first hand-(almost)made shafts

[rifmaniac]

hi
I've almost finished making 2 8mm threaded shafts for my Riffe Competitor 3XS;
I'm using stainless steel aisi 304L;
I would like to know if the differences between 304L and 17-4PH are that great; can any one compare both steels(density, stiffness, solidity...)?

[rifmaniac]

sorry, should have indicated it's an question post

[donmoore]

Yea, from the little I know about it the 17-4 PH is stronger and can be heat tempered. My book says 304 has a yield strength of 35 ksi and a Harness of 170 Brinell. 17-4 PH has a yield strength of 145 ksi and Hardness of 332 Brinell.

I think, with the heat treating, 17-4 PH is considered Stainless Spring Steel were 304 is just a stainless steel.
don

[rifmaniac]

?
that's a bit technical

[donmoore]

Okay, 17-4 is 2 to 5 times better in strength and hardness.

[ajwaverider]

Originally Posted by donmoore

Okay, 17-4 is 2 to 5 times better in strength and hardness.

Thats right
Hey Don where have you been?

[milhouse]

17-4 shafts (like Riffe) are really stiff, because they're heat treated. 304 is really smooth compared to 17-4, so forget to aim a bottom fish with a 304 shaft. In fact, aim one bottom fish is O.K. , aim a second one is a problem. your shaft will be bent after the first one. I make tahitian shaft with 304 SS,(6.5mm) and when I shoot on the rock at close range, the shaft make a 45 deg. angle at the flopper pin's hole. 8mm will be a bit stiffer, but you'll have fun to staight it back.

If you shoot a medium size fish, 15-20 pds, and that fish fights, you'll be able to see your shaft bending in front of your eyes. A trick is to bring many of those shafts, ready to be changed, and to put a new one each time it bend. At the end of your hunt, straight each shaft for the next hunt.

That's a lot of job, but at 4-5$ a shaft, make many of them.

[donmoore]

Hey Don where have you been?

Thanks ajwaverider, its nice you noticed my absence. I’ve been lurking some, but my free time focus was mainly in redesigning the stern of my boat. One of those jobs that stresses everything else in your life to the max. It’s almost done now, thank God!

milhouse, good first hand experience! Thanks for sharing it.
don

[poacher]

Look here
file http://www.aalco.co.uk/technical/dat..._Hardening.pdf.
This is 17/4 specs

[poacher]

and here
http://www.azom.com/details.asp?Arti...cal_Properties
Sorry guys didnt't work hard on it just quick search on google
but should give you some ideas of differences in steel grades 17/4 (630PH) and 304
Regards
Peter

[rifmaniac]

ok
thanks a lot
POACHER, those links are what I needed

but which one of these properties are related to shaft whip?

I m not really worried about the shaft being bent by rocks or fish
what worries me is shaft whip, Do you think I might have that kind of problems?

[GilbertG.]

Rifmaniac,
If shaft whip is what you're concerned about, its probably a higher bending stiffness that you want. Bending stiffness depends on the diameter of the shaft and E (aka elastic modulus, or young's modulus). So for two materials of the same diameter, compare E. The higher the E, the stiffer it is, and therefore more resistant to behaving like a javelin when you fire your speargun.

gil

[poacher]

Another steel spec site
http://www.nationalspeciality.com/round_bar_.html

[rifmaniac]

other question, now about pins;
what kind of pins would you use on your shafts?

here are a few I managed to bend, but I don't know if these shapes are any good:

[defofthecrown]

Sorry for the late reply. In the pinned shafts I've seen you just need a single post. Structurally one leg will be just as strong as two. They are weaker than shark fins so you'll need one pin for every band you plan to pull. The normal confiquration would be three pins and then a 'doghouse' to attach the shooting line. The best way to bend the metal is with a mandral. Basically find something hard w/ the shape your trying to copy and bend the metal against it. this will give you a much more uniform and professional look. I'd like to see some photos once you have them put together.