Sourcing a feed screw

[Darkbreeze]

So, sorry if this isn't the best area to post this question, but it seemed fitting.

I recently aquired a Snap On (Kwik Way) model 102 brake lathe and it seems the Crossfeed (Rotor) feed screw has a bad spot and catches every so often. Kwik Way is apparently no longer supplying parts for the model 102 or 104, or any other machines, which means Snap On has no source for them either. (Go figure, the local truck rep assured me, although I didn't get it from him, that Snap On would have parts available for this machine, pfft. Right.)

Anybody have a good recommendation on who I can contact in regard to potentially having a new feed screw fabricated, or whether somebody might have an idea if this is a more common screw potentially used in some other applications? I don't mind paying a fair price for the part, even if it requires somebody custom fabricating it as a one off, but it needs to be the real deal with a good quality final product. Any ideas are much appreciated.

Feed screw OE part number is 102 (or 104, depending on machine, but both are the same part) -1026-50 Assy, Crossfeed Screw RH

Thanks.

 

[matt_i]

Can you find (visualize) the source of the bind? Its probably a slight damage or even could be contamination in a certain part of the threadform. Many many times those issues can be repaired with a small file, just to dress down torn and folded metal.

Another tool is to clean everything up very well and then mark the offending spot on the male thread with a sharpie marker. Where its solid metal-on-metal bind, it will scrub off the sharpie mark and you know exactly where it needs to be relieved.

Theoretically a machine shop can make what you need, if its a 60 degree V-thread then probably no big deal if not too long. If its an acme or buttress thread then the price is going to escalate rapidly. Much easier if the rolled thread can already be located as a piece of threaded rod, and just the length and end-forms have to be cut.

 

[bbcc]

I wish I could help more but without hard specs on size and thread profile it's tough to make any solid recommendations for replacement. I can point you towards IGUS and the old standby McMasterCarr as potential candidates.

 

[MBfreak]

Hi.
Some feedback from restoring a soviet era PROFILA 1K62 lathe. Big, heavy, awesome build and very accurate
The machine was used in a maritime repair shop here in Sweden for 25 years and then slept in a shed fr 15 years.
We restored it totally and the only part needed replacing was the cross feed screw-It was worn down i the area most used, play was more than 0,3 mm.
It is a 26 mm dia threaded part with "rectangular" thread profile with 5 mm pitch. DIN standard 100 %. It rides in hard brass adjustable nuts so backlash can be set to almost zero.
We found a supplier selling 1 m long ground and hardened stock. Less than $100.
We machied it to be adapted to the non threaded shaft part, shrink fit and conical pin joint.
Good as new.
Try to find out the standard your was made to and do something similar, unless it is local damage that can be repaired.

Best of luck

Ola

 

[Darkbreeze]

Thanks for the replies everyone. I'm going to be doing the tear down sometime in the next two days, and I'll post back here with what I find, which might make sourcing a part or knowing what the next step needs to be a much easier or at least clearer, process.

 

[larry_g]

IF that is standard acme thread then BBCC has the correct answer, Buy standard stock and then turn the ends down to fit bearings and retaining nuts. However I would not go there until I had disassembled the the carriage and checked all the bearings and slides to rule them out as a problem. Have you taken anything apart yet to confirm that something else is not at fault?

lg
no neat sig line

 

[Darkbreeze]

"I" haven't. I'm in the process of doing that, as time permits around paying work. LOL.

The person I purchased it from supposedly did. However, they also indicated they had replaced the drum feed screw recently, which, while IT works fine, doesn't look like it's been recently replaced. Could be they replaced it with a used one or that it simply has seen more use since that was replaced than he was letting on, but he indicated that there were visual boogers on the rotor (crossfeed) screw. I really don't think he had it apart but I could be wrong. As I said, once I get it out I'll post back here and see what you guys think. Thanks.

 

[ttpete]

I'd check the screw for straightness. If there's a slight bend it can bind when it goes through the nut. If it's minor a little work with a press and V-blocks can straighten it out.

 

[Marctrees]

This is way past my experience, but it really seems to me you should be able to smooth out the defect, whatever it is, rather than start from scratch.

Or if not, submit the problem to a smart tool/die kinda guy. Marc

 

[gte718p]

I have yet to run into a feed screw I couldn't replace with McMaster Carr. The problem becomes identifying the screw when a manufacturer uses some arcane pitch and size combination.

