Measuring for the PA of an ordinary involute pinion gear

[blowlampParticipant @blowlamp]

Could you post the number of teeth and its module or DP?

Martin.

[John Stevenson 1Participant @johnstevenson1]

If it's Meddings it's 20 PA

Reason I know is I had a two speed drill once and it stripped one of the fibre gears and the other was about 1/2 worn.

Measured it up and looked in HPC catalogue and they did the small gear in steel but not the large one, can't remember how many teeth that was. Wasn't worried about the large one as it still had life in it.

Bought the small one in steel, sod the fibre, I know it's probably for silent running and a safety feature but I'm deaf [ what ? ] and a slipping drill is also a safety feature, not something that stops play for a week or so.

Machined it, bunged it in and job's a good un, still running AFAIK, in fact Meddings bought it back off me.

[MuzzerParticipant @muzzer]

For gear ignoramuses like myself, here's a simple article on pressure angles. Doesn't sound difficult to measure really but looks as if JS has solved the mystery already.

[Adam HarrisParticipant @adamharris13683]

John thanks for the confirmation it is 20 deg. I had been told that was most likely but I read that 14.5 deg , albeit uncommon post the 1950's,is useful if you preferred quiet operation of gears to strength, and so thought perhaps Meddings would have gone for "quiet" as their drills are so silky smooth when right.

[fishy-steveParticipant @fishy-steve]

Hi Adam,
I’ve been following this thread with interest as I have the same problem ie finding the PA of given gear.
In your post you mention 16DP. The same DP as my gear. It did cross my mind that you were looking to make the same replacement gear as myself.
I nearly spat my tea out when you went on to mention Meddings! !
Pesky Tufnol Meddings gears. I’ll be needing a 16 DP 20PA #2 cutter then.

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