Corby Lengths for 1/4'' Handle Slabs - Bore Depths

J. Keeton

J. Keeton

Joined
Nov 15, 2005
Messages
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Just wanted to run this by you guys. I've been using loveless fasteners for a while and what to move to corby not only for the look, but also since I can find them cheaper (Pop's).

I'm utilizing 1/8'' blade steel with 1/4'' Micarta or G-10 handle slabs.

The Corbies come @ around 1'' overall length. I want to accomplish two things: 1.) I want the Corby bolts to seat deep enough so that I don't grind into the void on the female end. 2.) I want enough handle material under the Corby head to support the fastener.

This is my plan (good plan?):
  • Shorten the female and male sections of the Corby bolts so that the made up over all length of the Corby is 0.9550'' when backed out ~2 turns.
  • Counter bore 0.135'' on each scale
    • This gives me 0.075'' to the female void (based of the depth of Corbies I currently have which are not from pop's)
    • This leaves 0.1150'' of handle material under the head of the Corbies.



  • Does this look like a good plan?
  • Is 0.1150" enough handle material on each side to support the Corbies
  • What is the best way (belt grinder? bandsaw? endmill?) to bring down the Corbies to 0.955"

Thanks for any input, I'm not a Corby pro yet.
JKeeton
 
In a perfect situation, the Corby bolt will be seated half way in the scale. For a 1/4" scale, that is 1/8" deep. On a 1/8" tang and 1/4" scales, the Corby female shaft would be 3/8". Shorten as needed, or buy the closest length.
The seat can be deeper, but you always want at last 1/16" of scale under the seat.
 
Thanks Stacy. I had read your 1/16'' recommendation on another thread. I'll shoot to beef that up a little bit, while still not grinding though the female end.

Do you still recommend the though hole in the tang being over-sized by ~30% when using Corbies?
 
Yes, I usualy oversize the tang holes by 25%, but 30% is just as good.

The 1/16" seat thicknes is a minimum, which comes into play on thinner handles.
 
The scales are usually shaped top fit after assembly, so there is no alignment issue.
With two bolts/pins, the holes can be closer to an exact fit, but with three you may have installation issues wihout the extra room.
Epoxy fills the gap and makes it structurally sound.

A machinist with a very well aligned drill press and good bits could probably do this with the holes being .005" oversize. I can tell you from experience that the average knifemaker won't.

The extra 25% in the hole only provides a little space. In a large Corby with a 5/16 head the shaft is .20" If the hole is 25% oversize, that means a .25" hole. This leaves a gap around the shaft of .025" … 25 thousandths. That is about the same as the thickness of a business card.
 
J. Keeton said:
How is the over-sized hole an advantage over a hole drilled to the shank size? Just ease of assembly or an actual structural benefit?

Won't over-sized tang holes make alignment of the scales harder during glue-up?
Click to expand...

Yes it does, I can spot an uneven front of the scale or one pin hole higher then another right away.

Some never seem to be able to see it.

If a maker clamps/super glue a scale on one side and drill holes through the tang, then do the same for the other side drilling through the pre drilled holes in the scale, and orientates right and left up and down of the scale, upon installing the scales and corbies will line up with zero problem.

I like to drill my tang holes just a few thousanths larger then the shaft, this way upon installing it has no choice but to line up perfectly.

Here is an example of 2 corbies and a thong tube installed in such a manner, the all just precisely slide into place with no slop easy peasy and I am no machinist.

Now the way I install corbies is I actually place the female corby up against the thickness of the scale and mark on the scale where I want the head to sit. I like to go deep and bore the hole as far as I dare leaving enough material at the bottom for the female to insert and the male to seat.

Then I test fit the scales on the tang and insert the female corby and see how much it inserts into the opposite scale and grind down until it is under the edge of the bottom hole.

Then I take that corby and test fit the female into it and you will see a gap, I then grind down the female end until that gap is gone.

This insures your corbies will seat all the way and have room to tighten down the scales.

You also will have enough of the corby head in the scale you will not grind it down to deep where the threading starts, been there done that.

There is nothing worse then having your scales installed and all cured and you grind to deep.



dBvLpFl.jpg
 
You guys rock, thanks for the information. Should be a breeze for me now after reading yall's suggestions!

Adam, With the loveless I've been using a similar method. I use a #28 bit on a 1/4'' loveless. Clamp both scales to one side of the pre-drilled #28 tang; then use the tang as a guide to drill though both scales at once. I use the bolts as alignment bolts when drilling additional holes. Haven't had a mis-alignment yet.

Your process for adjusting the length of the Coribies will be very helpful!
 
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