a turning test,) then a clock on an extended tailstock quill will give a false indication on a tailstock tilted up or down, depending on direction, and drills will jam and cut funny sized holes..
 
I think one also must accept that a .5 mm error is huge when we are talking of hundredths, and it should or could have been detected by even the most sozzled partygoing oriental on a Monday morning. So something is amiss, and the likelihood is that it doesn't originate in a China. (that doesn't mean it doesn't or can't - it means that on the blance of probabilities... because most kit is built on CNC machinery these days)
 
Before I started attacking this lathe, I'd like to see it set up within .0001" on a test bar and clock. (or by turning test, the permissible error on one collar being +/-.0002" max) Once one has the bed dead straight, which takes a lot of effort and time, its amaxing how things tend to turn straight an other errors disappear, because one can set hte tialstock accuratley (and easily).
 
If tests like that have been done, and we aree sure htat the bed is right, and the tails stock is then checked and shows not a constant "error" but divergence, then there is a problem. But until then I think I'd be a mite cautious.
 

Thread: Machining lugs
18/04/2011 22:04:55
Or you can use a bit of round with a square milled on the end. Raise a coupe of burrs to hold it correctly in its hole and silver solder. Best if the socket isn't a through hole, though that may not matter..
 
If the lug is on the end thin I'd mill a slot across the end and silver solder the appropriate bit of square in.
 
Or you can machine a length of bar with a ring on it and do it in several passes under hte mill with a dividing head - thats less elegant, because you then have to skin the final little facets off with a dividing head too.
 
If its a long slot(s) you can just mill the slots and loctite the bit of "spline" in , which is fine since the thrust is taken on the sides of the slot. If the machining is good and tight to width, the Loctite merely locates.
Thread: Travelling Steady Fixture for Thinning Narrow Diameter Bar
18/04/2011 17:49:22
The Chronos thing is very good.
 
For this particular job, I think I'd have turned a spigot (for alignment) and silver soldered the 2 bits of stainless together.
Thread: Cutting fluids
18/04/2011 17:42:58
Versaboss - I had that skinning problem with the Rocol. It got on everything.
 
Now I use Morris Edgeplus, which is soluble (20;1), odour free and doesn't produce that skin. Doesn't separate as easily as the Rocol either.
Thread: Precision Tailstock Alignment
17/04/2011 20:50:52
Gray - Swing. Yes I can see that it shouldn't be down to the alignment screws on the tailstock. Also, I can quite see that, if there was to be an error, you'd want it towards you. Depends on the type of bed. If it has vee guides than you are rather limited by that. If you have the Myford flat bed, with a gib strip, then were it out, you could possibly use those to get it right, if hte error was radial around the axis, and not simply a lateral misalignment.
 
Also I suspect that the pemissible error may well have something to do with quill stroke and size of machine? A given angular error will give varying indications depending on travel?
 
On both my machines, a 6 x36 long bed Chinaman, and the Myford, these errors are quite difficult to detect.
 
I wonder if these things shouldn't be very close to true, but if there is an error then it should be in a particular direction . Anyway - I for one m very happy with pretty much true to the limits of my measurng equipment. Both machines turn mighty straight, mighty parallel!
 
 
 

Edited By mgj on 17/04/2011 20:52:26

Thread: Clarkson Collet Threads?
17/04/2011 20:29:37
Tony is correct, but they are specifically slightly undersize - .003 to .006. The centre is 3/16. You need to make the shank of your arbor +0 to -.001 on dia.
 
Its all in The Model Engineers Handbbook, thread lengths etc, so its pretty easy to do. .
Thread: Precision Tailstock Alignment
17/04/2011 09:28:26
Graham - I may have misunderstood your post.
 
The "swing" left to right of the tailstock can easily be applied using the alignment screw, or by putting a second screw in near the front to take up any slcak in hte guideway.
Interesting to see that the quill should run high, because work tends to lift - unless one is doing something on a rear toolpost.
 
I actually went and checked both lathes last night, and they are running a lot closer to true than those figures suggest, though I accept that there will be errors due to oil films and wear, and of course the bed is set to turn true. But there is no rise, either lathe.
 
Scrim - are you sure you want to go slapping Turcite or whatever over the machine. If you know the error, then a shim between TS base and top will do the trick. Superglue them in place. If you need to tilt it fore and aft, then you put differing shims front to back. that way you will get it all aligned perfectly and without permanently deforming the machine just in case one of the measurements was wrong.
 
I had to do the same under the pedestal of a Warco Super Major mill. One very thin shim fixed it . A packet of steel shim is about £25 and is a lifetime buy.
16/04/2011 08:52:55
First question is "How far has this been taken down?" simply because a misalignment is only a malignment relative to a datum.
 
So I suggest, if you think the headstock is out, (seems so from your post), that using a proper accuurate DTI you align the headstock axis with the bed, in both planes, with no strain on the bed.
 
Then you can bolt the machine down and bring the bed in proper alignment with the headstock axis with the usual test bar shimming and turning tests. Then you can align the tailstock in both planes by using an accurately centred bar.
 
Or, in your secend paragraph is there a transposition - for headstock read tailstock?
 
If you reckon the tailstock is badly out in all these planes, and its easy to measure, then yes, you can shim and lock up. Best way if the headstock is true or has been trued, might be to bore it off the headstock and fit sleeves or a replacement quill. Then you know it will be dead true, assuming the bed is true. (That is how they make them)
 
Assuming that the quill is true. Have you done a turnover test of a bar in the tailstock MT to check the alignment of the quill axis.(might be something as basic as a flake of metal in the MT and a problem solved by a wipe with a scraper.)
 
Personally I wouldn't start trying to turn test bars with MTs on them, (especially when I am not certain of my centres) though of course it can be done. For that sort of critical work I'd buy a good one properly ground to fine limits and then use a DTI graduated in .0001" or metric equivalent.
 
It just seems to me that there is quite a lot that is unknown in the original post, and I think I'd get myself into a position where I was pretty definite about the errors and where they are before I started locking stuff solid.
 

Edited By mgj on 16/04/2011 08:54:42

Thread: oil filtering
15/04/2011 19:03:56
Problem is that they block after a bit and the holes get magically smaller and coated with something (if you use soluble oil - 2 sorts!)
 
My answer was simple to take a scrap bit of 1 1/2 od thin wall tube. Solder in a bottom, and make a loose fitting top. Bring the inlet in from the side at the bottom. Outlet tube rises from the bottom to near the top. This means that the coolant has to perfom a right angle turn and swirl - tends to drop the swarf out. (Cyclone technology or de-aerator for dry sump oil tanks according to choice) Drop a magnet in the bottom, on the end of a bit of string, and knot the string off through a hole in the top.
 
Works well - easy to clean.
Thread: Users comments on these machines
10/04/2011 09:48:45
I have the stick up type, and it has never been a problem .
 
Perhaps it depends on the size of the table compared with the size of object one is considering, but tables have 2 ends and you only have 1 powered feed unit? If I had to have a projection at both ends, for a one off (if ever), I'd dismount the power feed and hand crank.
 
It also I daresay depends on what one likes doing, and the amount of time available -
Thread: Boiler cladding material
08/04/2011 17:52:05
And Live Steam Models. I got all the 16 and 20g sheet for the TEs tender and boiler cladding cut to size and posted. tehy have also sent me steel sheet over 12x12 too.
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