Radius arm reaming

[aeytr5]

Rebuilding the rear sub-frame of an '89 Rover Mini. Everywhere seems to think that to re-insert the radius arm and pin, the inner bore of the radius arm needs to be 'reamed'. Not a process I've done before, and everyone seems to think you either have to buy a very expensive tool or pay a specialist with one to do it for you. Can anyone shed some light on why it's so necessary and if there is a simpler way of doing it?
Sorry if this all sounds thick, but I just can't imagine that all the boy racers in the 60s and 70s bought specialist reaming tools.

[Lotobear]

It is necessary and every garage back in the day had a set of reamers for this purpose, among others.

You can get refurbished arms on an exchange basis with new pins, needle rollers and correctly reamed bushes - it's not expensive and much less hassle that trying to do it yourself.

[aeytr5]

Lotobear said:

It is necessary and every garage back in the day had a set of reamers for this purpose, among others.

You can get refurbished arms on an exchange basis with new pins, needle rollers and correctly reamed bushes - it's not expensive and much less hassle that trying to do it yourself.

Thanks Loto - this sounds like a better plan and I'll look into it. But, out of idle interest, what is the actual purpose that it serves? I understand what it does, but what would happen if you reassembled without reaming?

[kev b]

When the new bush is pressed into place it deforms slightly because it is an interference fit, also back in the day manufacturing tolerances were not nearly as accurate as they are now.

After the bush is fitted the internal diameter is oversized and possibly out of round therefore a reamer needs to be passed through to cut the bush to the size of the pin, which is also subject to manufacturing tolerance variation.

All this faff is to ensure the pin and bush fit together perfectly, a couple of generations ago lots of bits needed to be reamed to fit, bolt-on perfectly machined components were not universal.

IE Mini radius arms, con-rod little end bushes, gearbox and engine bushes in motorcycles, in short lots of bronze bits in all types of machines.

[DVandrews]

As mentioned it’s likely that the internal dimension of the bushes following fitting will be both undersized and out of round, it’s much simpler if you can get an exchange radius arm as they are quite tricky to do. I have reamed a few in the past (long distant past), but the tooling I had is long gone.

Dave

[Shelsleyf2]

If you have an old pin/axle, cut a few longitudinal grooves in one end and use it as a reamer. It will be supported by the needle roller on the end. Was an often used workaround in period. I have done it when I didn't have access to the correct reamer.

[DVandrews]

Yup, have used that method too, use some RTD and remove any burrs before attempting it.

Dave

[Skyedriver]

Still have the two reamers (somewhere) from doing MGB front uprights (and Imp kingpins too)

[aeytr5]

Thanks all. Bought all the bits to rebuild the current radius arms a while ago so won't be exchanging them... I'll ring around to see who is able to do it, and, if that doesn't work, I'll give the bodge a go!

[NDT]

Have a look on theminiforum - lots of helpful stuff there on this topic.

[littleredrooster]

Reminiscing here, when serving my engineering apprenticeship in a large North-East factory, 'reaming' was threat of physical violence; viz: "If he doesn't pack it in, A'am gonna give 'im a good reaming"
...and on a similar note, another threat - "By the time Aa've finished with 'im, he won't know whether his a*seholes been punched, bored or coontersunk"

Sorry - fairly unrelated. It was a savage environment!

[Robmainstgarage]

If you end up doing it yourself then do the drivers side one first! At least then you'll practice on the side that easier to remove and redo once it's back on the car!