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home made speargun metal

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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J

Jordan Leigh

New Member
Nov 17, 2004
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I'm building a speargun and Im about to order the metal for the spear shaft. I'm going with grade 5 titanium because:

Tensile(KSI): 130
Yield(KSI): 120
Modulus of Elasticity(PSI-10^6): 16.4

which makes it almost twice as strong as steel for all three specs, and way lighter.

I found a place to get a 5/16"X57"...

Four Questions:
1) Anybody ever used titatium before?
2) Is there any reason not to?
3) For maximum compatibility, how much of the end should I thread for tips?
4) For a 5/16" shaft, what thread count/pitch are most tips?

I printed out the AB Biller patent and I'm basing my trigger mechanism off his... the guys in the machine shop at my work are helping me. I'm going to use stainless because the shop cant cut anything harder.

Three Questions:
1) How popular is the AB Biller trigger mechanism?
2) Has anybody ever had the spring clip inside it wear out?
3) Would a hard grade aluminum be acceptable?

I'd appreciate any help you could give!
-Jordan
 
I have an AB Biller SS Pro 42' for somewhat over 3 years and its never caused any problem, and unlike my other gear, i give the Biller a trashing every single time, and during the summers i use it on a daily basis and have never had any problems with it. The safety works great and the trigger is as crisp as the first day i got it. Its my cave/hole gun. i also had an extra notch cut into the shaft for an extra rubber.

in my opnion, and i could be wrong, using titanium could be troublesome because of its mass. a heavy shaft carries more enegry, and thus punch. im sure Iya and Mark can give you better advice
 
I dont think titanium are suited for a shaft, A friend of mine has one he bought in kroatia from the ussr team. They had them from the millitary for free. My friend tell it is a nice shaft but never uses it beacuse he is afraid of losing it...
No doubt titanium is harder to bend than steel but it is too pricey, you would not shoot in caves or cracks beacuse it can be stuck
And then you will catch less fish...

The best shaft with no comparing is the sea tec spears, The shaft is impossible to bend and the flopper is milled down in the shaft, I have heard that devoto sub also make very nice spears but have not tried one. Go with seatec cheap, the best and you wan´t mind setting a spear in a cave now and then
johan denmark
 
I wouldn't use the titanium for the exact reason you stated: it is way lighter than stainless. The reason most guys use heavier shafts (5/16 or 3/8) is for the extra mass and therefore the greater penetration that they carry. If your primary target is reef fish than a 9/32 or even 17/64 shaft will work fine. Sorry but I can't comment on the threading as I use a single flopper for my reef guns and a 5/16 pre threaded Riffe shaft with an Alexander slip-tip for blue water. Good luck with the gun and post some pics when it is done.

Brad
 
Welcome to the site Jordan,

Just to reiterate what i think you already understand: Titanium is too light. The Ti will accelerate very quickly, but it will also lose momentum too close to the muzzle of the gun. If you are making very short shots it would work, but it is far from the best material for shafts. If money is no concern you can aquire lengths of 17-4 ph stainless steel from www.mcmaster.com. The 17-4 is used by the premiere speargun manufactures in the states. It is sold in the anneald state and can be hardened after machining.

Also the biller mechanism is rated for three bands (~120lbs x 3=360lbs). The vast majority of people who build their own guns use a standard American square notch mechanism which will hold over a thousand pounds. If you are going to the trouble of making your own these would be far superior to the biller, and not harder to produce. I believe you can find a picture of the internals in Terry Maas' Blue Water Hunter book, or Kitto's speargun building website. Oh yea, the Aluminium would be way too light for this. There will be a ton of pressure on the sear which holds the notch of the shaft. A thick piece of SS will do. Personally I'd go w/ 316L b/c it's the most corrosive resistant and not too much more than the cheaper 303 series.

Please let me know where you get your SS springs from, I'm looking for a source.

