Key types – any advantages?

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Key types – any advantages?

Home Forums Workshop Tools and Tooling Key types – any advantages?

Viewing 16 posts - 1 through 16 (of 16 total)
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  • #311299
    Ignatz
    Participant
      @ignatz

      I've got to make a replacement countershaft for my ML10 lathe. This shaft has Woodruff keys at either end for the drive pulleys.

      I see that the cost for the correct Woodruff key milling cutter is pretty steep… most especially when considering that this is essentially for one-time use.

      Would an alternate straight, 'feather key' work just as well in this situation?  This is something that I could mill out much more easily with the tooling at hand.  (see illustration)

      key choices.jpg

      Edited By Ignatz on 10/08/2017 08:15:44

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      #18612
      Ignatz
      Participant
        @ignatz
        #311300
        roy entwistle
        Participant
          @royentwistle24699

          A feather key would be ok if fitted correctly

          After all it's what youv'e got on the motor

          Edited By roy entwistle on 10/08/2017 08:43:09

          #311307
          Brian Wood
          Participant
            @brianwood45127

            John Stephenson replaces them at every opportunity and any job that comes to him has straight keys put in as a matter of course.

            ​That would seem to be a good endorsement by someone with long practical experience.

            ​Brian

            #311308
            vintagengineer
            Participant
              @vintagengineer

              I assume woodruff keys are fitted as it easier to manufacture for mass production work, but tend to be weaker as they take out more material than needed.

              I prefer straight gears as you only need to remove a minimal amount of material from the shaft.

              #311315
              JasonB
              Moderator
                @jasonb

                Woodruff keys are often used on tapered shafts where it is easier to machine than setting the work at and angle to mill the slot and the taper takes the load and key just acts to locate the item on the shaft such a timing gears/pulleys.

                #311317
                ega
                Participant
                  @ega
                  Posted by JasonB on 10/08/2017 10:21:41:

                  Woodruff keys are often used on tapered shafts where it is easier to machine than setting the work at and angle to mill the slot and the taper takes the load and key just acts to locate the item on the shaft such a timing gears/pulleys.

                  I seem to remember that the Austin Seven had this arrangement on its halfshafts.

                  Either type of key seat can be machined on a vertical mill but the straight key way would perhaps be more difficult on a horizontal mill.

                  Woodruff keys and cutters are readily made in the amateur workshop.

                  I assume that model makers would aim for authenticity of key type.

                  PS Excellent illustration, Ignatz!

                  Edited By ega on 10/08/2017 11:02:24

                  #311319
                  Nick_G
                  Participant
                    @nick_g
                    Posted by JasonB on 10/08/2017 10:21:41:

                    key just acts to locate the item on the shaft such a timing gears/pulleys.

                    .

                    Motorbike flywheels and timing gears often have such as they may house the ignition sensor magnets. Quite common for such an engine to also have a 'wasted spark' in the cycle.

                    Nick

                    #311321
                    larry Phelan
                    Participant
                      @larryphelan54019

                      Can,t see how it would make much difference,the key is not going to fly out anyway once the pulley is locked in place,is it?

                      I suspect Woodruff keys are just easier and cheaper to make/

                      #311323
                      Speedy Builder5
                      Participant
                        @speedybuilder5

                        problem with Woodruff is that they weaken the shaft more than a flat key, but reduce the possibility of stress fractures caused at the ends of the flat keyway slots. Another problem with Woodruf is that they can 'rock' whilst the pulley is fitted to the shaft which can be a nuisance during assembly.

                        #311326
                        JasonB
                        Moderator
                          @jasonb

                          If they are being used as I mentioned above purely to locate the part on the shaft and not to transmit any power then they can be far smaller than a straight key that has to transmit the load so may not take as much out the shaft as the straight key.

                          Suppose it all comes down to using the right thing for the job in hand and designing the shaft to allow for what is cut away

                          #311330
                          Andrew Tinsley
                          Participant
                            @andrewtinsley63637

                            I lost the Woodruff key for my electric motor. In desperation I just bolted up the pulley wheel very tightly and ran the machine sans Woodruff key. It stayed that way for weeks until I sourced the correct Woodruff key. On disassembling, there wasn't any sign of the pulley wheel having spun on the shaft!

                            So I reckon your solution would do fine. Before people berate me for being idiotic. I was desperate to get a job done and it was worth sucking and seeing.

                            Andrew.

                            #311345
                            Ignatz
                            Participant
                              @ignatz

                              Thanks, everyone, for the feedback. I think that i can safely alter the design of the replacement countershaft to use those captive straight 'feather' keys. There is a tiny bit more fuss-n-bother making multiple passes with a small slotting end mill, but the end result should be far easier on the pocketbook. wink

                               

                              PS  Illustration prepared using Blender 3D software with a few adjustments in the Photoshop.

                              Edited By Ignatz on 10/08/2017 14:56:26

                              #311362
                              Bob Rodgerson
                              Participant
                                @bobrodgerson97362

                                Woodruff cutters are easily made by grinding down an end mill to the correct thickness. I used to use cutters that had maybe chipped a tooth but who,s flanks were still in good condition. They work well.

                                #311368
                                Howard Lewis
                                Participant
                                  @howardlewis46836

                                  If a key is needed PURELY for alignment, a short stud set into the shaft can be used. (Example: Stanadyne Fuel Injection Pumps) but ONLY for alignment; precious little use for transmitting torque.

                                  Howard

                                  #311385
                                  Neil Wyatt
                                  Moderator
                                    @neilwyatt
                                    Posted by Howard Lewis on 10/08/2017 18:36:45:

                                    If a key is needed PURELY for alignment, a short stud set into the shaft can be used. (Example: Stanadyne Fuel Injection Pumps) but ONLY for alignment; precious little use for transmitting torque.

                                    That's what I did for my dividing attachment

                                    Money spent on a woodruff cutter is not necessarily wasted, they have other uses, such as cutting horizontal slots using a vertical mill.

                                    Neil

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