# Broke my lathe PM1127



## Pcmaker (Nov 23, 2019)

I was swapping out gears to do some metric threading, did the usual insert paper in between gears before tightening everything. Turned the chuck by hand before turning it on to make sure everything's moving right

Turned on the lathe, it made some noise and before I could hit the stop button, I heard something fall apart. The gears fell off, thankfully not damaged, but found this part. It's the bolt that secures the change gears in place. It has a square head, with a button oiler on top. Snapped right off. 

I emailed PM and hopefully I can get the part soon. I have a 1 week vacation coming up and I had plans that involved my lathe. If my lathe was working, I could just make one up that would work, but I can't. One of these broken means no lathe work. Period. 

Does anyone know if these are common items I can order online for cheap? What are these even called. I've been having a hard time finding it on the diagram. I don't know how long for Precision Matthews to send me one and I'd rather buy a pack of these and have it arrive in time before my vacation.


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## darkzero (Nov 23, 2019)

Pcmaker said:


> If my lathe was working, I could just make one up that would work, but I can't. One of these broken means no lathe work. Period.



Lathe will still work to make one without change gears. Just means that you'll have no power feed.


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## darkzero (Nov 23, 2019)

Alternatively you can cut the rest of the broken threads off. Drill & tap it & stick a threaded rod in it. Could probably even get away with just a press fit & Loctite. Can just use a bolt with the head cut off for the threaded rod. May loose the oiler function but you could add that too if you wanted. At least that will get you back up & running if Matt doesn't have the part in stock.


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## markba633csi (Nov 23, 2019)

Sounds just like what I would do
M


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## Packard V8 (Nov 23, 2019)

Have you done an analysis of why it broke?  Your description indicates you set it up correctly, but do we think is was just old age did it in?

jack vines


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## Pcmaker (Nov 23, 2019)

I'm not exactly sure what I did, but I think I didn't tighten it enough and the gears moved while the lathe was turning.

As suggested, I drill and tap the broken piece with an m6x1.0 threaded rod from Amazon. My die can't start cutting into a 5.8mm rod for some reason. Probably all dulled out.

I hope I will be able to somehow get it in the lathe chuck to center drill and tap


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## Pcmaker (Nov 23, 2019)

I faced the part, then center drilled

I'm using a 4 jaw independent chuck, I"m gripping it by the square head. 

I'm having trouble with concentricity. I used an indicator on the end and got to .001, but the left side is off by .005. Not sure what to do to get it concentric

I need to get both sides close, I might have some issues when I start to drill and tap into it.


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## T Bredehoft (Nov 23, 2019)

It doesn't turn in use so concentricity is not needed.

I see, you're concerned that if it isn't concentric it won't also be straight. Yeah, holding by the square you run that chance. Hold it by the shaft if you can.


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## Pcmaker (Nov 24, 2019)

I'm afraid that while it's stationary, if it's not concentric, the gear won't be square to the banjo and will wobble slightly while turning


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## RobertB (Nov 24, 2019)

Pcmaker said:


> I'm having trouble with concentricity. I used an indicator on the end and got to .001, but the left side is off by .005. Not sure what to do to get it concentric
> 
> I need to get both sides close, I might have some issues when I start to drill and tap into it.



Instead of holding it by the square head, seat it deep enough in your chuck so the threaded section is in past the bottom edge of your chuck jaws and hold it by the round shaft. After you drill and tap it be sure and not seat your stud too deep so you don't block the oil passage.


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## Pcmaker (Nov 24, 2019)

I'll try that when I get home, but I'm not sure if my drill bit will be able to reach that far into the chuck.

An idea I was thinking of was to make a sleeve for the round shaft and make it thick enough that the chuck jaws will not be able to reach the threaded part. Then I add in a countersunk set screw to keep the part from spinning inside the sleeve

I hope your idea works because mine will require a lot more work to accomplish


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## RobertB (Nov 24, 2019)

A sleeve would work if you can't reach it with your drill. Instead of a set screw, just split the sleeve so it will squeeze together.


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## ttabbal (Nov 24, 2019)

I haven't tried it, but if you loosen the set screw in the adjustment nut at the top, I think you can remove it. That should make gripping the shaft easier. The oiler run through the middle of the shaft, so don't crank down too hard on the chuck or you risk crushing it. 

Then you use an indicator on the outside to get it concentric in the 4 jaw. 

Bummer about that breaking. I might have to make a couple for backups.


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## JimDawson (Nov 24, 2019)

First I'll offer an opinion as to why it broke.  Based on the position of the break, it looks like the stud was not screwed in all the way to the shoulder, so this would put enormous pressure on the weakest part of the stud, the threads.  The way that is made, it looks like it is intended to be screwed into the shoulder, tight, then the outer adjusting nut would be tightened to get the proper side clearance for the gear. In the picture is shows the adjusting nut at about the limit of its travel, and the length of the remaining threads showing is just about the length of the visible adjusting nut threads on the stud.

To dial in the stud properly in the 4-jaw.  You need to check both ends.  You state that on the left side you are about 0.001 and near the end it's around 0.005.  So put the indicator near the end, use a small hammer (preferably soft) to bump it into concentricity.  You'll need to work back & forth until you get it dialed in on both ends.


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## Pcmaker (Nov 24, 2019)

I had some success. I managed to get it drilled and tapped with m6 1.0, put my threaded rod in there and cut to length. Only issue is that, for some reason, there's a little bit of play when I wiggle it. I added red loctite, and put a nut on tight "pulling" on the threaded rod outward to straighten it while the thread locker does its thing. I think this'll work, and if not, I'll have to make the whole thing from scratch. I haven't heard from Precision Matthews yet but it's the weekend so we'll see. 

I'm hoping I can buy a pack of these things from them, as well as the parts that goes inside the gears that attaches 2 together.


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## Pcmaker (Nov 24, 2019)

I'm back in business. Everything is in working order. 

I have the gear arranged and set to thread 1.0mm

Does anyone know if it's normal for the lathe to be noisy if you have the gears arranged for threading? No matter what pitch, SAE or metric, my lathe is always noisy when the gears are arranged for threading. A lot noisier.


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## pdentrem (Nov 24, 2019)

Yes the gears will be noisy. If you place them too close together it is even worst. Use a piece of paper as a spacer between the gear tooth. Whether to use oil or grease is a personal decision. Grease tends to be quieter but debris can cling to it.


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## Mitch Alsup (Nov 24, 2019)

Grease the gear teeth.


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## Pcmaker (Nov 24, 2019)

pdentrem said:


> Yes the gears will be noisy. If you place them too close together it is even worst. Use a piece of paper as a spacer between the gear tooth. Whether to use oil or grease is a personal decision. Grease tends to be quieter but debris can cling to it.



I always use paper and setting up gears, kind of a pain in the butt actually

I should've gotten the PM1228 or PM1236...


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## Pcmaker (Nov 26, 2019)

Precision Matthews just sent me an email and they were nice enough to send me 5 of the bolts and they're also sending me 5 of the inner gear rings that hold 2 gears together for free.


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## Bob Korves (Nov 26, 2019)

Pcmaker said:


> Precision Matthews just sent me an email and they were nice enough to send me 5 of the bolts and they're also sending me 5 of the inner gear rings that hold 2 gears together for free.


Sounds like it might be a more common failure...


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## Pcmaker (Nov 26, 2019)

Bob Korves said:


> Sounds like it might be a more common failure...



Originally, they were going to send me the replacement bolt, I asked if it was possible to purchase a few of these items, and they said they'd send them for free.


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