Author Topic: Gear cutting  (Read 4368 times)

Offline cyfareddol

  • Newbie
  • *
  • Posts: 2
Gear cutting
« on: January 23, 2013, 01:00:44 PM »
I bought a set of plans to make an Eli Terry clock about 35 years ago and began to experiment with a lathe based gear cutter, I didn't own a band or scroll saw and routers hadn't been invented.   I used a length of bandsaw blade with the appropriate number of teeth fixed to a wood disc as an indexing device.  I did make some gears but they were not good enough and I left the project alone until now.
I have read in this forum about posters wanting an alternative to scroll saw cutting,  I now find this very hard on my focusing capacity. I have made an accurate 150mm dia.  60 tooth gear using my new machine. I have a 60 tooth circular saw blade on the outboard end of my lathe with a detent and friction on the blade.  The inboard end has  the gear blank between two scrap discs mounted on a faceplate and over the bed and faceplate is a carrier on which my router slides in a channel between stops.
The gear I have made has 4mm wide x 4mm deep slots and inserted oak teeth. It took about 30mins to make. I do have to sand the tooth profile but the difficult bit is done.
I have many saw blades with differing numbers of teeth but poor quality new ones can be bought cheaply and the tooth spacing is very regular.

Offline steve323

  • Newbie
  • *
  • Posts: 77
Re: Gear cutting
« Reply #1 on: January 24, 2013, 10:44:39 AM »
cyfareddol,

Are you using the saw blade just as a way of indexing the position of the wheel.  This gives you as many options as you can find tooth counts for saw blades.  24, 30, 40, 60, and 80 may be available.  64 teeth may be hard to find.  You could skip teeth or with multiple index pins you can multiply the number of positions.  Many metal working lathes or rotary tables offer dividing plates with multiple rows of evenly spaced holes.  This gives plenty of options for hole spacing.

What are you using to cut the tooth profile?  Do you have an involute tooth shaped router bit?  That would be awesome.  It would even allow you to cut the teeth in a long cylinder and slice it into many gears instead of doing them one by one.

thanks
Steve

Offline cyfareddol

  • Newbie
  • *
  • Posts: 2
Re: Gear cutting
« Reply #2 on: January 24, 2013, 11:46:16 AM »
My first gear was cut using a 4mm straight cutter, I inserted teeth with end grain wearing surfaces and then tried to shape the teeth with various sanders, very slow and difficult because I had no lines to work to. I failed to make the teeth exactly regular.

Next gear was cut first with 4mm tapered  cutter and then almost to profile with a modified round over bit but it still needed sanding and would be irregular.

I'm going back to inserted teeth next but I'll make the tooth profile on a long strip so the teeth will be finished when I fit them.

Offline steve323

  • Newbie
  • *
  • Posts: 77
Re: Gear cutting
« Reply #3 on: January 25, 2013, 10:49:58 AM »
I'm going back to inserted teeth next but I'll make the tooth profile on a long strip so the teeth will be finished when I fit them.

That seems like a good idea.  It may make the outer rim a little bulky because it has to have enough width to hold itself together and provide enough depth for a good glue joint.  The advantage is that every tooth will be identically shaped.

I always manage to change the profile slightly as I am sanding them.

Steve