Can you identify the pressure angle of this gear?

[Iceberg86300]

Rubbing is putting a piece of paper on top of the gear & lightly rubbing a pencil/piece of chalk over some gear teeth.

Same thing you would do with a headstone or monument with engraved names.

This should produce sharp edges, but the smaller the gear the harder it is.

When measuring the pressure angle draw a line from the start of the involute to where it hits the edge of the tooth. That should get you close.

Or just use a tangent line on the involute & eyeball it to the midpoint. I'd have to pull out machineries handbook or a gear book to get you better methods.

Or, like someone mentioned above, there are gear catalogs with various full sized gears for comparison.

Regards,

Steve

 

[benmychree]

"Optical scanner" is my trained eye ---

 

[Iceberg86300]

Thanks guys! Now you guys are making me feel dumb, what's a 'rubbing' and what's an 'optical scanner'?

I'm trying to learn the technique for future use so I tried the lines on the jpg and I can make the angle whatever my brain leans towards lol See the two comparisons.

Can you zip the high res versions of your photos & scan? I'm on Tapatalk & they came out around ~300x600 (photo) & ~600x550 (scan).

I tried sharpening them but the gear material & finish really skews everything. If you're careful then a bit of diluted white out can work wonders with that. Provides a ton of contrast for photos & scans. Good old Dykem can do the same w/o needing any dilution.

Also, a cheap digital microscope can serve as a poor man's comparator. Likely much cheaper than a set of gear gages, but obviously involves more work. It's a great reason to finally get that digital scope you've been wanting though Really comes down to how many you'll be looking at. If you go this route then make sure the specs will allow you to get a few teeth in view.

And I'm serious about the comparator, as long as you have references like gage blocks & pins & sometimes callipers. Relegated to small parts though.

Regards,

Steve

 

[stioc]

PROBLEM SOLVED solution below.

First off thanks for all the feedback, solutions and neat ideas and tricks. I think what I learned here is that for the occasional home shop the easiest method is to either find those catalogs and compare the actual gear OR better yet in my case I found this web based gear generator software with the intent to print the actual gear then compare. However, I didn't even have to print it out because the gear was rendered in the actual size right on the screen. I simply held up the actual gear right up against the screen.

This is essentially what @Iceberg86300 suggested but in reverse.



The comparison pic doesn't show the teeth line up because of the camera angle and me having the gear off center so the background image shows more clearly.


In reality the pressure angle difference on a gear like this was so small that I had to use a magnifying glass to eyeball the tips of the teeth, otherwise both 14 vs. 20 deg looked almost identical.