38 replies to this topic

[jime17]

Being tight fisted, i'm intrigued by the idea some have posted regarding making a reamer from a radius arm pin with channels ground out of it.

How would one go about this? Could I use a vice to hold the pin and a small angle grinder with a 115 mm metal cutting disc to cut some flutes about 3 inches along the length from one end, tidy up any burrs and away I go?

[grahama]

I would imagine that what you produce would not be tight enough on the tollerences required for this job. I am prepared to live and learn though if you get it right !!

Graham

[A-Cell]

Basically yes. 2 cuts, or slots diametrically opposite one another. About 2 inches long would be enough. They can be parallel, don't need to be fluted. Grind a chamfer on the end to act as a Leeds in and there you have. At the other end either use 2 nuts locked together so you can turn it with a spanner or I have seen one done with a T-bar welded to it.
The bushes are quite soft in comparison to the steel shaft so that's why it's possible to use it. Proper readers are made from tool steel obviously.

[jime17]

I must admit I was quite sceptical but people have reported success.

just a couple of follow up questions

should the channels be just the width of the cutting disc?

How deep should they be?

When you say grinda chamfer, do you mean to in effect taper the very tip of the pin to locate it nicely in the bush when you start the reaming process? (oooh matron)

[Ethel]

You'd have to be careful where you place the flutes or you could reduce the diameter. It'd also be a close call on having enough length to ream the whole bush while keeping the other end supported (and true) in the needle bearing. I got a reamer for not much more than the cost of a new pin from Tracey Tools (online), but have a go at making your own by all means.

[racingenglishcars]

I find an angle grinder easiest to make the flutes. I also prefer 3 flutes. They want to be made with an acute angle on the cutting side and only deep enough to hold the shavings. Clean occasionally while cutting. The angle grinder is also good for making the lead-in.

[A-Cell]

I must admit I was quite sceptical but people have reported success.

just a couple of follow up questions

should the channels be just the width of the cutting disc?

How deep should they be?

When you say grinda chamfer, do you mean to in effect taper the very tip of the pin to locate it nicely in the bush when you start the reaming process? (oooh matron)

Just width of cutting disc on an angle grinder and yes chamfer is to create a lead in to get it located in the bush to start the reaming process. You are effectively making a reamer. The shaft outside diameter is exactly right to give a running fit in the bush when reamed and the other end of the shaft runs in the needle roller to keep the parallelism, effectively you are line boring the new bush. Some people use fine grinding paste afterwards to lap the new pin in to the reamed bush.

I

[A-Cell]

I like the sound of racingenglishcars improvements, the 3 fluted cuts with acute angle on the cutting edge. Bit more sophisticated.

[jime17]

I like the sound of racingenglishcars improvements, the 3 fluted cuts with acute angle on the cutting edge. Bit more sophisticated.

Forgive my ignorance chaps...

I assume you mean angle the grind so that it creates a sharper edge in the direction of cutting rotation?

Also. I had been wondering about ethels point regarding the length of the pin being close. Could a socket on an extension be used to give max reach before the pin runs out of needle bearing to guide it? Or would a socket not pass through the needle bearing?

Thanks for all the advice guys

Edited by jime17, 09 January 2013 - 05:12 PM.

[Ethel]

The standard nut wouldn't pass through let alone a socket. You could thread some tube as an extension, or drill & tap for a smaller bolt & loctite it in*. The rake angle of the cutting edge will make a big difference, cutters "wedge in" to split material off, leaving a bigger hole than the diameter of the cutter. A tapered reamer leads in gradually so it shaves off material on a small area rather than biting in. You'd be limited to a chamfer shorter than needle bearing if it's to stay supported on "true".

*the grease nipple hole is a head start.


particularly note the end view, the cutting face is on a radius to stop it digging in, and there's a clearance angle to stop it binding & grinding with swarf. If you went for three flutes I'd consider doubling it to six on the leading edge. Maybe start with 3 first though, easier to add 'em than take away. A grinding wheel in a drill might also give a better finish. Finer grit & a squarer edge.

[jime17]

Hmmmmm. Getting more complex by the post.

still much appreciated though.

[A-Cell]

A couple of points. Above all this home made tool is not precision engineering. Only a few thou 5 or 6 need removing from the bush. The home made "tools" from the radius arm pin are only just long enough to do the job. The 2 nuts are locked onto the very end of the shaft. The one I saw with a T-bar would have just passed through the bush. Really just done to get the car back on the road.Also remember the bushes are very soft. The tool I made was only used on 2 arms, probably it's maximum capacity!
Ethel your precision engineering view is absolutely the right approach to achieve precision and do lots of arms.
by the way the Original 18G588 reamer was not tapered it was a parallel reamer and it also required a collar 18G588A to be inserted in place of the needle arm to ensure bush reamed on same centre line as needle roller.

[1984mini25]

Made from a £6 reamer off Ebay, an old radius arm pin, old mini tie bar...

[A-Cell]

Excellent. Lucky to find the reamer for £6 well done. Plenty of options now jime17

[jime17]

Excellent. Lucky to find the reamer for £6 well done. Plenty of options now jime17

yeah. Probably the refurb arm is the way to go looking at how complex it seems to do a diy job.
:-S