New Cross Feed Nut, Gib Adjustment

[kennyv]

Did some maint on my lathe over the weekend adjusted the clutch for carriage feed/ cross feed . Also installed a new cross feed nut .

Had to do some cleaning up cross slide mating surfaces , and a bad spot on gib side surface. Well without going crazy taking off too much material i got er working smoothly with the new cross feed nut however bc of excess wear (i am guessing on the front side ) where the cross slide has been past 50 years. I was able to get cross slide to run nice and smooth without gib tight/ cross feed nut off.
However with gib properly adjusted she was not able to smoothly pass the centerline . Imo without stressing the new cross feed nut. She moves smoothly but is tight on the screw in that area . Any tips and tricks for repairing better without scraping all surfaces?


Gib Question ?
Ohh as far as Gib I did end up taking off material off to get her smooth. I used bluing and an oil stone. However i am at my last of last of gib adjustment now because i did remove all of the scaring . So now soon i may need a new gib to get a correct adjustment . For now needed to shim about .004 on the front side of the Gib for correct ajustemt .

Any ideas anything i can do altogether for the crosslide other than shimming ?

thanks in advance
Kenny V

 

[4GSR]

Put the .004" shim on the back side of the gib. You don't want it on the side that moves. This is common procedure on many machines out there including my own. There is nothing wrong with using shims behind gibs.

 

[Rex Walters]

I suspect that re-scraping is likely the only good way to fix the binding issue (if it's due to wear as you suspect).

One comment, though: You may not need to scrape all surfaces. I was surprised to find on my lathe that the wear wasn't so much on the vertical-ish dovetails themselves, but actually on the flat horizontal surfaces. Because my original cross-slide was much shorter than the ways on the saddle, and because it spent most of 70+ years on the front portion, the horizontal parts at the front of the ways are noticeably smoother (no visible grinding marks) than the rear. I'd guesstimate it's just a couple tenths to a half thou of wear, but it's enough to raise up the cross-slide slightly as I move it to the rear, causing the dovetails to bind slightly. There may also be wear on the dovetails themselves, but the horizontal part will be a whole lot easier to scrape (once I'm more confident in my scraping skills!).

Regards,
--
Rex

 

[4GSR]

Rex is correct, scraping is the only way to completely fix the problem. And scraping and fitting dovetails are not easy to do. Takes lots of scraping practice and a good knowledge of scraping 101. One thing you could do, if you are brave enough to do so, is very carefully re-machine the dovetails and adjacent bearing surfaces, to remove any high spots. But doing this affects the gib, the alignment of the feed screw, as well as the sliding surfaces themselves, too.
I would not suggest doing this if it is not that bad.

 

[kennyv]

Put the .004" shim on the back side of the gib. You don't want it on the side that moves. This is common procedure on many machines out there including my own. There is nothing wrong with using shims behind gibs.

Correction what I meant by front side was the cross feed furthest towards the operator . As I shimmed the gib .004 on the wider side of gib on the non sliding side next to the gib adjusting screw . Well prob is fixed no longer needed .
SEE NEXT POST " Blue tells the story"
****** New cross feed nut is installed gib is adjusted perfectly and crosslide works smooth with full range. ****

 

[kennyv]

Well Good stuff OK problem solved and the best part is no shim needed to get her to work smooth with now the full swing . Glad i tossed this around . Unsatisfied with shimming for adjustment Last night I decided to take back apart and get to bottom of it all. Btw i was worried because prior to installing the new cross feed nut i did take out some of the scaring .
Here is what i did in order check for smoothness squareness and full range of motion with a properly adjusted gib. Blue tells the story ..

First thing set out to blue up all surfaces and inspect every avenue .. little by little i had isolated the two rough spots (where the was original the scaring was) One on RH side of dove tail / gib ( Gib side . ) The other was on opposite side towards front of cross slide. I found both these minor errors by bluing /using the gib to slide with my finger tips listening to feel any resistance . Than I put all back ran friction tests ( by hand no cross feed nut) which resulted in stoning 2 areas on the gib that left the most impression . Next after truing up these surfaces , put back together, felt /examined the bluing on all mating surfaces . ( again without the new cross feed nut ).

At this point I was very impressed everything felt great ,was able to adjust the Gib and get full range of motion with same resistance at full travel. Yea !!! than last but not least found the culprit as to why I could not cross the center line without resistance. Now this time I was confident it was not a drag issue due to the mating surfaces .This one happened to be a high spot inside the cavity where the cross feed nut sightly rubbed. When testing the cross feed nut by itself it was not an issue . However fully assembled it was enough to graze the surface . At that point I took material off the radius on the bottom of the new nut and bada bing end of story. All problems fixed , smooth, cross feed , new cross feed nut with a properly adjusted gib . . Blue told the story but not the whole story..lol... Hey thanks for listing and let me talk it out its been therapeutic .One happy camper again.

 

[Round in circles]

Scraping and things when not needed & your success in finding out what caused the problem ,

It reminded me of days gone by when I was apprenticed for three years at a full time technical engineering college , before being allowed to proceed to real stuff where peoples lives were at risk .

My main tutor was an ex navy hands on engineering officer who'd spent most of his service time aboard a submarine called " Dreadnought " , he always used to say TEA & Kiss usually works , especially if your a few hundred feet below surface and things go wrong .

Think Evaluate Act & Keep It Simple Stupid