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  #21  
Old 02-16-2024, 06:15 AM
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GWIZ GWIZ is offline
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Originally Posted by arizonian View Post
I have no clue what material the inserts are for and whether they are for roughing or finishing. Any help will be greatly appreciated.
Looks like the Insert holder has a 5 deg negative rake. that usually increases the life of the insert tip but that increases the shear pressure.

In general the tool holder is more for heavy cuts and will likely place quite a bit of pressure on the part, smaller parts will deflect/spring more.

The negative rake allows you to use more corners of an insert being able to flip it.

the negative is more for rigid machines.
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  #22  
Old 02-20-2024, 07:25 PM
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Default Another problem pops up

So now I found another small problem with my lathe. The tail stock is about .005" above the head stock. A "Last Word" dial indicator clamped in the 3-jaw chuck and reaching out to the TS live center reads high (positive) with the DI at the top and reads low (negative) with the DI at the bottom. The DI increments are .0005" and readings on either side are about zero. I have not cut a reference bar yet to check for taper. Might have to shim the head stock?
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  #23  
Old 02-21-2024, 09:50 AM
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Or…..quit thinking a three jaw chuck is accurate?

At least chuck up a piece, turn a section and clamp it to that.


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  #24  
Old 02-21-2024, 10:14 AM
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Originally Posted by greywynd View Post
Or…..quit thinking a three jaw chuck is accurate?

At least chuck up a piece, turn a section and clamp it to that.


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The chuck has nothing to do with it. I could clamp the DI off center, roll the chuck/headstock and come up with the same results. Center of rotation is center of rotation. I am indicating from the headstock to the tailstock.
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  #25  
Old 02-21-2024, 12:01 PM
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Originally Posted by arizonian View Post
So now I found another small problem with my lathe. The tail stock is about .005" above the head stock. A "Last Word" dial indicator clamped in the 3-jaw chuck and reaching out to the TS live center reads high (positive) with the DI at the top and reads low (negative) with the DI at the bottom. The DI increments are .0005" and readings on either side are about zero. I have not cut a reference bar yet to check for taper. Might have to shim the head stock?
Quote:
Originally Posted by arizonian View Post
The chuck has nothing to do with it. I could clamp the DI off center, roll the chuck/headstock and come up with the same results. Center of rotation is center of rotation. I am indicating from the headstock to the tailstock.

I'm sorta confused about your setup to get the measurements. The difference could be any number of things that would be easier to solve before starting to shim the headstock.

At what point along the ways are you measuring the tailstock height? It could vary down the length of the bed. Have you disassembled/cleaned the tailstock, or is there any slop in the mechanism? Have you checked the live center for runout? Even a small piece of debris in the taper could adjust the fit, a scratch or gall can really jack it up.

I'd be more concerned with a difference in the X axis than the Y.
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  #26  
Old 02-21-2024, 01:13 PM
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Tailstock has been removed and it and the ways cleaned up and lubed, then reinstalled.

New live center, but checked for runout anyways. Cleaned the bore of the TS with brakleen, checked for runout between the HS and the LC in four positions, rotating the base of the LC into each quadrant in the bore of the TS before rotating the chuck 360°. Checked the above with the TS sucked in all the way and locked, then checked again with the TS extended to max (4").

Keep getting the same result, HS is .005" lower than the TS.

Could there be a burr inside the TS bore making the LC point up? Possible. That's why I come here for advice. Only a bluing will determine that, so that will be next. Need to order some, old stuff is all dried up.

So forgive me for asking, not having a DRO and still learning. Is the X axis the cross slide, the tool height the Y axis and the the Z axis the carriage travel?

Back to original question, every time that I would center drill a piece of stock it seemed the drill bit would walk around before it would finally bite in, which is why I am going thru these steps.
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Last edited by arizonian; 02-21-2024 at 01:21 PM.
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  #27  
Old 02-21-2024, 07:37 PM
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Originally Posted by arizonian View Post
The chuck has nothing to do with it. I could clamp the DI off center, roll the chuck/headstock and come up with the same results. Center of rotation is center of rotation. I am indicating from the headstock to the tailstock.

