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  • Need a Gear

    Recently acquired, (read free), Shear Brake Roller sheetmetal machine that's missing one of the drive gears for the rollers. Buying one isn't working, so ... can I make one?

    Tools available are a Logan 11" lathe, Seig X3 mill, and a Spindexer with 24 stops ... and 24 teeth could do the job. The matching drive gear I have has 21 but if I can make one I can make two.

    I'm assuming the pitch dia. should be close to size of the rollers which is 1.655. 42mm?

    And that's all I know.

    TIA.

  • #2
    Index off your 21 tooth if you can..

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    • #3
      If you have the correct gear cutter you can make a blank for the missing gear. Connect both the blank and the gear together on a mandrel and use the original gear to set the depth and indexing for cutting the new gear.

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      • #4
        I've been looking at gear cutters which seem to come in 2 flavors. 14.5 degree pressure angle and 20. I don't know how to determine what angle my existing gear has. But if I made two at least they'd match.

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        • #5
          You can determine pressure angle by rolling the gear over some modelling clay. The resultant rack form has a pressure angle equal to the tooth angle.
          But you could just make a form tool the shape of the spaces on your existing gear and use that to cut the teeth on your new one. That's how I'd probably do it.

          Dave
          Just south of Sudspumpwater UK

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          • #6
            If you can't buy it you can make it is the general theme around here. Is this roller an antique or an import? If it's old American iron chances are it's 14.5 pressure angle. Can you provide more specific dimensions?

            If you want to fabricate a replacement I would go with making a form cutter modeled after your existing 21 tooth gear. With a little patience you can hand grind a piece of HSS. It might make a little noise for a gear mounted in a transmission, but for a hand crank application free-hand grinding the cutter profile for a gear should work fine.

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            • #7
              Woah doggie! You can't just pick any pitch and pitch diameter and expect the two gears to work. The pitch, the pitch diameter, and the spacing between the two gears are all related and they must match properly for the gears to mesh. In the absence of a third, idler gear,

              I am assuming that your center-to-center distance between the two gears is fixed. That does not allow much flexibility there. OK, these machines often have a bit of an adjustment in this distance, but not all that much. There is going to be a certain minimum distance, probably with the two rollers touching, at which they must still mesh and that is going to be your target distance.

              And the fact that this distance can be increased A BIT puts a limit on how SMALL the gear teeth can be. If the center-to-center distance is increased too much the gears will jam or break under the loads the rolling process places on them. You do not want that. So you probably need to stay close to the original design parameters.

              In short you will need to either make a duplicate of the original gear or make a pair of them that are very close to that original design to maintain the proper mesh.

              I would:

              With the two rollers in contact, MEASURE the center to center distance. That is probably just the diameter of each roller, but check. Call that "d".

              Count the teeth on the remaining gear. That is "N".

              Now you can calculate your Diametral Pitch. P = N/d

              If that does not come out very close to a whole number, then your gear is probably a metric one which is measured in Module instead of Diametral Pitch. The formula for that is: m = 25.4 / DP or m = 25.4*d/N.

              If your gear is metric, it almost certainly has a 20 degree pressure angle. If it is an English system (inch measure) gear then it could be either 14.5 or 20 degrees. I would suggest posting high quality, well focused photos of both the entire gear and a close up of several teeth of it here and we can probably tell which one it is by comparing it against known gears. I am not a big fan of the modeling clay method mentioned above because you would be rolling the gear on it's OD, not the pitch diameter and that will distort the "rack" teeth generated. There is enough difference between those two pitch angles so that they look significantly different in side-by-side photos.

              Once you know the pitch and pressure angle, a cutter can be either purchased or made. But that is a whole 'nother story. One step at a time.



              Originally posted by pntrbl View Post
              Recently acquired, (read free), Shear Brake Roller sheetmetal machine that's missing one of the drive gears for the rollers. Buying one isn't working, so ... can I make one?

              Tools available are a Logan 11" lathe, Seig X3 mill, and a Spindexer with 24 stops ... and 24 teeth could do the job. The matching drive gear I have has 21 but if I can make one I can make two.

              I'm assuming the pitch dia. should be close to size of the rollers which is 1.655. 42mm?

              And that's all I know.

              TIA.
              Last edited by Paul Alciatore; 05-20-2021, 05:16 AM.
              Paul A.
              SE Texas

              And if you look REAL close at an analog signal,
              You will find that it has discrete steps.

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              • #8
                45 years ago I was building a freelance model steam roller. I worked out a geartrain using gears from other peoples scrap piles and my own stock, but got stuck for a final drive gear of 70 teeth 10 dp.
                I had such a gear as part of the equipment for my pre 1914 Drummond lathe, but could not spare it. At the time I had neither skill , equipment nor knowledge to make a proper gear.
                When visiting a friend I saw a large washer being used as a weight on his power hacksaw and begged it. To my great delight it was exactly the OD I needed.
                I bolted it to my gearwheel. Drilled a 1/16 the hole at the bottom of each tooth, separated the blank from the gear, cut a vee to each hole and filed for a week, made a centre for the washer, tried my gear against a proper gear and filed for another week till the pair turned freely at a reasonable centre distance.
                The roller has run hundreds of miles, the gear still looks fit for many more years use.
                Do not be afraid of making an approximation for your needs.
                Regards David Powell.

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                • #9
                  Click image for larger version

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ID:	1943634 I have to admit - I have never made a gear from a scratch, at least not completely. But I would not hesitate making one, if I have to.

                  pntrbl, I suspect your gear is metric. For a spur gear the OD = m x Z, where m is module and Z is number of teeth. In your case 42 = 2 x 21, so your module is 2. I am pretty sure the pitch diameter should be equal to roller diameter so you can completely close the rollers and still be able to turn them. You cannot vary the number of teeth or module - it has to be the way the rollers were designed.

                  Many years ago I have made a sheet metal roller, mostly for very small work. Look at the attached pictures - it is a little rusty, but still works like new. The gears are to synchronize the rollers and to transfer the torque. The clearance between rollers is adjustable from 0 to 4 mm. With 4 mm clearance the gears are still engaged somewhat and will work. In my case the rollers are 54 mm in diameter and gears are m=3, Z=18. Big module is needed to cover 0 to 4 mm adjustable range. The design was not mine, it was copied from another unit. I did not make these gears either.

                  Your m=2 gears should not be too difficult to cut, but you need a cutter (buy or make) and a way to divide the blank for 21 teeth. My rotary table can definitely handle the job, but I have no cutters and no time. You can try filing the blank like David Powel suggested if this is all you can do. Maybe it is time to start looking for a dividing head...

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                  • #10
                    I am adding a couple more pictures of my roller. After looking at my post I realized the design was not clear.

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                    • #11
                      Mod 2 gears 21 teeth 20mm thick allegedly made from 1045 steel and induction hardened.. Are like 15$ on ebay.

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                      • #12
                        You might try this calculator-

                        https://www.technobotsonline.com/gea...alculator.html

                        If it does return as a metric gear then these people may have it-

                        https://www.khkgears.us/catalog/?c=f...gaAhvNEALw_wcB
                        I just need one more tool,just one!

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                        • #13
                          I have a 3-in-1 sheet metal machine, albeit one made in the USA. The "gears" on the rollers do not look like regular spur gears at all.

                          Would the OP please post a picture of the end which has all its gears, so we can see what they look like?

                          metalmagpie

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