How to work out pitch of pinion

[KEV THE REV 2319]

I've got some steel pinions here and I can see how many teeth , but don't know the pitch , how can I work that out ? , thanks .

[WillyChang 1814]

I go grab a spur of known pitch to compare...  

[Wooders28 4723]

6 hours ago, WillyChang said:

I go grab a spur of known pitch to compare...  

Try comparing an 05mod and a 48dp, 0.02mm of a difference 🧐😬

[WillyChang 1814]

4 hours ago, Wooders28 said:

Try comparing an 05mod and a 48dp, 0.02mm of a difference 🧐😬

Ah... I keep my DF03 spares quarantined far away in solitary confinement  in Dark Impact's kit box   whereas 48dp run free range everywhere else... I usually texta on the teeth count & type on Spurs anyway

I write on pinions too but often the ink gets washed off with motor spray. Too tired to break out the engraver to do every pinion. 

 

04m & 64dp are the biggest mixup risk  got near equal population of each size. Easiest way to tell is nearly all my 04m are Tamiya & they're not steel. 

 

For or multiples of same pinion, I slip them onto a piece of aerial tube. Holds them all together, handy to grab when packing for track. (Yeah there's 'overflow' as expected, I don't need to pack more than 2-3 each size. Extras live in usual tackle box. Tackle box has habit of spilling its lid, got tired of resorting contents every spill.)

[nbTMM 433]

15 minutes ago, WillyChang said:

04m & 64dp are the biggest mixup risk  got near equal population of each size. Easiest way to tell is nearly all my 04m are Tamiya & they're not steel. 

They are so close (<1%) that they are effectively the same thing though. The teeth on small gears are not usually 100% accurate, they just have to be good enough. The cutting tools that create the teeth have a tooth range, so that one cutter may create the teeth on gears anywhere from 50teeth to 100t. It'll be perfect making teeth on a 50t gear but by 100t is considered just barely close enough - if you want to make a 101t gear you should get a different cutter. For that reason, the inaccuracy between two 64dp or 0.4M gears may be greater than between a 64dp and 0.4M. I wouldn't be surprised if in the industry people use the metric and imperial cutters interchangeably between similar pitches
 

 

[speedy_w_beans 4272]

If you have digital calipers to measure gear diameter and know the number of teeth, this page of gear calculations should give you pinion pitch: Here

Count the number of teeth, N.  Measure the outside diameter, DO, with the calipers.  Calculate diametral pitch using P=(N+2)/DO or P=(N+1.6)/D0 depending on the style of gear tooth.  Calculate circular pitch, p, which is the pitch you're interested in, using p=3.1415926/P.

Done.