View Full Version : Mystery metal question...

04-10-2007, 12:56 AM
Well i just got home today to catch a phone call from school saying a jack-shaft i made them bent and wondered what they should do. I ran up there grabbed all the sprockets, bearings etc and came back home to make a new one out of solid piece instead of tubing. (this was for high mileage vehicle so weight was an issue) I needed a shaft that was exactly .750" because it was supported by press fit bearings, not the ecentric locking ones. The nominal .75" shafts didn't fit snug enough.

Well i found a shaft from a spicer-foote transaxle off a an old riding lawnmower. Well it worked out ok, but i had to make a hill-billy keyway with an angle grinder because nothing would touch the stuff. Carbide would turn it to a nice finish but HSS or M42 didn't do anything to it, just burned up the bits or endmills. My bandsaw cut about a 1/16" groove in it and then stopped cutting so i did it again with an angle grinder and a cut-off wheel. Any ideas what it would be? Does chrome-moly get that hard if its heat treated? The only stuff i've ever seen was some scraps that a guy had from building a go-kart. It was all annealed and machined nicely.

04-10-2007, 02:52 AM
Any ideas what it would be?

Rebar, perhaps?

04-10-2007, 03:32 AM
Mystery metal is good for post pounders.

A.K. Boomer
04-10-2007, 10:32 AM
It might be some kind of tool steel, I built a few T.S. parts for my bike crank, thought i had everything figured out, worked the stuff in the anealed state, got it perfect, heated and quenched, couple pieces warped, went to bring them around and hashed a half inch high quality carbide end mill --- I ended up stoning most of the deviation out because nothing else would touch it.

04-10-2007, 03:05 PM
I know that axle shafts in automotive and truck applications are very tough stuff by design. I don't know that any of the machining work done on them is done after they have been heat treated, so you may be attempting something that even the automakers don't do. I tend to believe they are probably forgings as the grain structure that offers is nice and tough and should have fewer stress points. Really, if you think about it, thats a lot of power to transmit through a single bar maybe 1-1.25" in diameter, so tough is important.

I have an old tractor axle shaft I saved and figured, as Evan stated, that it would make a better stake or pry bar than raw materials for machining. I don't even know if it would anneal back to a machinable state or not.


04-10-2007, 06:47 PM
Yea- i was in a pinch last night and that was the only stuff handy, but i had kept them for the splined ends. I was planning on using them again in a home-brew transaxle. It turned nicely with carbide and produced a finish similiar to cast iron but it came away in little curly chips vs the almost powdery swarf i seem to get with cast. Interesting stuff... i've also got the axle shafts from a blazer. Wonder what i can use those for - maybe a really freakin' big cold chisel or something?

04-10-2007, 07:50 PM
I made the spindle tooling for my mill from a car axle annealed in the fireplace:

The spline is visible on the leftmost cutter holder in the picture - I needed the whole axle for the number of tools desired.

It wasn't easily workable originally so I tried annealing it as an experiment; a good fire had it glowing red, then I buried it in the ashes to cool. After annealing it turned nicely with decent surface finish. As with all mystery metal, YMMV.