Tailstock Alignment?

Bob Korves said:
A bar mounted accurately in line with the lathe spindle can tell you if the spindle is parallel with the bed ways, both horizontally and vertically, and if off, by how much. This is used for aligning the head stock with the ways. A bar that has two equal diameter and concentric test rings at both ends of a bar, mounted between an accurate head stock center and an accurate tail stock center, can tell you if the line between the two centers is aligned with the bed ways, both horizontally and vertically, and if off, by how much. Both setups are checked against an indicator moving longitudinally with the carriage, and indicating alternately on the top and the side of the test bar.
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Thank you
 
darkzero said:
I thought about buying one of those test bars from Edge Technology when they first came out. I love all their products that I have. But I've been using the bar I made for TS alignment which has been working great so I don't see a need to buy that test bar.

I also have one of those MT test bars. It's surprisingly pretty nice for being from India. Mine is a MT5 so it's got some weight to it. Because of that I rarely use it, only for checking headstock alignment which only happens once in a while.

I use a 3" alumn round (well started out as 3") for testing taper any time I re-level the lathe.

View attachment 292152View attachment 292153View attachment 292154
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I was looking the mt test bars up and they say that theirs a centre hole in both ends and that they are "protected" i see the big end has it recessed but havent seen a good pic of the hole on the tapered end, is it still ok to use a drift to knock it out of the taper without damaging the center hole?

Stu
 
Cadillac said:
Mine has centers on both ends and I eject it with a wooded broom stick cut to length.
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Yeah wooden push stick I can see thats probably a good idea, thanks for info :)

They do look very handy and as you say the price isn't toooo bad on them at all.

Stu
 
ddickey said:
Another cheap alternative is to use a couple MT3 stub or machinable ends. Just make sure they are the same diameter.
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When I was looking at the prices on the MT ones, I started thinking "you know, I could get an MT3 for the head stock, then put the MT2 in the tailstock and butt them together with a center between them to get a 24" test bar... and if I turned that center from like-diameter bar I could put a lip on each end so the indicator doesn't even skip much ... wait a minute, what the hell is wrong with me."
 
You don't need a bar at all. Put your tail stock wherever you want and measure from there. Get two MT2's and use a sleeve in the HS. That way they will be the same diameter.
 
darkzero said:
I thought about buying one of those test bars from Edge Technology when they first came out. I love all their products that I have. But I've been using the bar I made for TS alignment which has been working great so I don't see a need to buy that test bar.

I also have one of those MT test bars. It's surprisingly pretty nice for being from India. Mine is a MT5 so it's got some weight to it. Because of that I rarely use it, only for checking headstock alignment which only happens once in a while.

I use a 3" alumn round (well started out as 3") for testing taper any time I re-level the lathe.

View attachment 292153
Click to expand...

Rather than a MT5 test bar I use a 1" diameter 10" long dowel in a 5C collet. The dowel is ground to within ,0001" and costs less than $40.00. The Hardinge 5C collet runout is supposed to be .00005". Given the original runout spec for the spindle on my Sheldon MW-56-P lathe was supposed to be. .0000 to .0006 at 12" using the collet and dowel pin method I should be able to get close enough for anything I need to do.

There was quite a discussion about using solid test bars in the MT 5 and 6 range a couple years ago on the Practical Machinist forum. Some felt the weight of a solid bar extending that far beyond the spindle would cause measurable sag. There were a few that recommended boring the bar, welding a hardened steel plug in the end, and regrinding it.

I do know the old school recommendation was that the maximum length of a work piece extending beyond the spindle should be no more than 5 times its diameter. I realize that guideline is for when the work piece is spinning and has the force of a cutter against it. However I can't help but think a MT5 test bar being as heavy as it is wouldn't be hard to get off center enough to cause some runout regardless of how perfect it's been ground. My REO brand MT5 dead center is only a little over 8" long and weighs close to 5 lbs.
 
Guys for us newbies I am having a hard time following along.Any pics would be nice of your setup on how you do both HS and tail which I need both also.Thanks for posting the Youtubes
 
stupoty said:
I was looking the mt test bars up and they say that theirs a centre hole in both ends and that they are "protected" i see the big end has it recessed but havent seen a good pic of the hole on the tapered end, is it still ok to use a drift to knock it out of the taper without damaging the center hole?

Stu
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Mine doesn't haven't anything "protecting" the hole, just center drilled on flat faces.
 
projectnut said:
Rather than a MT5 test bar I use a 1" diameter 10" long dowel in a 5C collet. The dowel is ground to within ,0001" and costs less than $40.00. The Hardinge 5C collet runout is supposed to be .00005". Given the original runout spec for the spindle on my Sheldon MW-56-P lathe was supposed to be. .0000 to .0006 at 12" using the collet and dowel pin method I should be able to get close enough for anything I need to do.

There was quite a discussion about using solid test bars in the MT 5 and 6 range a couple years ago on the Practical Machinist forum. Some felt the weight of a solid bar extending that far beyond the spindle would cause measurable sag. There were a few that recommended boring the bar, welding a hardened steel plug in the end, and regrinding it.

I do know the old school recommendation was that the maximum length of a work piece extending beyond the spindle should be no more than 5 times its diameter. I realize that guideline is for when the work piece is spinning and has the force of a cutter against it. However I can't help but think a MT5 test bar being as heavy as it is wouldn't be hard to get off center enough to cause some runout regardless of how perfect it's been ground. My REO brand MT5 dead center is only a little over 8" long and weighs close to 5 lbs.
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Never thought about the overhang & weight, makes perfect sense though. I bought the MT5 thinking it would be best to eliminate anything in between the bar & the taper in the spindle that could introduce additional error. Plus at the time the MT5 didn't cost much more than the MT3 bar I was originally looking at. I may have shot myself on the foot on this one.

Oh well, like I mentioned, I never use it & haven't used it for measuring anything yet. I bought during a flash sale or I had to use up my ebay bucks, I forget. When I first got it I checked it for runout & was happy but I don't remember ever checking the runout at the end of the bar hanging out. I'm sure there is sag. Boring it sounds like a good solution. I'll worry about it whenever I do need to align my headstock or maybe I'll just sell it. It just sits in a drawer anyway.

Even if I had bought the MT3 size, I suspect it would have sag as well.
 
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