15 replies to this topic

[Iain L]

After reading up and finding out that the new bearings/bushes (i forget which one) need to be 'reamed' to fit the shaft and most people just buy a recon arm because the reaming bits are expensive, im left wondering why a normal drill bit (obviously the correct size) can't be used?

This may be a dumb question and i may have missed something obvious but can anyone give me a reason?

Thanks Iain.

[Rich.]

I cant say for sure in this application, although i would assume its the same as any other, but a reamer is usually used instead of a twist drill bit due to accuracy, reaming a hole gives a far more accurate size than a drill bit ever could.

Rich

[Iain L]

How tight should the shaft be going into the bearing/bush?

[keefers]

I have squeezed in new bushes/bearings with a sash cramp, insert shaft from bearing end and view where the bush is tight, i then used a dremel to shave the bush, does take a fair bit of time, as you dont want to take too much off and end up back to square one.

Edited by keefers, 04 February 2011 - 10:44 PM.

[ibrooks]

A drill makes a hole that's maybe sort of nearly round and somewhere around the size that's written on it. To make a hole that's as near as possible perfectly round and an accurate size you need to drill it undersize and then use a reamer to finish it maybe even two - one that's still undersize and then a second one that is the desired final size.

An extra complication with the bush in the radius arm is that it MUST be parallel with the bearing in the other end. You can't do that with a normal reamer shoved in from the outside of the arm. The proper tool is a reamer that has a precision ground shaft behind the cutting flutes which runs in the bearing and it is inserted through the bearing side of the arm to come out on the bush side. This ensures that the hole in the bush is dead parallel with the bearing.

They should be reasonably tight when fresh but not excessively so - it's a feel thing that comes with experience. You should be able to turn it by hand without undue force. What is very obvious is that there should not be any tight spots as it turns - it should be smooth all the way through 360degrees.

Iain

[Cooperman]

The reamer size is 13/16". To try to drill it out would require a very long drill and you would need to be very careful as to how rthe drill flutres went through the roller bearing to aviod damaging that bearing with the drill.
The plain bush, if drilled, would have a poor finish and the bush would not last long. It would be a real 'bodge' job. If you tried to drill it from the other end the drill would not run parallel to the roller bearing at the other end.
It would be near impossible to open out the bush with a Dremel and get any sort of accurate parallelism on the bush.

[Darkscamp]

what length reamer would you use for this job as i'm looking at boosting my tool collection to accomodate doing radius arms

[adamt117]

When i did my radius arms i couldn't get hold of the reamer, so i made a sleeve that had the same press fit as radius arm and pressed the new bush into it. I then put this in a 4 jaw chuck on the lathe and machined it out with a boring bar. The only thing with doing it this way is you have to make sure the bush is clocked in the chuck spot on true, otherwise if it isn't when you put the bush in the arm the shaft wont line up in the arm. Ive found when doing it this way you can get a much better and closer fit.

[Dan]

In what way is this not the normal question? "How can I avoid doing this job properly?" is the normal question on the subject. If you don't have the tools to do it, or the engineering and machining expertise to come up with another way to do it (as the suggestion above which is quite a good idea and the only real alternative I've heard) then getting someone with the correct reamer to do it for you is the only way.

[Ethel]

A drill bit only cuts on the end, the flutes are only there to clear swarf. I got a nine inch reamer, just long enough to fit right through the arm, for £20. I've made up a bush to support it in place of the needle bearing, but I've yet to try it out.

I've successfully "reamed" bushes in the past using production paper taped round a suitably sized socket.

[Yoda]

I've successfully "reamed" bushes in the past using production paper taped round a suitably sized socket.

this is similar to what i usually do! but just use an old shaft modified/extended to fit drill chuck with the addition of Emery or production paper. or a piece of tube with a slot to take a folded bit of emery in the end as a sort of flap wheel and line it up with the other end through a plastic homemade bush from a solid cotton reel.

Edited by customcart, 05 February 2011 - 12:58 PM.

[Iain L]

Thanks for replys, simple answer to my question is its just not good enough then. Will do what most do and just get the recon arms, will save alot of hassle by the sounds of things.

Cheers

[Big_Adam]

I just gave my machine shop man the rebuild kit and £10 and went back a week later to pick them up.

Cleaned, new bushes and bearings put in. All I had to do was add the washers and stick them on the subframe.

[Southy]

what length reamer would you use for this job as i'm looking at boosting my tool collection to accomodate doing radius arms

It's a special reamer for the job about 2ft long with a collar about 3/4 the way up the shaft which sit's perfectly inside the roller's to keep the reamer running true, with the actuall reamer section about 10cm in from the bottom of the shaft. Will try and get a picture of it on monday.

[Cooperman]

My reamer, which I've had for years and got for nothing, is about 10" long. The shank is too small a diameter after the flutes end, so I've built it up with 2" wide tape to the diameter of the shaft and it works fine. I always ream by hand rather than use a power tool to drive the reamer through and this gives a very good bore finish. It does come up slightly tight on the pin, but turns ok and the bushes do last a long time once done properly, which is really the only way to satisfactorily do this job.