Bushing rocker spindles

t ingermanson · 2026-02-10T10:55:56-0700

Why not do a bit of everything? Enough of an interference fit to make you comfortable with localized heat, retaining compound, a bit of peening around the outside, and a grub screw through the exposed front of the boss into a little hole in the bush, and don't forget that there are better spindle cover plates these days to help eliminate spindle rotation, the whole reason why we're here, and your only mode of failure once in play.

There's very little required of this hole. It's easy to get wound up, but go slow, take it easy with little bites with the boring bar, and you should be fine. This material loves to be machined. Tidying up a bit of eccentricity once in position should not be a problem if you give yourself enough material. Practice a couple times and then you'll be answering our questions! You've got this!

t ingermanson · 2026-02-10T11:12:33-0700

Fast Eddie said:
why not fit super thick bushes, ie with only a pilot hole, loctite the suckers in, then bore them in situ ?

I think you're onto something, but super thick bushes would require the ID of the bore in the head to be large (duh...), which may weaken the boss, and would definitely change how it expands and contracts with the heat used to set the bush (worst case, the boss could crack as it cools unevenly), or the bush would have a thick wall, which would change how it expands and contracts with the heat, as well as the ultimate interference of the fit. If you went with too thick of a wall in the bush, when you went to bore it out, you could change how tightly the bush fits into the bore in the head and it could potentially come loose. There's a needle to thread here. How big the eye of this needle is, I don't know, but a couple/few tests would say a lot.

As usual, it's all about the prep and plan, for what seems to be an easy task.

Fast Eddie · 2026-02-10T11:22:32-0700

t ingermanson said:
I think you're onto something, but super thick bushes would require the ID of the bore in the head to be large (duh...), which may weaken the boss, and would definitely change how it expands and contracts with the heat used to set the bush (worst case, the boss could crack as it cools unevenly), or the bush would have a thick wall, which would change how it expands and contracts with the heat, as well as the ultimate interference of the fit. If you went with too thick of a wall in the bush, when you went to bore it out, you could change how tightly the bush fits into the bore in the head and it could potentially come loose. There's a needle to thread here. How big the eye of this needle is, I don't know, but a couple/few tests would say a lot.

As usual, it's all about the prep and plan, for what seems to be an easy task.

I only meant to make the bush thicker initially, by not machining out the ID. Once firmly loctited in place, machine the ID.

Peteyoung75 · 2026-02-10T12:54:51-0700

Thanks folks that all makes sense. I’ll be back on it at the weekend (hopefully) so we’ll see what happens. I’m quite to just peen or pin so do a couple more tests.
Cheers

Bushing rocker spindles

t ingermanson

t ingermanson

Fast Eddie

Peteyoung75

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