Gear tooth chart

Gear tooth gauges are available but are extremely expensive, like $100 for a set. Can't afford that nor do I need
those. Silly prices for some bits of stamped sheet metal!

Where can I get a printed, or printable, gear tooth chart I can use to identify various gear pitches? I've been all over Google with no joy. I just need something I can hold a gear up to and identify what the pitch is.

Anyone?

Pete

Well you can pay $100 I suppose, but most people make do with something cheaper.

That's a screw pitch gauge, not a gear tooth gauge!!! Geeezzzz.

Pete

I think it was Davall Gears that used to give out a free plastic disc about 3" dia with a wide range of teeth moulded on the circumference, whether they still do I don't know, and I don't know what happened to mine.

John

I found this company in India:

http://www.measuringtestinginstrument.com/kristeel-precision-gauges.html

They do what you're after for 1,100 Rupees (about GBP11.50 or USD16.50 ) for a set of 22 gauges.  Didn't look to see how much postage was, though!  Gauges are available in metric module 20° and DP 14.5°.

John

edited to improve clarity!

Edited By John Hinkley on 11/06/2016 06:47:41

Try. HPC gears at Chesterfield. They have downloadable catalogues. SH Muffet. Daval. They are all searchable on Google

Boston Gear show the profile of each of the DP gears that they do in this pdf which you could lay the gear against. I don't know of a chart that will show the tooth shape as the number of teeth change as well as the DP/Mod.

You should be able to determine roughly what size of tooth you're dealing with by measuring the tooth depth. If it's a metric gear (Module), then the tooth depth is a little over twice the Module - e.g. if the tooth depth is 2,25mm or so, it's possibly a 1 Module gear.

If you're dealing with a DP gear (perhaps more likely in Model Engineering) then the method is similar. Full depth of tooth on a DP gear is 2.157/DP. So if your tooth depth is a little over 1/8", then it's probably 16DP.

Once you've determined the approximate pitch size, then you can use the David Brown Base Tangent method, whereby you use a vernier caliper to measure over 2 or 3 teeth (it depends on the number of teeth in the gear) and you can then decide whether it's (say) 8DP or 3 Module.

Be aware that there are two standard "pressure angles" for gears - 14.5 degrees and 20 degrees. This affects the shape of the teeth and hence the Base Tangent measurement. Older DP gears may well be 14,5 deg, most module gears are 20 deg.

Machinery's Handbook gives dimensions for BTM, but in my 1957 edition they hadn't invented millimetres.

Roll the gear over a fairly thin layer of plasticine, and it will leave behind a 'rack'. You can then measure pitch and estimate the angle by looking at it from the side more easily than by looking at the gear.

Neil

I seem to remember the black silhouettes were on this forum somewhere, I'v got a print out somewhere, but I don't think I have it on my hard drive. Ian S C

Silhouettes are in the link I posted earlier

Peter

Sandgrounder is right about Davall Gears give away gear size disc, I have scanned mine and put a couple of hole dimensions in to enable the correct sizing, it is only for MOD gears 0.5 to 6.0

Emgee

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Thanks Jason. The problem is that there is no associated 'scale' with which to size it while printing. This is true of
all the profile charts I've found. Google is rife with them!

Pete

Thanks Emgee! I'll print that out. I don't need a Mod size gauge yet but I just might.

Pete

John, I'll be contacting them pretty soon. That price is realistic for a gauge like that and, from what I can see on their web page they should be able to make one of those pretty well so there is a low risk I'm sure.

Thanks,

Pete