Brain picking: Need some ideas/direction

Koz · 2005-06-01T16:23:14+00:00

Hi folks. I was hoping that someone here might have an idea that would send a project a different direction; Basically inspiration to get off the path that things are stuck in. I believe I've asked this before but am re-addressing the issue as nothing has been resolved yet.Here's the situation: We need to take a long 1/2" dia CRS rod, drill the ends 1-1/2" deep x 5/16 and insert a 3" long hardened and ground dowel pin in the end. The pin doesn't get much tension but gets some torque in the form of tens of thousands of cycles over it's life.Quantity is about 1000 ends a month so it's not enough to get really fancy or a high investement (IE induction hardening a journal on hardenable rod instead of using the insert). Cheap and servicable is the order of the day.We've tried using a hydraulic compression fit (heavy press in) which held ok but didn't like the repetative stress cycling for long enough. We've also tried perimeter welding the joint which draws out some of the hardness (bad) and takes a little too much time. Currently, the procedure is to cross drill the 1/2" rod with a small hole about an inch from the end and plug weld into the hole and to the pin. This works OK but there is a very small (5% or so) failure rate over time.Any thoughts on a better procedure to use off the shelf dowel pins (or whatever) and get the cycle strength we need? Other ideas? I'm just trying to "break out of the box" here in my thinking. Labor needs to be in the range of a couple of bucks per end.ThanksKoz

Jun 01, 2005 21 Replies

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Bob Engelhardt 21 years ago

A 5/16 hole in a 1/2" rod leaves a 3/32 "wall". That's not much in CRS. Depending upon the radial loads, the CRS could be stretching enough to loosen the pin. If so, a longer pin would improve things.

But, what do I know, Bob

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