Help needed with making a special reamer

I need to make a special reamer, and any advice from the group would be much appreciated.
I've been asked by a friend to ream the oilite bushes to size in the
rear suspension arms of a classic Mini Cooper. For those unfamiliar with Minis, each rear suspension arm (cast iron) has two bearing points about 6 inches apart. One is fitted with a needle roller, the other with a thin wall bronze bush. A ground spindle fits the two bearing. From memory the needle roller is roughly 15 mm diameter, and the bronze bush about 20mm diameter. When the bearings and spindle are replaced, it's necessary to ream the bronze bush to size. As I understand it, the hand-operated factory tool has a long pilot which fits the needle roller, with a reamer section on the other end. Needless to say, this tool is VERY expensive, and purchase is out of the question for one job.
Can anyone offer any suggestions or tips as to how I might go about making a suitable reamer in my home workshop? I have reasonable collection of machines and associated tooling (lathe, mill, T&C grinder etc).
TIA
Mike
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On Sun, 6 Jan 2008 10:22:26 -0800 (PST), snipped-for-privacy@virgin.net wrote:

Find someone who already had a decent set of adjustable reamers, and make up a pilot to centre on the other bearing?
Easier to adapt an existing reamer than make one from scratch.
Where are you located? We have an adjustable set that covers that range of sizes.
Peter -- Peter & Rita Forbes Email: snipped-for-privacy@easynet.co.uk http://www.oldengine.org/members/diesel http://www.stationary-engine.co.uk
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On 6 Jan, 18:22, snipped-for-privacy@virgin.net wrote:

Of the top of my head: take spare (scrap) rear raius arm pivot. obtain a couple of sets of power plane blade inserts. long thin carbide ones. mill slots into radius arm pivot at appropriate place to take the plane blades, probably 3 or more slots. turn arm down fractionally so it has clearance in new bronze bush. fit plane blades into slots and secure at correct diameter. possibly braze? (details left as an exercise ;)
Dave
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On Sun, 6 Jan 2008 10:22:26 -0800 (PST), snipped-for-privacy@virgin.net wrote:

For a one off application a D bit cutter should do the job.
Start off with the correct diameter silver steel. Form the pilot at the far end and machine a short flat at the required reamer location. The flat should leave a D section a few thou thicker than 1/2 diameter.
Most of the section between the pilot and the D section should be a few thou less than the initial bore of the installed bush but with an undercut just before the D section.
The undercut is needed to leave a clean starting edge for the reamer action. File or grind a small clearance over most of the forward edge of the undercut D so that there is cutting clearance for the clockwise D bit edge.
Ideally the device`should be hardened and tempered, but for one off use on bronze untreated silver steel should be hard enough.
good luck
Jim
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snipped-for-privacy@virgin.net wrote:

> > The quickest and easiest method favoured by manufacturers with this scenario is press a 15mm ball bearing through the bush. No pilot required. Of course in production they would use a carbide ball due to production numbers.
In this case, machining the head of an old pivot to size, with a nice big polished radius, well lubricated and then pulled through by the nut will do the job also. Maybe a better option, as one can incorporate any clearance required by the sizing.
Before someone raises the spectre of closing the pores of the oilite bush over, this has been the factory service advice for sizing the oil pump drive oilite bushes in Mopar engines for decades.
Or they can visit: http://www.ballomatic.com/process.htm
Tom
O & OE as regards the grammatical content of this post.
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Many thanks guys. A great set of ideas here.
First off I will try Dave Baker's well-described solution, mainly because it means I don't have to make a reamer at all!
If the bushes are a bit tight when installed, I'll finish off with a ball or ball-end tool as per Tom's suggestion.
Thanks again
Mike
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wrote:
Many thanks guys. A great set of ideas here.
First off I will try Dave Baker's well-described solution, mainly because it means I don't have to make a reamer at all!
If the bushes are a bit tight when installed, I'll finish off with a ball or ball-end tool as per Tom's suggestion.
Honestly you won't. It'll take you a day or more to make such a tool, or the several different sized ones you'll need to actually make to work out how much material they really shift. You'll ream it with a fixed reamer on the lathe and tweak it with an adjustable one later or just do it with an adjustable one from scratch like I would. If you want a tenner on it let me know.
--
Dave Baker
Puma Race Engines
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wrote:

Apart from the sheer amount of grief making such a set of tackle you really can't do it that way by hand anyway with any precision. Ball burnishing needs to be done at some speed and it's particularly important that the process doesn't stop at any time or you get a ridge in the material. There's also always some springback and hence some buggering about to find the size of ball needed to achieve a finished size in the bore.
Then these particular bearings aren't in fact nice soft porous oilite, they're normal bronze with a lubrication groove and several thou undersize not just a few tenths. You'd have a hell of a job pulling anything through them at that amount of fit even if it could swage that much material out of the way which I frankly doubt. I think it would stand more chance of ripping the bronze off the steel backing or just getting stuck half way through.
Frankly this is a simple enough reamer job and no need to unduly complicate it. In fact despite my patent "method" in the previous post if I was given this to do for only two bushes and little prospect of anything I made up specially getting used again in the future I'd just adjustable ream them a few tenths at a time from the end they push in at until the shaft fitted through cleanly and I'm quite sure it would be as good a job as anyone would do with the proper tool or a machine ream. Like I said before it ain't rocket science and a few tenths of clearance one way or the other won't make a scrap of difference to the car.
Equally it wouldn't take a decent machinist very long to bore out the steel bush holder I describe and it gives you the comfort of an accurately fixtured machine ream for all, or at least the vast bulk of the material. With more than one set to do it's a no-brainer. With only one set to do you pays your money and makes your own choices.
--
Dave Baker
Puma Race Engines
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Dave Baker wrote:

> Apparently my solution is beyond your experience or skill levels. Your rather crude rebuttal certainly indicates thus.
Reaming rocker arm bushes? With an adjustable reamer? Ever heard of a Sunnen hone?
As an advocate of pilotless, adjustable reamer, reaming, you aspire to a skill level that I'd prefer not to know about.
Tom
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