Sorry, you’re correct on that one, brain was kind of foggy after a long day.

Unless there is some foreign material somewhere, good chance it’s been like this since new.

Does your tailstock base have the front to rear adjustment? Any chance there is something going on in there holding something up?

Another thing I would check. Extend the tailstock spindle, and check at front and rear. Assuming no wear or droop, see if it’s parallel. If it’s nose high, or ass high, the tailstock isn’t on the same plane. Maybe that will narrow down an issue.


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  #28  
Old 02-21-2024, 08:22 PM
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Working, working, working...Making some progress.

After Dubby's suggestion of a burr in the TS bore, I pulled the TS again and blued it with Prussian Blue. Don't know if that is the go to, but it is what Merle's had in stock. Maybe a black sharpie would have been better... No high spots showed as shinier than the rest.

I scraped the base of the TS with a razor instead of just wiping it down, it showed just a hint of brown down the middle of the flat way. After reassembly, the highs and lows were reduced to .003".

Cut a reference bar from a piece of stock. The difference between diameters was .003", the TS end larger than the HS, so the TS needs to move toward the operator. Set up a DI to track the movement and adjusted the TS, than cut another reference. It's not right on the money, but it is much closer. The centers of the reference cuts are spaced 10-1/2" and the length between cuts are undercut .030". Again, thanks goes to Dubby.
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  #29  
Old 02-22-2024, 11:45 AM
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Quote:
Originally Posted by arizonian View Post

So forgive me for asking, not having a DRO and still learning. Is the X axis the cross slide, the tool height the Y axis and the the Z axis the carriage travel?
Yep, you got it.

Quote:
Originally Posted by greywynd View Post

Another thing I would check. Extend the tailstock spindle, and check at front and rear. Assuming no wear or droop, see if it’s parallel. If it’s nose high, or ass high, the tailstock isn’t on the same plane. Maybe that will narrow down an issue.
This too. All but one of my tailstocks has had some level of slop in it due to the nature of the mechanism inside. The one that didn't was almost impossible to use. The parts have to be able to move unfortunately. The clamp lock can be used to take up some bit of it when starting holes. If you've got it too loose or too tight, it can change the position as well--or previous abuse could have created an issue in the barrel.

A little gunk is all it takes to make a big difference. When a bunch of those stack up, it gets frustrating. I'd be tempted to check the bed for level again, and even adjust it one way or the other to see if you can change your measurements.

Ultimately though, the manual calls out shimming the headstock as the only way to alleviate the Y offset on the tailstock. It's possible that at some point the machine has been apart, or it got bounced hard enough (or crashed really hard) that it'll need it. That's a lot of damn work though and I'd be tempted to live/work around the issue.


As to keeping your bits from wandering during drilling operations, that's always a struggle. Your facing cut on the material will usually make a bigger difference than alignment. The facing tool height can be adjusted to get rid of the little 'nub' with a lot of trial and error. The importance of center drills comes in when starting the hole, as you want it very sharp and very rigid so it cuts instead of walks. The closer you can set the drill chuck to the headstock the better as well.
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  #30  
Old 02-22-2024, 07:49 PM
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Quote:
Originally Posted by greywynd View Post
...

Unless there is some foreign material somewhere, good chance it’s been like this since new.
...

Another thing I would check. Extend the tailstock spindle, and check at front and rear. Assuming no wear or droop, see if it’s parallel. If it’s nose high, or ass high, the tailstock isn’t on the same plane. Maybe that will narrow down an issue.

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Likely since new when my dad bought it 20+ years ago.

I did get the taper down to .0005" today with repeated cuts on the reference bar. It's to the point now I'll have to undercut some more if I want to chase that last half thou. I think I'll leave it where it is.

I did run the indicator across the top of the bar after my cuts and it barely moves the needle in the same direction as the difference in diameters so I'm going to call that a win and quit messing with it.
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