Stainless material for output gear

[MrClean]

I am designing a spur gear set to be used in a remote controlled device. The output shaft gets exposed to nasty environments (salt water, grit, etc.) so must be SS. In the interest of reliability, keeping number of operations down, etc., I’m planning to make the output shaft/gear from a single piece of metal. Gear o.d. about 1.5”. Shaft about 3/8” dia x 3” long. AGMA 2000-A88 Q8. Couple of questions:

1. I’m considering 13-8 PH vs. 17-4 PH for the output shaft/gear. The obvious goals are to keep performance up and cost down. Toward that end, I was thinking of simply buying material in the heat treated condition – Rc 33-38, machine the blank, cut the teeth, check over-pin measurement, ship the part. No grinding of bearing journals or teeth. Which material would you recommend – 13-8 or 17-4?

2. Pinion material: I know stainless against stainless is a bad combination for gears. How about SAE 4140 for the pinion?

Any other comments or suggestions would be appreciated.

 

[diamondjim]

If it must be stainless steel, why can the
pinion be something other than SS?

I think a high nickle steel like 8620
or 4320 may be helpful if you are allowed
to use these for the pinions.

 

[Philrock]

Diamondjim - thank you for your suggestions for pinion material.

The ouptut shaft is exposed to harsh environments; the pinion is not. The pinion should not be SS because SS against SS has a strong tendancy to gall.

Any thoughts on which SS for the output shaft / gear?

 

[diamondjim]

Have to plead ingnorance on both ss materials.

 

[tbuelna]

Custom 455 is a standard cres gear material.