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Reaming a large diameter by hand

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ChrisB23/10/2019 17:37:23
435 forum posts
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I need some advice on how to go about reaming a series of bushes in situ, ie using a hand reamer.

To better explain myself I'm adding a diagram. The hole in the fitting is 42.50mm dia. (material aluminium) The fitting is 18mm wide. The bush is 42.55mm OD and 39.55mm ID (material aluminium). The bush is first press fit in the fitting. Then the bush needs to be reamed to 39.68mm (that would be a 1 9/16" reamer).

I'm using an adjustable straight flute hand reamer to get the hole to size but I'm struggling to get a decent finish, the reamer is grabbing the bush and chatters leaving a very poor finish.

Am I using the wrong reamer or using it incorrectly?

IanT23/10/2019 18:07:52
1363 forum posts
137 photos

Haven't reamed aluminium for quite a while Chris but I think with that sized hole you'll need a bit more meat than 0.13mm (5 thou) to get the reamer to cut properly. The reamer needs to be pretty sharp too or it will just rub.

Regards,

IanT

Neil Wyatt23/10/2019 19:40:05
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If it was steel I'd be looking at 15-20 thou.

Use loads of lubrication as well.

Neil

old mart23/10/2019 19:55:28
797 forum posts
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It is difficult to get a good finish with any straight flute reamer, let alone an adjustable one. You will likely end up with a bellmouthed hole. I would go for a different approach, namely, boring the bush to finished size, and making it a sliding fit in the housing, (0.001" clearance), and using Loctite, 601, 638, 620 or equivalent.

Edited By old mart on 23/10/2019 19:56:50

Hopper24/10/2019 13:03:42
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The job is very narrow (18mm) in relation to the 40mm diameter, which is a big ask for a straight flute adjustable reamer. Not much guidance and not much length for the leading tapered part of the blades to cut on. Chatter city. It may help if the job can be clamped to the table of a mill or drill press that is then used to hold the reamer firm and square while it is rotated by hand to cut the hole to size.

I think I too would be looking at pre-sizing the bush in the lathe then install it in the job. Either as suggested or by making it a one thou interference fit and make the ID one thou larger than required. Or make it a tad undersize and finish it off with a brake hone or similar.

Depends a bit too on what the application is and therefore what tolerances etc are involved. Bit more info would help.Have to wonder, why an ally bush in an ally fitting? Repair job? On what? Can the bush be pressed in then the whole fitting mounted in the lathe and the bush final bored to size?

 

Edited By Hopper on 24/10/2019 13:09:37

Edited By Hopper on 24/10/2019 13:11:56

ChrisB24/10/2019 19:23:05
435 forum posts
174 photos

Thanks for the replies. Up till now I was boring the bush (sleeve) on the lathe in a 5C collet chuck which gave good results, the problem is, I need to work in respect to a specific process as listed in a manual, and unfortunately this call for reaming in situ not boring on a lathe.

The bush is actually a sleeve into which a spherical plain bearing is inserted and staked (similar to a hydraulic ram rod end bearing) That's the reason the bush is aluminium as it needs to be cold worked and form a lip.

The process calls for the sleeve to be press fit into the fitting. The sleeve is then to be reamed to the diameter of the spherical plain bearing. The bearing is inserted into the sleeve and staked to form "swage".

When I do it on the lathe there is a bit of guess work - I have to compensate for the slight reduction in diameter of the sleeve when it is press fit on to the fitting, otherwise the spherical bearing will bind.

I'll take a couple of photos tomorrow, it will help explain better.

vintage engineer25/10/2019 09:25:22
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I would set it all up in mill so as everything is straight and rigid.

Andrew Johnston25/10/2019 13:03:22
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I'm not sure what is meant by an adjustable hand reamer? Something like this:

adjustable reamer.jpg

This type of adjustable reamer is intended to take out minimal material per cut, mainly for repairs or fitting oversize pins in the field. They're not easy to use or particularly precise, and as Hopper says the hole in question is really too short.

Without knowing the application the design sounds a bit of a dogs breakfast. We use plenty of push fit bearings in aircraft and they're all staked into steel housings, so I'm puzzled as to the use of aluminium. Personally I'd corner the designer and quiz him on the design and machining instructions.

