Reamer size questions

[Neil WyattModerator @neilwyatt]

Posted by PANAGIOTIS EVRIPIOTIS on 30/11/2019 15:03:28:

Hello again everyone, I am having some second thoughts regarding reamer sizes for different kind of fits.

Just to get a good grasp could someone explain in the case of a shaft that is .250 with a tolerance of +- 0.0002, what the size of an H7 reamer would have to be to achieve a tight fit? (to be able to disassemble with a punch and mallet

One last question would be if anyone know of any vendors that sell hardened stainless steel dowel pins, maybe from 416 or 440c steel. So far in Europe I see that the standards are either soft stainless steels or non stainless hardened steels.

Thanks for your help everyone

As you have an accurate shaft, you actually want an H6 reamer to get a 'medium drive fit'.

Neil

[DustyParticipant @dusty]

Panagiotis, the problem you have is that if you require the pins to able to disassemble from the plate, after a few times that this occurs the fit will become less. You will eventually get to the stage when the pins will fall through the hole, well that might be a little extreme but you get my drift.

[Sam StonesParticipant @samstones42903]

Did you intend that pun about the drift Dusty?

[PANAGIOTIS EVRIPIOTISParticipant @panagiotisevripiotis95835]

Ok I will rephrase my question. Let's consider the following scenario.

I have a very accurate shaft as I mentioned above (+-0.0002 tolerance) of 1/4 inch.

I need to find the appropriate H7 reamer to get a tight fit therefore it has to be a bit undersized. The tolerances of H7 reamers are available online and I know for a fact that this scenario can be achieved.

So the questions is what should be the size of that H7 reamer to get that fit. As I said I will go undersized, my problem is how much I should buy.

@Dusty

I see your point. When I said that I want the user to be able to disassemble it, I meant if he has too and to my mistake I didn't mention frequency. This disassembly will happen very rarely if ever therefore I will avoid what you said. Also I don't go for a press fit because I want the user to have the option of removing the staff.

[VersabossParticipant @versaboss]

As far as my knowledge goes, a H7 reamer has a positive tolerance from the nominal value. So you would hardly get a 'tight fit' (whatever that is) with such a reamer. I don't understand why you don't jump on the metric reamers in 1/100 mm steps. I could name easily 2 or 3 shops in Switzerland which send tools anywhere in the world.

About fits in general, there is a nice utility called ModelEngineer's utilities (www.alanjmunday.info). Enter your values and see what you need.

Kind regards.
Hans

[VersabossParticipant @versaboss]

Seeing just now that my link above does not work. But the utility can be found here:

https://modelengineersutilities.software.informer.com

Kind regards,
Hans

[Tony Pratt 1Participant @tonypratt1]

6.34mm reamer at H6 tolerance should work for you, in theory hole would be 6.34 to 6.349 mm. Best to do a trial run on a piece of scrap first.

Tony

[PANAGIOTIS EVRIPIOTISParticipant @panagiotisevripiotis95835]

@Versaboss

Firstly, I would really like to use just metric but in order to do that I need to understand the theory. How lower should I go to get a tight fit in the scenario mentioned above if my reamer is exact and has no tolerances. If I get a number for that then I can make my own calculations, account for tolerances etc. and see what I am going to buy to achieve that.

By the way give me please the names of these two shops.

P.S. I can download the resource from your 2nd link but it seems broken. It fails to extract

@Tony

That's the answer I am looking for to get an understanding

[Mike PooleParticipant @mikepoole82104]

You could make your own toolmakers reamer to any size you want, cheap and easy to make. Google will supply the how to make.

Mike

[VersabossParticipant @versaboss]

Dear Mr. Evripiotis,
well I will do my best. First, to my big grief I had to discover that the M.E. utilities stopped to work correctly. Some of the buttons are ok, but the 'Limits and Fits' are now unusable. It is the latest version, and is on my computer (W.10) since umpteen years. I tried to load them on my Laptop (W. 8.1), but I could not unzip the file… Some of the buttons show now a black background, and the 'captions' are invisible, and 'calculate' does nothing.
It would be worth an own thread, why a program suddenly can stop working correctly.

Now to the reamer problem.
One address I know is the Brütsch, Rüegger toolshop:

brwtools

The other is the manufacturer Re-Al:

Re-Al

Hope I could help you a bit.

Kind regards,
Hans

[PANAGIOTIS EVRIPIOTISParticipant @panagiotisevripiotis95835]

@Versaboss

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.

Regards,

Panos

[Martin KyteParticipant @martinkyte99762]

Posted by Dunc on 28/11/2019 14:53:51:

Surprised that no one has mentioned machining your own D-bits.

How about making your own D-bits?

(There you go)

;O)

or stone the corners off a 1/4 inch drill and use that. It will drill undersize when following a pilot hole.

[PANAGIOTIS EVRIPIOTISParticipant @panagiotisevripiotis95835]

@Martin

I on't have a lathe to do that, so I will need to find precision ground hardenable steel rods to do that. Also with my experience and the machines that I have I am not sure I can make as accurate tools as I need

[JasonBModerator @jasonb]

6.33mm or 6.34mm would be the most likely but there are so many other variables that can affect what size the reamer actually cuts that you will have to do a few test cuts. The final size will be affected by one or more of the following.

Pilot hole size

Material being cut

Dry or lubricaed

How the reamer is held (fixed or floating)

What machines you are using eg a drill press will likely cut larger than a milling machine, handheld drill even more likely to be oversize.

Condition of reamer, it will wear with use.

What you conside a push fit may be another mans press fit.

[Neil WyattModerator @neilwyatt]

Another idea – use a hand reamer and just use the tip, which is tapered, experimenting until you get the fit you want.

ideal for locating pins.

Neil

[Neil LickfoldParticipant @neillickfold44316]

You can make a lap, and lap the od of the reamer smaller to get it to the diameter that you require. This works very well with machine/chucking reamers. Lapping a hand reamer does not work so well however.

Neil

[S.D.L.Participant @s-d-l]

Posted by PANAGIOTIS EVRIPIOTIS on 02/12/2019 13:35:42:

@Versaboss

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.

Regards,

Panos

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

Steve

[Tony Pratt 1Participant @tonypratt1]

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.

Tony

[JasonBModerator @jasonb]

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 1Participant @tonypratt1]

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

Tony

[S.D.L.Participant @s-d-l]

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.

Tony

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,

Steve

[VersabossParticipant @versaboss]

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,
Hans

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

[PANAGIOTIS EVRIPIOTISParticipant @panagiotisevripiotis95835]

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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