# Carriage Slide Nut Replacement???



## Kroll (Jun 28, 2015)

Guys I have finally started to use  my my lathe more and more and now found out that I have a  little to much play in the cross slide so the nut needs to be replace.I have the 12" Sears 101.28940 and looking in the download section is part #33 537-041 Carriage Slide Nut.I have found  a couple on ebay for 35.00 and they are new never been installed.I was wondering if others have replace their carriage slide nut and if that cure the play in the cross slide?There is no side to side movement just towards/backwards from the nut.I watch a Utube while back where a guy replace his and it was just to tight so he had to machine his to get his to fit.Thanks guys for the advice and pointers----kroll


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## RJSakowski (Jun 28, 2015)

I have an Sears/Atlas 6" lathe and replaced the lead screw nut years ago.  It will help to take up some of the play but do not expect it to remove all play.  There will also be wear in the lead screw and there may be some clearance in the bearing adjustment.  The latter can be fixed with an adjustment or shims.  To assess the lead screw contribution, move the cross slide to the far inboard position.  This is a region where it is least likely that you have wear.  Set a dial or test indicator up to measure the slide movement and record the dial readings where  you first see the slide move.  Check out the center of travel as well as this is probably where most of the wear occurs.


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## RJSakowski (Jun 28, 2015)

On the 6" lathe at least, the lead screw nut is held in place by a single flat head screw which also fastens the lead screw cover.  Make sure that screw is tight.  If it is loose , it contribute to the backlash.


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## Kroll (Jun 28, 2015)

After reading this,I ran out and check the screw that holds the nut well it was tight.I would say that I can pull/push the slide at lease 1/16.


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## wa5cab (Jun 29, 2015)

Kroll,

With a sixteenth inch of movement, if it were all attributable to the nut, you would have virtually no threads left as the thread thickness can't be much more than that.  Have you adjusted the cross-feed screw end float?  You do that by differential adjustments of the nut that secures the crank and the nut between the crank and the dial.  Best done with the carriage nut run off the end of the screw at the rear.  And it will be easier to do if you have a thin pattern (tappet) open-end wrench for the nut between the crank and dial, and a box end for the crank nut.

If you do replace the cross feed brass nut, also order a couple of 9-87 Washer, Carriage Slide Nut.  These are actually shims.  The original illustrated parts lists show it as one round washer, but they are actually rectangular shims.  I think that the copy of the parts lists in Downloads have been corrected but if the washer still shows as round, let me know.

Anyway, to properly install the nut, first adjust the screw end float to minimum.  Then install the new nut but only run the round head screw down to finger tight.  Pull back on the cross slide and start turning the crank until the screw engages the nut, and then retract the carriage until the nut again runs off the screw.  Push the carriage and turn the crank until the threads grab, and then about 8 more revolutions of the crank.  Loosen the round head screw slightly and then with your fingers carefully tighten it until it just touches the top of the cross slide.  Note the position of the slot.  With a screwdriver, fully tighten the screw, noting how may turns or fractions of turns the screw makes.  The screw is 20 TPI which is 0.050" per turn.  Calculate the shim thickness required from this and the number of turns and fractions of turns.  Crank the nut back off of the screw, install the shims (if needed), back the nut fully onto the cross feed screw, and fully tighten the round head screw.


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## Kroll (Jun 29, 2015)

Thank you Robert,I will check into that.I don't remember seeing any shims which means that I lost them I guess.I will have to enlarge the drawings to see if the shims are round or rectangular and just to double check to see if their there or not.If I do need some shims,where can they be purchase from or is this something that I will have to try and make?
OK Robert,I think I understand now and I see its part#35 (9-81).I think I will take it apart again and just go through it.Thanks for taking the time and doing a fantastic download section


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## wa5cab (Jun 29, 2015)

RJSakowski said:


> On the 6" lathe at least, the lead screw nut is held in place by a single flat head screw which also fastens the lead screw cover.  Make sure that screw is tight.  If it is loose , it contribute to the backlash.


On the 9", 10" and 12", the screw holding the cross feed nut is a separate part and is a round head slotted screw.


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## wa5cab (Jun 29, 2015)

Kroll,

You're welcome.

The shim could be stuck to the bottom of the cross slide.  Or it might not have been there to begin with.  My 3996 didn't have one originally.  But when I installed a new nut last year, the new nut needed one.

You can buy them from Clausing or make them.  I forget what the thickness is but if you find that you need one and decide to make it, determine what thickness you need and buy the nearest standard shim stock.

I forgot to add earlier that while you are determining what thickness you need, when you have the carriage in position over tighten the feed screw thrust bearing adjustment snugly..  If it is a little or a lot loose, the screw will droop and move around.


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## ELHEAD (Jun 30, 2015)

Was awaiting my new $35 cross slide nut when I first read your post. Got it yesterday, installed it today. Vastly Improved the sloppy condition that I had been experiencing. I don't believe there is any wear on the screw, just the nut,
STEEL/BRASS  Which is harder?


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## wa5cab (Jul 1, 2015)

Why, steel, of course.  And the coefficient of both static and dynamic friction of steel on steel is lower than that of brass on steel.  Which is one reason that no one used brass for gibs.  However, a steel nut would be more expensive than a brass one, all other things being equal.  Which I assume is the reason that feed screw nuts are usually made of brass.


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## hoekma (Sep 6, 2015)

Hi guys, does anyone know the dimensions (particularly the thickness) of the 9-87 washer/shim that goes between the cross-slide nut and the cross-slide?  I can't team to find it on google.  Sears wants $30 for that little piece (now part number DP9-87) which seems just crazy for that part. I'm hoping to find a washer at Ace Hardware that will do the same thing or to make something if not.

Thanks!


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## wa5cab (Sep 6, 2015)

You aren't going ti find any washers at Ace that will work.  As I said earlier, you may not need any of the shims.  My 3996 didn't have one.  But the replacement nut needed one, although I decided to put the original nut back in.

Prices at Sears were typically somewhat higher than prices at Clausing on parts that Clausing still has on hand.  However, Clausing had the shims last year so I can't account for Sears asking $30.  Unless they've got the part numbers screwed up and quoted you something else.  I can't recall what I paid for the two I bought from Clausing last year but it wasn't anywhere near $30.  If you need to buy anything else, like the nut, call Clausing.  If you don't need anything else and you already have a good pair of ten snips and a set of Arch punches, the sheet of shim material you'll have to buy will probably cost about as much as the shipping (UPS has no increments under one pound).

In any case, the dimensions of 9-87 are as follows:

Length  1"
Width 3/4"
Thickness 0.011"  (probably a nominal 0.010")
Hole is in the center.
Hole diameter 0.375"
Corner radius about 1/16".


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## Rob (Sep 6, 2015)

As Robert said you may not need it. It is there to align the hole in the car rage slide nut with the crossfeed screw.  My original cross slide had one and when I went to the t slot cross slide I put it back in. When I would bring the cross slide all the way out it would bind. I ended up removing the shim and that solved the binding problems I was having.


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