reamer question

I have to cut some 22mm diameter pockets for bearings. They have to be a fixed to press fit fit, ie not moving around any under load but still separable with a puller or a mallet.
Normally I'd cut them on a lathe, but I have a few to do, they will be in expensive and already part-machined parts, and even with the best intentions sometimes you get impatient and cut just a smidgeon too big...
So, I was wondering whether I could ream them. It would be done on a lathe or mill, with the hole and reamer concentric and parallel.
Quality 22mm carbide (the part is in a nickel alloy similar to inconel) reamers being kinda expensive, I thought I'd ask here first whether reaming would be accurate enough before buying one.
Also, what size hole would you recommend?
TIA for all replies,
Peter Fairbrother

"Peter Fairbrother" wrote in message
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Turn to a press fit, maybe a few thou under and press them in - if you overshoot use Loctite bearing retainer
Save your money on the reamer :)
Andrew

On 09/10/18 17:51, Andrew Mawson wrote:
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I would say in that size a couple of thou would be a heavy press fit and could cause issues with the bearing internal clearance leading to issues (hot running) depending on the service conditions. You should be able to look up the recommended housing dimensions on the SKF site and likely other bearing makers sites.

On 09/10/18 15:15, Peter Fairbrother wrote:
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Would a boring head fitted with a carbide tool be suitable? Once set it should hold its dimensions.

On 09/10/2018 19:13, Clifford Coggin wrote:
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That is a great idea that will use in the future when presented with a similar problem. Richard

On 09/10/18 19:13, Clifford Coggin wrote:
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Should, and probably would - but how do I prepare the hole? If it's with a boring bar - then I'd need two boring bars.
Peter Fairbrother

On 12/10/18 18:53, Peter Fairbrother wrote:
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A drill?

On 13/10/18 09:07, Clifford Coggin wrote:
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I suppose I could start with a drill, but the bottom of the hole is flat. A drill then an end mill possibly, but I reckon I'd still need to go over the bottom with a boring bar.
Also, it might be some months before I finish cutting the seats (they go in several different parts and I expect it will take some time to finish developing the pumps they are part of), and I wouldn't want to tie up a boring head for that long.
So back to my original question, does anybody know, is a reamer accurate enough to provide a defined fit?
ta
Peter Fairbrother

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As you need a flat bottom, wouldn't you be better to use a slot drill rather than an end mill to achieve the full depth and then finish to size with a boring bar?
Alan

On 13/10/18 17:54, Alan Dawes wrote:
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I never worked out which was which, slot drill vs end mill. There will be central holes in the pockets for the shafts in I think all cases, so does it matter?
Peter Fairbrother
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In that case, provided the diameter of the central hole is larger than the area uncut by the end mill, then probably not. A traditional slot drill has 2 flutes (cutting edges) and cuts across the centre of the hole so can be plunged into the material whereas an end mill has 4 flutes but is not centre cutting. I'm not sure if the 2 wider flutes on a slot drill are better at stopping swarf from interfering with clean cutting than the 4 narrower flutes of an end mill. Probably the best compromise is a modern 3 flute end mill in carbide eg from JB Cutting Tools.
Alan

"Peter Fairbrother" wrote in message
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Reamers into blind bore are always a problem, as the end of the reamer will be slightly tapered
Andrew

On Sat, 13 Oct 2018 17:14:04 +0100, Peter Fairbrother
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Reamers can be very accurate. I just reamed about 300 oil bearing sintered bronze bushings to .7505-.7507. Once I got the speed and feed right I had no problems. But the first few were a little oversize because the reamer wasn't exactly centered in the lathe. My mistake in setting up. The end of the reamer will have a chamfer so any bearing you press into the hole must have a corner radius large enough that it doesn't interfere with the undersized diameter at the biottom of the hole. Reamers can also chatter. Straight flute reamers are more prone to chattering. If I had to do 20 blind bores to fit a ball bearing I would bore them. The bores could be roughed and the bottoms flattened. Then they could all go back into the machine for the sizing cut, with the boring bar never being moved once the size is established. This means feeding the boring bar in and out with the bar cutting both directions. The reason I was reaming the bronze bushings was because I needed a short cycle time, which was 5 seconds per pair. Boring would have taken much longer. And the job is a repeat job, so the setup is paid for over very many parts. Eric

On 13/10/2018 17:14, Peter Fairbrother wrote:
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Why must the bottom of the hole be flat? Why not go deeper and fit the bearing using a hold-off/spacer ring if necessary?

In exotic materials like you use. I would in production go
1/ 21.5 drill 2/ 21.8 flat bottomed drill or slot drill. 3/ david brown floating reamer to size.
Job could be done in either lathe or mill.
David brown reamers are adjustable and can be dressed with only as much chamfer as you can allow, they will work up to a square face. . They are very expensive but come up on ebay frequently. In practice once set and locked they will hold tenths with no problems.
Regards Colin
Note to self.The word locked is important got one set and passed by inspection 24 componants latter had 2 pass final inspection and 22 rejects.
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