Bed twisted or Tailstock Offset.

[KevinM]

My lathe cuts a taper of 0.003"in a 16" cut. I have leveled the lathe as best as my equipment will allow me. How do you tell if the taper is due to tailstock offset or a twisted bed?

 

[sdelivery]

Just guessing but if you only have .003 taper in 16 inches your doing pretty damn good.
Put an indicator on the tail stock so you can see how much your moving it.
With that amount of taper I would not move it more than .0005.
Over that length it will not take very much to bring it the rest of the way in.

 

[MyLilMule]

If you have validated that the bed is not twisted, then it only leaves bed wear or a misaligned tail stock.

Leveling a bed is not what you really want, getting all twist out is the real goal. It goes by extension that if all parts of the bed are level, then the bed isn’t twisted.


Sent from my iPhone using Tapatalk

 

[markba633csi]

Questions:
1) what brand/model of lathe?
2) are you using a tailstock center for the above test? if so then:
3) you should do a 2-collar test without the tailstock
-M
PS 0.003 over 16" ain't bad

 

[KevinM]

So the only way to tell is to level the bed (not necessary level but a flat plane) first, fresh cut and correct any taper with the tailstock?

 

[T Bredehoft]

.003 in 16 inches is better than .001 in 5 inches, not bad at all. We must assume you're working with the right end in a center in the tailstock. Did you check in the middle to see how much spring you have?

 

[KevinM]

Questions:
1) what brand/model of lathe?
2) are you using a tailstock center for the above test? if so then:
3) you should do a 2-collar test without the tailstock
-M
PS 0.003 over 16" ain't bad

PM1022V lathe.
Used tailstock center.
0.003" over 16" is fine for most of my work. I was just curious as to how you would know whether it is the bed flatness or tailstock offset.

 

[KevinM]

.003 in 16 inches is better than .001 in 5 inches, not bad at all. We must assume you're working with the right end in a center in the tailstock. Did you check in the middle to see how much spring you have?

I did not check spring. I am more curious than worried about the taper at that length.

 

[mikey]

PM1022V lathe.
Used tailstock center.
0.003" over 16" is fine for most of my work. I was just curious as to how you would know whether it is the bed flatness or tailstock offset.

Best way to tell for sure is to do a 2collar test to check if the lathe is level. If it is, use a test bar between centers to check and adjust the tailstock. You can make a test bar or buy one from Edge Technology.

 

[KevinM]

Best way to tell for sure is to do a 2collar test to check if the lathe is level. If it is, use a test bar between centers to check and adjust the tailstock. You can make a test bar or buy one from Edge Technology.

Aaaah, I can see clearly now (the rain has gone). Without using the tailstock you are only measuring the bed. Correct bed and then use the tailstock and adjust the tail. Two rounds of chemo has turned my brain into 'nanner puddin'. Thank you all for enlightening me. Seems pretty basic now.