# Cast leadscrew nuts vs. machined



## smarrocco (Jan 27, 2017)

I've read a lot of information on cast leadscrew nuts (moglice, various epoxy/teflon/magic dust recipes). Many people have made their own to what sounds like great success, with little or no backlash because of the casting directly to the leadscrew itself. After doing the math, substances like Moglice, while expensive, amount to very little actual cost per nut. I can find no obvious issues with wear. I'm well aware of the issues with machines solutions such as anti-backlash assemblies machines from various brass pieces that can manually tightened and calibrated. I've done plenty of casting of resin, various epoxies before and it is hardly difficult for a hobbiest with some patience. I currently abuse Sherline equipment and deal with the anti-backlash solutions for that often My system runs manual and under custom CNC control and I have plenty of correction for backlash. It brings to mind a question:

If cast leadscrew nuts work so well, and are not that expensive, why aren't they more common or standard issue?


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## willthedancer (Jan 27, 2017)

I personally would never use a polymer for my half nuts. In my mind it is an uncertainty. I have an old worn out set for my Clausing. When I get to it, I will make up a threaded mandrel, tin the half nuts up and pour them in babbitt. Reading an old article, many outfits noticed that iron and bronze half nuts always shed some powder, and wear the leadscrew in the process. When they went to babbitt half nuts, the half nuts lasted a very long time, and wear on the screw stopped. Good enough for me.


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## 4GSR (Jan 27, 2017)

Moglice in the putty form would be the only one I would use.  I used it to bring back the saddle height on my L & S lathe.  Its tough!  Now the issue to me would be using it in a set of half nuts on a lathe that has a lead screw with a keyway cut down the length of the lead screw.  I think it would crap out over a short period of time.  Next thing, regardless what polymer you selected, it has to be lubricated with lots of oil while in use.  Just my gut feel from actual use of Moglice.  
Now, having said that, what would be a good metallic bearing material to use?  Bearing bronze, cast iron, or babbitt?


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## chips&more (Jan 27, 2017)

I think you mean feed screw and not lead screw, correct? You are talking about the screws that drive the table in X & Y. The cast material is porous so it can retain oil/lubricant and extend life. But has less surface area so I suppose it could not last as long but would be easy on the feed screw. And then on the other side of the coin. Something like aluminum bronze is very tuff and will probably wear out the feed screw first. It’s a coin toss on what you want to replace in the future. A feed screw or a feed nut depending on which one is cheaper and easier to replace I quess…Dave


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## Jimsehr (Jan 27, 2017)

Have you looked at evanut ? Lots of info there.
Jimsehr


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## 4GSR (Jan 27, 2017)

The cast in place Moglice is not porous.  That's why I say you have to keep it lubricated.  660 bearing bronze and 454 navel bronze makes the best nuts and give you better wear properites against a steel leadscrew or feed screw.  I also like to make my feed screws from either 1144 T,P,& G, or drill rod.


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## tweinke (Jan 27, 2017)

I have also read quite a bit of the Evanut postings on the web and have them book marked I think.


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## roadie33 (Jan 27, 2017)

This is something I thought to try next time mine gets loose.

For the cross slide, use the old nut.
Bore it out as much as possible.
Drill a hole thru to the bore on a side.
Make a end-cap for each end to fit over the screw.
Blacken the screw, place inside the bored out nut with end-caps holding it in center.
Preheat nut.
Pour Babbitt in thru drilled hole and now I have new very tight tolerance nut.


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## smarrocco (Jan 28, 2017)

Yes, I mean the screws that drive the x and y axes.


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## smarrocco (Jan 28, 2017)

Jimsehr said:


> Have you looked at evanut ? Lots of info there.
> Jimsehr




Yes. The evanut seems like a nice experiment to be sure. Like a lot of forum threads, the evanut discussions seemed to end soon with 'it is wonderful' but have no long term follow up that I could find. Hence my concern of "if it is so great why doesn't everyone use it?"


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## tweinke (Jan 29, 2017)

Thinking I read a follow up after a year on a cnc mini mill and the user was still satisfied. The only question in my mind about them


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## tweinke (Jan 29, 2017)

Wow that went badly, the last post wouldn't post.  Any how to continue/ finish the post again, The only question in my mind about them is wouldn't they trap grit and wear the lead screw?


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## smarrocco (Jan 29, 2017)

tweinke said:


> Wow that went badly, the last post wouldn't post.  Any how to continue/ finish the post again, The only question in my mind about them is wouldn't they trap grit and wear the lead screw?



Funny, tweinke,  I thought for a minute that you were about to reveal a big secret when all of a sudden someone snuck up and gagged you at the big moment!  shades of the castle Camarrrrg from Monty Python.

The grit issue seems to come up in discussion, but I can't imagine it would be any worse than a tight backlash nut system pressing grit against the screw threads. I do wonder if it would merit something like a 'slot' cut across the length of the moglice nut for lubricant access.


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## bill stupak (Jan 29, 2017)

I have made Evanuts from Delrin for the y axis of my mini mill and the cross slide of my 12" Craftsman lathe. The one on the mill was done about 2 years ago. It had almost no backlash when I first did the mod and now has about .005". The lathe nut was done about 6 months ago and has about .003".


