What steel to use
 

For what drive are you doing this???????

Several people have looked into it in the past and the cost would be huge for a small run of gears.

Pm RPMRam or call him, Gary 612-247-7081, he has #3,#4,#5 and #6 gears that he had made and he sells them . He can tell you ..

If you have someone with the expertise to manufacture gears ,they should know what steel to use .
8620 is pretty generic steel for gears . May work for awhile.

8620 is just a mild steel.
Even case hardened wouldn't be tough enough to be worth making gears out of.
A tool steel such as 4140 would seem better.
There are a ton of coatings beyond heat treat hardening that could be beneficial.
A nitride might be one.
You will have to consider mating parts.
What do you want harder and last.
What do you want softer and to wear?
Not an easy one size fits all.

You do not get forged steel.
Tooling is made and hot steel is pressed/formed/hammered to shape.
Does not come in bars, sheets, or rolls or anything like that.

9310 is a semi common gear material....but thats just the start of it

Aermet 100 is my go to material choice if I keep braking other things inside a transmission. It aint cheap but it seems to hold up to the abuse.

Gears
 

I'm not a metallurgist but I've been around material testing for more than 40 years, so I know a little.

I think a lot of this will be about your manafacturing and finishing process and how you want the gear structured. For example; a more ductile base with a hard surface, etc. Base metal selection is important, process, and treatment/finish process such as heat treat, cryo, quench etc is just as important, you'll again need to consider your manufacturing process, are you going to forge the blanks then cut them, is it a block and CNC'd, and how your physical manf process will effect the metal vs the end product you want.

You might want to talk to a metallurgist as it gets complicated quick.

Heat treating aligns the grains of the metal but different heat treat processes create different results. A lot of the time heat treat is used to relieve stress created in Manf due to localized heating such as welding so even just the heat treat needs to be spec'd and checked to make sure the process is yielding the desired results. Some times the heat treated cuts corners and gives you back an interior result.

Why don't you start with what the problem is your trying to solve is by making gears out of different base metal?
1 ) Is it cracking, sheering, excessive wear, etc
2) I assume your making no design changes to the gear itself, just remaking the exact same part?
3) Are there others gears that mesh with this gear(s) and what metals are they made out of and finished and how will the two interact.

You might be creating more problems than your solving or you could just make em, run em and see what happens.

Either way good luck, post up the results.

You could also call big silver cats company and see what they say about the gears for you.
https://www.offshoreonly.com/forums/general-boating-discussion/335303-start-finish-building-our-50-skater.html

If you are still interested, my neighbor just had a batch made for Bravo drives and did a ton of research on the subject, they will be getting installed this week for some real world testing.
PM me your name and number and I will have him give you a call.

Have you looked at using S7? I talked to several people who would know about their opinion on toughest most durable steel and consensus is that S7 is the way to go. If you are already making gears, you need to talk to George at AADS (517) 858-1123. He does a lot of high performance drive builds, he is an expert on the subject.

Pm me his info, Id love to talk to him!

Roger that.

I am currently in the last phase of testing of my super high performance replacement XR lower gearsets. They are CAD designed using state of the art metal, machining, and finishing processes. I will have them ready to sell end of 1st quarter 2020. I will be doing testing soon on super high performance XR upper gearsets. They should be ready by end of 2nd quarter 2020. I have attached pics of the lowers.https://cimg7.ibsrv.net/gimg/www.off...facea739c4.jpg

Stay tuned here on OSO and FB for updates 1st quarter of 2020.

what about upper gears, dont more failures happen in the uppers than lower ?

Not yet. There may be some changes before production that may or may not affect pricing. Of course they will be more than the Merc junk as one would expect. Stay tuned....

If you need someone to test upper gears for you, I am your man. My 28' cat destroys them

these guys have been producing gears for years, maybe a good source of information at the least, best of luck, regards, click on the link Home

Those are some nice looking pieces!