Lead screw nut

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darwenguy

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Hi all, can anyone help me find a replacement lead screw nut for my lathe. I cant find any suppliers that list this part.
Its an old imperial machine and the thread appears to be 3/10 in diameter.
I do have another lathe so could possibly make a new one if i cant find a replacment.
Pics of the part...
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Brian Rupnow

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See this thread, it gives good instruction on how to make a nut to match your leadscrew.---Brian
 

VicHobbyGuy

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Another approach similar to the Evan nut: Delrin (acetal) can be heat-formed to make a nut. The difficult part -for me- was to enclose the Delrin in a metal housing strong enough to attach to the saddle in the limited space available.
 
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ccolby

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Hi all, can anyone help me find a replacement lead screw nut for my lathe. I cant find any suppliers that list this part.
Its an old imperial machine and the thread appears to be 3/10 in diameter.
I do have another lathe so could possibly make a new one if i cant find a replacement.
Pics of the part...
View attachment 139291
View attachment 139293
View attachment 139296
View attachment 139297 It appears that Excel Machine Tools is still trading. Have you contacted them directly to see whether the nut is still available or whether they can email you a dimensioned drawing of this part?
 

Richard Hed

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Hi all, can anyone help me find a replacement lead screw nut for my lathe. I cant find any suppliers that list this part.
Its an old imperial machine and the thread appears to be 3/10 in diameter.
I do have another lathe so could possibly make a new one if i cant find a replacment.
Pics of the part...
View attachment 139291
View attachment 139293
View attachment 139296
View attachment 139297
I would just make one. Shouldn't be too difficult. Probably do as SmithDoor says. Can you send a photo of the screw?
 

Weldsol

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Hi there I take it you have tried these people ?
where are you in UK

Paul
 

Apprentice707

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I made an exact copy of a Myford nut in acetal for my Super Seven and fitted it in June 2013. I use my lathe most days and am pleased to say the backlash is less than 1 thou, which is far better than I have ever achieved with the genuine Myford monkey metal part. Luckily the Myford nut has a round body that is encased by the saddle casting. I am sure Darwenguy will come up with something.

Good Luck

B
 

terryd

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Hi all, can anyone help me find a replacement lead screw nut for my lathe. I cant find any suppliers that list this part.
Its an old imperial machine and the thread appears to be 3/10 in diameter.
I do have another lathe so could possibly make a new one if i cant find a replacment.
Pics of the part.........

Hi Darwenguy,

Try the guy who runs this website, he probably won't have spares but he may have some information on the threaad. I haven't dealt with him but many others have and apparently he is a great help most of the time and is very knowledgeable.


TerryD
 

djc

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If you zoom in on the manufacturer's plate, it says PL918. It is a generic 9 x 18 imported lathe. Waco used to make one among many others. The 9 x 20 lathe has superceeded it but many parts will be common. Online information about the later 9 x 20 machines is abundant. All are said to be copies of the EMCO Compact 5 or 8 (don't remember which).

3/10 inch corresponds to no standard imperial or metric size, so you will have to measure to a greater precision. It would also be helpful to measure the pitch of the thread. If you cannot do this, describe or photograph the dial on the end of the screw so we know how far it moves in one revolution.
 

terryd

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If you zoom in on the manufacturer's plate, it says PL918. It is a generic 9 x 18 imported lathe. Waco used to make one among many others. The 9 x 20 lathe has superceeded it but many parts will be common. Online information about the later 9 x 20 machines is abundant. All are said to be copies of the EMCO Compact 5 or 8 (don't remember which).

3/10 inch corresponds to no standard imperial or metric size, so you will have to measure to a greater precision. It would also be helpful to measure the pitch of the thread. If you cannot do this, describe or photograph the dial on the end of the screw so we know how far it moves in one revolution.
Hi djc,

the nameplate also shows that it is an Excel lathe made in Coventry in the UK (the original poster is UK based so it is more than likely that it is an actual Ecxel lathe as described here:


However the saddle and cross slide look a lot like the ones Emco used on their larger lathes such as the Maximat V10 etc. The guy at Lathes.co.uk has some spares so he may be able to help. It would help if we could have accurate measurements with a micrometer or vernier caliper and as you say, the pitch, if he can't manage that perhaps a photo of the broken nut alongside a metal engineers rule would help.

TerryD
 

timo_gross

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When I had a damaged ball screw nut, Instead of going mad trying to find the right replacement nut. I just bought a new brand name ball screw and nut.
The local dealer "copied" the end of the ball screw (step, bearing seat and thread ) based on the original.
I modified the nut to fit under the machine table.

Greetings Timo
 

djc

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...it is more than likely that it is an actual Excel lathe as described here:


I wonder if you have looked at that page yourself and considered the complete lack of similarity in everything but name between his machine and the machines shown there. The ones there are of a completely different generation and corporate set-up.

