Pins, Corby Bolts, Rivets?

V

Vaunripped

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Nov 20, 2010
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I spent yesterday working on my my knife, hand filing the bevel into 5160 is not the most fun I have ever had. I almost drilled the holes for the hard ware to mount the slabs, I didn't, what stopped me was that I have yet to get any.

After a little looking, it hit me how many options there are for doing this. This being my first knife I figured I had better ask people who know.

Is there a big difference in the strength and or toughness between pins, corby bolts, or rivets? Is there any sort of "guide lines" that y'all use to pick what kind of fastener you use? Strength and toughness are big for me, as it is going to be a hard use knife, or at least that's the plan for it.


Thanks for any and all help y'all can provide.
 
Much of a muchness, really on strength/toughness grounds.
There are other considerations, though. Wood that is prone to movement is probably best done with pins, there are more of them and they go close to the corners and edges, so they help the wood stay where it's put (obviously not a consideration for artificial materials).
Rivets can be an issue if the material is fragile with impact forces. A miss-strike or hitting too hard can see bits of your material cracking, flaking or flying off.
Aesthetics can be an issue, loveless bolts always have that "bullseye" look even if the bolt and the nuts are the same material. It can be a feature or it can detract from the look. Corby bolts limit your choices of materials/finishes, plus you need a step drill and you can find your edges lifting if the material is prone to movement.
Hidden pins and mosaics rely solely on the glue bond to keep the scales attached to the tang and your clamping forces when glueing up are very important. The pins only prevent the scales shearing/slipping on the tang. Modern glues are pretty strong though and you might be surprised how difficult it can be to knock glued on handles off.
Hope that helps with your choice, dont forget though "Pictures, or it didn't happen!"

EDIT: RE; Corbys, I meant the pin material choices are limited with corby's and also I think they show up "ovalled" or misaligned drill holes more than other options IMO
 
Well that gives me more incite than I had to start with. I plan on making some micarta out of some old carhartt pants that have been waiting to get patches for a year or 2 now. The "looks" aren't a HUGE part of this as long as it works well, and don't break, like I said this is going to see hard use, to the point of almost abuse. I plan on doing all the things that I refuse to even think about doing with my "store bought" knives. I want a nice tight fit more to keep out all the nasty stuff that will rust the tang than for looks.

Yes I know, pics more pics!!!! When I get back this afternoon or night, depending on how long it takes for my shoulders and neck to mess with me. Ill do up a WIP thread with were I am so far.
 
For toughness, durability, and holding power, you can't beat some type of bolt. I mostly use them with 3/16" shafts and 1/4" heads. You'll need a countersink to use them. www.popskinfesupply.com has them both and he has the cheapest price on handle bolts. Hope this helps.
 
FWIW, Corby bolts come in 5 diameters from 1/8" to 3/8", and in brass, niclkel, copper, stainless, aluminum, and steel. They also come is about four lengths.

I have found nothing that beats a Corby for ease of installation and strength.
 
bladsmth said:
FWIW, Corby bolts come in 5 diameters from 1/8" to 3/8", and in brass, niclkel, copper, stainless, aluminum, and steel. They also come is about four lengths.

I have found nothing that beats a Corby for ease of installation and strength.
Click to expand...

Absolutly.
Stan
 
Mechanical fasteners are stronger under more conditions than straight pins and glue. Worry about which glue is best (see "Glue Wars") after you use a mechanical fastener of some kind - first things first.
 
I'm with Stacy, Stan and BMK. Bolts are the bomb, and it's nice to use epoxy of some kind with them. IMHO the bolts hold everything together, the epoxy seals it up from moisture.

If sealing the tang isn't an issue, you can also cut the slots in corbies a little deeper so they can be removed with a screwdriver after being ground to final shape. Chain-ring bolts will also work this way, they are kind of expensive but don't need to be modified. In either case, I would probably recommend a non-permanent Loc-Tite type adhesive to keep the threads from coming loose. Having said that, I rehandled a Becker chopper with remo corbies and no adhesive at all, and the client says he's done a lot of chopping with it and the bolts didn't shake loose.
 
Thanks a ton for all the help. I have decided to go with bolts of some sort, either corby or chain-ring bolts. I looked at a lot of the "Glue Wars" threads and still really don't know what one to go with.
 
I use T-88 slow cure structural epoxy. Structural epoxies are strong in themselves. Bonding epoxies only make a strong bond.

I will share another part of my book with you chaps. This trick is one I developed, and do not know of any other maker who uses it. If making knives in batches, it speeds things up as well as increases accuracy . It eliminates waste ,too.
The process I have developed is this:

Glue up one scale to the tang and let cure overnight. Use the lightest gripping clamps you can get. HF sells them for about $0.75 each...get a couple dozen. I clamp both ends and the middle, but the grip is just enough to squeeze out the excess epoxy.
Once cured, clean off the tang ( belt sander) and drill 1/8" holes through the center of the tang holes ( BTW, I drill the blade tang holes at 150% the shaft size of the bolt being used)
Glue up other scale.
Using the first drilled hole, drill through both scales with an 1/8" bit, then re-drill with a bit the size of the Corby shaft.

