Tailstock alignment

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dml66
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Joined: Fri Apr 29, 2022 8:21 am
Location: SW Washington State, Steelhead Country

Tailstock alignment

Post by dml66 »

Today I tried the technique I learned here for starting a drill in a piece of round 3/8" stock. The stock was chucked in the headstock's ER collet chuck. I chucked a 3/8" spotting drill very lightly, in the tailstock's ER collet chuck. Once I verified I could wobble the drill, I started into the workpiece. As was described here, the bit wobbled a little, then settled right to center. I think all my neighbors heard me laughing :D . Once I'd made a staring hole suitable for a #30 bit, I chucked that bit similar to the spotting bit and let it find it's way, the result was outstanding.

Anyway, it occurred to me that if the starting hole is at the lathe's center of rotation, if I replaced the tailstock's ER chuck with a dead center, then moved the center to the starting hole, would that not be the perfect place to align the tailstock for minimum offset? In other words, adjust offset until the point of the dead center is in the center of the hole?

I realize alignment is 3-dimensional; this lathe allows for tailstock alignment in one plane only, furthermore, the adjustment process is it's own exercise in frustration. But, if lateral alignment isn't achieved, it seems I'll be confined to tapered turning.

Thanks!
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Bill Shields
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Re: Tailstock alignment

Post by Bill Shields »

Use a dial test indicator.

You will find that adjusting the tailstock is a bit more involved than just eyeballing to a drilled hole.
Too many things going on to bother listing them.
dml66
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Re: Tailstock alignment

Post by dml66 »

Bill Shields wrote: Sat May 14, 2022 8:52 pm Use a dial test indicator.

You will find that adjusting the tailstock is a bit more involved than just eyeballing to a drilled hole.
Fair enough, I have no problem discovering the required alignment, regardless of how the delta is determined.

My concern is how to make any requisite changes using a paint covered setscrew on the back of the tailstock, and a cap screw underneath the tailstock assembly?

Guessing the location based on hitting the target once doesn't seem much worse than really knowing the target and having no way to hit it. It's metrology without feedback.
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NP317
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Re: Tailstock alignment

Post by NP317 »

By knowing the thread pitch of the sideways adjustment screws,
you can calculate the tailstock movement per screw revolution.
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Harold_V
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Re: Tailstock alignment

Post by Harold_V »

You need to understand that an aligned tailstock doesn't necessarily equate to a lathe that cuts straight when machining between centers. That's due to minor height differences between the headstock and the tailstock, which are almost never in true alignment with one another. That, too, is related to the length of the part being machined. Lots of variables to consider. In a perfect world that wouldn't be true, but that's not the world we live in.

My recommendation: Align your tailstock to the best possible condition for drilling holes. When turning between centers, it's entirely possible you'll have to make adjustments to achieve a straight turn.

From this you may see the importance of having the bed leveled---the term used with aligning the ways of the lathe. Level isn't critical, but no twist is. Twist results in tapered turning. The closer you get the bed to being straight, the fewer issues you'll have with tailstock alignment.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
dml66
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Re: Tailstock alignment

Post by dml66 »

Points well taken Harold_V.

Even if I manage to get the tailstock "perfectly aligned", it's only going to be that way at that location on the ways, with that position of the quill, and with that instance of whatever alignment tool is chucked, or centered. My guess is I could align it, start over and get a different answer, lol.

Since I don't have a contract making rocket parts for NASA, I should be able to make the things I want satisfactorily with this starter lathe 👍.
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miken
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Re: Tailstock alignment

Post by miken »

Harold_V wrote: Sun May 15, 2022 3:31 am Level isn't critical, but no twist is. Twist results in tapered turning. The closer you get the bed to being straight, the fewer issues you'll have with tailstock alignment.

H
Not trying to argue this point as I do understand what you mean, but in some cases you need to twist the bed on purpose to remove taper. When my bed is perfectly leveled (nearly no twist at all showing on the level (0.0002/10) from Head to Tail) I cut a slight taper. Likely due to wear in the middle. I have to intentionally twist the bed slightly to remove the taper.

Mike -
12" Atlas Commercial (3990) 12" Back Geared, Undermount, Screw Cutting Lathe with Quick Change Gear Box (6802), Universal Compound X-Y Vise (1614), Taper (6822), Milling (500A) and Grinding Attachments (10-450)
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Harold_V
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Re: Tailstock alignment

Post by Harold_V »

miken wrote: Thu May 19, 2022 3:17 pm
Harold_V wrote: Sun May 15, 2022 3:31 am Level isn't critical, but no twist is. Twist results in tapered turning. The closer you get the bed to being straight, the fewer issues you'll have with tailstock alignment.

H
Not trying to argue this point as I do understand what you mean, but in some cases you need to twist the bed on purpose to remove taper.
Understood. No argument perceived. One does what ever it takes to compensate for conditions beyond one's control. That would not be advisable for a machine in good condition, which yours apparently is not.

In a perfect world my comments are true. Unfortunately, our world is a little lacking, especially for the home shop types, where the typical machine isn't built to industrial standards and often is lacking in high precision and rigidity.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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