Gallery, Projects and General > How to's

Cutting Spur Gears -- A neat technique

<< < (5/8) > >>

fatal-exception:
I spent hours last weekend making a cutter as pictured by the OP for 20DP gears. It did not work at all for cutting the actual gears. The cutter cut just fine, but the geometry of the finished teeth was, well, non existent. The teeth are pretty much triangular with no involute to them at all. I think I will try to replicate what this cutter does in a solidworks model. I should be able to see if this was doomed from the start, or it's a scale issue.

Has anyone else tried this method with a larger pitch tooth? The gears made at 48dp look good. Wish I could say the same.  :coffee:

Now I've cheated and bought an 8 piece cutter set off e-bay for $100. Completely against the spirit of Mad Modder...oh well, I gave it a shot.

Joules:
Well done, you gave it a go.  :clap:   And have new found respect for a fellow modder. 

PekkaNF:

--- Quote from: fatal-exception on May 05, 2017, 06:27:29 PM ---I spent hours last weekend making a cutter as pictured by the OP for 20DP gears. It did not work at all for cutting the actual gears. The cutter cut just fine, but the geometry of the finished teeth was, well, non existent. The teeth are pretty much triangular with no involute to them at all. I think I will try to replicate what this cutter does in a solidworks model. I should be able to see if this was doomed from the start, or it's a scale issue.

Has anyone else tried this method with a larger pitch tooth? The gears made at 48dp look good. Wish I could say the same.  :coffee:

Now I've cheated and bought an 8 piece cutter set off e-bay for $100. Completely against the spirit of Mad Modder...oh well, I gave it a shot.

--- End quote ---

What do you think went wrong? I never tried this method, but (to electrical engineer) it looks like if you get the cutter profile correct, lace it to centreline of the "disc" and have depth set right it should produce nearly correct tooth form.

Is it possible dwell on this one more? I see this a learning experience.

Pekka

John Stevenson:

--- Quote from: sparky961 on February 22, 2017, 07:33:20 PM ---
--- Quote from: xo18thfa on February 22, 2017, 01:24:34 AM ---Quenched tool steel is too brittle at this point and needs tempering.

--- End quote ---

In practice I've found that no tempering is needed when working with brass or other soft metals like aluminum.

In fact, for a one-off tool that's going to see little use you can often get away without tempering the tool for most materials found in the home shop.

--- End quote ---

Very true.

True story based on real world experience.
Few years ago I used to make proper form cutters using a full sized Eureka attachment, 1" bore model.
These were made out of gauge plate which is the flat version of silver steel or drill rod as known in America.

These were machined and then sent away for professional hardening and tempering. Cost wasn't a problem, what was a problem was the profile had to be exact.

When they came back the faces of the cutter were ground, one face one way, the other face the opposite way so all the burrs were thrown ff the cutter as believe it or not these also provide clearance.

Then fitted to the machine, basically a wood router they worked very well but the life before regrinds wasn't as good as using HSS and was a bit of a disappointment.
On one set because we were pushed for time we self hardened the cutters but didn't temper them, just ground them and put them to work.

This set cut far better and lasted longer. We determined that the heat generated from grinding was enough to take the brittle edge off the file actual tips that did the cutting.
After that it was make, harden, grind and use.

fatal-exception:
So I had a chance this afternoon to simulate this cutter, cutting a gear in Solidworks. I setup up the DP, PA, OD, and tooth count as variables and used them to do an extruded cut on the outside of a simple cylinder, which is driven by the OD variable. Then a circular array of this cut is done 'Tooth count' times to form the gear.




Here's the larger gear with more teeth.


Maybe I wrote off this method a bit hastily. Oddly enough, in theory, this should work, even with 20DP and larger gears. The only place it gets a bit whacky is with low tooth counts, the crest of the tooth takes on a more triangular shape.

Honestly, the gears don't look all that great, but when put together in an assembly and constrained at the correct distance apart, they mesh and have no unwanted interference during the contact time, so again, they should work.


Now I have to go home and figure out why my real world example didn't work. Maybe I was a bit too sloppy setting up the DOC....

Paul

Navigation

[0] Message Index

[#] Next page

[*] Previous page