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Well I guess I’ll be taking my lathe saddle apart now.

At the risk of offering advice, what about milling off the damaged portion and drilling and tapping into the end of the shaft to accept a new shaft for the gear?
There's probably a load of other ways to fix this, and I'm sure that our more experienced members will be along with different options.
 
This is a reason why many people have two lathes. So if one goes down you can use the other one.

Otherwise you have to re-assemble your lathe, make all parts you need and then de-assemble, fix and re-assemble again - lots of work.
 
Redneck_Sophistication said:
The end of the shaft you can see two different grain structures in the break. Really tempting to weld or otherwise try and repair this :/
Click to expand...

The two different grain structures along with some minor discoloration is what caught my eye and caused me to think fatigue was at play. But after your close up photo, it obvious that it is a torsion failure. The two different structures are not really different. They just have a different failure direction because the two quadrants dissected by the pin result in different force distributions. The grain is the same, the fracture surface just looks different because of the direction.

We machinists all have different welding skill sets. Personally, I wouldn't even think about welding that shaft. If I couldn't find one, I'd make one.
 
Susquatch said:
The two different grain structures along with some minor discoloration is what caught my eye and caused me to think fatigue was at play. But after your close up photo, it obvious that it is a torsion failure. The two different structures are not really different. They just have a different failure direction because the two quadrants dissected by the pin result in different force distributions. The grain is the same, the fracture surface just looks different because of the direction.

We machinists all have different welding skill sets. Personally, I wouldn't even think about welding that shaft. If I couldn't find one, I'd make one.
Click to expand...

I would also make a brand new shaft. Running in my mind through how I would do it - proper v cut, weld it - I realize that you would need to turn the shaft on the lathe to remove extra weld material and drill out for the pin. Also both parts of the shaft would be distorted a bit by welding process so if this goes somewhere precisely you would have a problem as well.

This certainly requires more skill the average welding - you need to have experience in shaft repair.
 
@Brent H is a two hour drive from you. I'd be tempted to see if he would be willing to take on making a new shaft and pinion gear for you.
 
I do understand the complexity of welding a shaft and the issues it could create. It’s just tempting.

Here’s another bad idea:

Amongst a couple boxes of tooling I’ve bought I found this indexing pin?? It is polished and exactly .500, the same as the shaft end.

I could mill off the broken end of the shaft, drill a half in hole (I’m sure I have a .500 reamer there’s a ton in the one box) drill though and pin this shaft into the main shaft and pin the gear on.

If it works I could make a new shaft on the lathe to have in reserve if it fails in the future.
F9DE7D00-D4C1-4429-8089-ADB655BCDBCD.jpeg
 
Redneck_Sophistication said:
I do understand the complexity of welding a shaft and the issues it could create. It’s just tempting.

Here’s another bad idea:

Amongst a couple boxes of tooling I’ve bought I found this indexing pin?? It is polished and exactly .500, the same as the shaft end.

I could mill off the broken end of the shaft, drill a half in hole (I’m sure I have a .500 reamer there’s a ton in the one box) drill though and pin this shaft into the main shaft and pin the gear on.

If it works I could make a new shaft on the lathe to have in reserve if it fails in the future.
Click to expand...

In my opinion, that's better than welding the old shaft at the break.

But you already have some rack gear damage and you didn't damage the saddle. What will you do if your weld job fails and does much more damage the next time around? I dunno. I really think a new shaft makes more sense. Have you evaluated the shaft hardness and material properties yet?
 
Redneck_Sophistication said:
Craig. 100%
My original plan was to put a call out to the forum for who’d could make me one for cash.

Since there is no finding parts for this thing anywhere!
Click to expand...
Craig seems to know where you are. He is kind of like the grand wizard or seer for all things like that. I'm a mere mortal. Roughly where are you?
 
Susquatch said:
Craig seems to know where you are. He is kind of like the grand wizard or seer for all things like that. I'm a mere mortal. Roughly where are you?
Click to expand...

