How to evaluate wear on lathe ways?

[dansawyer]

This topic has been somewhat covered, however I would appreciate some additional input. I am trying to assess the bed ware of a 1957 Clausing Colchester round head lateh.
The Good: I placed a 30 inch piece of 3/4 drill rod in the lathe. I placed a thousands reading dial indicator on the cross slide and zeroed it on the top of the bar near the chuck. The chuck end centered nicely and read about 1 thousands run out at the chuck. I placed an active center in the tailstock and firmed it up to a center hole in the drill rod. It read less than a thousands run out at the end near the tail stock. The Test: When I slide the indicator along the top of the drill rod I measure less than a thou run out along the length of the rod. Then to check straightness of the rod I rotated the rod a squarter turn and repeated the test with simular results; I repeated this a second time by rotating it another quarter and remeasuring witht the same result. I conclude from this, first the rod is relativey straight, and second the carrage-ways are in alignment and straight for the length of rod. I should be able to perform relatively good work in this section of he lathe.
The Bad: Frist, when I position the carrage near the head and tighten the locking bolt and then move the carrage toward the tailstock it definitely binds about 8 inches out. If it loosen the nut about a sixth of a turn it then slides smoothly for another 8 inches and then binds again. If I loosen another 1/6 turn it slides smoothly to the end. I read from this there is measurable ware in the head end of the ways. Second, if I place the indicator on the carrage and zero it on the flat top of a V way and move the carrage I measure about 10 thou between the full tail stock end and the chuck. Both of these indicate measurable ware.
What a mIssing between these tests? Are they the best ways to measure ware?

 

[markba633csi]

The binding test tells you there is significant wear, but you can still make good parts on a worn lathe. Making accurate long parts will be more difficult.
Remember there will also be wear on the sliding surfaces of the carriage too, not unusual for a lathe that old.
Regrinding the bed is usually not worth the cost unless you have a brother in law with a grinding shop
-Mark

 

[dansawyer]

I am trying to reconcile the two observations. I assume based on the process the rod is straight. The 'vertical alignment' test showed no significant variance across the length of the test, about 18 inches. There is no doubt two tests indicate way ware; that said the vertical alignmnet test does not indicate any actual operational error.
Is there anyway to reconcile these observations?
I will find a piece of stock and perform a taper test.

 

[rabler]

Where did you mount the indicator on the carriage? Near the front or back? If it was tilting that would matter. The carriage can also rock left to right if worn.

I don't know if that lathe has hardened ways, but if so, the carriage will wear significantly more than the ways, and often in an hour-glass shape around the front v, more wear near the ends. Trying to slide a feeler gauge between the ways and the carriage on front and back of the v-way, both left and right side, can be useful to assess this.

You can also use and indicator to see if the carriage rocks when you press on each of the four corners.

 

[Richard King 2]

To All the new members:

When I do it. I first thing is to align and level the bed. If it has a twist in it, your check is no good. It sort of reminds me of that they used to call "The Rolley Dads Test". I haven't seen it for a long time. It would get it close, but not the best way. On a lathe the most unworn areas are the tail-stock (TS) ways, under the chuck and on the far right end. Most of the time they are like new there. So stone under the chuck and set the bottom of the TS on the ways and hopefully you have a machinist level .005"/12" or better accuracy. Then dismantle the TS and use the bottom as a sled to measure things. Set the level on the stoned flat area of the TS base as it is on the ways closest to the chuck or remove the chuck and set it nearest the headstock, then level the machine front to back and set the level on the long ways and level it so the bubble stay on a line. I use a Starrett 199 level that is calibrated to .0005/12" But if you have a Starrett 98 level .005"/12"is Ok if you align the bubble on a line. Then pick up the TS base up with the level still attached to the TS base and move it to the far right end and set it down. Then adjust the base leveling screws to get both ends the same, It will take a few back and forth moves to get it perfect.

Then crank the saddle to the far right eend of the lathe bed. Remove the level and replace it with a mag base and dial indicator. Move the TS base back to the chuck end and rest the indicator stem on the saddle ways and slide the TS base down the bed and watch the indicator. on 99% of lathe beds the saddle ways near the chuck get worn the worse. The TS ways don't.

If your thinking of buying a used lathe a simple way to se if the machine has been used a lot is to take a flash light and look at the rack under the bed. Compare the rack teeth near the chuck where the rack pinion never goes to the rack teeth in the middle where it gets used a lot.

Hopefully that helps.
Welcome everyone to a Super Forum.

Rich

PS Photo shows how I have checked twist and wear using a aluminum T sled I made for a huge lathe and Starrett 98 level.