Drilling detent hole, looking for 2nd opinion

C

CyberDog

Joined
Jul 4, 2018
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Hello people,
I am looking for 2nd opinion about my intended modification. If you think I can screw up good knife, please let me know!

I want to drill detent hole in my speed assisted Kershaw Knockout m390. I am doing this because I want to increase detent. It is ok as it is, but little stronger would be better.

I bought micro cemented carbide drills from ebay for 4$. ( https://www.ebay.com/itm/10pcs-Ceme...-Drill-Bits-0-6-1-5mm-Option-NEW/371863094243 )
I know they are cheap drills. I hope they will finish this one job I have for them.
I will use drill press.
But I'm not sure what rpm speed I should use for drilling.

My plan is to take out detent ball, then assemble back knife with perfectly centered blade. Then I will drill through existing hole in frame-lock into the blade with 54# (1.4 mm). I just want to mark the spot, not drill real hole.
After that, I will take knife apart. I will drill in blade in marked spot with #57 (1.1mm). Required depth is 0.0144 inch (0.365 mm).
After that I will assemble knife back and check how strong detent is. If it is still weak, I may decide to increase detent hole to #56 (1.2 mm).
 
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Those drills should hold up fine, just be extremely careful not to let them "suck" into the hole. If the existing hole is close to the size of the drill, they have a tendency to grab and "corkscrew" into the hole. This will snap your drill right off.

Also, notice that your "increase" is actually a decrease. Going to the next smaller "number" drill is actually a larger size, not the other way around. Is there a spring behind the detent ball? Increasing the spring rate might be a better approach.
 
Great advice, thanks!

From what I read, increasing detent hole size increases detent strength because bigger part of ball fits in hole, thus more strenght (up to the size of ball ofc). Ball is 1/16" or 1.588mm.

There is no spring behind ball. The force of frame-lock is pushing ball. Hole is drilled through frame lock and 1/16" ball is pressed into this hole. Purpose of this is to prevent frame-lock from grinding against blade because it would wear frame-lock out. But normal manual knives use this same mechanism for holding the blade inside. Detent hole is drilled in blade and ball fits right in.
My knife doesn't have detent hole because it is speed assisted and torsion bar holds blade inside.

Yk428LG.jpg
 
Ahh, gotcha. Technically, there is a spring, but it's the frame lock bar, so there's no way to increase the spring rate. In that case, your best bet probably is to add the hole. As far as RPM, run your drill press wide open. You won't be able to get anywhere near optimal RPM for a carbide drill that small with a drill press. If you could, I'd recommend 8,500 RPM. Start small and work your way up so you don't overdo the detent force.
 
All my speedsafe knives don't have detent holes... They rely on the spring. I don't think modifications to the detent is going to help. But hey I dunno for sure if it helps. You might as well just de assist and then modify for un assisted flipping.

https://kershaw.kaiusaltd.com/blog/pocketknife-technology-101inside-kershaws-opening-systems
SPEEDSAFE® ASSISTED OPENING KNIVES
One common type of tech in a modern pocketknife is known as assisted opening. Assisted opening knives have a mechanism in the handle that assists the user in opening the knife, so it's ready to use quickly and easily. It also makes it easy to open the knife with one hand—very convenient when you’re steadying something in one hand while you need to cut with the other hand.

Kershaw was the first to bring assisted opening knives to a wider market—launching a revolution in opening systems. Originally designed by Hall of Fame knifemaker, Ken Onion, Kershaw’s SpeedSafe® knives flew off the shelves. Today, almost all knife companies offer some sort of assisted opening knife, but none matches the popularity or proven durability of the original.

HOW SPEEDSAFE WORKS
Most Kershaw SpeedSafe knives open with a “flipper.” Others are equipped with a thumb stud, while still others have both a flipper and a thumb stud.

Yet the heart of SpeedSafe is its torsion bar. Closed, the torsion bar helps prevent the knife from being opened by gravity; it creates a bias toward the closed position. By applying manual pressure to the thumb stud or flipper, you can overcome the resistance of the torsion bar. This enables the torsion bar to move along a track in the handle and assist you to open the knife. Opening is smooth and the blade locks into position, ready for use.

OPENING A SPEEDSAFE KNIFE WITH A FLIPPER
The flipper is actually part of the blade. When the knife is closed, it protrudes from the back of the handle. By pulling back on the flipper, you can overcome the resistance of the torsion bar, allowing you to open the knife. When the knife is open, the flipper moves to the bottom of the handle and often becomes part of the blade guard, which helps protect your hand from the edge of the blade. The flipper is easy for both right- and left-handed people to use.

speedsafe_flipper_CU.gif


OPENING A SPEEDSAFE KNIFE WITH A THUMBSTUD
A thumb stud is a metal stud attached to one or both sides of the blade, near the blade’s spine. Instead of pulling back on the flipper, you push outward on the thumb stud. That outward pressure overcomes the resistance of the torsion bar, allowing you to open the knife. Most manufacturers include thumb studs on both sides of the blade so assisted opening is easy for both left- and right-handers.

thumbstud-open_BLUR-animated.gif


IS A SPEEDSAFE KNIFE A SWITCHBLADE?
No. There are many unique features of SpeedSafe knives that make them quite different than knives that are considered switchblades. Unlike a switchblade, SpeedSafe blades DO NOT deploy with the push of a button in the handle or by gravity alone. Instead, the user must overcome the torsion bar's resistance to engage the assisted opening that SpeedSafe provides. Because of this, SpeedSafe knives fall fully outside the Federal definition of a switchblade. However, there may be local regulations affecting what you can own and carry. Please be responsible and know what applies in your area.
Click to expand...

Or you could ask Kershaw for a replacement torsion bar. Sometimes they make revisions to these and they look differently than the original.

As for making your own detent hole. Check youtube. Some really useful videos on how to make a detent for folding knives. Basically tighten the closed as much as possible with strong rubber bands or zip tie and then drill your hole through without going through the other scale. Then insert new detent ball into the frame lock.
 
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I know that speed assisted knives don't have holes, torsion bar holds blade inside. I want to add hole to increase detent. Current detent is not bad at all, I just want it to be little stronger. This way combination of torsion bar and small hole would provide stronger detent.

I was thinking about de-assisting it, but I actually like assisted knife, it opens reliably every time. The only problem is that torsion bar brakes every now and then (mine already broke on new knife and I'm waiting for replacement).
 
I'm not sure why it wouldn't.
I will report back when I do it.
I did watch many youtube videos about it yes. That's why I'm confident about doing this.
 
CyberDog said:
I'm not sure why it wouldn't.
I will report back when I do it.
I did watch many youtube videos about it yes. That's why I'm confident about doing this.
Click to expand...
I'm confident that you can do it. I'm also confident that it won't work in the way you are thinking it will work in the end.
 
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