Thread: lathe levelling

Originally Posted by morrisman

I am about to open a can of worm with this topic

You know this isnt RDM right?

Originally Posted by morrisman

Anyway tapping the tailstock over isn't precise enough

What is this "tapping" of which you speak? Don't you have a dial gauge or DTI?
Isnt there two bolts you can work against each other to move the tailstock accurately?

Originally Posted by morrisman

So by twisting each corner of the bed , it seems to have done the trick ?

Bed wear shouldn't be an issue.Turning between centers shouldn't need bed twisting, you should be able to do that with the tailstock.
You've now aligned the bed to the tailstock... not the other way around.



But.... if it got the job done.......

Stuart

Originally Posted by Stustoys

You know this isnt RDM right?


What is this "tapping" of which you speak? Don't you have a dial gauge or DTI?
Isnt there two bolts you can work against each other to move the tailstock accurately?



Bed wear shouldn't be an issue.Turning between centers shouldn't need bed twisting, you should be able to do that with the tailstock.
You've now aligned the bed to the tailstock... not the other way around.



But.... if it got the job done.......

Stuart

Hi Stuart

Yes the tailstock has 2 tiny screws each side , but these don't have enough force to move the tailstock across , it's far too tight . All they seem to do is lock the tailstock in position.

It's weird , but for some reason - when the 4 bed adjusting screws are all taken out of the equation - with no twisting - I cannot get any repeatability with my trial cuts , its only when the 2 diag. opposed bed screws are tensioned up, that all seems fine and the repeatability is good . Mike

Hi Mike,
You may find now that if you try to turn a different length between centers it may not cut straight. Stu is right, use the 2 bolts to "torque" the t/s into alignment. With a dial on the t/s it is fairly easy to move the t/s half the dia difference the lathe has cut.

Ew

Originally Posted by Ueee

Hi Mike,
You may find now that if you try to turn a different length between centers it may not cut straight. Stu is right, use the 2 bolts to "torque" the t/s into alignment. With a dial on the t/s it is fairly easy to move the t/s half the dia difference the lathe has cut.

Ew

hi Ewan

Yes , I see your point . But I did test a different length of bar with trial cuts and it still works OK . Mike

WRT the t/s not moving with the screws, i find you need to loosen the bed lock off a little and it will move more easily. A dial monitoring the movement means it is hard to go too far. You also need to be sure of how the screws work. On the antrac the screws are threaded into the top half of the T/S (they are really long grub screws) and just push on a block on the bottom half. The other lathes all have the screws threaded into the bottom half of the T/S. When i first went to adjust the Antrac i had no idea what was going on, i actually had to pull the T/S apart to see just how it went together.

One other thing though, with the lathes you own, why are you trying to do such precise work on the lightest and least rigid?

Ew

Originally Posted by Ueee

WRT the t/s not moving with the screws, i find you need to loosen the bed lock off a little and it will move more easily. A dial monitoring the movement means it is hard to go too far. You also need to be sure of how the screws work. On the antrac the screws are threaded into the top half of the T/S (they are really long grub screws) and just push on a block on the bottom half. The other lathes all have the screws threaded into the bottom half of the T/S. When i first went to adjust the Antrac i had no idea what was going on, i actually had to pull the T/S apart to see just how it went together.

Well I'll just delete my post then lol I wrote pretty much the same thing including the head scratching when you come across your first tailstocks that moves "the wrong way"

Stuart

Originally Posted by morrisman

It's weird , but for some reason - when the 4 bed adjusting screws are all taken out of the equation - with no twisting - I cannot get any repeatability with my trial cuts , its only when the 2 diag. opposed bed screws are tensioned up, that all seems fine and the repeatability is good . Mike

Could be the saddle is worn to match the bed in it's relaxed (twisted) state, and when you untwist it you're getting poor contact and instability.

Or it could be the opposite. If you are right about the bed being straight when relaxed, maybe the saddle is rocking and when you put a twist in, it stabilises.

It's hard to understand from what you've written.

Originally Posted by Ueee

One other thing though, with the lathes you own, why are you trying to do such precise work on the lightest and least rigid?

Ew

Yes , its just my backwards methods, doing it the hard way I am trying to tweak the Sheraton to a good accurate standard , by doing this I hopefully will learn about the ins and outs of lathes . Sometimes an anomaly comes along that doesnt add up . Its all part of the mysteries of machining . Mike

Originally Posted by Bryan

It's hard to understand from what you've written.

Seems pretty clear to me ! Stuart and Ewan have understood the situation rather well

This guy is using shims, but its basically what I am doing

http://www.youtube.com/watch?v=Dvs5YiDl_90

Originally Posted by morrisman

This guy is using shims, but its basically what I am doing

Ok now I'm confused as well......leveling a lathe shouldnt have anything to do with turning between centers.....


Stuart

p.s. Its said you shouldn't put the level on top the the ways like that...... that surface isn't necessarily ground parallel.

[QUOTE=Stustoys;1774337].....leveling a lathe shouldnt have anything to do with turning between centers.....


Ok , I must have lathe theory the wrong way around. From what you guys are writing, It seems that the only reason for turning a taper between centres is because the tailstock is out of alignment In other words there are no other reasons at all

It could be, the bed is worn towards the headstock, causing the tool traverse to lower . Mike

[QUOTE=morrisman;1774386]

Originally Posted by Stustoys

.....leveling a lathe shouldnt have anything to do with turning between centers.....


Ok , I must have lathe theory the wrong way around. From what you guys are writing, It seems that the only reason for turning a taper between centres is because the tailstock is out of alignment In other words there are no other reasons at all

It could be, the bed is worn towards the headstock, causing the tool traverse to lower . Mike

I would think that there would have to be an awful lot of bed wear for it to cause you to turn a taper purely from tool height variation.

Simon