Good Luck,
Chris
 
Jordan Leigh said:
I'm going with grade 5 titanium because:

Tensile(KSI): 130
Yield(KSI): 120
Modulus of Elasticity(PSI-10^6): 16.4

which makes it almost twice as strong as steel for all three specs, and way lighter.
Click to expand...


I believe you are mistaken in the strength comparison to steel. However, I think you should go ahead and try it for your spearshaft and share your experience with using this material with us.

I would recommend not to use your grade 5 titanium and stick with heat treated 17-4 PH since it is stronger and stiffer for a given shaft diameter. True, it is a heavier material than titanium, it's a compromise.

17-4PH Heat Treated to H900
Tensile Strength: 190 KSI
Yield Strength: 170 KSI
Modulus: 28.5 x 10^6 PSI

As far as the Biller trigger, I don't own one but I've read the Biller patents on his spearguns. Aside from a certain feature of his muzzle design I am not impressed at all about his guns, especially the trigger mechanism. In my opinion he wasted a lot of money protecting designs that are easily surmountable. Maybe he just had a lot of money. Anyway, his trigger design should work as long as you use an appropriate gage of stainless steel for both the mechanism and the housing. 300 series stainless should work fine. I would recommend a thickness of 3/16" for the trigger and sear just to be safe. Make the trigger length longer if you want it to pull easier under heavy loads. A longer trigger provides more leverage to overcome the friction between the trigger and the sear. DO NOT USE ANY KIND OF ALUMINUM!!!! Plenty reason why. No bullshit. Trust me, you will be sorry if you do!

Gil
 
Just a note on Aluminum. I forget the scientific terms of it but over time Aluminum loses it's strength. If you take a piece of steel that can support 1000lbs and you put 500lbs on it every day for years it will never break. If you take a piece of aluminum and do that same thing it will eventually break, although I'm not sure after how long. But anyway like GilbertG said, there are a lot of reasons not to use it.
 
The idea of a lightweight spear is interesting. There is a never ending debate on hunting calibre bullets for rifles. A small diameter bullet has a higher velocity and a flatter tragectory whereas a large calibre is slower and generally has less range. Smaller bullets at high speed in theory have the same energy as larger bullets at slower speed. Energy = mass x velocity squared.

A lighter spear could travel faster and more accuratly and still have considerable stopping power. Overall the rifle calibre is generally resolved with large calibre for big game and smaller calibre for light game. So maybe a light titanium spear would suit a euro gun for use on smaller fish. However to optimise performance you might need rubbers with a faster rate of contraction. A gun set up like this could be deadly for Euro/Med conditions, especially if you could achieve a flat trajectory. There would also be a big plus in less recoil due to the theory of momentum and equal and opposite forces, hence even better long range accuracy.

This is definitely an idea to run with and is probably only not popular due to cost in mass produced guns and the custom gun market mainly being about hunting big blue water fish.

Someone try a titanium euro spear set up with special rubbers and let me know.

Dave
 
My two cents...

We are not talking about impact or stopping power. There is going to be virtually no temporary cavity from a spear impact no matter the material. Penetration is key, not energy transferral.
The lighter the spear the faster it will go; this will aid penetration. The steel may be better and hold the energy for longer retaining penetration ability at higher ranges.
Titanium may be an interesting choice for a short gun designed for shooting fast moving fish at short ranges.
One thing i notice whenever i see tech specs for spears are that they are all spring steel. Designed to flex and returned to shape. I don't think your titanium rod will have the same properties. Titanium is not as flexible as spring steels.

But please don't let me put you off giving it a try, it could well prove worthwhile.

Just for fun I made myself a titanium stringer. Why not?
 
Agar4Life said:
My two cents...

We are not talking about impact or stopping power. There is going to be virtually no temporary cavity from a spear impact no matter the material. Penetration is key, not energy transferral.
Click to expand...

How foolish of me. I didn't realise how wrong I was. I bow to your expert opinion.

Dave
 
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