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reamers - eBay lot vs Shars set - over, under, or exact

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  • reamers - eBay lot vs Shars set - over, under, or exact

    As I make the parts for the wobbler air engine for class, I want to get some of the tooling required for my home shop. I don't have any straight chucking (or hand) reamers, and I need at least a 3/16" and 3/8" for a force fit as well as an RC5 fit. When I reamed the 3/8" hole in the aluminum crankshaft, the dowel could be inserted by hand, meaning it was too loose for a force fit. I reamed another hole more quickly, and it seems like just barely a force fit. The reamer was supposed to be an exact size, but it miked a few tenths over.

    I found what appears to be a good assortment of used reamers (including an MT1 shank 3/8")
    http://www.ebay.com/itm/11-Supeream-...T/311278121925



    The same seller has a large number of other items from a machinist's estate sale:
    http://stores.ebay.com/WVTools/Machi...=p4634.c0.m322

    Another lot:
    http://www.ebay.com/itm/281583625970

    I was going to buy new 3/16" and 3/8" reamers from Enco, using the 15% + free shipping coupons, but I decided to look elsewhere. Those two reamers would be about $20 - not bad, but I would like a wider assortment, and I'd like advice on whether to get an over/under set or exact sizes. I probably won't need to use them very often and I don't need extreme tolerances. If a situation arises where I need specific sizes, I can always get them.

    http://www.ebay.com/itm/SHARS-14-PCS-0-124-0-501-HSS-Chucking-Reamer-Set-NEW-/330919956166 (Over/under $67 + $6 ship)

    http://www.ebay.com/itm/330966664843 (7 piece $40 - out of stock)

    http://www.amazon.com/Grizzly-T10085...rds=Reamer+Set ($62)
    http://pauleschoen.com/pix/PM08_P76_P54.png
    Paul , P S Technology, Inc. and MrTibbs
    USA Maryland 21030

  • #2
    Use "spring" or "grooved" dowel pins:

    https://www.google.com.au/search?q=d...2&ved=0CC4QsAQ

    https://www.google.com.au/?gws_rd=ssl#q=dowel+pins

    Comment


    • #3
      They are called roll pins or spring pins here. They come slotted and coiled.

      As far as the original question regarding the reamers, both sets, exact and over/under, are helpful in different situations.
      Last edited by MichaelP; 02-24-2015, 01:04 AM.
      Mike
      WI/IL border, USA

      Comment


      • #4
        You do not use spring-or grooved-or roll pins for precise locations. Standard 3/16 (.1875") dowel pins are +.0002". Use a .1873" reamer. Standard 3/8 (.3750) dowel pins are +.0002". Use a .3748"
        reamer. Ream at slow speed and lubricate. If you can not get a reamer that is .0002 undersize than use a full size reamer and lightly stone the top of the flutes. Careful when reaming aluminum! Use a lubricant approved for aluminum.

        Comment


        • #5
          The dowel pins are used as axles (shafts) so the spring type won't work. For aluminum, it seems like the hole can be enlarged slightly just by running the reamer a bit longer or with multiple strokes. If I were designing the engine, I would use steel for the crank, and I might use drill rod (which can be machined to either a force fit or clearance fit), and I'd probably use bronze oilite bushings or ball bearings. I have also made a force fit hole in aluminum by using a machine taper reamer from both sides just large enough for the shaft. It may also be good to knurl the shaft for the force fit, but that won't work for dowel pins if they are hardened. The instructor suggested Loc-Tite.

          I found a pretty good calculator for fits:
          http://www.amesweb.info/FitTolerance...eImperial.aspx

          An RC6 running fit for 0.375" is -0, +0.0014

          RC5 is -0, +0.0009

          FN2 for 0.375" is -0, +0.0006

          For 0.187" it is -0, +0.0005

          I'm not sure how to achieve such tolerances, or to measure the hole. I do see that McMaster has reamers that can be specified in increments of 0.0001", so I guess you just have to obtain the exact size for the spec.
          http://pauleschoen.com/pix/PM08_P76_P54.png
          Paul , P S Technology, Inc. and MrTibbs
          USA Maryland 21030

          Comment


          • #6
            Those reamer sets are so expensive. I am still looking to get one but at $200 or so, and I will need to get both a metric and imperial set to be complete, thats a good $500 or more, and before you include shipping.

            Mostly I end up buying what I need as most of the time, I figure even if I have a set, I probably won't use the majority of them. I just like the idea of having a set, because its flexible and I can pick and choose if I ever need it.

