# Deflection And Gib Adjustment



## fast204 (Oct 8, 2016)

_Can anyone point me in the right direction on proper gib set up? When taking face cuts I found that I was getting .04" deflection from edge of work to center. I removed the carriage lock plate and resurfaced, that seemed to solve face cut deflection. When making long feed cuts using the carriage im getting around .01" unless I keep pos pressure on the cross slide handle. My thought is the cross slide brass nut is worn.? Any thoughts? _


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## Ulma Doctor (Oct 8, 2016)

your thoughts may be correct, if there is play between the shaft and nut.
the materials resistance to cut will generally take up any backlash present.
it's especially noticeable on heavy cuts on worn machines
another check would be the tailstock alignment


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## fast204 (Oct 8, 2016)

There is definite play between screw and nut. I figure it would not be wise to tighten the gib up to compensate as there is zero play left to right.? Also is there a walkthrough on proper gib setup?


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## westsailpat (Oct 8, 2016)

Sean , I'm not really sure what you mean . Are you saying that when you take a long face you get .04 deflection ( taper ) on the face of the part ? I think I'm seeing a two part question , so please let me just comment on the first part for what it's worth . When taking a face cut , long one or short  I would lock the saddle when making the cut . Also I would have a travel dial indicator in place to make sure that the saddle has not moved .  I hope that helps .


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## Ulma Doctor (Oct 8, 2016)

the gibs are there to compensate for wear. 
to adjust, simply back off the nuts on the side of the compound rest and engage the setscrews with a screwdriver.
turn the screw clockwise to tighten the gib, counter clockwise to loosen the gib.
there should be 3 or 4 setscrews, dependent on the model of the lathe
regardless you'll loosen all the gib nuts up, and start from the center out adjusting the gib screws.
i give a turn until i feel contact and back off a touch. then while still holding the setscrew i'll adjust the lock nut until it locks.
i'll give a motion check with the handcrank and readjust the last gib i touched if anything feels irregular
repeat until all gib screws have been adjusted and the compound rest has a snug or very slight drag under well oiled conditions

i hope the explanation was satisfactory, if you have other questions about the process feel free to ask


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## wa5cab (Oct 9, 2016)

This isn't usually a problem but some operations or cutters tend to pull on the cross feed, causing it to be able to move as much as the backlash.  And some longitudinal cuts may seem to cause the cross-feed crank to turn.  A solution for both of these is to replace one of the two center gib screws with the T-handled gib lock screw as used on the milling attachment.  Use it to lock the cross feed before each pass.  You may need to shorten one leg of the "T" to prevent its jamming on the saddle wings, making it an L-handled screw.


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## fast204 (Oct 13, 2016)

I was able to get out of the face cut problem by re surfacing the saddle lock plate, no matter how tight I tried to lock it I was still able to move the hand crank, once I resurfaced I am able to lock down before face cutting.
I like the idea of a gib lock as on a Bridgeport and will most definitely look into this as my next move.
I would like to know more about the gib adjustment as I am not sure that there are lock nuts on mine. it could be as simple as the p/o removed them or it just did not have them? sorry about the delay in response it has been a long week,
thank you!


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## Round in circles (Oct 14, 2016)

Another thing that often gave me  deviations from the expected was that the tool holder  .  Mine was allowing the tool to turn a fraction on each pass. I also discovered that the whole tool post was rotating a minuscule amount on the cross slide when doing heavy cuts or using ta long  boring bar set up ..

I ended up with a new QCTP and lapped the thing down onto the cross slide face , using engineers blue ( hone made ) to get the witness marks and scraping off the high spots with a ground square edged lump of hack saw blade,  before using a very fine green diesel injector nozzle lapping paste to to get the best final finish . Now it stays put when it's clamped down .

 It was surprising to see the 8 thou or so hump raised in the middle of th tool post mounting channel  done by one of th two former owners using a standard high tensile hex headed bolt & a brass washer instead of the corect  "Tee " nut & stud to tighten  the tool post down with .


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## wa5cab (Oct 15, 2016)

Sean,

I have never seen a torque spec for tightening gib screws.  And if there were any published, very few would have the torque driver that light, anyway.  You just have to learn to calibrate the wrist.    It's a trade off between how tight you can tolerate the cross feed and how loose you can tolerate the gib.

The nuts should be on the screws.  Else the screws will certainly move under vibration.  The nuts on the compound are just machine screw nuts.  The ones on the cross slide and carriage gib screws are thin-pattern or jam nuts.


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