# Bronze Cross feed nut....ain't eating !!



## rafe (Jul 24, 2013)

I knew this was coming ,sort of.... there was a lot of slop when I first got it. I did some threading yesterday and it seemed to be getting worse ....today it gave up. I disassembled it and the feed nut has very little thread left.(shot) The feed screw is showing some wear too. I measured a first thread that has seen little if any wear it's
.067" in the middle where wear is most severe .047" I could most likely live with that but I think I'd rather do it right....seems like some play in the thrust bearing too.
Can someone or more offer me advice on this. it's a 14 1/2 " South Bend. I could mate some acme threaded rod (8tpi) to the shaft, get the new part, make a new part but all I have is my 6"atlas....The bronze bushing needs new or sleeving? Any way all feedback is appreciated and helpful ...Thanks in advance and regards R


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## george wilson (Jul 24, 2013)

Wouldn't the cross feed thread have to be left hand?


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## Richard King (Jul 24, 2013)

If the factory price is to high.  Check with Green Bay Mfg.  They sell stock Acme screws and bronze nuts.  You have to machine to fit.   More later...I'm to on cell...I have hate it...Rich


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## fastback (Jul 24, 2013)

I remember a while back that Jeff over at Tool4cheap was selling some cross feed nuts for Southbend lathes for around $35.00 (I think).  You may want to give him a call.


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## 12bolts (Jul 24, 2013)

rafe,
This thread has the basics http://www.hobby-machinist.com/show...ss-slide-lead-screw-nut?highlight=acetal+feed
but if you google acetal feed nut a few other sites will also come up with some threads. There is one excellent thread by a poster "matt"?? i think??
Cant find it at the mo. He runs through the whole process from go to whoa. Very informative and lots of pics.

Cheers Phil


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## davidh (Jul 24, 2013)

12bolts said:


> rafe,
> This thread has the basics http://www.hobby-machinist.com/show...ss-slide-lead-screw-nut?highlight=acetal+feed
> but if you google acetal feed nut a few other sites will also come up with some threads. There is one excellent thread by a poster "matt"?? i think??
> Cant find it at the mo. He runs through the whole process from go to whoa. Very informative and lots of pics.
> ...




Evan  (Williams) on the other site I believe


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## iron man (Jul 24, 2013)

I dont know if this helps but brass taps really easy so I made my own left hand tap for my lathe out of drill rod it looks crude but it will tap through a 2" long piece of brass like it is nothing. I have also taken a piece of pre-made threaded rod harded it with a hardening powder cut some grooves in it for relief and used that as a tap it leaves a very nice tight thread. If your screw is 10 tpi I can thread a piece for you.. Ray


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## rafe (Jul 24, 2013)

So ....at this point I'm thinking of getting a foot (min. they will sell) of acetal rod and forming a new nut on  a couple of feet of 3/4-8 lh acme threaded rod ... I think I have 11/16" now I don't know if that would be an issue ....and getting this fixed myself ...I'm thinking I could cut off the worn threaded rod and join (fit) the fresh piece of acme  ....otherwise I'm looking at over $300 in parts which I dont have. the hard part is  the 6" lathe may not be up to the task, but I think I can put the SB back together and use the compound for turning the threaded shaft of course I wont need it to drill the other piece (tailstock)......or I could just buy a bronze nut and put up with the backlash .....that would be quicker...i'll sleep on it  OR I can drop from 11/16 down to 5/8" (which some of them were) and get the nut and threaded rod for around $80 and get it up and running, that's most likely the way to go ?? tools for cheap $58 (do-able)....the smaller SB's are less


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## george wilson (Jul 24, 2013)

MSC sells left hand acme threaded 1/2" x 10 tpi rod. It comes in different levels of precision. The real precise rod gets expensive. You only move the cross slide a small amount when finish turning a shaft to an accurate diameter,so I doubt you need real precision rod. 

For the feed screw of a milling machine's table,it would be different. You might move the table a considerable number of inches to accurately drill holes.

They also sell steel nuts for the rod. Steel isn't the best answer,but for a home shop,I don't think you'd wear out the threads any time soon. Keep it oiled. The RPM on the cross slide is never anywhere near fast. It is the best way to get by cheap.


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## rafe (Jul 24, 2013)

12bolts said:


> rafe,
> This thread has the basics http://www.hobby-machinist.com/show...ss-slide-lead-screw-nut?highlight=acetal+feed
> but if you google acetal feed nut a few other sites will also come up with some threads. There is one excellent thread by a poster "matt"?? i think??
> Cant find it at the mo. He runs through the whole process from go to whoa. Very informative and lots of pics.
> ...