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## tweinke (Jan 29, 2017)

Nice to hear from someone who has actually done it. Any comments on the process and procedures that you used? I ask because my Shoptask 1720xmtc could use a new nut for the lead screw due to backlash getting bigger then I would like.


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## bill stupak (Jan 30, 2017)

tweinke said:


> Nice to hear from someone who has actually done it. Any comments on the process and procedures that you used? I ask because my Shoptask 1720xmtc could use a new nut for the lead screw due to backlash getting bigger then I would like.


.

I used the same procedure as described in       http://bbs.homeshopmachinist.net/th...-leadscrew-nuts-the-easy-way?highlight=evanut.

In a nutshell, you take a piece of  Acetal/Delrin bore it to the minor thread diameter you need, slit it in half, clamp it over the lead screw you are using, apply heat to the screw, then apply more clamping force when the Acetal begins to melt, allow to cool,  machine the piece to the required shape.  Evan goes in the details much better than I can explain and there have been many follow on threads, some using different types of Acetal, different methods of heating and such.  It really is fairly easy to do and I will probably be doing a couple more in the future. The biggest problem I had was with the first one in that it was very tight on the screw and I had to work it quite a bit to get it to to spin free. This problem was addressed in some of the follow on threads, with various methods to alleviate it.   Bill


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## tweinke (Jan 30, 2017)

Thanks for the reply, When it warms up out in the shop will do a test nut and see how that goes. Thanks again!


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## mikey (Jan 31, 2017)

smarrocco said:


> If cast leadscrew nuts work so well, and are not that expensive, why aren't they more common or standard issue?



I've wondered the same thing myself and I bet a cast Zamack nut on a Sherline leadscrew would work well. My Emco lathe uses Zamack leadscrew nuts with the typical slotted backlash adjustment feature. An Emco lathe has zero backlash on both the cross slide and compound and is smooth as silk. Moreover, the nuts can last for decades. I suspect Emco used Zamack because it casts very precisely and has properties suitable for the application. Currently, Zinc-based alloys (probably some Zamack alloy) are often used to cast nuts for precision leadscrew applications and the reasons stated for using this material is precision in casting and accuracy in use. If I were going to attempt to cast a leadscrew nut, I would use Zamack and cast it in a block around the leadscrew and then machine it to the dimensions I needed.


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## Jimsehr (Jan 31, 2017)

I needed to make some plastic disks for a guy and for material I went to Walmart and bought 20 of their white plastic cutting boards. Then I cut the disks out of them. So I had the left over pieces in the scrap bin and just to see what would happen I took a few pieces out of the scrap bin and made an evanut out of the scrap. I just put the 2
Pieces over the threads on a bolt and heated the bolt. I had a hard time unscrewing the bolt. But it worked good enough for me to try it on a leadscrew when I get around to it. 
Ps Walmart must have thought I had a hell of a kitchen.
Jimsehr


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## willthedancer (Feb 1, 2017)

mikey said:


> I've wondered the same thing myself and I bet a cast Zamack nut on a Sherline leadscrew would work well. My Emco lathe uses Zamack leadscrew nuts with the typical slotted backlash adjustment feature. An Emco lathe has zero backlash on both the cross slide and compound and is smooth as silk. Moreover, the nuts can last for decades. I suspect Emco used Zamack because it casts very precisely and has properties suitable for the application. Currently, Zinc-based alloys (probably some Zamack alloy) are often used to cast nuts for precision leadscrew applications and the reasons stated for using this material is precision in casting and accuracy in use. If I were going to attempt to cast a leadscrew nut, I would use Zamack and cast it in a block around the leadscrew and then machine it to the dimensions I needed.



I like Zamak too. It is pretty fabulous bearing material. Same reasons as for my appreciation for babbit.


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## KBeitz (Nov 22, 2018)

I've done a lot of real castings using Babbitt.  One day I needed a acme nut for
a pin router. I know that your to smoke the truning part so what your casting wont
stick to that part but I wanted to try something all new. I cast the nut using JB-weld.
I greased the acme rod instead of smoke. The casting worked great after I got it
loose from the rod but hey... Who would have thought that JB-weld sticks to grease.
Wow did I have a time getting the nut to turn at first... So far its working great. I have
been using it for around a year now.


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## Eddyde (Nov 22, 2018)

+1 on the JB Weld. I used it to successfully repair a gear casing on a Bosch Brute demolition hammer. The pocket that holds a sleeve bearing, receiving the main gear shaft, had worn out and became so enlarged the gears would no longer mesh. I cleaned out the pocket well and coated it with JB weld, inserted the bearing and put the gears in position to set the bering correctly. I only hoped it would make it through the next job but that was 10 years and a couple of dozen jobs ago...


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## KBeitz (Nov 22, 2018)

I'm now repairing something like that using LOCTITE 660 Retaining Compound .


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## BaronJ (Nov 22, 2018)

tweinke said:


> Thanks for the reply, When it warms up out in the shop will do a test nut and see how that goes. Thanks again!



That was exactly how I made the precision nut for my hight gauge.
I just turned it down for a press fit.  The silicon grease helped to reduce the tightness when unscrewing it from the rod threads.




If you look carefully you can see the joint.



That bit underneath is the top of the frame.


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