Gear cutter question

[Cogsy]

Have a look at the site I posted, the cutter/'hob' is just a straight rod with several v's cut into it, then some flats are milled to form the teeth. The most difficult bit (once the math is complete) is grinding the lathe tool the correct angle. Here's the link again.

 

[V 45]

Here's the type of cutter I've been trying to make. I've made several but none the right shape.How Do I cut a R.100 (100 degree radius) on a lathe tool bit?

 

[kvom]

What is the purpose of the mechanism? If constant velocity or a perfect mesh isn't needed you could cut triangular teeth much easier with a single cutter.

 

[V 45]

It's for the Hoglet engine gears. .. reduced

Edit: Here's what I tried today. It doesn't seem to be working out. The cutter has a 3/32" radius, it's the closest I could do with tools available. Which equals .093 radius. I used index circle 18 on my rotary table plate. Using 3 turns plus 6 spaces. It's a 90-1 table. I'm using a 5/32" lathe mandrel and used a .155" reamer for the center hole. I turned a aluminum blank to try it. The blank actually started to slide down the mandrel. I have the thicker end towards the tail stock. I was thinking about putting a metal tube over the mandrel to stop this. The project gears will be brass. Thoughts?
It posted the pics sideways !!

 

[V 45]

Any help with this?
Thanks again

 

[steve-de24]

The mandrel holding the gear blank is too flexible - it needs to be as rigid as possible. I would make one similar to the one you have holding the cutter. Diameter sticking out of the three jaw should be a piece of bar just smaller than the diam across the roots of the gear teeth, then a shoulder down to the gear shaft diameter - a good fit on that diam - then a thread for a nut. Between the gear blank and the nut you need to make a big washer - outer diam same as the bar. Make sure everything nuts up hard with no interferences in the corners, undercut the corners if necessary. A centre at the end of the bar for the tailstock as well.
Make sure the direction of the cut the gear cutter is making is towards the shoulder on the bar.

Take a look at gear cutting set ups on the web. Make it as rigid as possible.

Good luck
Steve

 

[user 23363]

I used this author's setup; he describes the "rig" in detail after a few pages. Shows how to make a single-tooth cutter pretty quickly, and some other things. I had a good time doing it.

http://users.picknowl.com.au/~gloaming_agnet/cq9325rev7.html

I like the way you made your cutter; that's another way.

I used the Ivan Law book too. There's a good computer program to download, referred to on Steve Bedair's site. I used it to make sure I had the gear-blank's diameter correct, and it worked for me.

Also see myfordboy's vids on YouTube, he uses the Ivan Law book. Which I downloaded on Scribd.

Pete

 

[gus]

I used this author's setup; he describes the "rig" in detail after a few pages. Shows how to make a single-tooth cutter pretty quickly, and some other things. I had a good time doing it.

http://users.picknowl.com.au/~gloaming_agnet/cq9325rev7.html

I like the way you made your cutter; that's another way.

I used the Ivan Law book too. There's a good computer program to download, referred to on Steve Bedair's site. I used it to make sure I had the gear-blank's diameter correct, and it worked for me.

Also see myfordboy's vids on YouTube, he uses the Ivan Law book. Which I downloaded on Scribd.

Pete

Hi Pete,

Ivan Law's book is a must have and must read for first timers/newbies going into gear cutting. I am in the very last prepping stage to start Howell V-2 Engine which had so many gears to cut and mesh with pin-point center drilling. The gear vendors usually run out stock of the particular gears we want and as such we end up with DIY gears. Been fun cutting gears. Happy New Year from faraway Singapore.

 

[Jasonb]

Just looked this thread up after your query elsewhere.

As Kvom says us 0.5MOD cutters.

Your 0.589" ctr to ctr distance is 14.96mm or near as dam 15mm

20T PCD = 10mm

40T PCD = 20mm

Distance between ctrs = (10 + 20 ) / 2 = 15

You also give a gear blank dia for one of the gears of 0 .431" this again is basically 11mm

To get the OD of a gear the calculation is (Number of teeth +2) x MOD

So we get (20 + 2) x 0.5 = 11

 

[petertha]

I highlighted the number. On the drawing the arrow is pointing to the very tip of the tooth. I attached the page I'm working on.

I'm not sure if an additional complication might be 'pointing' to a tooth edge vs. defining the diameter. I'm referring to the 0.444" and 0.431", but I also see a corner fillet radius of 0.010". Depending on the cad program & how the dimension are picked/defined, it could be picking up center to fillet edge (which is shorter than) center to nominal tooth circle OD?