Great thread on PM I think it was his name was Evan...maybe that's the one you saw? Anyway I may go that route  if not this time at a later date Thanks


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## 8ntsane (Jul 24, 2013)

Here is a few more places to check out.

http://www.roton.com/

http://www.nookindustries.com/Product/ProductLine/Acme-and-Lead-Screw-Products


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## 12bolts (Jul 25, 2013)

davidh said:


> Evan  (Williams) on the other site I believe



Yep that was the guy, dunno where 'matt' came from.....




rafe said:


> Great thread on PM I think it was his name was Evan...maybe that's the one you saw? Anyway I may go that route  if not this time at a later date Thanks



Cheers Phil


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## george wilson (Jul 25, 2013)

The Evan I know posts on the "Home Shop Machinist". I have been a friend to him and exchanged many PM's. He's a brilliant guy,but really in declining health. I don't know if he is still alive. I quit posting there because the atmosphere is just too hostile. Guys like Lazlo,Stevenson,Muller,and a few others are a PITA gang that make it unpleasant to post there,so to heck with the lot of them. Evan always got harassed by them. I don't know why he stays there.


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## iron man (Jul 25, 2013)

From what I have read so far the plastic nuts work great in the beginning but tend to wear out quickly.. Ray


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## Todd (Jul 25, 2013)

look for jay hawk machining on ebay, he sells the crossfeed and compound nuts for many of the home shop type machines, including southbend.  i got a combo of crossfeed and compound for my heavy 10 from him for like 50 bucks.  they work well and took out most of my back lash, i should have re made the screw but it is still better.  i think he sells the feed rod as well.


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## rafe (Jul 25, 2013)

Here is the plan. I found a sleeve nut at 5/8-8 LH acme which (I'm going to double check after I post this) I believe I can turn down a little and bore the worn out cross feed nut I have (a little) press it in and secure ...and that is done! I will also purchase 5/8-8 acme rod cut off the worn acme from the shaft and sleeve the shaft over the new acme rod pin or silver solder. That should work ...I can't find 11/16-8 but that shouldn't be a problem ?? that is the question ,I can't see the 5/8-8  making any difference. I like the acetal idea but I probably won't wear the bronze out in this lifetime....Let me know if you foresee any faults with this plan Thanks and Regards

PS i'll post pictures as I go


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## rafe (Jul 27, 2013)

Soooo, I got the threaded left hand 5/8 acme rod .....Needed a foot but had to buy a 3' piece from McMaster-Carr which was here overnight for regular shipping price(Nice) I also ended up getting a new nut 5/8 LH Acme, but that is not here yet....I was going to try to locate another lathe to use because my other lathe is to small for the rod to fit through,then I got to thinking....and ended up putting the crossfeed back on where I needed it and tightened down the gib then used the compound as the crossfeed....that worked out ...last photo was the new threaded rod being turned ...The pics should speak for themselves?


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## rafe (Jul 27, 2013)

rafe said:


> ....seems like some play in the thrust bearing too.
> Can someone or more offer me advice on this.



This crossslide does not have the thrust washer set up, They must have started that after 47...There is however a lot of play in the dial .024....I am tempted to put in a thin washer to take out some of the play (does anyone know what the play should be??) but don't know if it's even nesessary to worry about it....I don't think I want to modify it for the thrust bearing set-up.  Thanks and regards


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## Chuck K (Jul 27, 2013)

I had to fix the cross feed on my 14 1/2 a few months ago.  I couldn't find the 11/16 screw unless I wanted to pay for a custom order.  I ended up getting a 11/16 nut from Jhawk and cutting my own screw.  It worked out well but it would have been a lot easier to do it your way with 5/8.

Chuck


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## wa5cab (Jul 28, 2013)

Rafe,

I don't own an SB and don't know what the typical minimum backlash is.  However, the back lash (that shows up in dial reading) has two sources.  One is clearance between the cross feed screw and nut threads.  There is little that can be done about that other than reducing it to a minimum by replacing both parts.  The other is end float in the feed screw.  On a machine without ball thrust bearings, the theoretical minimun is zero.  Or if you prefer, zero+.  Get it any tighter and the crank gets difficult to turn.  On my Atlas this is adjustable and I'd guess that after several tries I could typically get it down to .001-.003.  