Andrew

ChrisB25/10/2019 18:29:24
435 forum posts
174 photos

Yes that's the type of reamer I have, it's no good for this application.

Posted by Andrew Johnston on 25/10/2019 13:03:22:

Without knowing the application the design sounds a bit of a dogs breakfast. We use plenty of push fit bearings in aircraft and they're all staked into steel housings, so I'm puzzled as to the use of aluminium. Personally I'd corner the designer and quiz him on the design and machining instructions.

Andrew

Incidentally the application is for an aircraft component. I have been replacing and staking these bearings and sleeves for years - boring the sleeve on the lathe and then installing on the component. Unfortunately an audit found that I'm not following closely the process as specified in the relevant manual, so as the process states that the sleeve should be reamed in situ and then staked, I have to adapt my method...the problem is reaming the damn sleeve with a reamer is proving next to impossible unless I'm missing something!

This is what the sleeve and bearing looks like

20191024_165259.jpg

The fitting after removal of the old worn bearing

20191025_115710.jpg

This is the sleeve partially installed into the fitting. The sleeve needs to be fully driven in and then reamed to size.

20191025_115608.jpg

The finished installed bearing with the staked sleeve retaining the bearing

20191025_115511.jpg

old mart25/10/2019 19:06:34
797 forum posts
77 photos

You will have to make a fixture to hold the reamer dead straight, and buy a proper spiral fluted reamer. There is not much of a chamfer on the hole to keep the bush in place after staking. Does the reamed bush get inspected before fitting the bearing? Could you get away with lapping the bush? I have fitted lots of these type and the variation where the bearing fits directly in the hole and has a grooved edge which is staked. Roller staking was used.

You may be able to get away with careful measuring and only ending up with about 0.05mm undersize, then use the reamer to rub out the rest.

Edited By old mart on 25/10/2019 19:12:03

Hopper26/10/2019 10:37:28
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3776 forum posts
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Yes. I think if you don't go for the expense of a fixed size spiral flute reamer etc, Old Mart has the only way around it. Make the bush a thou or two undersize and give it a nominal reaming to meet the red tape requirement.

The reamer referred to in your manual may well have been a special tool that consists of a spiral fluted reamer with a stepped end section that is a neat fit in the unreamed bushing so it guides the reamer through the job. Similar to factory reamers for doing small end con-rod bushings. Even at that smaller diameter, using an adjustable reamer can be challenging.

Edited By Hopper on 26/10/2019 10:41:19

Andrew Johnston26/10/2019 10:46:13
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4941 forum posts
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A fixture and a custom reamer is the way to go. Do the drawings call out a tolerance and surface finish value? I don't suppose the aircraft manufacturer can be identified, but it would be useful to know. So I can avoid flying on them. smile

Andrew

ChrisB26/10/2019 14:09:58
435 forum posts
174 photos

I placed an order for a spiral flute 1 9/16 reamer with a custom lead which fits the sleeve, it's going to be expensive but I'm not the one paying for it. I see how it goes from there. Thanks for all the input gentlemen, much appreciated.

Yes the manual calls for a tolerance, 1.5623 in to 1.5629 in but no surface finish.

You'll have a hard time trying to avoid flying with this aircraft manufacturer Andrew, I think he produces roughly half the aircraft flying in the world!

Hopper27/10/2019 05:12:03
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3776 forum posts
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Posted by ChrisB on 26/10/2019 14:09:58:

I placed an order for a spiral flute 1 9/16 reamer with a custom lead which fits the sleeve, it's going to be expensive but I'm not the one paying for it. I see how it goes from there. Thanks for all the input gentlemen, much appreciated.

Yes the manual calls for a tolerance, 1.5623 in to 1.5629 in but no surface finish.

Your'e welcome. That probably would have been the first suggestion if you had mentioned in your original post that you were doing commercial aircraft repair work. I thought you were just bodging around in your home workshop on a shoestring budget like the rest of us! Unusual situation where a LAME seeks advice on this forum. Says something about the quality of work on here I guess.

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