Where can I get a reasonably priced MT2 Test Bar?

[Nelson_2008]

I see a few on ebay, but it seems they're all in Europe for some reason, and they're kind of expensive.

Considering the market for poorly-aligned-from-the-factory mini-lathes, it's hard to believe that none of these import tool companies in the U.S. have them, but apparently they don't.

[wildwestpat]

Hi Nelson

Unless you have a special reason for wanting to get an MT precision test bar I suggest all you need to do is spelt out on John Moran's web site
http://www.gadgetbuilder.com/Lathe_Align.html

This is a good place to make a start on checking out your machine and I think helps explain the high cost / rare as hens teeth availability and price of these test bars. Most people would use the methon or a derivation based on John's web site description as they would have the necessary dial test indicator as part of their basic tool kit.

The only use I can see for these test bars is for rapid repeat setting and associated resetting of the compound slide after turning short tapers. Even then there are other methods of achieving the same result. Checking the MT in the head stock for concentricity with the bearings and alignment on axis is another possible use but as there are no adjustments to correct this other than remaking the Morse Taper I don't see the need for such a test bar unless you are in a production environment and there are other / better ways of achieving the required accuracy to a better order than using a test bar.

Hope this helps - regards Pat

[japroach]

For reference, here is probably the cheapest UK one you found:
http://www.rdgtools.co.uk/acatalog/M...Test_bars.html $55 shipped

[mactec54]

Nelson_2008

This is a part you can make on your machine between centres

[Nelson_2008]

@Mactec54:

Well, that is a part I *should be* able to make on my machine (maybe some day), but I am one of the unfortunate people whose lathe came from the factory all out of alignment.

A test bar would be nice for the situation I'm in right now - trying to straighten out the factory's mess.

@wildwestpat:

Yes I visit John's site frequently and I've been corresponding with him about lathe alignment.

It seems to me that a test bar would be helpful right now not only as a test aid, but also as a means to get a quick rough alignment.

[knudsen]

Glad you posted the link, Pat. I was looking for that site yesterday.

Could you use an MT2 collet and a straight test bar? Probably have to take the tail stock apart to secure it with a bolt. I don't know if it would work or not; not had mine apart.

[mactec54]

Nelson_2008

Even high end high big dollar Lathes, have to be set up so what you have is normal

Your machine can make this part right now, Not Maybe Some Day

You can also do it with a straight bar with a centre in each end, which you can also make on your machine it does not matter how far out your machine is this is a easy fix

To make a straight bar just get a piece of ground stock, put this in your chuck, Get this running true, & no more than .500 out of the chuck, with a centre drill, drill the end of the shaft, this will be out because the tail stock is out, next mount a small boring bar in your tool holder, & set your compound slide at 30deg & recut the centre in your shaft, you can now check the centre with the od of the shaft & both should run the same 0-0, if not recut it untill it is

When this is correct/done turn the shaft around & do the other end the same way,

Now you have a test bar that you can put between centres, & with your indicator can move your tail stock, untill you have 0-0 on the length of your test bar

If you don't have 2 centres, just put a piece of stock materal in the chuck & turn a 30deg point/ center on it , you are ready to go & set up your tail stock

[Nelson_2008]

First, both the headstock and the tailstock are wildly out of alignment. Moreover, the tailstock is so sloppily machined that it cannot simply be "moved" or adjusted with any predictability and/or precision.

(Although yesterday I modified it, but I haven't had time yet to see how much the mod will help).

You say that "even high end big dollar lathes" have to be set up, but frankly I'd be very surprised if a non-cheap-Chinese-minilathe was delivered in the same kind of poor alignment condition that mine was.

Also it's not clear to me how just having a straight bar will help with the angular alignment of the tailstock.

Lastly, being relatively new to machining, I feel I need something that I can trust to be relatively true - a starting point.

[wildwestpat]

Hi Nelson

Suggest you take a look at the detail in the method of setting the head stock parallel with the lathe bed in both the horizontal and vertical directions as set out by Rollie Dad. The paper may be old but the method is reliable and does not require anything other than a length of rod and a means of holding it in the spindle. That means of holding could be a chuck of any description or a collet. The link to Rollie's Dad's paper is:-
www.neme-s.org/Rollie's_Dad's_Method.pdf

Large errors in headstock alignment are rare in these small oriental lathes BUT the tail stock alignement can need a lot of correction. There appear to be differences in quality between the factories that make these machines as well as between the different badging - could be that some importers drive the price down so their stuff gets less quality control. If you are having grave doubts about the headstock have you approached the importer for a replacement? Many people have been sent replacement parts FOC.

