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Glenn Brooks wrote: ↑Fri Jul 27, 2018 10:19 pm
John, it strikes me you could put helicoils in the bronze worm gear in lieu of drilling and tapping on top of the interface. Certainly if your attempts to tap the hole go awry, you could use the inserts and do just fine, I think.
Glenn
I'm not sure how that would solve the problem. Even the helicoil needs a threaded hole to screw into. I have managed to find ways around this type of situation so far, but is it possible that an over-sized round hole could be bored in the correct location and then a steel or bronze bushing could be pressed in and threaded?
I know it isn't always going to be acceptable, but in some situations like this, could a smooth bore be made in one material and a threaded hole made in the other, then excess material removed so that what is left is half of one hole and half of the other?
Even if you can make perfectly positioned and sized holes you will likely have the same issues with the tapping. Rather than pressing in a solid bronze bushing and then tapping I would use press fit threaded inserts unless the holes were out of position in which case the solid bushing would let you correct.
Attached is a photo of the culprit, it's a worm gear that I want to attach to one end of an engine rotisserie that I'm making so that I have control with a load on it. I basically used GlennW's approach, two holes are tapped, one hole was plunge cut to 3/8" diameter with a pin installed as it was too far off to do much else with. I have installed oversized threaded brass plugs that were drilled and tapped afterwards to the correct size, but I didn't think it was necessary in this case. Thanks for all of the suggestions and helpful hints, John