Imperial thread terms help please

Can anyone help with an explanation of a couple of terms. Google is useful but not completly understanding a couple of things.

Specifically 5/16 face. Whats this?
16 pitch is the tpi perhaps
Bore interference fit for boss means it will have to be pressed into a hole, or something will be pressed into the hole in the centre of this ring gear…

Any help much appreciated.

The width of the contact surface?

Are there any more views/elevations on the drawing?

I thought I was pretty good at reading engineering drawing/sketches, but that makes my head hurt.

It’s gear tetminology.

Pitch = (teeth +2)/od.

50+2/3.25 =16

https://www.mcmaster.com/info/how-to-choose-a-gear.html

5/16″ wide tooth

I can’t see anything refering to a thread on that section of drawing.

It’s all  relating to a gear, 50 teeth @ 16 diametral pitch with 5/16″ face width (effective width of the gear).

Found a calculator here https://evolventdesign.com/pages/blank-calc?srsltid=AfmBOoobxsgp7bOTdcdnGaOVADYR222NDQDWhikOLjACyVzdLvpKHGvL

Number of Teeth: 50
Diametral Pitch: 16
Pressure Angle: 14.5 degrees
Gear Type: External

Outputs
OD Reference: 82.5500 mm 3.2500 in
Pitch Diameter: 79.3750 mm 3.1250 in
Root Diameter: 75.4063 mm 2.9688 in

Addendum: 1.5875 mm 0.0625 in
Dedendum: 1.9844 mm 0.0781 in
Working Depth: 3.1750 mm 0.1250 in
Whole Depth: 3.5719 mm 0.1406 in
Circular Pitch: 4.9873 mm 0.1963 in
Tooth Thickness: 2.4936 mm 0.0982 in
Base Circle: 76.8467 mm 3.0255 in

Tapered face of an individual tooth. Terminology with drawing here, scroll down… https://themechanicalengineering.com/spur-gear/

something will be pressed into the hole in the centre of this ring gear…

In engineering “boss” can mean any of a few things. It could be part of a shaft that the gear is mounted on and it can be the hole that a shaft is fitted into; it protrudes

Interference for suggests that the gear won’t be turning around the boss but driving whats on the other end.

There should be some specification for the pressure angle aswell shouldn’t there?

Unless otherwise stated, you’d assume standard pressure angles for the gear teeth, which in this case being DP (essentially imperial), would be 14.5deg.

My concern with that drawing, is somebody has scored out the 50, replaced it with 46 (not an issue if you do need a different gear ratio), but also added M=0.6. The M 0.6 would imply that they’re trying to convert a DP (imperial) gear, into a MOD (metric) gear, which would open a whole new can of worms.

If you want to learn all about gears, I can provide details of a book which is either ideal bedtime reading because you want your mind numbed before sleep, or a great source of insomnia if you want to work things out the old fashioned way.

Also, if you want to try modelling gears, have a search for Gearotic Motion.

Interference suggests that the boss dimensions are already known, so the machinist can machine the gear to be a suitable interference fit for the boss (A copy of The Machinery’s Handbook would be the standard reference for lots of these things)

What moff & mc said. Only caveat being if the gear is from a machine built prior to the mid’50’s it may well have a pressure angle of 20°. Getting DP 20PA involute gear cutters is either next to impossible or very expensive.

I have a full set of DP16 14.5PA cutters if you needed a gear making and had a better drawing.

I have a 1964 copy of the Machinery Handbook. It’s an excellent source of information for make pretty much anything on a lathe or milling machine.

Getting DP 20PA involute gear cutters is either next to impossible or very expensive.

Thats why god invented shapers.

I have a 1964 copy of the Machinery Handbook.

by JR Hartley?