The current Excel machine tools are at: Home - Excel Machine Tools and sell the same imported machines as everyone else. Please have a look there and consider the likelihood that their business model will provide support and spares for a discontinued 1987 machine.

His best chance of success is either the brand name grandmother of the lathe, EMCO, or the current generation red-headed step-grandchildren, 9 x 20 imports.
 

Bentwings

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I would make a new one out of bronze.

Dave
Yes I agree . However there is a guy on you tube that has made an electronic lead screw . I think it was for the typical 10x 22” lathes quite innovative . I don’t have his site but think you find it by searching . It’s quite long series but very well detailed
 
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Hi djc,

the nameplate also shows that it is an Excel lathe made in Coventry in the UK (the original poster is UK based so it is more than likely that it is an actual Ecxel lathe as described here:


However the saddle and cross slide look a lot like the ones Emco used on their larger lathes such as the Maximat V10 etc. The guy at Lathes.co.uk has some spares so he may be able to help. It would help if we could have accurate measurements with a micrometer or vernier caliper and as you say, the pitch, if he can't manage that perhaps a photo of the broken nut alongside a metal engineers rule would help.

TerryD
Sorry, but the "name plate" is a sellers name plate, at least the Jet name plate had the Made In China legend in very small letters. That sucker is one of the generic 9X20 Chinese lathes. I know, it's a 918 in this case. But 920 is sort of the generic term for these machines, the Jet branded machine was a BD920N.

They are or have been sold by many different companies, although supplies seem to have dried up with recent events. In North America Jet, Enco, Grizzly, at one time Harbor Freight, I think Princess Auto, most of the catalog machine tool outfits, and just about every other tool importer has sold or still sells this model. The good thing is that being so common most importers MAY have replacement parts. I owned one of these machines for around 15 years, and own a Compact 5 CNC which I'm retrofitting to modern controls, so I have up close hands on knowledge of both machines.

Here's one version offered in the US.


The PRC 920 lathes are not in any way related to any of the higher quality machines other than general layout and dimensions. If anything, they take their design and manufacturing compromises from the lower cost Atlas lathes sold in the mid 1900's by several large retailers in the US.

The Chinese 920 models sold in the US typically (always?) have metric leadscrews and imperial dials, so you always miss dimensions on any good sized cut if you trust the dials. Replacing ALL the hardware with good stuff and adding a stiffening clamp down plate to the compound pillar is almost required before you can use the machine to it's fullest capability. I did some good work on mine, was glad to have it rather than no lathe, but am glad to have a different machine today.

A search on fixing and upgrading 9X20 lathes will likely turn up many options for sorting out some of the issues with these lathes.

In spite of shipping costs, it may be easiest to see if Grizzly has a replacement part available, they are a firm that has made at least a good effort to stock spares for the machines they sell. Odds are UK machine importers may have parts as well, just not folks I have any knowledge about. Shipping on one of your kits to the US wasn't unreasonable, don't know if that's true going the other way though...

I sort of recall that my cross slide screw was just a normal V thread with 1mm pitch, although I don't remember if the diameter matches any available taps. The cross feed dial was graduated to indicate 40 thou per turn, but a dial indicator would tell you a single turn was in fact 39.4 thousands of an inch.

If in a real bind, remember that you can lock the cross slide in place using the gib and gib screws, and control depth of cut with the compound. Everything else still works OK I think? This would allow you to fabricate a tap fairly easily using silver steel / drill rod. If you use it to open up an acetyl replacement you won't need to even harden it, and unhardened it would probably work fine for a single use in brass or aluminum. Don't be hesitant to give it a try, taps for limited use in normal V thread form are easy to make, I've made dozens of oddball taps over the years, after making the first one I had to wonder why I'd been so hesitant to try :)

Best of luck sorting it all out,
Stan
 

SmithDoor

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Yes I agree . However there is a guy on you tube that has made an electronic lead screw . I think it was for the typical 10x 22” lathes quite innovative . I don’t have his site but think you find it by searching . It’s quite long series but very well detailed
I have made few in pass.
I purchased a L/H 1/2" - 10 tpi acme tap just for lead screws.
Made job simpler.

Dave
 
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this nut can be made in brass - measure the minor diameter of the acme screw, make a brass piece whose outside dimensions match the damaged nut, then bore it to a little smaller than the value you measured. if you can't afford a tap, then notch the end of the acme screw for 2 or three threads and put a short taper on it, sharpen the notch and screw it (with a back and forth motion and lots of lubricant) into the brass and that will cut the threads. the steel isn't hardened but it is hard enough to cut brass once. you may want to taper the entry to the hole a bit also.

