Clausing 5903 Crossfeed Screw repair.

[Tim9]

I ordered a new Acme 5/8”-10 LH threaded rod from Roton Products. Finally getting around to making it work on my 5903 lathe.
The threaded screw has a dowel pin which attaches it to the Crossfeed dial. The biggest issue is that there is a raised part of the Acme thread which is a bearing surface for a bronze bearing in the housing. Anyway, the diameter of this area is 0.62445
cant show a pic of micing it because I only have two hands. But digital Mitutoyo mic gave me those specs. No way would I get that with my other mechanical mics.

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[Tim9]

My plan is to use the Clausing to cut down the threads on a portion of the new threaded rod, and then make a bronze bushing to have that part which is .62445

This is going to be more time consuming than I want, but I’m just not at all happy with the way my little South Bend lathe has been performing. Something is wrong with that lathe too.

 

[Tim9]

So I disassembled the screw.... took a bunch of measurements with some poorly drawn prints I made..... put the screw back together and installed it on the lathe. Then I chucked up the screw. Here’s where I went down a stupid rabbit hole again. I forgot I had some ER25 collets which go up to 5/8”
So I tried to use copper protectors on the Acme Screw. Big fail . The last pic is the “completed” bushing mounted in the ER collet which is surely much better than the soft copper spacers. . I used my Best Test and miced the inner bore. While rotating.... 0.008 out of round. Damned thing would bind when trying to turn the Crossfeed if I left it like this. So....starting over. As an afterthought.... if I didn’t have the collet, I probably could have wrapped some 10 or 12 gauge bare copper wire in the threads. That might have worked better.

 

[Tim9]

As you can see in the last pic above... I even made a Delrin bushing to hold the back of the screw centered.
But the copper jaw protectors were a fail. I turned a bushing bore to specs and I had turned both sides of the bushing. Then Loctite on the screw in the middle pic with a tailstock live center which I had hoped would do the trick. But when I check for out of round, after waiting for the Loctite to dry....... my inner diameter was wobbling 0.008

 

[Tim9]

That’s when plan B.....er25 collets and collet chuck. Just amazing how one false start gets a poorly thought out plan put into action. But I’m thinking that the collet
will make a huge difference.

 

[Tim9]

I think the final diameter of the screw after turning the threads off, was something like . 4330
i made a little test bushing so I’d end up with a real tight fit for the bronze bushing to new screw. This worked great. I ended up with a super snug fit. Nice popping sound when putting on then pulling it out. So Loctited it with red Loctite and stood up so Loctite fills all gaps. Really hardly any gap in my opinion. Tomorrow I’ll drill and pin the threaded side of the bushing which is Loctited. Then turn outer diameter to accept gear and make that raised mating surface of 0.62445 And then the end to accept the gear which is 0.59595
and also bore it 0.43735 to accept the dial end.
Tomorrow I’ll also disassemble the original screw in the lathe....measure some more to double check my specs... before I try turning the other end of the bushing. Just want to make sure I’m on the right track. Like I said.... my crappy “prints” even have me guessing on a couple of the spec. Anyway.... the design is a little odd because the gear has to slide over the bronze bushing and the shaft of the dial end the slides in it. A dowel pin locks all three parts together.

 

[Papa Charlie]

Nice work, that ACME thread was a bit on the worn side.

 

[Tim9]

Nice work, that ACME thread was a bit on the worn side.

Yeah Charlie. I was getting like 0.070 backlash most of the time. Tomorrow I’m hoping all goes smoothly. Need to bore the other side of the bronze.... turn outer diameter two different specs, and then drill for the pin. And have to dill pin to line up with the hole in the dial side of the Crossfeed. That’s going to take some thinking before I screw the pup.

 

[Alcap]

I'll be following your repair since the lead screw on my 5914 is worn too . I also saw the replacements made on ebay and figured that would be the way I would go if it got worse but maybe reading your thread will give me confidence to try making one

 

[Tim9]

Alcap. If it goes as planned.... other than the first screw up.... it’s not too bad. My two big mistakes.

first.... must have the screw in the collet. The copper just won’t get the screw centered properly. Especially since it’s 24” long. So the back end inside the spindle is causing the screw to drop in the back and then high in the front. I didn’t show it yet. But because on the first fail I ended chopping a couple of inches off.... Now the back end of the screw doesn’t come out the other side of the spindle. So I made a Delrin bushing.... 1-3/8 outer diameter and a tight fit for the Acme screw on its inner diameter. I kind of pushed that bushing in the spindle so it’s supporting the back side.
If I were to do it again....I’d buy a 3’ length of Acme screw so I would have hang out on the back side of the spindle which can then be supported with a spider or bushing.
My second screw up was trying to turn the bushing and then mount it on the shaft. This time...I bored the bushing to the smallest diameter to accept my small boring bar....in which I can then bore to final diameter. But it’s not bored to the .4330 yet. I’ll be boring it to the .4330 which is the size of the shaft of the dial end of the Crossfeed .... only after the bushing is mounted on the screw. And I’ll size outer diameters also only after it’s mounted to the screw. This should give me a closer to needed final product.

like I mentioned earlier. The first try was very poorly executed. I turned the bushing separately (or coupling ) to specs and then mounted it on the turned shaft of the screw. That added another unnecessary error in my opinion. Much better mounted to the Acme thread shaft and then turn to specs.