Notched or fin shafts

[gingebailey]

MrX yeah i flush everything after every outing. Have tried contacting Cressi a couple time but had absolutely nothing back. Iam just gonna chalk it down to one of them things.

I actually make knifes and tools as a bit of a hobby so I've kept the old spears and might use them for something down the line. Might make a small gun and just add the notches or some fins.

 

[CCspearo]

I’ve had cressi shafts snap in the same place. I’ve also had notched cressi ones snap some years ago now. I think they must have a batch problem as they have changed the design AGAIN from notch, to pin insert, to shark fin now fused to the shaft.

My buddies cressi spear snapped on the pinfin in 2016. I put it back together and welded it all round with a stainless welding rod and ground it smooth and it is still going today. I think if you drill a dirty great hole in a 6.3mm spear you are asking for trouble.

I ground a v in the cracks so the weld penitrated to the pin and the spear ended up stronger than a new one.

 

[Mark Laboccetta]

On a single band speargun, like most European guns come stock, a notched shaft is fine. Just make sure unless it's really a CHEAP gun that the shaft is stainless steel (AISI 630 also known as 17-4PH in the USA). The reason for this is that the notches being the weak point tend to get stressed, and with Galvanized or "Plated" shafts it's even worse. 17-4 is usually brown or satin colored because it's heat treated first and it gets its name "spring steel" from the common use of this stainless steel used for springs. So if your gun comes with one band, and you don't want two, just make sure the shaft is stainless steel and the notches will be fine.

As far as breaking goes, yes the notch is obviously a weak spot but I've had shafts last more than 10 years when used with a single articulated wishbone. Everybody hates on metal wishbones, they're easy to load and they never break. Again, for a single band gun that's all you need. If you change yoursetup or have multi bands then by all means use a shark-fin, tabbed, pin, "mini shark'fin" shaft and soft wishbones. Here's a picture of a couple popular sharkfin shafts. One is laser welded and the other is Tig.

 

[Mark Laboccetta]

This is I have to admit a poor design. The shooting line hole is directly beneath the sharkfin. Under severe stress or bending the heat applied from the weld has already caused stress near the shark-fin and the hole there adds to it. The other one break at the shark fin too because of the stress from the weld. It's likely those were tabbed on after heat treatment.

View attachment 55815View attachment 55816Anyone else had the spear crack where it is inserted into the shaft? Has happened several times to me when they are left over the winter.

 

[DivingNomad]

Everybody hates on metal wishbones, they're easy to load and they never break.

I hate them with passion, they do break even the articulated metal ones from big name manufacturers. I have seen it happen often enough.

Sorry for contradicting you, but this has been my experience and the experience of many others I know. I am sure that there are special type of metal wishbones that are stronger, I have seen titanium ones, but the average available ones are an injury trap.

 

[gingebailey]

This is I have to admit a poor design. The shooting line hole is directly beneath the sharkfin. Under severe stress or bending the heat applied from the weld has already caused stress near the shark-fin and the hole there adds to it. The other one break at the shark fin too because of the stress from the weld. It's likely those were tabbed on after heat treatment.

The hole you are seeing under the fin is the hole thats drilled in the spear for the fin to be pressed into. There is no welding on this spear. Somehow moister has gotten between the fin dowel and the spear and corrosion has set in. When this happens the corrosion needs space to expand and the spear cracks.

 

[Mark Laboccetta]

I see what you mean.

I hate them with passion, they do break even the articulated metal ones from big name manufacturers. I have seen it happen often enough.

Sorry for contradicting you, but this has been my experience and the experience of many others I know. I am sure that there are special type of metal wishbones that are stronger, I have seen titanium ones, but the average available ones are an injury trap.

There certainly are. The main difference is the type of steel used. In a good articulated wishbone the stainless is heat treated, it has some flex and therefore doesn't just bend and crack. In the less expensive ones, particularly the Chinese made stainless ones they use a 308 stainless and they give up bend and shear. It's just a preference. To me, on a single band gun a Dyneema wishbone is a nuisance and shark-fins aren't a requirement. I view this setup more ideal however on smaller guns, that typically are only set up for a single band 85-90cm or less.

Gingebailey - I stand corrected you are correct. The pressed sharkfins have never worked well. Omer introduced that same system whereby they were pressed and glued in on the Sporasub line of "America" sharkfin shafts in 2010 and they were a disaster.