            Comment


            • #7
              I had the same happen, turned out to be the tailstock was out 1/2 a thou and making the hole bigger, worth looking in case
              Mark

              Comment


              • #8
                If you have a reamer or drill that is slightly oversize, and you have eliminated the mechanical sources as bobslab suggests, you can use a controlled etch to remove a few ten thousandths.

                Copper sulfate/sodium chloride is relatively harmless and nice and predictable. see this.

                I experimented with it a few years ago as an alternative for etching pattern welded steel for knife making. WWAN, but IIRC the rate was on the order of .0006" per hour. All the ususal chemical warnigs and cautions. You must also remove all traces of oil for this to be effective. A hot solution of calcium carbonate, washing soda, or powdered dishwasher soap works great for this.

                paul
                paul
                ARS W9PCS

                Esto Vigilans

                Remember, just because you can doesn't mean you should...
                but you may have to

                Comment


                • #9
                  Out of context quote..........

                  Originally posted by PStechPaul View Post
                  The same seller has a large number of other items from a machinist's estate sale...
                  Why not pursue that same route to buy your reamers? Garage/estate/tag sales, machine shop auctions, etc.? If they are not wrapped, tubed, dipped in tool dip or covered with tool netting, don't buy them. Reamers shouldn't be rolling around in a box like common nails.

                  If you think your going to acquire complete sets, then you'll want #1-#60, 1/64"-1/2", letter A-Z, over and under dowel pin sets.

                  Comment


                  • #10
                    I've never had any luck buying used reamers that are sharp. Dull reamers don't cut correctly or on size, so I've given up and just buy new ones in the sizes I need. For me, it is cheaper in the long run.

                    Comment


                    • #11
                      Originally posted by PStechPaul View Post
                      I'm not sure how to achieve such tolerances, or to measure the hole. do see that McMaster has reamers that can be specified in increments of 0.0001"
                      You don't need such high tolerances for building simple model engines. An inexpensive set of gage pins (.001" steps) would be very handy and sufficient for your needs. Mine are Chinese in MINUS .0002 tolerance, and I found them to be quite useful.
                      Last edited by MichaelP; 02-24-2015, 11:36 AM.
                      Mike
                      WI/IL border, USA

                      Comment


                      • #12
                        Without the correct method of holding a reamer talking about reaming to tenths is meaningless.

                        The holders I have are specifically made to hold reamers and have radial float. That is, they can self locate on an existing hole to follow it.

                        Holding in a drill chuck or other rigid device may not work since they can guide the reamer not allowing it to follow the hole. If the rigid holding device is not perfectly centered on the bore it can act more like a boring bar and enlarge the hole by its amount of un-centeredness.

                        Comment


                        • #13
                          You can make a reamer cut over or under its size by stroking the cutting edge with a HSS lathe bit. Use on the inner surface to make oversize, outer surface to make undersize.

                          For one off reamers, D reamers can be made from drill rod in a few minutes. It is a worthwhile project to undertake as it is unlikeky you will always have the reamer needed, and waiting for shipping or driving to the tool supply every time a size is needed is not a good use of time or financial resources.
                          Jim H.

                          Comment


                          • #14
                            Keep in mind chucking reamers are different than hand reamers. Chucking style reamers have straight cutting edges. In your first link all except the one 4th from the right are chucking reamers. They are meant to be fixtured in a collet or floating holder. They will never give you a true bore when used by hand.

                            Hand reamers on the other hand have spiral flutes like the one 4th from the left in the first link. They literally screw themselves through the hole reaming to size. Having said that I doubt you'll be able to ream to within .0001" by hand. Over the years I've reamed thousands of holes for dowel pins and never had to be within .0001".

                            Most standard ground and hardened dowel pins are .0001" - .0003" oversize so they can be pressed into place.

                            Undersize dowel pins are generally .0002" under the specified size.

                            Oversize dowel pins are either listed as .001" oversize or .002" oversize. Even then they have a tolerance range. The .001" oversize a have a range of +.0009 to +.0012. The .002" oversize have a range of +.0019" to +.0021".

                            Attempting to ream to .0001" is an exercise in frustration. I doubt you'll be able to hold that tolerance more than 10% of the time unless you have a precision jig borer something like this:

                            http://www.ebay.com/itm/Moore-Jig-bo...item4ae58083c6.

                            Comment


                            • #15
                              Chucking and hand reamers can both be had in spiral or straight flute styles. Straight flute are for use in plain bores, spiral flute for use in bores which are interrupted such as those with keyways.
                              Jim H.

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