Also make sure you have the headstock aligned first to the bed (both horizontally as well as verticaly. Then and only then check the tailstock for correct centering. Check that the tailstock does not rock on the bed with the clamp done up tight. Some tailstock castings have a very rough surface and high spots are not unknown! Bemove all burrs and use engineers blue to check for any high spots that coud cause rocking of the tailstock on the bed. The method of offsetting the tailstock is crude but does work given patience. The other common problem is that the center of the tailstock is at the wrong height and this requires the headstock or the tailstock to be raised by shimming.

Good luck what ever you decide about the test bar. Regards - Pat

[Nelson_2008]

Hi Pat,

Thanks for your reply.

Up until recently, the stuff I've been making on the lathe was "short and fat" -mostly experimental transformer bobbins made from various plastics. And the tolerances were loose.

Then, I went to make some longer pieces where I was trying to hold the OD within tighter tolerances, and I found I couldn't do it.

At first I thought it was due to tailstock offset, as I was turning the piece down between centers using an expanding mandrel. Then I tried turning some larger diameter tubing, not using the tailstock, and the taper was almost as bad.

The first thing I checked was the headstock alignment, using "Rollie's Dad's Method", and I found that the headstock was tilted down and toward the operator by 0.003" and 0.011" respectively (measured over an 8" span).

Then I bought a DTI from Shars and measured the tailstock offset as per "Gadgetbuilder's method", and found that it was offset horizontally by about 0.011". (The vertical offset was under 0.001"). It was also horizontally twisted by about 0.0015" per inch or so.

As far as I'm concerned, this lathe was delivered by MicroMark in an essentially useless condition.

Anyway, I've drilled and tapped two holes on the left side of the tailstock, and I've installed 3 ball-point setscrews (I also replaced the original setscrew on the right hand side with one), and it seems this modification allows me to adjust the horizontal offset of the tailstock without causing a large angular alignment error and vice-versa.

Hopefully in a few days from now, I'll be able to work on aligning the headstock, and then I'll align the tailstock to it.

Anyway, I'm still debating about buying the MT2 test bar.

Regards,
Nelson

[wildwestpat]

Hi Nelson

Gosh you are having a right tussel with your mini lathe. I assume you have corrected the tilt down of your head stock and sorted out the alignment with the bed. Checking the alignment of the head stock to the bed will also reveal any twist in the bed casting. There has been a lot of debate about the twist that can be introduced by clamping the mounting feet directly to the supporting bench. Adding twist may or may not be a good thing - my personal prefference is to use rubber mountings with a degree of give so that the bench cannot twist the casting. The bed castings of these small lathes can easily be twisted and this makes it relatively easy to correct provided the mounting bench is stable of course! On one of the lathes I have had to sort out I had to add some shim material to raise the center line of the tailstock.

I have also noticed a marked difference in quality between the various mini lathes and the overall quality has also improved over the years. Before you go much further it might help if you check the bed for any twist that may have occured. The twist will show up on machining a length of parallel bar as variations in the taper over the test length. A uniform taper just means that the tailstock is offset with respect to the headstock. Also with a twisted bed you will not be able to get a uniform reading with your DTI as the tool post is traversed from one end of the bed to the other even when the tailstock is perfectly centered and aligned with the headstock. Sorting out all these problems can be a bit daunting and a methodical method of tracking down the problem starting at the headstock should get your lathe running well.

Good luck and I hope you soon have your lathe correctly adjusted - regards Pat

[Nelson_2008]

Well I was able to align the tailstock to a degree that will hopefully be enough for anything I'll likely be doing.

The horizontal offset is now somewhere between 0.00025" and 0.0005", depending unpredictably on how it happens to clamp down any particular time. Given the crudeness of the design of this thing, I think I'm probably into the range of diminishing returns with this number.

The vertical offset is somewhat worse, but I didn't try to do anything with that yet.

I fiddled around with the horizontal angular alignment until I had it about the same as the vertical angular alignment, which was about 0.00075" per inch or so...indicating off the outside of the ram (and I'm not sure how good of a reference this is).

The three ball-point setscrews seemed to make it easier to move the tailstock sideways without twisting it.

Maybe tomorrow if I get a chance I'll try to do something with the headstock alignment.