CNC Plasma Table

[EdK]

Very nice Greg! A situation where the shaper is perfect for the job.

Ed

[f350ca]

Good point on the accuracy Andrew, hadn't thought of software fixing problems. As for number of strokes, I never counted, can't believe I didn't with the boredom. Took about 1 1/2 hours to cut 8 inches, the distance between the pins, thats about 50 teeth, so 1 1/2 minutes per tooth, probably 1 minute cutting at close to 1 sec per stroke maybe 50 or so strokes. The first say 50 thou depth was effortless, 5 or 10 thou per stroke. the next 50 maybe 3 or 4 and the last 25 1 or 2 thou. Had the clapper box swung at 14 1/2 degree so all the cutting was on one side the same as threading with the compound swung.

[f350ca]

Now I need to make some pinions.
I could spend hours reading or use the internet and the vast knowledge on this site.
For the OD of my blank
OD=N+2/P for a 20 diametral pitch gear with 16 teeth the OD should be .900 inch

the root diameter

RD=N-2/P so .700 for the same gear

The whole depth of the tooth

WD=2.157/P so 0.10785 again for the same gear.

These don't line up, the WD would give a root dia of 0.6843

Whats what, is the root dia an imaginary circle and the whole depth gives clearance at the bottom of the tooth?

[Mayhem]

I don't know much about the math behind gears Greg but one of the free programmes I have downloaded has a gear calculator in it. Below is the data it returned when I entered DP and N as you listed:

   

The programme is called Metal Shop Calculator and can be downloaded HERE

[f350ca]

Thanks Mayhem,
Thats interesting, it gives a different whole depth than the calculations I found. From what I gather changing the whole depth alters the tooth clearance.
I plan to have the pinion on a spring loaded arm to give zero backlash to the rack, so the whole depth may not be that critical.
Will down load the software, thanks.

Spoke too soon, no Mac version as usual.
Will get it the next time I have the windows side booted up drafting.

[f350ca]

Needed a mandrel to mount the gear cutter. (I have a Chinese one that I use on my slitting saws, the run out is so bad only one tooth cuts, the blades should last forever using one tooth at a time)
Wanting minimal runout and too lazy to mount the 4 jaw and dial it in I tried trimming the last few thou on the mill. Shows zero runout now, will be interesting to see how it is after we remount it in the collet.



Bored the bottom washer to make the mandrel more universal.



Assembled

[f350ca]

My first attempt at a spur gear. 20 tooth, 20DP 14 1/2 deg PA




Made two so far tried 0.108 total depth from the calculations I'd found, 0.112 total depth from your program rolls much smoother Mayhem.
Need to file the top corners of teeth on the racks, they drag just a touch with the pinion pressed in tight.

[Mayhem]

Nice work Greg. Glad my post was of use.

[Shawn]

This photo makes me want to go cut a rack on my shaper, very cool. And the DRO on a shaper is awesome.

Shawn

Edit: just saw the mandrel finished on your mill! Brilliant idea, I will be using that one next time.

[f350ca]

Doing the finish cut on the mill worked really well, you could tell by the sound of the cutter every tooth was working. (unlike my slitting saw mandrel) That was actually a second attempt, turned one on the lathe in one setup to get minimal run out with a 1 inch shank, then found out I don't have a 1 inch 8R collet, the run out was horrible in my collet chuck.