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Reamer size questions

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S.D.L.02/12/2019 21:46:47
217 forum posts
37 photos
Posted by PANAGIOTIS EVRIPIOTIS on 02/12/2019 13:35:42:


You certainly helped a lot, thank you for that info.

Could you make a suggestion regarding size please so I can make my conversions and order metric reamers.

Say that I have, as I mentioned before, a shaft of 1/4inch +-0.0002" and I want to achieve a tight fit, meaning that I will need for example a set of pliers and some force to remove or a mallet.

Now I can easily find for example H7 reamers who according to standards have a tolerance of +0.00059" in the range of 6mm to 10mm(if I am reading correctly).

In order to achieve such a fit with the above circumstances what should the reamer size be in inch or metric?

P.S. I know I am probably not using the term "tolerance" correctly but you get what I mean.



Bit of a mixture here as a H7 reamer comes from the metric hole based system where the hole is -0 / + a bit so the shaft is normally over but we can work back. Imperial was typically shaft based hence the over and uner reamers the USA has

So shaft 0.250 +/- 0.0002 = 0.2502 /0.2498 which converts to metric of 6.345 / 6.355

If we look at class of fit H7/p6 (Locational interferance) the tolerance is between +0.000 / -0.020

See here 3/4 way down for description of fits Fit Types

See here 3rd table down Fit Table

so our hole should be between 6.345 and 6.333

so we need a 6.333 reamer H7 which should give 6.333 -6.345

Hope you can follow the logic


Tony Pratt 103/12/2019 07:02:04
1125 forum posts
5 photos

Quote 'so we need a 6.333 reamer H7 which should give 6.333 -6.345', you surely are not suggesting that such a thing actually exists? I think the OP is more than a little confused at this stage with all the suggestions coming his way.


JasonB03/12/2019 07:24:00
18113 forum posts
1995 photos
1 articles

Tony, go back to the first page where I suggested a 6.33mm reamer and linked to a supplier who has several options such as hand, chucking, stub etc. and also read the other posts were suppliers of reamers in 0.01mm steps have been suggested. Not seen them available in 0.001mm increments though.

Tony Pratt 103/12/2019 07:31:27
1125 forum posts
5 photos

Jason, of course 6.33[in H7 & H6?] reamers exist, but the suggestion of a 6.333 will totally confuse the OP.


S.D.L.03/12/2019 10:18:37
217 forum posts
37 photos
Posted by Tony Pratt 1 on 03/12/2019 07:31:27:

Jason, of course 6.33[in H7 & H6?] reamers exist, but the suggestion of a 6.333 will totally confuse the OP.


I set out to show the working of how to get to a calculated size so that if a transition fit or greater interference was required it could be worked out. the links should go to the appropriate tables.

Its a fact that limits and fits are designed at the .001mm level even if some rounding is dome from 6.333 to 6.33.

Jason was spot on with the size but the question was repeated about the amount of interference required, example given,


Versaboss03/12/2019 14:38:59
444 forum posts
56 photos

I can only repeat the numbers given by Steve above, 6.33 mm for a drive fit for a 6.35 (1/4" ) shaft.

Kind regards,

Edited By Versaboss on 03/12/2019 14:39:47

PANAGIOTIS EVRIPIOTIS05/12/2019 09:32:31
19 forum posts

Ok everyone thanks a lot for your input. I think all this has given me a better understanding on the matter!

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