I want to make a hole in which to mount a grub screw, what do you guys suggest… Fill with resin/milled glass then drill/tap? Or implant a chunk of abs or pvc and drill/tap that?
Hey Shwuz.
What’s the intended purpose of the grub screw insert??
If it’s just for a fin most just use plastic and I’d imagine pvc would hold up well… Then there’s plastics like delron or chinook finbox plastic that seems to have fibers in the mix…
If it’s load bearing like a kiteboard footstrap insert , the inserts fishnsurfn suggest above have fantastic holding power and strenght, although look at their individual price per insert especially for stainless which is really the only way to go for such inserts imho… They’re pricey, but the most secure…
I’ve tapped epoxy and milled carbon as well as milled glass and it holds up quite well, perhaps better than plastic if mixed right… The only down side is the feeling of resistance or a “gritty” feeling you get when tightening in the grub screw, most likely due to the abrasive nature of the cut fiber ends in a tapped out mixture… I’m sure you could eliminate this gritty feeling with a dab of vasoline on the end of the grub screw before insertion though…
I’ve followed your posts on board builds, and I’m sure you have scrap carbon on hand… It taps out extremely well and is quite strong…
I’d give it a go if overall pull -out strength is not your concern…")
On an added note: if you tap out the carbon/glass epoxy mixture, finer thread pitches seem to work better for overall strength Like #10-32 as opposed to 1/4"-20, or such… The smaller thread height and a greater number of threads per inch of length tend to shear off less when tightening the screws due to less concentrated load on each of the vertical thread heights , as well as having a greater number of load bearing threads per inch…
Shwuz
Cast in a stainless or brass threaded Insert. http://www.mcfeelys.com/threaded-inserts More durable than plastic etc.
or use foot strap inserts, very strong. Eg at fiberglass supply the 2 hole version is part number R65-5305 2 Hole, Adjustable Strap Insert, Chinook (#341)
If you go with an insert, a material like nylon would be able to hold threads a little better than abs. Abs is fairly open celled and expands and contracts with temp. fluxuation. I'd want a more dense material for screwing into. The threaded brass inserts work well ONLY if they are secured to a proper substrate. I suppose you can acomplish that by making your own with epoxy and milled fibers. You can even make the pour and vibrate a little to condense and get any air out while casting. Good Luck.
tblank wrote :
You can even make the pour and vibrate a little to condense and get any air out while casting. Good Luck.
Good point tblank.
I recently bought a food vacuum bagging kit that features a hand operated vac. pump and special vac. bags that have built in check valves that hold vacuum really well.
If you mix up a carbon/glass epoxy goop then place it in the vac. bag while in a strong container, you can vac. evacuate all the bubbles out of the mixture in minutes… The vac bag hand pump deal works great for bagging glass onto bamboo fins as well!
Better Idea, Kiterider. The vac is way mo' betta.
Hi Shwuz -
Have you tried casting the plug with the grub screw in place? Wait for a complete cure, unscrew, and you should have a perfect set of threads ready to go.
Of course no plastic is going to be as tough as stainless or brass.
no replies to legitimate questions.
Must be on holiday
Thanks for all the input everyone! I’m thinking I’ll go with the inserts idea. If I’m pouring resin anyway, I may as well be pouring it around some high-quality threads.
Shwuz,
I have used helicoils on the end of the screw set in epoxy and milled fibers.
They leave a metal set of threads in the hole, useful if lots of removing and installing.
I usually spray the screw with some final net hair spray(release agent(forgot the chemical name)) let them dry, wind on the helicoil, set in the thickened resin with some sort of rig to keep the screw plumb, sometimes I will shove some roving through the buried end(tang) of the helicoil to give a bit more pull out resistance.
I cap for foot strap inserts with 4 or 6 oz ( whatever is onhand).
This also works neat for undercoaming rod holders and (hidden fasteners, blind screw inserts etc. Can’t wait to see what this if for.
Pete
I’m going to try a travel board with the same kind of system as the imagine eco boards. Super-simple, and if it works well it should cut build time in half, easy. They used set screws to hold the carbon rods in place, eliminating the need for a pope-type clamping system. I’m also thinking that if I can set the screws at an angle and put a lip on the inner rod, I can use the pressure of the screws to draw the halves together. More to come!