I broke my Smithy (again)

[BGHansen]

Could you clamp the broken pieces together with a flat head head bolt (to give some working space outside the bolt head) and drill holes for brass pins?

Bruce

 

[WobblyHand]

Looks to me as if you could cut the NEW TOO LONG one in half and have two.

That's what I was thinking too. I'd use a slitting saw and slice off what was needed. If you get more than one more it's a bonus. But I'd be looking into making replacements as well. I'd try a 3d printed one for giggles. You do want it to be sacrificial, so the lower strength is not much of a downside. If it works, you can get it made in a slightly stronger plastic material.

 

[tq60]

It appears to be hollow.

Get a Dowell or other item in the midde then epoxy it.

The Dowell will snap so it can still break under stress.

It will work for now...a DOFUR...

Sent from my SM-G781V using Tapatalk

 

[Inferno]

I probably should have been more clear.
The machine uses two lengths of the same part. Last time I broke the long one. This time I broke the short one.
I am considering g turning this long one into two shorter ones to get me by for now. This gives me time for solutions.

The part is hollow since it goes on a shaft which brings up something I hadn't considered. This part spins on a shaft. So any replacement part has to be able to handle that as well. Direct plastic won't work without putting g it on a metal sleeve.

It's really a design flaw in the machine to not have a bearing in there of some sort.

The good thing, though, is that it won't be that important once the modification is done. Other than threading, the whole assembly will no longer be used.

I'm going to check out that website. Always looking for resources.

 

[RJSakowski]

Delrin is a fairly tough plastic and has good lubricity properties. Another thought for a material is to melt down some pot metal and make a slug. The melting temperature is fairly low and a mold can easily be made in some fine sand in a tin can. Machining would be simple if you have an RT or a spin indexer.,

If you ar using brass or aluminum, you could purposely add a break point to your design so that it fails in a controlled manner. A ,mid point groove comes to mind.

 

[Inferno]

Delrin is a fairly tough plastic and has good lubricity properties. Another thought for a material is to melt down some pot metal and make a slug. The melting temperature is fairly low and a mold can easily be made in some fine sand in a tin can. Machining would be simple if you have an RT or a spin indexer.,

If you ar using brass or aluminum, you could purposely add a break point to your design so that it fails in a controlled manner. A ,mid point groove comes to mind.

I have a bit of Delrin. I could machine that instead of brass. Without a oil impregnated blank, brass might not be a good idea. Aluminum is definitely out.
There's a bushing on Ebay I could machine down if needed.

 

[Inferno]

Well, I looked a little harder and I can still buy the longer one, it seems, so I cut the longer one in half using a hacksaw and the jaws of my lathe as a guide. The cut was pretty straight and will yield 2 shorter shafts.

I milled the rough edge to just 0.15mm shy of the 18mm I think the other one was (can't get a perfect measurement from a broken cast part). Why? Because it was a super tight fit before. It has room to move.

Then I filed the sharp edges and put a bevel on the splines, freehand.

After all that I went to fit it in the gears and the replacement part seems defective. One of the splines won't engage when the other three do. I tried all of the possible rotations and it just won't engage.
There's nothing too critical about the fitment so I'm going to hand dress the offending spline. It should be OK.

I'll be buying a pair of the long pieces soon in case they get discontinued also.
Also on the list will be a 4 jaw chuck. I had to do the bevels by hand because it's impossible to put this part in a 3 jaw chuck.



The bevel on the left is the factory one. The hand-ground bevel is on the right.


I'm still going to look into better options going forward because this is a mistake I've made 3 times, now. Two broken gears and a broken taper pin. You'd think I'd learn but I'm sure I'll make this mistake again.

 

[Heezea]

Just thinking out loud, but is it possible to pack out the jaws of the 3 jaw chuck to let it hold it?

 

[Inferno]

Just thinking out loud, but is it possible to pack out the jaws of the 3 jaw chuck to let it hold it?

Probably but on something like this, the effort just wasn't worth it. Plus, I don't have enough materials to be able to do that qquickly. I'd spend more time making shims than it's worth.

 

[Inferno]

Crisis averted.
After making a tiny adjustment to the factory fit it's now as perfect as can be. No more than 0.0015 slop without changing the center so it should work perfectly.