10 Replies Latest reply on Feb 11, 2016 12:34 PM by Anna Wood

    inch vs mm prints and available tooling

    Derek Eldridge

      I'm being pushed to produce mm sizing on prints rather than inches.

      I was looking at available tooling and it would appear that ANSI Metric drills are provided every .05mm. (~0.0019in) in the range from 1mm to 2mm.

      ANSI Inch drills on the other hand, are not spaced evenly in the same corresponding range of (.040in to .0785in)


      But, when you look at reamer sizes available from Mcmaster;

      Metric reamers, available in the above range, include only 1, 1.5, 1.6, 1.7 and 2mm.

      Inch reamers available in the above range include every .0005" throughout the range. A lot more control on accuracy.


      With that said, It would appear to me that if you wanted tight locational or reciprocating fits, inch tooling is the only way to get it. (within the sample size range)


      I'm told that outside the United States, all machine shops are using metric tooling only, and do not have access to inch tooling.

      First, is it true that outside the United States, inch tools are not available or used?

      Second, are more metric tool sizes available outside the United States?

      Is there a different metric standard than ISO or ANSI that includes more drill sizes that may be used outside the United States?



      Why are reamers not an option in the solidworks hole wizard?

        • Re: inch vs mm prints and available tooling
          John Stoltzfus

          As for hole wizard reamers - you can show custom sizing, adjust the sizing to match the reamer, then save it as one of your favorites in the temp folder.

          • Re: inch vs mm prints and available tooling
            Mike Pogue

            This is interesting. Quick search shows metric reamers available in .5 mm increments, just as you said. But there is no way that this is sufficient to control fits. I'd like to hear from somebody who works mostly in metric.

            • Re: inch vs mm prints and available tooling
              Chris Saller

              Machine shops around the globe can use any size.

              On the drawing call out only the finished hole size, let the machinist figure out what size reamer to use...if one is needed.

                • Re: inch vs mm prints and available tooling
                  Derek Eldridge

                  This is almost the answer I'm looking for.


                  Though, I'd like to hear from an OUS machine shop that can confirm that they have access to inch tools, or do they have more metric sizes available to them.

                  Also, when machining OUS, are they working in metric or inch on their machines.  (In Other Words, are they converting my inch prints to metric or vice versa?)


                  What I believe is going on here, (in my situation) is that our OUS service techs are having a hard time finding inch wrenches and allen tools. So they requested that we use all metric hardware... Then, by way of the telephone game, we arrived at upper management pushing all metric prints for all machined components.

                    • Re: inch vs mm prints and available tooling
                      Mike Pogue

                      It's not that they can't get inch tooling--of course they can. It's 2015, anybody can get anything. It's more that it's very surprising that in order to ream a 5.1 mm hole the answer is to look up the nearest inch size reamer, in a country that does not use the inch system at all.

                      • Re: inch vs mm prints and available tooling
                        Anna Wood

                        The rest of the world uses metric.  Shops outside the U.S. work in metric.  Working in metric will make it much easier for your suppliers outside the U.S. to machine your parts.


                        Any good shop in the U.S. should be able to handle metric as well with no problems.


                        To elaborate on what Chris said, put the metric sizes and tolerances you need on your drawings and let the shops decide on the appropriate tools and techniques to meet print.

                          • Re: inch vs mm prints and available tooling
                            Derek Eldridge

                            Thank you. Everything you have said makes sense. "And I hear that the rest of the world is doing it", all the time. I want to understand how. I have to say, just because everyone else does it.... If everyone jumped off..... You get what i'm saying. 8-) That said, I'm more willing to adopt it, if I understand it.


                            Would it not be prudent, and cost conscious, to apply available tool sizing into your design?

                            If a milled part can hold a tolerance on a .125 inch hole to ±.0022" (per Machinist Handbook 26, Page 630). And Reaming can get you ±.0004". I feel I want to make sure the machine shop doesn't have to buy a special tool; or worse, have a custom tool made. I would think either would drive my cost up.


                            So if the shop doesn't have a inch reamers, or availability to purchase inch reamers, how would they get the tolerance I need for a Class LC7 or RC8 Fit. (.0008-.0038" and .0030"-.0066"). A metric reamers is not going to cut it. (no pun intended)


                            Oh yea, considering the rest of the world, What standard are they using for Limits and Fits?

                            • ANSI Standard Fits
                            • American National Standard Preferred Metric Limits and Fits
                            • British Standard for Metric ISO Limits and Fits
                            • Or another I'm not yet aware of.

                            I've been using the ANSI Standard Fits for a while, and find the later two confusing. I'm willing to spend more time understanding them, but would like to know what the rest of the world is using.

                            • Re: inch vs mm prints and available tooling
                              Mike Pogue

                              I disagree. While you do not specify tooling on a drawing, it is important for designers to understand the tooling that is required in order to design feasible, economical parts.

                              • You should pick standard sheet-metal bend radii
                              • You should employ forming tools your shop already has
                              • You should use standard punches
                              • You should select hole sizes related to drill bits that exist
                              • You should not ask for a back-chamfer that requires a mill that nobody can make or buy
                              • You should probably not send a tightly toleranced hole to a machine shop in Europe that will require them to buy a special reamer when they have a hundred standard reamers that they were expecting you to use.


                              Right now, the OP (and I am with him) are having trouble understanding what EU machine shops are expecting. Surely somebody on this forum has intimate knowledge of metric tooling.

                        • Re: inch vs mm prints and available tooling
                          Robert Conklin

                          Also on a sort of similar topic:

                          Counterbores for metric socket head cap screws…

                          Our shop has the tooling for these sizes, as shown here in the McMaster catalog:

                          Metric C'Bores  -  McMaster Carr.JPG


                          The sizes shown here, from the MSC catalog , are what Solidworks call out in the holewizard:

                          Metric C'Bores  -  MSC 01.JPG

                          We prefer the McMaster sizes and we are constantly changing the callout when placing holes with the holewizard,
                          I know I could change the MDB file to reflect the preferred sizes BUT Why can not Sloidworks  have an alternate
                          choice built in? Why does SW use the sizes they have in the holewizard?

                          What is the rest of the world (Non USA) really using?