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Understanding the change gear axles on the PM1127

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ColdGarage

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I bought an 1127 recently and have very slowly been getting familiar with it. I recently had my first attempt at threading, which was semi-successful. However, I'm not sure I'm changing the gears correctly. In particular, I don't understand exactly what I should be doing with the retaining nut that threads onto the axle. They're little round slotted nuts with a grub screw. None of the tools that shipped with the lathe seem to work with them (although the lathe did come with two hook spanners that I've yet to figure out a use for).

When I put the gear couples on the rail I first tightened the axles into the T-nuts. Then I threaded the retaining nuts on to the axles. You can't tighten the nuts down fully or the gear won't turn, so I tightened them until they were barely tight, backed them off a little, and then tightened the grub screw down (a rather awkward operation). Am I doing this correctly? The grub screw is quite little and it's tightening onto the threads of the axle, so I can't believe it has much power to prevent the nut from turning. And why is this such an odd nut? Why not simply use a hex nut with a grub screw or even just two jam nuts?

I have to be missing something here, but honestly I don't have a particularly strong mechanical background. My google skills have lead me to discover that this kind of nut seems to be used for gear retaining, but I don't understand what's special about it.

As a side note, how long does swapping gears usually take you? The thought of having to deal with changing belts and swapping gears every time I want to do threading is a little daunting.


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ttabbal

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They are a little weird... Took me a while to figure them out as well.

You should be able to pop those out of the sleeves in the gears. You don't need to remove the set screw thing on the top. The setup is so you can adjust the nut on the top so that when tightened on the T-nuts, the gears spin freely without a lot of play. Dial that in, snug the set screw, and then leave them alone. You use the square drive on the top to drive them. There should be a little driver that looks like a chuck key in the tool box that will drive them.

When changing the gears, I do this..

Loosen the quadrant bolt and lay it down.

Loosen the 2 outside gears with the little square drive key.

Remove the gear sets and use a hex key to get the last set.

Push out the square drive axles. It might take some work the first time. I drilled out the sleeves with an X drill. It makes them a snug fit but still easy to remove.

Push out the keyed bushings/sleeves from the gears. This was difficult for me the first time and I ended up filing the OD down to get them to fit. Test frequently, you don't want them sloppy.

Wipe the gears off, and reverse with the new gears to install.

It takes a while to change the gears. With the cleanup I did on the parts, I can do them in about 15 minutes. I suspect that time will drop as I do it more. I try to hold off on threading until I can do a few at a time so I'm not constantly swapping between feed and threading gears. That's not always possible, just depends on the parts you are making. Using taps and dies for some of the smaller threads also keeps you from having to swap gears as often.
 

ColdGarage

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Thank you. I guess if I had used my head a little I would've realized there's no reason to remove those retaining nuts. I had watched a YouTube video of someone changing gears on a different lathe and they did have to remove them, so it didn't even occur to me to just leave them in place. Oh well... learning new things, I guess.

Fortunately for me, I didn't have any trouble tapping out the axle or the bushings and I was able to get them into the new gears just as easily.

Honestly, I could have used a die for the threading job at hand, and I probably should have. I was mostly interested in the learning experience. That said, yeah, I think I will approach future projects strategically to avoid changing gears. I only get a couple hours per evening as it is to work in the garage.. I don't want to spend half of it fiddling with change gears.
 

ttabbal

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That's pretty much the same with me. Limited time, so plan operations to be efficient. At least, that's the goal. I won't go so far as to say that I always achieve it. :)

Nice to hear that some of the bushings are the right size. Hopefully they have that sorted out now.
 
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