Atlas TH42
#1
Hello all, new to having a lathe, I recently purchased an atlas th42 which needed some work, I've taken the apron and cross slide off to rebuild but also the power feed doesn't work. Inside the gearbox to switch direction of the lead screw, is the Selector supposed to be keyed to the lead screw? Nothing from the gear end is keyed to the shaft so I can't see how it's supposed to turn, the only thing I presume should be keyed is the Selector shaft. I'm not sure how to upload a picture here to show you. Thanks
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#2
https://www.dropbox.com/s/488s48uefydhv6...0.jpg?dl=0

The part circled in this picture, is that supposed to be keyed to the lead screw? Thanks
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#3
They don't show a great amount of detail about the lead screw in the parts breakdown I found but I am guessing that shift collar (9-50A) has to be keyed or splined to the lead screw. Also note that the left drive gear (9-48B) appears to be pinned to the stub (9-52A). That is possibly another shear point as well. Taking it apart should reveal all.

   
Willie
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#4
(12-28-2019, 12:31 PM)impman76 Wrote: I'm not sure how to upload a picture here to show you.

Here you go: Attaching Pictures
Ed
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#5
That's Brill thanks, I'll have it apart Monday and see what's going on, hopefully it's just missing a keyway as opposed to broken, parts seem to be a pain to come by!
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#6
I have taken it apart, the Selector sleeve is indeed keyed to the lead screw, by leaving the bolts loose in the opposite end bearing it rotates fine now, I believe it has a slight bend in the screw, however when I engage the power feed it stalls the screw, like the load is too much, same happens if I tighten the end bearing, should it stall if too much load is applied? Seems odd as surely taking a deep cut on power feed would be quite a load? Not sure what to do next, thanks
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#7
It sounds like you didn't actually remove and disassemble the reverse gear assembly from the lathe, so all I can offer is this. It seems to be either a key or the pin has sheared off in your gear set. The fact that the lead screw started turning at all was a result of friction between two parts instead of being solidly connected via the key or the pin. I am assuming that key is an integral part of the inside of the collar and not a separate piece, as in molded in to the collar itself. (Zamak?)

Questions:
Are the dogs of collar fully engaging into each end of the drive gears? (Power is transmitted to the lead screw through different paths depending on the direction.)

With the lathe running and the lead screw is 'stalled' can you see if the drive gear (9-48B) is turning or not?

If you remove the collar (completely) can you see a fully formed key sticking out inside the bore?

It's actually a pretty simple mechanism, but you are going to have to take apart in order to fix it anyway. Like 'Nike' says... Just Do It!   Smile
Willie
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#8
I only had a few minutes so I didn't pull the whole thing off, yes when the lead screw stalls as does the first gear of the "diff" however when the lead screw is out and the change gear is removed I cannot turn the diff gear separately to the shaft, feels pretty fixed and everything engages fine, I'll see if I get time tomorrow to have the whole lot off.
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#9
After doing a little more searching I found a video you may find helpful. https://www.youtube.com/watch?v=gwg232nf_e8

Toward the end of the video I was finally able to get a look at one end the end of shift collar. The 'key' for the collar is actually one of the dogs that is oversize (extended) more than the rest so that it slides into the keyway on the lead screw. I'm guessing you'll find that dog has been sheared off most likely. Personally I would still check the pin on the drive pinion though. Even though it feels secure it could still be cracked or partially sheared. Smiley-signs003
Willie
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#10
I highly recommend obtaining the parts manual for your lathe as it will make restoration/repair much easier.  If you do not have one I found this source:  https://ozarktoolmanuals.com/ozarkshopta...craftsman/

No connection to the seller.

I'm also certain there are other sellers of the manual and probably one or more in merry old England which would eliminate customs and international shipping.
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