MT5 Test Bar

Still runout between centers is not good.

Is there any part of the taper exposed at the spindle with taper inserted?

If so, measure that as it is at the surface of the spindle and rest does not matter.

You are measuring close to spindle and it should be good here.

If not mark the high or low spot on the bar and spindle then also witness mark via a line across both spindle and bar.

Now remove your bar and rotate 90 or 180 and repeat measure.

If your spot did not move issue is spindle, if moved and followed mark then bar.

Next, clean the bar taper well with clean rag then paint it completely with a sharpie or perm marker.

Insert and seat bar then remove and examine.

Looking for ink transfer and tiny shiny spots indicating high spot.

Good luck.

If bar is bad return it.

Sent from my SM-G781V using Tapatalk
 
Every test bar I've had my hands on has been defective. My count so far is 5: ones in both MT3, and MT5.

Just for fun said:
How am I supposed to line up my headstock
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To rough align your headstock

Insert an indicator in a mount in your 3 jaw chuck. It doesn't matter -at all - if you 3j chuck is worn, or out of alignment.
Set your tailstock barrel so your tailstock just protrudes from your tailstock.
Indicate the outside of your tailstock barrel.

make your headstock indicate as good as you can by adjusting your headstock.
Then indicate in your tailstock by taking successive measurements of the barrel at tiny extension, half extension and full extension.

this will get you to about .001 or .002 per foot assuming skill level, indicator, mount, condition of the tailstock.

then, and only then can you apply the 2 collar test to finalize your alignment.

For a hobby lathe and for most small work. .001 per foot is more than sufficient.
 
I'm going to try another from the same company. Free shipping both ways on a replacement, if it is the same which I expect it will be I will then pay to return it and align it another way.

They said I just have the new one by the end of the month, I'll let you know how it goes.
 
Have you measured the bar taper? Is it actually a MT5? Many of these parts received from afar can have all sorts of defects. I bought a MT4-MT2 sleeve. The MT4 taper wasn't MT4. The taper only touched on the outer 2mm of the spindle taper, so it really wasn't properly aligned. A tiny spec of dust would throw it out. The taper was more tapered than MT4, so it appeared to fit, but it was not a proper fit. I got screwed over on that one.

Gouged the spindle taper a bit, and never got my money back. Cleaned up the spindle taper, but have become very cautious about precision stuff, and tapers in particular. If you have a mill and a DRO it is a pretty easy setup to measure with some 123 blocks to indicate along.
 
I did not measure it; and I already have this one packaged up for return. It felt good and snug like it was correct when I installed it. Like I said I took it out and reinstalled it several times at different rotations around the spindle. I can certainly measure the next one they are sending me. How exactly do I do that? If I think about it a bit, I could probably figure it out, but if you have some guidance that would be great!

Tim
 
Cadillac said:
Put the bar on some v blocks and a surface plate. That will tell you what’s going on.
Click to expand...

Unfortunately, I don't have a surface plate.... Yet.

Best I can tell, post #8 kind of explains it. When I put the bar between centers, the bar itself measured true but the taper is out .0007.
 
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May be best to look at what changes to give different readings. The bar whether accurate or not remains fixed in the headstock, the moving part ( the variable ) is the carriage. This is what the indicators are fixed to and could be moving in relation to the test bar as it changes their readings depending on what direction it was last moved. Perhaps you could lean on the carriage to see how much the indicators move.
 
Just for fun said:
Unfortunately, I don't have a surface plate.... Yet.

Best I can tell, post #8 can't of explains it. When I put the bar between centers, the bar itself measured true but the taper is out .0007.
Click to expand...

Your test tells you everything in this case. The centers define a reference. From that reference, the bar cylinder is concentric but the taper is not. Although you are measuring whether the taper is concentric to the center holes, because you know the cylinder is concentric to the centers, you now know the taper is not concentric to the cylinder.

Using v-blocks would allow you to use a different reference. If you place the two blocks on the cylinder, you could measure the taper and determine whether it is concentric to the cylinder, without involving the center holes.

You don’t need a surface plate if you could use v-blocks with cylindrical bearing surfaces. Like described here:

To be clear, your approach seems quite good. It would have been a little more difficult if the cylinder were not concentric with the center holes. I’m just trying to discuss other options for interrogating the test bar.
 
Just for fun said:
I agree, the bar is defective ... How am I supposed to line up my headstock with a bar that has run out?
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Tim, there are some of us who have been aligning headstocks for decades without a single calculation or test bar, relying instead on test cuts on test bars held in the spindles of the lathes that are being adjusted. I am one of them, and I feel that this is the most accurate way align a headstock. I won't go into the other methods but know that anytime you use a MT test bar you are relying on the accuracy of the bar and the fact that a perfect interface between the bar and your spindle must be accomplished, something that is not likely to happen with a cheap bar from India. My advice is to return the bar for a refund and do some simple test cuts as below.

  • Find a bar of easily cut material; an 8-10" long piece of 12L14 or 6061-T6, about 1.5" OD, will work well. Stick that in your 3 jaw chuck so about 4-6" of it sticks out and lock it down.
  • Using a freshly sharpened GOOD HSS tool, take a 0.010" deep cut from the end and turn up near the chuck. Repeat this with a 0.003" deep cut, then with a 0.001" deep cut and strive for a good finish. Note that the tool must be ground well by someone who knows what they're doing. A square tool with a 1/64" nose radius as described elsewhere on this site works well for this purpose. If you cannot grind such a tool then I suggest you PM @Z2V or @ttabbal and have them grind one for you. Either can do it for a very reasonable cost and it will be worth it.
  • Once your test cuts are done, measure the OD up near the chuck, in the middle and at the end of the rod. This will tell you if the headstock is out of alignment and will also tell you which way to rotate the headstock.For example, if the OD on the tailstock end of the bar is larger than the chuck end then the tool is farther away from the spindle centerline on the tailstock end and you have to rotate the headstock in a CW direction to correct it.
  • Repeat your test cuts and rotational adjustments until there is zero deviation in the OD at either end of the rod. At that point, the headstock is aligned with the ways. How close you get this adjustment is up to you; both my lathes are at zero.
  • Once you align the headstock you can proceed to level the lathe and then align the tailstock.
Hope this helps.
 
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