Lathe Spindle out of Alignment with Bed Ways

dansawyer

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The lathe is new to me, it is an older Clausing Colchester 13x36. It shows signs of moderate ware, it does not show signs of outright abuse. I am trying to assess its condition and how far out of spec it is. I have been struggleing with measuring horizontal spindle alignment vis e vi the ways, I believe I have found a method.

I took two sets of measurements with an 8 inch diameter face plate attached to the spindle.

The first set indicated the plate was square to the spindle. At 60 degree increments I measured run out from 1 1/2 inches to the far edge of the plate using an dial indicator attached to the cross slide. All 6 of the readings were essentially the same at about 3 thousands. The fact that they are all the same indicate the plate is square to the spindle. (This ignores any error between the ways and the cross slide. )

The second was a bit more complicated. I attached attached a right angle plate to the face plate with a clamp with the exposed surface vertical. I then affixed a dial indicator to the cross slide reading square to the exposed edge. The setup is such that if the ways were square to the face plate then moving the carrage on the ways should result in no change to the reading.
I took a series of 4 readings. I started with the indicator close to the face plate and moved the carrage out 3 1/2 inches. I then rotated the face plate 90 degrees, reattached the angle plate in the same relative position to the ways, and retook the measurement. In all 4 cases the readings were the same, they started out a 0 and moved to plus 3 thousands in 3 1/2 inches. Given that the face plate is square to the spindle I conclude the spindle is out of alignment with the ways by about .001 per inch.
(Unfortunately the head is machined to ride on the Way V's. )
I have been unable to detect measurable run out in the spindle. The runout of the surface of the face plate while rotating the plate is less that .001.
 

matthewsx

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I’m no expert but I believe the first thing you need to do level the lathe. There are lots of threads on here but the two collar method is generally considered best.

I’m sure others will be along soon who can give better advice.

John
 

MrWhoopee

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Interesting technique.

Chuck up a piece of 1.5 + in. diameter aluminum about 8 in. long. Do not use a center. Take a light cleanup cut on the od to make it round, then take a very light cut with a sharp tool and check for taper. That will tell you what you need to know.
 

benmychree

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Best to relieve the test bar between a band left at the left and right hand ends to eliminate tool wear on a long cut, if there is a difference in diameter between the two bands, visualize what adjustments in leveling would correct that evident twist in the bed ways.
 

machPete99

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If the ways are worn (and they likely are) the carriage is probably moving down and forward as you move it to the right.

At some point (past the main wear area) it will probably move back. Try putting your indicator on a long rod so the carriage is further down the bed and see if it looks better.

If the head truly is off you can try putting 2 pieces of thin shim stock (.001" ?) under the V section of the head at "opposite corners". The tailstock may need to be shimmed as well to compensate for the head being higher.

Unfortunately, trying to compensate for wear in one area will result in things being off in another area.
 

markba633csi

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The error you're seeing is probably due to wear. I watched an old Colchester factory video the other day and with the care they put into making these machines I can't see it being anything other than that.
The question being is it going to affect the parts you are planning to make? Unless you are making parts for the Mars lander I wouldn't think so.
Most of us with worn lathes, me included, have ways of compensating for error. Personally I think using a worn machine makes one a better machinist because it makes you think more about what you are doing and why.
-Mark
 

MyLilMule

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If you haven't made sure there is no twist in the lathe bed using a precision level, anything else you try will be pointless.
 

dansawyer

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If you haven't made sure there is no twist in the lathe bed using a precision level, anything else you try will be pointless.
The lathe is mounted on a 3 point system, 2 at the head and one at the tail. I have a precision level and there is a very small amount of twist. The level is calibrated at .0002 per 10 inches or 20 micro inches. If I pull on the tail stock with about 30 pounds of force the twist goes to neutral.
(There are a pair extra feet at each end that I am not using. I could change to those feet and adjust out the twist. However it is so small it is unlikely is is the source of what I am observing. )
 

MyLilMule

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If your issue is due to bed wear, and you really need it aligned to a tenth, you can try introducing a slight twist in the bed to compensate for it. Of course, that's going to knock it out somewhere else. Outside of having every surface reground and scraped, I'm not sure what else you could do. Provided it is NOT due to headstock alignment. The headstock on my SBL is pinned in position and rests on the ways. There's not much I can do about align it. I haven't seriously checked mine yet (just finished rebuilding it recently) and need to do all these steps yet.
 
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