Mark

As I understand it D is for tap pitch diameter tolerances. Usually slighty greater than the corresponding H number, Always +, larger than nominal.

How that relates to reamers I don't know.

Clive

Apart from anything else, what is the service available from these Am a zon suppliers – compared to a good model engineering supplier?

How many users actually use these devices in the optimum manner (to achieve the expected tolerance)?

Cheapness is not always a merit. Think here whether a commercial user/buyer would even consider these cheap buys.

I wonder if these figures are aimed at the American market which uses a shaft based system rather than our Hole based system. That would also tie in with the 6.5 to 13 range being close to 1/4-1/2" but if you look at say Zeuz that is 6-10 and 10-18 ranges.

The ARC ones work for me and I have bought all the common size machine reamers and now seldom use my collection of hand reamers built up over a number of years. Will still depend on pilot hole size, material, wet or dry cut and obviously the actual size of your shaft rather than nominal.

Edited By JasonB on 16/05/2022 08:00:45

I have never used Amazon for anything other than books and, for what it is worth, no longer use the model engineering suppliers for reamers, milling cutters etc.

The industrial suppliers are quite happy to take your money, are no more expensive and usually give a next day service. I can recommend, just as a satisfied customer, Drill Service (Horley) Ltd.

JA

The H7 column doesn't look right to me either – looks like over a thou interference would be within limits on a 7mm shaft!

I tend to go by the limits and fits shown in the Zeus booklet.

And I don't know if I'd buy from a supplier who thinks Glass-Hard Steel is anywhere near 40 HRc… (?! )

Totally agree with JA, buy from an industrial supplier, they cannot risk their reputation supplying rubbish to the professionals, I have been using Drill Service for many years and can recommend them, no connection with the company only a satisfied customer.

ARC actually have quite a large commercial customer base, obviously not for the machines but cutting tools etc do also go to business and further education, etc

If you look closely at the table there is actually a – behind the 40HRC suggesting steels over 40HRC and the box to the left has -40HRC which would be steels under 40HRC not that Glass hard steel is 40 HRC

The bottom line of the chart shows which of the two reamers is better suited to each material. Above that to the left the HSS reamer has a circle and the Carbide reamer has a triangle. So they are suggesting the carbide reamer for the hard steels & stainless and the HSS one for the easier cutting steels, CI, Aluminium and copper. 

Edited By JasonB on 17/05/2022 07:54:04

After a bit more research I think I can confirm that D tolerances primarily refer to the pitch diameter of metric taps. Presumably to avoid confusion with H tolerances which, strictly, were intended for holes.

I gather American practice is supposed to be to use GH rather than H for tap pitch diameter tolerance but this seems to be honoured more in the breach than observance.

For practical purposes it appears that D tolerances pretty much follow H tolerances with the same number.

I was unable to find a simple, straightforward explanation on the internet. the more detailed and potentially useful the presentation the more [deliberately?] confusing the explanation.

This link from Guhring **LINK**

https://www.guhring.com/media/InteractiveCatalog/jkko1oebbiy/files/basic-html/page32.html

has one of the less confusing presentations on the second page! I advise having headache pills, or at least a wet towel, handy before reading.

It all begs the question as to what a D4 tolerance has to do with reamers.

The Guhring reference above states that each D limit = 0.013 mm followed by a couple of examples that seem to make no mathematical sense at all.

Clive

Do you mean you wasted thousands of pounds of taxpayers money so likely a defence contractor? I don't like to blow my own trumpet like some on here but 49 years in precision machining working across various industries gives me a fair idea what is and what is not possible. Oh and my last 2 years of paid work was for a defence contractor who will remain nameless.

Tony

MichaelG

Thanks.

I have downloaded the document which should be useful, not that I will be reaming copper.

JA