Place on the shoulder jig and drill for the Corby bolts:

The shoulder jig is just a block of 2X4 wood, a 1.5" long piece of round stock the size of the Corby shaft ( from an old drill bit), and one Corby bolt female side.
Place a blank block of wood in the Drill press vise to act as a backing block, and lock everything in place when drilling the handle out for the Corby bolts. Don't move the block or vise after drilling the handle out. When drilling the handles, set the quill stop tallow the bit to drill about 1" into the block.

When all the handles being done are drilled out for the shaft size, place the piece of round stock in the hole made in the block by the drill as it passed through the handle. ( see last paragraph for the handle shaping step to be done at this point)
Place the scale on this shaft hole size stud, and use the counterbore from the other side. Move the handle from hole to hole, boring all the seats on that side.
Remove the shaft hole size stud, and counterbore the block hole deep enough to insert the Corby female part and have the body stick out about 1/4".
Flip the handle over and place the bored side holes on the new stud. Counterbore the holes as before.
All this sounds complicated, but all it is is a way to always align the top and bottom of the hole. It doesn't matter if the scales are parallel or not. It will work with a tapered tang, odd or tapered shaped handles, antler, ivory, etc.

Once all the shoulder seats have been made, check the Corby bolts by dry fitting, and when all is right epoxy the bolts in place.

The advantage of gluing up the scales and then drilling the seats is that there is no issue of misalignment caused by any of a dozen variables in the scales and the tang.
First, when you glue up the handle scales, every space gets sealed and all is snug. There is no excess pressure to cause scale ends to lift up and make gaps where they were not before tightening the bolts down. You can use just enough clamp pressure to assure a thin and even glue line.
Second, once the epoxy is cured, you can cleaned up the scales on the grinder and inspect the tang/scale joint all around. If there is a problem, it only takes a knife blade and a mallet to split the scales off the tang, and fix the problem ( a little heat will help,too).
If all is well, drill the scales for the shaft size. It should be a good slip fit,not tight.
Then pre-shape the handle to remove about 80% of the excess wood.
Now, do the shoulder drilling as above. The pre-shaping before the drilling and adding the Corby bolts eliminates the scorching of the handle by all the rough grinding, and eliminates wasted Corby bolts when a handle flaw is discovered in shaping. The bolts don't get glued in until the handle is ready to finish. The bolt shoulder depth is easily controlled, as you will know how deep it needs to be once the handle is pre-shaped. The more wood under the shoulder, the stronger the mechanical bond.






So - strong epoxy + a strong fastener + installing in a strong way = a super strong handle.
 
bladsmth said:
(BTW, I drill the blade tang holes at 150% the shaft size of the bolt being used)
Click to expand...

Stacy, I am still unclear why you choose to engineer so much "slop" when using bolts; personally, I've had much less trouble keeping things aligned when I keep my hole/bolt tolerances fairly close. (just snug enough that the bolts will fit through the tang and scales without needing to be forced.) I definitely agree on leaving room for expansion when using pins or rivets that will be peened, I just don't get the need for such high tolerances when using threaded fasteners.

In any case, It will behoove me to try it your way, and I apologize to Vaunripped for my off-topic comments.
bladsmth said:
So - strong epoxy + a strong fastener + installing in a strong way = a super strong handle.
Click to expand...

Absolutely :thumbup:
 
I agree that it sounds like a lot, but with a 1/4" shaft, the 150% oversize hole is 3/8". That allows .060" on each side for any misalignment in drilling. I have drilled the holes at .050 over the shaft diameter - 19/64 or N size for a 1/4" shaft ( which is considered sloppy from a machinist point of view) and had to use a diamond burr to make the bolt go through properly. When dealing in hundredths of an inch, there isn't much room for error. On a smaller bolt or rivet, the error range drops into the thousandth category.
50% oversize sounds huge, but huge is relative.

Another reason for the wider hole, is that I glue on one scale, sand the tang down to remove the epoxy that came through the tang holes, and drill the holes out by eye. Now my eye is pretty good, but if I'm just a little off center, I could be getting close to the tolerance of a snug fitting hole, but will have room enough with the larger 150% hole. Also, remember that I and probably drilling 30-60 tang holes at a time ( 10-20 knives). I am not spending much time lining them up at exact center.

Since I started using the jig method, I probably don't need to oversize the hole more than 25%....but you do need some slop.

Final comparison - when you drive a car between a parked car and an oncoming car, it looks like a tight fit....you may even hit the brake and wait for the car to pass....... but the space is probably 150-200% the width of your car.
 
Wow, thanks a ton for the info, should help out with my knife a lot.

Would I want the same amount of "slop" if I left the slabs unglued for removal or replacement of broken slabs or bolts later down the road?

Thanks again for the help.
 
If you aren't going to glue the scales on the tang, then all you will have is the mechanical bond. In that case you would want the closest fit possible without binding.

Unless the knife is a take-down model, I can't see any reason to not use epoxy as well as bolts.
 
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