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  • Keyway questions

    I am rebuilding a gear box for a farmer and have run into a small issue. This gearbox required me to make a couple new shafts which require keyways. I can cut normal keyways with no trouble, but these shafts have woodruff keys. Four different sizes and I don't have any woodruff key cutters.

    These keys connect the shaft to bevel and worm gears. It's a high torque, low RPM, reversing deal and no set screws clamping the keys in. I'm worried that if I just cut a standard keyway for a square key, they will rock too much and damage parts.

    If I go with the original woodruff keys, how do I determine cutter size? Width is a no brainer, but diameter kind of puzzles me.

    If I decide to go with an alternative, is there anything wrong with doing a rectangle key? Same width and length, but double depth to prevent rocking.

    I'm stumped and need to get stuff ordered. New gears will be here tomorrow.
    Please help....

  • #3
    Just for future reference shafts receive key seats, bores such as gears, pulleys, etc have keyways.

    I recommend you purchase a copy of the Machinery's Handbook as it has your answer along with thousands of other answers and information. Personally I think you'd be better off cutting Woodruff key seats in the new shafts.

    Comment


    • #4
      Radius? Find a chunk of wood, sidemill some grooves in it. See what one the key fits best in.

      Alternatively, buy the $20 set of radius gages. (little stamped peices of sheet metal with known/marked inside and outside radiuses on each gage)
      Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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      • #5
        That book is on my list of things to get when I finish my current jobs and get paid.

        I have the old keys, but they don't have any markings. Do I need to match them up at the store so I know if they are 810 or 1010 or whatever, then buy the cutter to match? Two of the keys measure about 1 1/4" long. From info found on Mcmaster's site, these may require an 1 3/8" or 1 1/2" cutter. Does that sound right? I wouldn't think they would use an 1 1/4" dia. cutter. There wouldn't be anything left for the shank.

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        • #6
          Just buy the right tool and be done with it. Charge it to the job. They are not that expensive.

          Take pieces of round stock and compare them to the radius of the key.

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          • #7
            Key ways and seats are not rocket science. You can modify any key to fit your needs or repairs. The only problem is that if some one goes to repair it at a later date they also will be dealing with non standard key dimensions. You are correct about not wanting any play in the key or slot, "no rocking". This is especially important on things that abruptly reverse directon. For these kind of applications I like a tap fit key. I went through all this when I had to make a new axel tube for my lawn tractor. All the key slots were shot from rocking. Years of forward and reverse took it's toll on it.

            JL................

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            • #8
              Originally posted by Boostinjdm
              Two of the keys measure about 1 1/4" long. From info found on Mcmaster's site, these may require an 1 3/8" or 1 1/2" cutter. Does that sound right? I wouldn't think they would use an 1 1/4" dia. cutter. There wouldn't be anything left for the shank.
              Yes the cutter will be larger in dia than the length of the Woodruff key.

              BTW, you probably do not need a brand new copy of Machinery's. A used one should be more than adequate and will cost much less.

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              • #9
                the keys length does not matter, its the radius in them that matters.

                They are only a fraction of a circle, Hence the length is NOT the diamiter.

                Figure out what radius they are by seeing what radius they 'fit' into. That will be the radius of the cutter you need.
                Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                • #10
                  Here is a link that should be able answer your questions.

                  http://www.ecs.umass.edu/mie/labs/md...druff_key.html

                  Comment


                  • #11
                    The chart from the MIT site is good.

                    I was going to suggest this:

                    Measure the width first. Next, using a depth gauge with a pointy end, measure the depth of the keyway. Add 1/2 of the width to the depth, now you should have the height of the key. Look it up in a Machinery's Handbook, you'll have the required cutter number and it's dimensions.

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                    • #12
                      I matched up the keys so now I know what size cutter to get. One is an 810, the other a 1010. Now for another question. Can I take multiple cuts with the 810 cutter to make the 1010 key seat? I know it isn't proper, but has anyone successfully done it?

                      Comment


                      • #13
                        Originally posted by Boostinjdm
                        I am rebuilding a gear box for a farmer and have run into a small issue. This gearbox required me to make a couple new shafts which require keyways. I can cut normal keyways with no trouble, but these shafts have woodruff keys. Four different sizes and I don't have any woodruff key cutters.

                        These keys connect the shaft to bevel and worm gears. It's a high torque, low RPM, reversing deal and no set screws clamping the keys in. I'm worried that if I just cut a standard keyway for a square key, they will rock too much and damage parts.

                        If I go with the original woodruff keys, how do I determine cutter size? Width is a no brainer, but diameter kind of puzzles me.

                        If I decide to go with an alternative, is there anything wrong with doing a rectangle key? Same width and length, but double depth to prevent rocking.

                        I'm stumped and need to get stuff ordered. New gears will be here tomorrow.
                        Please help....
                        Why is it at this late stage that these questions are being asked instead of asking them before taking the job on?

                        Comment


                        • #14
                          Part of the thrill, worry and learning process--

                          Surely part of the process of becoming a successful " Home Shop Machinist" is undertaking work which is just a little more advanced than you have done before and economically and quickly getting it done?. Sometimes you may think you know what is involved only to find a new challenge hidden somewhere in the job. Thats when to ask your friends or here to get sensible advice and to follow it through to a successful conclusion. Once in a while you may have to say you cannot do the job, or advise that your repair would be inferior to the purchasing of a new part, a sensible customer would appreciate that honesty. I do not think many of my customers would appreciate me If I needed to analyse every job that lands here in great detail before I would consider whether I could or would do it for them. Much of what I repair is long out of date and there are no original spares available, so ingenuity and adaptation are both needed. Hope this is encouraging David Powell.

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                          • #15
                            Buy the correct keyseat cutters. That way there will be no Should've, Would've, Could've done it right. You will sleep much better!

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