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Old 03-06-2019, 01:08 AM   #1
theslothh
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Enlarge hole for shooting line in shark fin

When I bought my Pathos gun last year I changed out the 7mm spear that came with it for a 7.5mm. I went to rig up the old spear and the hole in the sharkfin is too small for 1.8mm mono. Just wondering what the best way to bore this out would be? My main concern is making sure that there are no sharp edges inside the new hole and what the best way to smooth out such a small hole would be? Are there any special tools or tricks for this?
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Old 03-06-2019, 02:32 AM   #2
parker
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Re: Enlarge hole for shooting line in shark fin

Unless you have really good metal filing skills, I’d say it’s safest to buy a new shaft. It doesn’t take much of a burr to snap a line under pressure.
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Old 03-06-2019, 04:33 AM   #3
e.m.p!
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Re: Enlarge hole for shooting line in shark fin

�� not sure if you're joking about buying a new shaft. Anyway – first, carefully work with a dremel and a cone shaped head. Then put a toothpick into a drill, dip into cutting compound and off you go. After you've gone through a couple of them, swap for dyneema, again dip in cutting compound and move back and forth.
With that you'll get your shaft tabs and line holes to a mirror finish and your rubber will perish way before you'd need to replace wishbones
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Old 03-06-2019, 06:27 AM   #4
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Re: Enlarge hole for shooting line in shark fin

It's good to learn this skill no matter what - especially since buying a new shaft is no guarantee of burr free holes or rounded sharkfins. Perhaps the high end shaft makers don't send out shafts with these line cutting defects but it happens quite a bit from the big euro brands. Just today I had the dyneema shooting line break at the hole of a shaft after about five days of use - I had simply forgotten to polish that hole even though I had done the sharkfins.
Luckily it landed right on top of a pinnacle so I could retrieve it:-)
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Old 03-06-2019, 07:07 AM   #5
theslothh
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Re: Enlarge hole for shooting line in shark fin

Sounds like a solid plan, thanks guys!
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Old 03-06-2019, 07:38 AM   #6
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Re: Enlarge hole for shooting line in shark fin

Or you could skip all of that and use these.
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Old 03-06-2019, 12:46 PM   #7
doyenofcastle
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Re: Enlarge hole for shooting line in shark fin

Abrasive cord will do that
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Old 03-06-2019, 01:49 PM   #8
Behslayer
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Re: Enlarge hole for shooting line in shark fin

Common issue if you plan on using thicker mono, or chafe guard.

First bore out the hole to your required diameter. Wear Glasses. You can use a Drill bit which matches your current hole and give a little pressure downwards and influence the position of the centered hole so that it is a little lower so you still have enough meat on top. Probably a 1/8" bit will work for this. You can then smooth out the hole using a bit the actual diameter of your line. For example a 5/32" or 9/64". Then take a Larger Bit like a 1/4" or 3/8" and give a shallow push and deburr and soften the edge of the hole. You could then further polish but honestly just doing that should be enough. Especially if you use any form of Chafe Guard.

There's a bunch of different options for Chafe Guard. Those Stainless Spring Coils are for serious Reef Scraping. But you can use Nylon Tube, or Dyneema Tuna Fishing Chafe Guard, but you can also take a little piece of your Dyneema Reel Line and wiggle your Mono through it and make a Chafe Guard.
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Old 03-06-2019, 04:22 PM   #9
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Re: Enlarge hole for shooting line in shark fin

Solid thread, learned more than one thing
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Old 03-12-2019, 06:40 AM   #10
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Re: Enlarge hole for shooting line in shark fin

If you are going to use a Dremel anyways, you can always use the cone shaped felt burs smeared with polishing compund... and that should do the trick nicely.

I polish the holes and sharkfins of every shaft I buy and use, no matter the manufacturer.
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Old 03-12-2019, 02:09 PM   #11
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Re: Enlarge hole for shooting line in shark fin

Anyone building or working on guns need a Dremel tool, don't buy the copies. They usually come with a bunch of bits including the felt tipped cones.
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Old 03-13-2019, 06:06 AM   #12
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Re: Enlarge hole for shooting line in shark fin

Quote:
Originally Posted by popgun pete View Post
Anyone building or working on guns need a Dremel tool, don't buy the copies. They usually come with a bunch of bits including the felt tipped cones.
If you are feeling "macho" enough you should also get a straight grinder with assorted carbide bits. 600W or more, less is for pussies. Variable speed is nice not to burn wood.

I have both and I use both when perpetrating my wood guns. The Dremel lacks the required grunt sometimes... out comes the straight grinder.

For polishing compund, you can buy big blocks (cheap) from industrial supplies. The stuff thar dremel sells as an accesory is outrageously expensive!
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Old 03-13-2019, 11:04 PM   #13
RichT
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Re: Enlarge hole for shooting line in shark fin

Out of the hundreds of spear shafts we’ve rebuilt, I find that the vast majority of shaftmakers take lots of shortcuts which include not countersinking line holes or flopper holes.
Even fewer actually polish the holes.

Shafts are not straightened properly particularly after welding and some don’t even weld around the entire Shark fin which is just plain dangerous as salt gets under the fin where the weld is most vulnerable.

Euro manufacturers appears to take the most shortcuts in my observations... I believe there are only 3 manufacturers in the World(All in USA) that actually use the correct type of 17-4 stainless steel that should be used for spearshafts and that is centerless-ground steel. Nobody else uses it because it much more expensive.
Centerless-ground steel is much straighter than normal and doesn’t have the surface stresses so it stays straighter much longer. With repeated use.

Another issue I see is heat treating is not being performed properly a good portion of the time and it’s probably one of the reasons stainless steel shafts have lost market share to spring steel shafts.


Back to original question: The correct way to fix an undersized hole is to use a reamer to enlarge it, then a countersunk to clean the burr. Finally, the hole shoul be polished.
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