Announcement

Collapse
No announcement yet.

bevel gears?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • bevel gears?

    Pardon me for being such a NOOB, but I've started a project that requires gear cutting....I'm OK with straight cut gears, I have the mill and a rotab, but how to cut bevel gears has me baffled. Can somebody point me in the right direction? (and none of that digital stuff...I'm retired, not rich.
    No good deed goes unpunished.

  • #2
    Dear Mr Salt Mine

    Do a web search for a book called Gears and Gear cutting by Ivan Law.
    It's not expensive, it's one of the cheap and cheerful Workshop Practise series #17

    This book covers cutting parallel depth bevels which are far easier to cut than standard bevels.

    It has to be the definitive book on gear cutting for the HSM.

    .
    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



    Comment


    • #3
      A very good book

      I'd agree with John.

      I usually don't bother with "learned books by famous machinists" but Ivan Law's book really is an exception, and as John says is pitched just right for the HSM-er.

      I bought mine through/from Amazon.com and it was surprisingly good value for the money.

      Comment


      • #4
        Here is some information to get you started. It from an old book out of copyright. I don't recall the title but it's in my library.







        Free software for calculating bolt circles and similar: Click Here

        Comment


        • #5
          Free software for calculating bolt circles and similar: Click Here

          Comment


          • #6
            The Colvin and Stanley book, mine is from Lindsay, is pretty good and between that and machinerey's handbook you have what you need.

            NOBODY, apparently from what I have heard that includes Ivan (although I don't personally have his book), explains bevel gears completely in any of the "normal" books.
            1601

            Keep eye on ball.
            Hashim Khan

            Comment


            • #7
              back to basics

              DON'T get bogged down in the "hi-tech" stuff as its not needed most times in the HSM shop. Get the basics right first and move up/on as you may need or want to later.

              Ivan Law's book will show you all that you probably need to know in layman's language as well as show you how to make the blanks as well as cut the bevel gears using the common old garden variety of "numbered cutters" (as used for spur gears) as special bevel gear cutters are expensive.

              All that bevel gears are is two cones rolling against each other. The length of the sloped sides is the same. The "gear ratio" is the same as the diameter ratio at the end of the cones - simple as that.

              If friction would do the job to stop "slip" (it won't) there would be no need for "teeth" - but of course there is. So as for gears there is some of the cone/s cut away (grooved) below the pitch line (where the cones are in contact) and some metal plonked onto the parts above the the cones that weren't cut - voilla - bevel gears.

              But get Ivan Law's book. Its not expensive and is a good read.

              Give Machinery's Handbook a miss for time being.

              Comment


              • #8
                Originally posted by saltmine
                Pardon me for being such a NOOB, but I've started a project that requires gear cutting....I'm OK with straight cut gears, I have the mill and a rotab, but how to cut bevel gears has me baffled. Can somebody point me in the right direction? (and none of that digital stuff...I'm retired, not rich.
                Do you need to match to an existing gear(s) or are you cutting all the gears needed? It makes a difference in what your solutions are going to be.

                Comment


                • #9
                  Machinery handbook covers the correct way to cut bevel wheels where as in Evans text the depth is generated to the cone point.

                  Ivan's book doesn't cover that method but one called parallel depth bevels that was used widely in WWI to enable simple machine shops [ which is what the HSM er is ] to generate working bevel gears. These can't run with normal bevels and have to run as pairs.

                  With correct bevel wheels cut with a form cutter on a mill with dividing head at the ROOT angle you have to do 3 passes per tooth, one central, one with the quill raised and the DH rotated slightly one way and the last cut with the quill lowered and the DH rotated the other way.
                  However it leaves two portions of the tooth form that cannot be machines without compromising the shape and these have to be hand filed to obtain the correct clearance and smooth running.



                  This happens because the cutting action is fixed i.e. quill and head locked at a certain position. A Gleason gear generator gets by this as it rotates as cutting and generates the shape from rack shaped cutters.

                  Correct bevel gears also require special bevel cutters although normal cutters can be used as a fudge.

                  Parallel depth bevels OTOH can be cut with normal gear cutters and require no hand filing to fit which makes them idea for a home shop.

                  .
                  .

                  Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



                  Comment


                  • #10
                    I recommend 'Advanced Machine Work', its a Lindsay reprint of a 1920s American publication, and it covers exactly how to cut 'proper' variable depth bevel gears. Its available from Camden Minature Steam Supplies in the UK, but as its a Lindsay reprint, must be available in the US too.
                    I had never cut any gears before, let alone bevels, but with the aid of this book, I cut all the gears including the bevels, for a 4" traction engine. Don't worry, there was no digital stuff when this one was written!

                    Regards
                    Richard

                    Comment


                    • #11
                      Well, then, I won't be bothering with the Law book.

                      I have no interest whatever with "almost but not quite" bevel gears that cannot run with others, although I HAVE cut a number of bevel gears that DO run with other pre-existing bevel gears.

                      The "two pass (or really actually three pass) method does a fine gear which will work well. JS described the procedure with a vertical mill like his beloved Bridgeport, but you do different things with a horizontal mill. They accomplish the same result.

                      If you pick your cutter correctly, and do a couple "adjustments" your filing is minimized. At least it was for me.
                      Last edited by J Tiers; 01-31-2009, 10:44 AM.
                      1601

                      Keep eye on ball.
                      Hashim Khan

                      Comment


                      • #12
                        Thanks guys. I guess I needed a nudge in the right direction. Cutting beveled gears doesn't look that difficult once somebody explains it.
                        I can see now that setup is the critical deal. I read one guy's account on how he made beveled gears on a Sherline lathe and mill....with the help of a CNC program...If he can do it with CNC on a Sherline, I sure as heck can do it manually on a HF lathe and mill.
                        No good deed goes unpunished.

                        Comment

                        Working...
                        X