Machine reamer diameters?

[Andrew TinsleyParticipant @andrewtinsley63637]

I have inherited around 50 MT1 and Mt2 machine reamers. They have all been resharpened and have not been used since. I assume that they are now undersize, which isn't a problem as I can machine rod to fit.

However what is the best method of measuring their diameters? Using a micrometer gives very inconsistent readings and I am a little bothered that I might damage the flutes. I suppose I could use them to ream a hole and then measure the diameter, but I don't fancy doing this for 50 reamers!

I feel I am missing the obvious! has anyone got any suggestions?

Andrew.

[Andrew TinsleyParticipant @andrewtinsley63637]

[Anonymous]

If they are machine reamers they cut on the chamfer at the front, not on the flutes. So they should have only been sharpened on the chamfer. So the size on the flutes shouldn't have changed.

Andrew

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello Andrew,

The flutes are as sharp as the lead in, which made me think that the flutes had been sharpened too. I was always under the impression, that it was the lead in that was resharpened, until I read conflicting statements from GH Thomas and Professor Chaddock. One said that the diameter of the reamer was reduced on sharpening and the other claimed the diameter was the same. Now this may have been a simple typo or confusion with hand reamers, but they were talking of machine reamers. Hence I have been uncertain of the truth ever since!

It does seem logical to only sharpen the lead in portion of the reamer, so maybe that is what has been done, To be sure, I can bore a single hole with any reamer and check it with a precision bore gauge.

Thanks,

Andrew.

[IanTParticipant @iant]

From the 'Cutting Tool Handbook' – SKF Dormer Tools

"To obtain the best results when reaming it is essential that the reamers are made to 'work'. It is a common fault to prepare holes with too little stock left in them. If only a bare amount is left in the hole before reaming, the reamer will scrape and rub and quickly show wear with consequent loss of diameter.

It is essential to understand that parallel (machine) reamers only cut on the bevel lead and that parallel hand reamers with bevel and taper leads may cut on both but that neither do any cutting on the parallel lands on the body."

I've not sharpened any of my reamers but I have (carefully) stoned the odd 'nick' out (some slight edge damage) – as far as I know without changing the nominal size. If/when I do sharpen any – I would only touch the cutting edges as advised by Dormer…

Regards,

IanT

[not done it yetParticipant @notdoneityet]

Yes, if all of them were sharpened at the same time, it might be prudent to at least check out a couple or three to see if they cut to nominal size or undersize?

You might find that the difference might mean 2 reamers of same value cut different sized holes – ream with the smaller and then check if the other one takes out more metal?

as I can machine rod to fit.

Under-size reamers would be a pain for making gears (for instance) to fit on a precision shaft… But as always YMMV.
Unless you are thinking of disposing of them, it might be prudent to check only if and when necessary.

[Andrew TinsleyParticipant @andrewtinsley63637]

Thank you all. I have tried one reamer and according to my precision bore gauge, it is within less than 0.5 thou of nominal size.

If it had not been for the two experts disagreeing, I would never have given it a second thought and just used them as normal!

Andrew.

[Howard LewisParticipant @howardlewis46836]

I was once told that lubricating a reamer would make it cut oversize, but have never really checked, so cannot confirm or deny.

One risk with a reamer, is that if held slightly off centre, it will cut oversize, because it is effectively acting as a boring bar. So tailstock alignment needs to spot on.

I made myself a Floating Reamer Holder. The ER25 head holds the parallel shank of a Hand Reamer, and three shop made ER32 collets hold the MT1, MT2 and MT3 reamers. Because the Reamer can float, it should follow the drilled hole without the risk of any side force being applied to it.

Howard    Fat fingers again!

Edited By Howard Lewis on 13/12/2019 15:09:53

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello Howard,

After some disasters with reaming, many years ago. I made myself a floating reamer holder and have never had a problem since.

Well worth the effort for anyone who does reaming! Even if you get the tailstock dead on horizontally, pound to a penny the centre height of the tailstock isn't the same as the headstock. My Myford is definitely out vertically and that helped to muck things up all those years ago! It took me ages to realise what was going on.

Andrew.

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