Different types of spur gear stock

I have found spur gear stock (which I plan on cutting up to use in a transmission) in both the Stock Drive Products and the McMaster Carr catalog.
For a given DP and tooth count, the prices are radicaly different. I was wondering what the difference between the two gear stocks are and if the cheeper one (from McMaster Carr) is strong enough for the last reduction in a transmission.

You can buy 12in of 20DP 16 tooth gear stock from McMaster Carr for $27.80 (this works out to about $2.32/in). I do not know what it means, but it is labeled as being “cold-rolled steel gear stock.” The part number is 6847K21 and it is on page 1014 of the catalog.

You can buy 6in of 20DP 16 tooth gear stock from Stock Drive Products for $37.67 (this works out to about $6.28/in). There is no indication to the manufacturing process, but it is carbon steel and the gear stock comes with a shank. It can be found by going to https://sdp-si.com/eStore/ and then clicking on “gear” tab -> “pinion wire & spur gear stocks” -> “spur gear stock” or by going to this catalog page.

I am wondering if anyone knows why there is 271% difference between the two gear stocks and if there is any reason why one would be better than the other.


All I know about the SDP pinion stock is that it isn’t your standard carbon steel, it is in fact, 12L14, easy to machine steel. So it’s about 60 ksi yield. I don’t know the material props of the McMaster steel, but if it’s a standard carbon steel it’s like to be a ton cheaper per pound, which might explain part of the difference.

If you buy from SDP, check your gearstock carefully. We have had issues in the past with some of their gearstock having teeth that are actually at an angle to the surface of the gear.

My team purchased gear stock from McMaster back in 2002. We used it in two places on the tranny with a small Atwood and had no problems. The same gearboxes lasted through 2 regionals, usage in Relay for Life, and continue to run today.


It doesn’t say on the website but you could definately call or email mcmaster-carr and I’m sure they could tell you what type of steel it is.

You will need to make sure to match the pressure angle of the gears to the stock that you are ordering. The SDP gear stock is listed as having both 14-1/2 degree pressure angle and 20 degree pressure angle. The Mcmaster-Carr stock is listed only as 20 degree pressure angle. It is not a good idea to mismatch these and the life of the gear teeth with be reduced and they will not mesh properly.

Go over to http://www.efunda.com/ and look up 12L14 steel and 1018 or some such mild steel. 12L14 has some lead content to make it easy to machine. It’s not 4140 pre-hard or “stressproof” steel by a long shot.

You might check with these folks: