Reaming - the basic principle?

Peter, as advised you should carefully drill about .005" undersize, making sure that the drill is correctly ground otherwise it could drill oversize. Also you will find the drill will cut better on phos bronze if you grind a negative rake on it, to prevent losing control of the drill. As your reamer may not be exactly the size you are looking for you may be best drilling the hole under size and then have the bush 'honed' at a local engineering firm. Hones are adjustable and will enable you to achieve the exact class of fit that you require. They will also 'true up' the hole, if sufficient material remains (dependent on how good you drill the holes they may not remain truly in line).

 

Hi pete, the idea is to ream the bush after it's been drifted home ,as it will deform slightly (close up),
Hence the small amount they take off.

 

For what it's worth at this late date regarding the sizing of plain bearings in bronze, gun metal, white metal or aluminium.

My training is a bit old school but based on an education in engineering over 40 year using publications like Caxtons, Newnes and the The Machinery's Handbook amongst others I was always taught:

Any reamer is only as good as it's last sharpening

After reaming the bush/plain bearing should be scraped to remove high spots (Not previously mentioned in this thread but still the only proper way of doing this)

You should never use any abrasive on plain bearings because the abrasive (Especially carborundum) will embed its self in the surface of the plain bearing and then grind away at the shaft when reassembled causing premature failure plus Honing will not give parallel or straight bores compared with reaming and scraping

Well maintained and cleaned expandable reamers if made by a quality manufacturer such as Churchill (who invented them), Dormer, Taylor & Jones etc is for light work every bit as good as standard reamer and every bit as accurate.

Quality machine shops would have sets of cutting tools for non ferrous material and separate sets of cutting tools for non-ferrous materials, these would include things like hand files and reamers, when a reamer no longer cut non-ferrous material well it would be either demoted to the ferrous set or resharpened

There is no real way of resharpening a non-expanding reamer successfully with the edge of a steel rule (Old machine shop myth)

Any plain bearings that rely on a push/friction/interference fit will crush down and reduce the ID when fitted

Remember when dealing with bushes you are dealing with the cumulative error of 4 separate tolerances; 1. The shaft OD Tolerance, 2. The Bush ID Tolerance, 3. The bush OD tolerance and 4. The housing bore ID, if all of these are on the highest limit then the bush ID will crush down and it's ID will reduce by 3 times the top limit, and that's the bit you have to remove plus however much the shaft is over nominal plus running clearance. This is why Churchill and Alfred Herbert worked together to develop the expanding reamer which is the right tool for this job

If you finish a plain bearing/bush in a 3 jaw lathe chuck you will end up with an ID with 3 high spots, 4 with a 4 jaw chuck and so on

Never use grease on an Oilite bush, use oil

Hope this helps

 

When a hole is drilled it is rarely round, reamers correct this. In the case of the bushes, when they are pressed into the housing the internal diameter cannot be guaranteed. Reaming after fitting is the only way of ensuring a perfect fit. I had to do it with the cross shaft bush in the steering box of my MB Jeep.