The place to start is taking some measurement of the screw.

 

[kbs2244]

Threaded rod is a common industrial supply item.
The OEMs buy it by the 10 foot piece and cut/shape it to their specs.
Measure what you have and you are on your way.

But check for a burr or bend first.

 

[larry_g]

Or if not, submit the problem to a smart tool/die kinda guy. Marc

Are you saying the tool and die guys here are not SMART?

lg
no neat sig line

 

[Darkbreeze]

Off topic, but I gotta say, I've been checking out the, rather long, E-tek 56 Chevy truck thread. That guy is pretty good. It's pretty damn nice work.

Anyhow, back on topic, the tear down is done and it seems, so far at least, that the entire question I posed is moot because I can't see a damn thing wrong with the crossfeed screw at all. No nicks or buggers on the threads, rolls perfectly flat on a piece of 3/8 steel plate and on a known flat piece of safety glass. My machinists rule doesn't see anything bent about it either.

There was however about a half teaspoon of metal shavings in and around the valley that the feed screw rides in, some portion of which was definitely ON the threads of the feed screw and I'm guessing there's a good chance that it was likely to have been causing the intermittent bind when a spot with debris would run up against and into the feed screw nut. I decided since I've gone this far I might as well disassemble the entire machine and replace one of the roller chain pulleys that I can see has aggressively worn on one side of each tooth, and clean up all the other pulleys as well as replace the chains and belts.

I imagine I'll go through the whole works in the next couple of days and get back to you guys if I encounter any issues since it's clear to me that I came to the right place with my question as many of you have significant knowledge in the area of industrial or mechanical machinery beyond what I can claim. Thanks for all the input so far.

 

[gte718p]

Shavings are coming from somewhere. I would install the cross slide without the feed screw and make sure it is not binding anywhere.

 

[Darkbreeze]

Shavings are coming from somewhere.

Heh. LOL. Yeah, it's a brake lathe, shavings are coming from EVERYWHERE. The crossfeed screw runs directly perpendicular to the mounting location for rotors and drums, so it's impossible to entirely keep minute chips from getting in there as designed. I think I'll try to fabricate some additional skirting to redirect anything that might fly that direction.

The cross slide moves freely across the end plate, and aside from the feed screw and feed screw nut, there's nothing else that could bind on the crossfeed assembly. It's possible the problem is at the other end of the lathe, but the drum feed assembly works fine so I am doubtful of that. I'll definitely look at that possibility though.

 

[DenisG]

I'm not familiar with your machine, but many lathes have gibs to eliminate play on the ways for the cross feed and carriage. Google "lathe gib adjustment" to see if that addresses your problem.

 

[kbs2244]

Is there maybe some sort of brushes on the screw option on the housing openings to keep gunk from getting in?

 

[Darkbreeze]

No brushes. There's a skirt on the business end but the back end is open when the slide is all the way forward, to the point where you can see a bit of the feed screw and the feed screw valley. That's why I'm thinking some kind of leather or other type of skirt on THAT end that doesn't allow the valley to be exposed at ANY point in it's travel might be a good idea.

The nutted end of the feed screw is only accessible from the bottom of the end plate, so again, doubtful anything can get in that way. Pretty sure metal flakes can only get in there one way, and that's through the top of the valley when the cross slide is all the way forward as when beginning a cut.

And actually, maybe not even that, as now that I think about it, seems there IS an accordion style skirt that mounts over that valley. Forgot about that as it was one of the first things I took off. Kinda baffled now how debris can get in there but I know **** has a way of finding it's way into anywhere you don't want it to, regardless of what it is. That includes dirt, mice, kids and flakes of metal, among other things.

 

[Dr Stan]

On engine lathes virtually all feed screws are Acme threaded since about WWII. Have not repaired a brake lathe so I'm not sure about the thread form.

In any case I've purchased Acme threaded rod from a supplier in or near Racine Wisconsin. They make all sorts of rods with different thread forms, L & R handed, single or multiple leads, different materials, etc, etc. You may want to Google "threaded rod racine" and see what pops up.

 

[Darkbreeze]

Nice, I'll look into that because regardless whether the feed screws need replacement now, or not, they will at some point, so I might as well figure out where I'm going to get them. Thanks.

 

[Darkbreeze]

So, just thought I'd come and post some pictures of the project and results. Thanks to everyone who chipped in with some advice.