Or contact Chris at littlemachineshop.com and see if he has it, he imports a lot of stuff from China, or at least he used to.
 

pete

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Without question that's one of the off shore generic 918 lathes as Stanstocker has already said. But listing a single dimension of 3/10 is 100% meaningless. Measure the lead screws out side dimension at probably the most unworn area near the tail stock end with at least a good caliper, a micrometer would obviously be far better. Then provide information if it's a left or right hand screw. And if it's an imperial measurement based lathe, what the exact TPI pitch is or in metric if it's a metric lathe. Some of the off shore machines used a mixture of imperial dial markings with metric pitch screws. Maybe of less importance if your replacing both the screw and nut, but you should also identify if the original screw and nut is the proper ACME thread form or in some cases more standard 60 degree threads were used on some of the very cheap and poorly built machines. Your pictures seem to indicate it is ACME, but that also might be really excessive wear I'm seeing. So without any fairly accurate measuring, there's literally no way to be sure of what you have never mind recommend where any replacements might be found. Plus there's issues where the machines components and design were changed during the lifetime of it's production run. Parts produced for a newer or older lathe may or may not be even close to what any earlier or later lathes had.

By the looks of it, the OEM nut was cast iron and almost for sure very poor iron quality at that due to what appears to be a coarse grain structure. And given the lathe way score marks etc, that lathe has had a pretty tough life with poor maintenance and lubrication. So from those indicators it can be assumed the lead screw is also worn well past needing to be replaced. I'd say that today very few of the better machine tool manufacturers now build there own lead & feed screws or the nuts. They go to company's that specialize in producing those items. Even the skill and knowledge to correctly straighten feed screws after machining is a fairly complex process.

If you can't find direct drop in replacement parts? An added bit of back round information is required. Technically using the term lead screw for any slide being moved with a screw & nut is correct because that lead term describes a better degree of screw pitch accuracy and a known movement distance over each full or partial rotation of the screw that matches the dial markings. But that term also creates complications when searching for any replacement screws or nuts because most or maybe all manufacturers use the more descriptive term feed screw and feed nut. And in general, the lead screw and nut term is reserved for the lead screws and half nuts for the lathes longitudinal power feed or during single point threading in something like a user manual. It's still easier and you'll get better results during a search using that feed screw/nut description. Fortunately there are numerous specialty company's that do produce what the OP is looking for. Roton, SKF, Helix Linear are just a few of them. But I don't know who the better known manufacturers would be in the UK. One further issue the OP may face is his lathes lead screw appears to be fairly small in diameter. With those accurate measurements he would have to search through those manufacturer's web sites that give thread diameters, pitches, available screw lengths and nut over size dimensions to see if there even available in the correct diameter, length and pitch. If so? The matching feed nuts are machined by the manufacturer to be well over sized to allow re-machining to fit the required mounting design his lathe or any other machine might have. In the case of half nuts for example, those manufactures would expect any end user to machine the nuts out side diameter round and properly concentric to the internal thread and then soft or hard solder the bronze nut into something like a precision bored steel carrier. At that point you'd then machine the steel to fit the half nuts actuation assembly and then split it in half unless that oversized nut can be machined to fit on it's own. It's fairly involved and accuracy is very important, so only the OP can properly access if he has the required skills to do any of this. If not you'll need to find someone who does. There's at least some manufacturer's who offer machined ends on the feed screw to the correct length and diameters so it at least would be ready to go. That's also really expensive because your paying industrial prices for industrial quality machining and accuracy. But if the lathes head stock through hole is large enough to fit the feed screw diameter, then machining the feed screw to length and diameter on it's plain un-threaded ends could be done using the lathes cross and top slide.

Just in case it's not already obvious to some, any screw pitch and matching nut could be used. But not if you expect the longitudinal feeds and change gear or gear box settings for the correct power feeds or when single pointing a thread. So it's mandatory you accurately match whatever that lathe came with originally. Cast iron material for the nuts can and is used on a number of usually older machines because of the built in quality's cast iron has as a wearing surface. I don't know of any manufacturer using any alloy of brass to machine feed screw nuts from because of it's softness. There's vast difference between brass and bronze alloys, yellow metals despite there appearance are not equal and aren't interchangeable. The lead screws surface finish and environment those half nuts are expected to live in would have a very much reduced life span with any brass I know of. Bronze is chosen instead because of it's much better lifespan outweighs it's higher cost. Replacing both the nut and feed screw also gains you known alloys of each material that have proven to work well over long periods of time. So part of there cost is your paying for the correct materials science and mechanical engineering behind what your buying.

Edited to add, it appears I was mistaken and your instead talking about the cross feed nut. I'll leave it as I wrote it since most of that would still apply to the cross feed screw and nut.
 

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