MT2 test bar review

I was having some problems with machining a longish (for me) shaft on my Atlas 618 and I've chased my tail on alignment issues, so I decided to get an MT2 test bar and figure out what was going on.

Bought this MT2 test bar from Amazon for $28

pics





straight part is a bit over 11" long, also has 60deg centers at both ends



cleaned all the packing grease off it with some isopropanol, then mic'd the straight part (I tried not to handle the bar during the process). Found that it was within 0.01mm (0.0004") along its length and I rotated the bar 90deg at each point too. That's the limit of my ability to reliably measure something. I could have used a tenths mic but I'm not sure how much I would trust a tenth or two variation.

cleaned the spindle taper and gently tapped it in - 0.0015" radial runout at the spindle nose, ~0.004 at the end of the bar, with 0.004 axial runout away from operator at the end of the bar. Bletch. That's not good.

Blued up the taper of the bar with dykem and found


some major burrs. Then spent several hours very carefully filing/ sanding down burrs in the spindle taper until I got a fairly uniform Dykem removal. Still not perfect, but I have an MT2 reamer set on its way to finish the job. Radial runout is now down to ~0.0005" at the spindle nose and between 0.001 and 0.0015 at the end of the bar. Axial runout remained, but both the bar and my MT2 dead center seated much more securely and more easily compared with before.

No pictures of the rest as it was pretty boring and tedious. Took the head stock off the lathe, cleaned off the paint and other crud at the mating surfaces, then stoned them. Maybe a little less run out, but not by much. There was no free movement with which to adjust the headstock, so I VERY carefully took a smidgeon off of the 2 diagonally opposite mating surfaces to allow the headstock to rotate fractionally. I'm talking about barely removing machining marks, that little. Put headstock back on and then spent an hour or so trying to tighten the headstock bolts to get the runout down. Finally managed to get axial runout to 0.0005 or less from one end of the bar to another. Rotated the bar and the measurement repeated.

Then used the bar between centers to get the tailstock aligned and got that down to less than 0.01mm over the length of the bar (had to use my metric DI instead of my imperial DTI). Also found that there's a 0.0005" variation about 10" from my spindle. Wasn't in the bar - didn't vary with rotation and the diameter readings before, in and after it were the same - so must be something to do with wear in the bed.

Finally tested the face of my spindle with the DI and took the lightest of skim cuts to get rid of some burrs. Spindle face runout was then down to 0.005mm or less (needle barely flickers). Then recut both my 3 jaw and 4 jaw backplates, getting the 3 jaw radial runout down to ~0.0015 and the axial runout on both to 0.01mm or less. Couldn't get my homemade ER25 collect chuck to less than 0.0025" so I'll be remaking that.

Anyway, pretty happy with how it all worked out and very happy with the test bar. No guarantees that the next one would have been the same, but it's astounding value and I really wished I'd done this all earlier!

.0004" is quite a lot of taper for a test bar.

mattthemuppet2 said:

I was having some problems with machining a longish (for me) shaft on my Atlas 618 and I've chased my tail on alignment issues, so I decided to get an MT2 test bar and figure out what was going on.

Bought this MT2 test bar from Amazon for $28

Click to expand...

@mattthemuppet2: I bought similar from eBay, but I got the 2-bar MT2 & MT3 set.
Looking at all the different sources, (Amazon, etc.) I notice that no matter the supplier, they all seem to come from India. I am not sure if they all start from the same factory, or if it is just a major India industry.

Anyway - mine was these --> LINK
ATOZ brand, they claim to be accurate to 1 to 2 microns. On the diameters maybe? It does not seem consistent with it's own specification Max run-out : 0.0001".
I know that to be 2.54 microns. For what I can do, or need, that is entirely good enough!
Except for some gauge blocks and a 0.001mm micrometer, it's the most accurate stuff I have. I just have to trust it.

benmychree said:

.0004" is quite a lot of taper for a test bar.

Click to expand...

not the bar, the run out of the spindle at the end of the bar due to the spindle not being exactly aligned with the ways. Couldn't detect any variation in diammeter of the bar using my mics

graham-xrf said:

@mattthemuppet2: I bought similar from eBay, but I got the 2-bar MT2 & MT3 set.
Looking at all the different sources, (Amazon, etc.) I notice that no matter the supplier, they all seem to come from India. I am not sure if they all start from the same factory, or if it is just a major India industry.

Anyway - mine was these --> LINK
ATOZ brand, they claim to be accurate to 1 to 2 microns. On the diameters maybe? It does not seem consistent with it's own specification Max run-out : 0.0001".
I know that to be 2.54 microns. For what I can do, or need, that is entirely good enough!
Except for some gauge blocks and a 0.001mm micrometer, it's the most accurate stuff I have. I just have to trust it.

Click to expand...

looks like mine, same company too. I think they're like Shars - importers of asian tooling. The bar is better than my ability to measure it so it's already an order of accuracy higher than the work I do. Without a surface plate and known good V blocks I don't think I could do a better job of "testing" it. Either, proof is in the pudding and I already have more confidence in the accuracy of my lathe, plus my ability to detect when it goes out of alignment.

You guys keep costing me money.

we do our best

Honestly though, when i started out some years ago a test bar was in the $100+ range, so pretty far out of reach for a hobbyist on a budget. For this kind of money it's not a hard decision to make and it's the most direct way of checking alignment you can get.

I have been occasionally thinking about getting a test bar for years, always hoping to run up on a cheap one from a clueless flea market vendor. Last time I looked on Ebay (couple of years ago) they were averaging $60~$100. Here I am scanning down the list of topics to see if one looked interesting, clicked and found you already did the legwork for me. Amazon was the cheapest and it'll be here in two days from the same vendor on Ebay that quoted 1 month shipping time and for more money. I can usually talk myself out of spur of the moment purchases, not this time. Both my big lathes have LOO spindles and I'd already acquired the MT4.5 to MT3 spindle adapter for a center so I can get right to work. Thanks!

cool beans! Glad I could help Hopefully your lathes won't have as many alignment issues as mine had as the headstock mounting is definitely going to be more robust, but checking it will still be a worthwhile activity. Simply using it for tailstock alignment is worth the price of entry, the rest is a bonus.

@mattthemuppet2: Umm.. Oh dear. @Holescreek may be the only one so far who came right out and admitted he was going to risk the scene of cleaning up/reaming his spindle and/or tailstock, subjecting it to test bar, and definitively measuring until the truth is out. He blames the cost on us!

Do you suppose there are actually a whole legion of lurkers out there who have been motivated to fork out real $$ on the test bar stuff we are discussing?

Re: Your picture of the Dykem ink in post #1. It looks like substantial contact both at the front and the back of the taper. I know many tapers on the end of tooling have a deliberate void zone, undercut in the middle, forcing some taper contact at front and back, so it won't rock, but I am pretty sure this trick is done to the tool shank only, not anywhere up a spindle.

Were you expecting a pretty much complete Dykem removal?