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How to connect rods with small holes

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PaulR:
For the current project (Stirling engine) I need to connect rods that have holes around 1.5mm diameter, for example the displacer rod and the link to its crank. The former is of tool steel, the latter I haven't decided on, maybe brass or aluminium. I think the fit will need to be quite loose.

I haven't got the equipment to thread anything of that size so I'm considering either 11 or 12BA screws and nuts (only in steel as far as I can see) but I wonder if 1/16" brass (or steel) split pins might be better. Any recommendations?

Jasonb:
If this is a wrist pin then I would make a bolt with just the end threaded for a nut*. M1.6 or 10BA if you can enlarge your holes to 1.6mm. Splitpins are seldom round so you may get a sloppy fit.

I sometimes drill one side of the clevis clearance and tap the other rather than having a nut

Charles Lamont:
If the two parts sit side by side, as a sort of lap joint, then the pin needs to be fixed in one member, otherwise the sheer forces on the joint will rapidly result in oval holes and a waggling pin. On the other hand, if one of the parts has a forked end, then the pin can be free to rotate in both.

 (Hmm, "Waggling Pin", is that, as they ask in modern parlance, a thing?)  :???:

PaulR:

--- Quote from: Jasonb on October 29, 2025, 08:49:31 AM ---If this is a wrist pin then I would make a bolt with just the end threaded for a nut*. M1.6 or 10BA if you can enlarge your holes to 1.6mm. Splitpins are seldom round so you may get a sloppy fit.

I sometimes drill one side of the clevis clearance and tap the other rather than having a nut

--- End quote ---
I haven't got the gear for threading these small sizes yet, that's why I was wondering about split pins but yep, I had a feeling they wouldn't be accurately round. I've done the same as you one or two of the previous engines when it comes to a clevis.

PaulR:

--- Quote from: Charles Lamont on October 29, 2025, 08:53:23 AM ---If the two parts sit side by side, as a sort of lap joint, then the pin needs to be fixed in one member, otherwise the sheer forces on the joint will rapidly result in oval holes and a waggling pin. On the other hand, if one of the parts has a forked end, then the pin can be free to rotate in both.

 (Hmm, "Waggling Pin", is that, as they ask in modern parlance, a thing?)  :???:

--- End quote ---
Yes, it's a 'lap joint'. I could make a pin (there room to enlarge it to 2mm) and Loctite that into the displacer rod half of the joint. I guess if it's long enough the other rod would find it's natural position and not wander off...

Waggling pin is definitely a thing now you've written it down  :Lol:

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