It ain't rocket science LOL.... Look at his intro post.

canadianhobbymetalworkers.com

Greetings from Hamilton/Cambridge area Ontario

Hello all, been building welding and fabricating for most my life. Always wanted to get into machining and damn Abom79 and CEE on YouTube have been pushing me. So I looked and few weeks back found a millwright who was moving and bought his rebuild Bridgeport and lathe, the lathe was actually...
canadianhobbymetalworkers.com canadianhobbymetalworkers.com
 
Craig is sorta omni present around here isn’t he?

I’m in southern Ontario, Hamilton/Cambridge area. Near the lions ;)

I haven’t evaluated the steel at all, nor have anything to do so.
 
YYCHM said:
It ain't rocket science LOL.... Look at his intro post.
Click to expand...

Actually, yes it is. To find that, you have to remember it or at least know how to find it. You are being too modest. I don't remember things like that but I do remember those folks who do. (Don't ask me to explain that.) It's been my observation that you have some kind of superhuman ability to remember who said what when. So ya, it might not be rocket science, but it is definitely amazing, admirable, and impressive! Go Craig!


Redneck_Sophistication said:
Craig is sorta omni present around here isn’t he?
Click to expand...

Yup, he is!

Redneck_Sophistication said:
I’m in southern Ontario, Hamilton/Cambridge area. Near the lions ;)
Click to expand...

Lions? You have lions there? JKg..... I know all about Hockey!....... LOL!

There are lots of machinists in your area who could help you. Sniff around a bit on other posts and maybe send out a PM as appropriate. We all like to help.

Redneck_Sophistication said:
I haven’t evaluated the steel at all, nor have anything to do so.
Click to expand...

Easy to do a rough evaluation with common tools. Google steel identification - grinder test, file test, torch test, hardness test, acid test, etc. You will be amazed at what you can learn with very simple tools. Might not be as good as a metallurgical lab could do, but it would give you a rough idea of what you are up against. My guess looking at your photo and the application is that it's nothing exotic.
 
Redneck_Sophistication said:
I could mill off the broken end of the shaft, drill a half in hole (I’m sure I have a .500 reamer there’s a ton in the one box) drill though and pin this shaft into the main shaft and pin the gear on.
Click to expand...
For best results, the drill, bore & ream should be done on a lathe as it will be hard to hold that long shaft on a vertical mill. One would want the insert to run as true as possible to the rest of the shaft. Using the same size pin as the original one will give the same shear strength to the finished shaft as you had before it broke.

If your pin is not hardened, I’d use it as an insert in this repair; it is already to size and just needs two cross holes for pins.

I’d even try to salvage the gear for the time being. If you can file the damaged teeth there is probably enough left of them for engagement on the rack. Just clock it such that the two damaged areas (the one on the gear and the other on the rack) do not coincide as the carriage is traversing. This is not a high speed set-up and you should get away with quite a bit of tolerance.
 
Redneck_Sophistication said:
I’m in southern Ontario, Hamilton/Cambridge area. Near the lions
Click to expand...
Near African Lion Safari? My daughter has been working there the last couple of seasons.

I'd be glad to help if I can. I'm not entirely clear what problem part looks like, exactly. A hardened shaft is outside my scope, but I can probably muddle through a reasonable size piece or any regular steel.

Craig
 
I'm assuming metric components? Once upon a time I had to get some metric gears, some of which were less common. I was aware of McMaster-Carr in the USA but unsuccessful convincing them I was the Purchaser for a large manufacturing firm or educational facility. I found exactly what I needed at Maedler in Germany which was actually cheaper & they shipped to Canada. Recently I discovered they now have a USA based N-AM outlet & will ship. Maybe check them out along with other options. There may well be Asian sources too, lots of metric but not so much imperial. Good luck.

Maedler North America – Maedler parts for sale in North America

maedlernorthamerica.com maedlernorthamerica.com
 
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