Machinists and mechanics, help please!

Guys, I’ve got a machine issue and I desperately need some help. I’m inches from the finish line on this project but I’m totally not knowing how to proceed.

I have a shaft that had 2 bearings on it. Both bearings were seized to the shaft. A replacement shaft is expensive, and would take time to get, and then they come with the bearings on so I may end up with the same problem when I try to remove the bearings. So the bottom line is another part is a risky solution. I’m trying to save the part I have.

I worked like a dog for 4 hours today removing the seized bearings. I tried pullers, heat, marinades, a press, etc, etch, etc. Finally, I had to resort to cutting the races VERY carefully with score marks and then breaking them off with a chisel. Unbelievably, I got BOTH bearings off without scoring or messing up the shaft. I couldn’t believe I managed to do it. The victory was so close I could taste it.

And then it all went in the sh!tter. Both ends of the shaft are tapped to receive a bolt. In the process of using a hammer or puller, I effed up the threads in one end. Bugger.

Okay, so normally I’d just retap the threads but here it gets weird. The bolts that go into the shaft measure 9.87 MM and have a 14 MM head. The pitch of the threads is a 1.25 MM. What the actual eff are these bolts?

So then I screwed everything up. I assumed they were 10 MM. I mean they are bigger than 9 mm. I’m measuring top of thread to top of the thread. So I tried to retap the thread to 10 MM X 1.25. It tapped fine, but then I ran the bolt in and totally buggered up the first 1/4 inch of threads on both the bolt and the shaft. The bolt just doesn’t fit.

Can anyone help me with what I’m doing wrong and what do I do now?

1. Any ideas about this weird bolt measurement? 9.87 MM. I’m sure of the thread pitch at 1.25, but is this a 10 MM bolt or something else? 10 MM bolts I have all mic out at 9.95 to 10.XX. Why the hell would these bolts be so small? The can’t be SAE, the thread pitch is wrong.

2. I only ran the tap in about 1/2 of an inch so I didn’t bugger up the threads in the entire hole (About 2 inches deep). I also buggered up the bolt threads, but again only about 1/4 inch of them. So I still have parts to work with.

Machinists and mechanics, what do I do now? Man, I’m going crazy after all this work, I’m so close but I don’t want to eff this part up. Ug.

If anyone happens to be close-ish and willing to lend in-person expertise, I’d gladly come to you with cash, beer, whatever. I’m in the east metro, but I’d gladly come to anyone willing to help.

Many thanks guys.

Grouse

If you have enough room drill it out and run a 7/16 tap in it.
The machine won’t care if it has sae or metric bolts in it.

If you are stuck on metric,put a heli-coil in it

A standard M10 should have a 1.5 pitch. I’d double check pitch

Check the pitch with a caliper over 1″ and divide it up. Or lay a 1.5 and 1.25 pitch bolt on top of the original bolt and see what mates up.

I would go with Iowa boys idea. My guess is you had sae threads by mistake. Some metric sizes and standard sizes are so close to each other that it is hard to tell the difference.
On the plus side when it does happen it makes a great lock nut.

PM sent

Craig Sery wrote:

A standard M10 should have a 1.5 pitch. I’d double check pitch

“standard”? is that a technical term?

Metric bolts have both a coarse and fine pitch series, similar to SAE bolts having coarse and fine pitch.

A “standard” fine pitch M10 is a 1.25 pitch.
A “standard” coarse pitch M10 is a 1.5 pitch.
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TheFamousGrouse wrote:

So I tried to retap the thread to 10 MM X 1.25.

Grouse, did you lay the tap up against the bolt to see if the thread count was the same? Did the threads on the tap and the threads on the bolt “mesh”?

Are you sure it’s not M10 x 1.0? Odd I know but do exist. also available M10 x 0.75.

Grouse, just a suggestion, next time you have to pull a bearing or whatever and you encounter internal threads at the end of the shaft like that, take another bolt and drill a pocket dead center of the bolt head, just deep enough so your puller will center in that pocket.
Screw the bolt in and pull against that instead of the shaft itself.

You could up size like others have suggested. One other option providing you have over a 1/2 of internal thread is to simply drill out the damaged threads with a 3/8 bit. (For maximum bolt strength you need 1 1/2 of your thread diameter in length.) This assumes your existing bolts are in good shape.

FYI. I just went and measured an M10 x 1.25 bolt we have in stock at work and here is what it measured.

Hopefully you have the correct pitch and just running the tap in there will help. If the tap decides to start cutting without aligning to the existing threads you could wipe all the threads out of the hole. It’s just a gamble. At least you should have the option of doing a heli-coil if that happens. McMaster carries them for M10 x 1.25.

I checked to see if we had a kit for this on hand but unfortunately we don’t. Otherwise I’d tell you to run it up to Andover for a quick repair.

Got any pictures of the situation? Just curious of what you’re working with here.

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Update for everybody.

IDO to the rescue. A very gernous forum member bailed me out completely.

My HUGE thanks to Andy. He picked up the part, rethreaded the end that was messed up, procured bolts and the whole thing was done before noon. Is he awesome or what?

So a little bit more on what was actually going on.

My measurement on both the bolt size and thread pitch were correct. It actually was a 10MM bolt X 1.25 threads.

Sheldon was absolutely correct, I hosed up the first thread when I used the puller, so tip of the day award belongs to him regarding how to protect that thread. I NORMALLY would have put the bolt back in the hole to center the puller on, but I was too worried about breaking the head of the bolt and then having a busted bolt stuck in the hole.

Regarding metric thread pitch, just an FYI for those that deal with this stuff a lot. Metric comes in 1.0, 1.25, and 1.5 thread pitch for many bolt sizes. The most common are 1.0 (fine) and 1.5 (coarse), but 1.25 pitch is hardly rare and in most cases hardware stores carry all 3 types, so when it comes to metric you really have to watch your thread pitch.

IDO to the rescue once again. Thanks a lot guys! Appreciate all the replies.

WTG Andy

to Andy!!