corby bolt installation

shamu

shamu

Joined
Jan 18, 2010
Messages
217
hi BF,

I just got setup w/my first drill press, and the difference in alignment is awesome. i have a question regarding the most effective (considering cost of new bits and the likelihood i'll use differing sizes as i progress) way to drill my holes.

I want to install 5/16 (shoulder) x 7/32 (shaft) corby bolts. i contacted the fine folks at usaknifemaker.com, where i bought my bolts, and they suggested:

http://usaknifemaker.com/pilot-shaft-for-counterbore-7-32-od-with-3-32-shaft.html
http://usaknifemaker.com/counterbore-5-16-w-1-4-pilot-for-large-corbys.html

even if the counterbore was in stock, i'm not sure i'd want to buy counterbore/pilot bits for each corby specification. i watched the walter sorrells youtube vid on how to make a step bit, but i'm not confident enough in my skills yet to start modifying perfectly good drill bits.

would using a step bit be a good way to proceed? if so, i was considering:

http://www.amazon.com/Neiko®-10197A..._cp_469_3?ie=UTF8&refRID=1R7SVPNNC1HN3GQKTE58

thanks again BF
 
shamu, I don't think a step drill bit would be a way you want to go--I hate to say it but I think paying for the actual specific bits the best way to go. These I found on E-bay: http://www.ebay.com/itm/32082274386...49&var=510050673087&ssPageName=STRK:MEBIDX:IT

Another way to approach it is to drill the right sized hole for the 'skinnier' shaft all the way through both of your scales, and then place the correct bit for the head of the bolts, and drill a small amount into the hole you drilled for the shaft a small ways into the outside of your scales.

I'll be interested in other responses, I use pins and peen them myself, but I have thought Corby bolts would be good to use sometimes.

Best--Don
 
I ordered my bits from knife kits, The step is nice and square and gives a solid foundation for Corbys.
 
I use the 1/4 HSS Step Drill .182 Pilot 1-1/4 Long from TruGrit.

Perfect every time.
 
.217 is to accommodate the threaded barrel
 
A tapered step drill would absolutely NOT work.

The only way drilling with multiple drills would work, is if you have the part fixtured rigidly. That way the bits would come back down in exactly the same spot every time. Just trying to hold the part and lining up the bits would result in off-center/warbled holes.

$25 for getting it correct, right from the start... is ridiculously cheap and free from $500 headaches. :)
 
The purpose made steps drills are great. I initially used them more to drill out 416 or mild steel butt caps and used corby's to secure them. The bits don't last quite as long if you do that and now I hard solder the nut to the inside of the cap after milling a pocket, but those bits do work for multiple applications. ;)
 
I get my bolts and counter bore from Pop's Knife Supply. He makes them both. They are 1/8'' shaft and 3/16'' head. Use a #30 bit for the first hole and go all the way through. Then set your depth on the drill press and use the counter bore. Perfect holes every time. Well worth the $20.
 
thanks for the advice everyone -- ordered the truegrit bit. and another tool closer to a semi-respectable-hobbyist-shop...yet another step closer to marital hostility?
 
There are a few basic tricks of the trade that pretty much guarantee the bolts will fit right. Start with good counterbore and a drill bit to match the shank size. It is best to buy your counterbore from the guy who makes the rivets. Pop's makes his rivets and the counterbores are made to match them perfect. If mix-matching rivets and counterbore bits, test the match before proceeding. You want a smooth fit with no binding or need for force. Counterbores wear in use. They have to be replaced every so often.


1) Drill both scales completely before any shaping. You want flat and straight sides when drilling.

2) Give yourself some room in the tang holes of the blade. If the Corby shank is .218", drill the tang at least .250. Once the tang is drilled, set it on one scale and mark the center of each bolt hole on the wood.

3) Drill only one bolt at a time. Start at the first rivet from the front and drill that hole through both scales (Clamp or tape the scales together). Use a good quality SHARP bit that matches the shank size ( same as the pilot). Then drill with the counterbore to make the seats. Put a Corby in each side, and screw together finger tight with the tang in place. Adjust the depth of the counterbore seats if needed. Just make the bolt snug, don't torque it down hard.

4) Now, with the front Corby bolt still in place drill the shank pilot hole for the rear bolt. Counterbore and install the back bolt.

5) Drill and install any center bolts as previously done on the ends ... one at a time.

6) When installing use the slowest resin you can get. I recommend 24 hour cure resin. This will give you an hour or two to leisurely install the handle on the knife.
 
Stacy,

Do all 5/16 corby bolts have 7/32 shafts? In the spirit of your advice to buy bolts and bits at the same place, i noticed that shaft diameter wasn't mentioned here:

https://trugrit.com/index.php?main_page=product_info&products_id=3738

Also, how do you manage to get precise enough w/the drill to go from .218" to .250" (in your example)?

Finally, for the pilot hole -- i can just use a smaller bit to make the initial hole? or do i have to have a special pilot bit for this application?

thank you
 
Matt R said:
I get my bolts and counter bore from Pop's Knife Supply. He makes them both. They are 1/8'' shaft and 3/16'' head. Use a #30 bit for the first hole and go all the way through. Then set your depth on the drill press and use the counter bore. Perfect holes every time. Well worth the $20.
Click to expand...

yep , the answer right there . pop also has them in 5/32 pilot with 1/4'" head
 
shamu said:
Stacy,

Do all 5/16 corby bolts have 7/32 shafts? In the spirit of your advice to buy bolts and bits at the same place, i noticed that shaft diameter wasn't mentioned here:

https://trugrit.com/index.php?main_page=product_info&products_id=3738

Also, how do you manage to get precise enough w/the drill to go from .218" to .250" (in your example)?

Finally, for the pilot hole -- i can just use a smaller bit to make the initial hole? or do i have to have a special pilot bit for this application?

thank you
Click to expand...

That bit is long enough to drill from one side of the handle material and a pilot hole to the other side. Flip and finish drilling for the corby head.

Those drill bits make life so much easier.
 
Matt R makes a good point. As Corby's are all "custom order" parts, the ones from different suppliers can be different in diameter, etc. I found that out when I ordered the 1/8 shank "micro" Corbys from a couple of different places because of availability. The allen head ones that I got from Jantz IIRC along with the drill, were a little bit smaller than the slot head ones I got from elsewhere and the blades in question had been drilled to Jantz size before they went to Peters, so no joy on the other ones. it is a good idea to keep your bolts and bit in the same bag if you are begin from different suppliers.
 
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There are a couple ways to install Corby bolts and a few different sizes of Corby bolts. Since I also use Loveless bolts and acorn bolts I have found that using a specific drill with the pilot diameter and final counter diameter for each size of fastener is the best and I keep them with the fasteners and labeled. I would drill the holes first as Stacy suggested except when I installed bolsters in which case I profile the scales with extra material to account for tiny shifts when the epoxy is wet and I epoxy the first scale on and then drill the holes when the epoxy is dry by using the same drill as the pilot portion of the drill and then finishing with the pilot/counterbore . I do this to get a perfectly tight fit of the scale against the bolster. Then I epoxy on the second scale and let dry and repeat the process. I put some thread locker or epoxy on the Corby screw threads and tighten them lightly. This works for me and I only do it this way to get the tightest possible fit of wood to bolsters. It takes more time but I stress less. The photo is Corby bolts in Micarta. Larry

KStRZ9gm.jpg
 
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