If yours isn't adjustable, what you could do is first run the cross slide off the end of the feed screw (assuming that you can do that) to take the nut out of the equation.  Rig a dial indicator to measure screw end float.  Buy an assortment of thicknesses of of appropriate diameter bearing shims from some place like McMaster and play with them until you reduce the end float to the minimum you can get it to without having objectional drag on the crank.  Then reengage the nut with the screw and see how much backlash you have.  That's as good as it's going to get.  Same principle should apply to the compound.


Robert D,



rafe said:


> This crossslide does not have the thrust washer set up, They must have started that after 47...There is however a lot of play in the dial .024....I am tempted to put in a thin washer to take out some of the play (does anyone know what the play should be??) but don't know if it's even nesessary to worry about it....I don't think I want to modify it for the thrust bearing set-up. Thanks and regards


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## rafe (Jul 28, 2013)

wa5cab said:


> Rafe,
> 
> I don't own an SB and ............. Same principle should apply to the compound.
> 
> ...



Thanks for the information Robert, I am thinking of taking some of the play out and calling it good ....Before the nut stripped I had a little over a full turn of backlash
that is about as extreme as it gets before failure, and fail it did ....so with a new nut and screw It should be a drastic improvement and I am thinking I may put a thin spring washer to the right of the gear on the shaft (see shaft on blue box)...another sleeve goes over the shaft and mates with that flat surface,and the play shows up there when the dial is tight and on the dial when that area is tight, I don't see what that could harm I'll shoot for .005 play


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## wa5cab (Jul 28, 2013)

Rafe,

I assume that by spring washer you mean Belleville washer.  That will work and if the washer load rating is adequate will reduce the end float of the cross feed screw to zero.  At least while not turning or facing.  However... first, and a minor objection, it is always going to increase the effort (torque) required to turn the crank.  And second, if you put the washer against the right side of the gear everything else will be OK while turning and while facing from outside toward center.  But while boring or facing from center out, the cutter reaction force will be against the washer trying to flatten it more.  And the actual "Y" (front to back) position of the cutter may not be where you think it is.  So a spring washer might not be a good idea.

Robert D.


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## rafe (Jul 28, 2013)

Hi Robert,I think the Belleville is a cone that's not what I meant, I was thinking of the bent type?? I am a little confused on the actual consequence of that gap and the effect it will have on the crossfeed screw and the crossfeed nut. I am trying to visualize it
and can't quite get it ...I have put the shaft together and may post a photo of that.  Although you have got me thinking that it might be better to make a brass washer to close it down some, rather than put any force in there. 

PS I re-read your earlier post and to clarify what I'm saying is, I don't think the gap I'm talking about will cause backlash on the dial, just a gap there (End play)  or if pushed straight in will cause the gap to be next to gear, however I think it will play a part in wearing out the nut and should be minimized ....Regards


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## wa5cab (Jul 28, 2013)

Rafe,

OK.  I'm not sure but those may be called wave washers.  In any case, the results would be the same.

Backlash in the cross feed screw is an aggravation perhaps but even if you reduce the feed screw end float to zero you still in setting the cutter position have to compensate for the nut to screw clearance by always approaching the dial setting in the proper direction.  For turning and OD to ID facing, this is clockwise.  For boring, it is CCW.

Robert D.


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## rafe (Jul 29, 2013)

Well, it's back together and it works like a dream thanks to Jayhawk machine tool on E-bay for the fast shipping on the nut and mcmaster carr for the acme rod .......super fast shipping and all the advice on here. I don't foresee any problems on the crossfeed for a while and this will make threading a little quicker .....


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## rafe (Aug 21, 2014)

Still going strong .....can't believe it's been over a year ....seems like yesterday


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## projectnut (Aug 22, 2014)

george wilson said:


> MSC sells left hand acme threaded 1/2" x 10 tpi rod. It comes in different levels of precision. The real precise rod gets expensive. You only move the cross slide a small amount when finish turning a shaft to an accurate diameter,so I doubt you need real precision rod.
> 
> For the feed screw of a milling machine's table,it would be different. You might move the table a considerable number of inches to accurately drill holes.
> 
> They also sell steel nuts for the rod. Steel isn't the best answer,but for a home shop,I don't think you'd wear out the threads any time soon. Keep it oiled. The RPM on the cross slide is never anywhere near fast. It is the best way to get by cheap.



McMaster-Carr also sells different grades of left hand thread Acme threaded 1/2" x 10 tpi rod and left hand threaded Acme nuts.  The highest grade aren't cheap, but the are high quality.  Like the OP I waited just a little too long before replacing the rod and nut on my Seneca Falls lathe.  I was able to buy the rod and a generic nut and make the necessary modifications on the mill.


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