Fly cutter sizes for cutting nail nicks in folder blades?

Drew Riley

Drew Riley

Well-Known Member
I'm not sure if I should be posting this in the folding knife forum instead, but I'll give it a shot here first:

I've been reading through what seems like dozens of pages worth of threads, and have even posted the question in a couple of other knife forums, and though I've received a handfull of replies, I've yet to receive a response that answers my specific question.
The funny thing is, I've seen a handful of other makers ask the exact same question on the other threads I've been searching, and nobody has answered them either!

I'm not sure if the question is too simple, too complex, or if this is some closely gaurded secret, but I figured I'd give it one more try and see if anybody on this forum could give me an answer. hahah

My question: What size/diameter fly cutter should I get for cutting nail nicks into folder blades?

I'd imagine I'd need a size for small blades as well as large blades. Are there any recommendations?

I'd appreciate any help I can get. Thanks guys!
 
I don’t think it is any secret. I believe most people use whatever size they happen to have. I have a 2 inch fly cutter I ended up with somewhere down the line and am looking at a 3 inch for longer nicks. Shape the tool bit to cut the nick and run it slow. Feed it in to the depth you want your nick, about 55% of the blade thickness works pretty well. When you get a tool bit that works well, make notes and take some pictures of it so it is easier to re-sharpen or make another one when you need it. It will take a little trial and error to get it working the way you want.

I use a stone most of the time and cut them after blade is hardened and ground.

For long pulls I use a slitting saw and cut them before heat treating. I use a .040 thick 2 ¼ inch diameter 132 tooth saw. If you want to use these get a good arbor and run them slow also.

Craig
 
Craig said:
I don’t think it is any secret. I believe most people use whatever size they happen to have. I have a 2 inch fly cutter I ended up with somewhere down the line and am looking at a 3 inch for longer nicks. Shape the tool bit to cut the nick and run it slow. Feed it in to the depth you want your nick, about 55% of the blade thickness works pretty well. When you get a tool bit that works well, make notes and take some pictures of it so it is easier to re-sharpen or make another one when you need it. It will take a little trial and error to get it working the way you want.

I use a stone most of the time and cut them after blade is hardened and ground.

For long pulls I use a slitting saw and cut them before heat treating. I use a .040 thick 2 ¼ inch diameter 132 tooth saw. If you want to use these get a good arbor and run them slow also.

Craig
Click to expand...

Thanks Craig. I was only joking about the secret. I just wanted to narrow things down a little better, as there a several availale diameters for fly cutters.

Can you tell me approximately how long the 2" cutter makes your nail nick?
 
Another thing to consider if you are going to use a flycutter is the bit that you use stay away from the china bits even the cobalt are junk compared to USA made bits, so far the best bits that I have found are Cleveland T15 Mo Max. After you find the right geometry for the bit grind one of these to the shape bring it to a high polish and it will last you for a lifetime, just touch it up with an fine arkansas stone before each use.

Tony
 
Fly cutter diameter is kind of arbitrary, as is wondering about the width of a nick cut by one.

I have several fly cutters I made while in school.

The actual cutting diameter is dependent on how far out you stick the bit.

I can get the same cutting diameter from a 1" fly cutter as I can from a 3" cutter, just stick the bit out further.
Now the 3" cutter will support the bit better, and give you better results, but both cutters can achieve the same cut.

Tell us how long you want your nick to be, and how deep you would like to cut, and I'll give you a diameter to set your fly cutter.

For example, a 3/4" wide nick, .060" deep needs a 2.4" diameter cutter, so a 2" or smaller fly cutter.
The same 3/4" nick, but .080" deep is only 1.84" diameter....

Heck, I just Googled a calculator before I clicked post.
You don't even need me...
http://www.1728.org/circsect.htm

Calculate for Chord and segment Height.

Chord = Width of the nick
Segment Height = Depth of Cut

I always forget how easy it is to find a calculator for just about anything you need nowadays.
I get ready to post the formula I just used, and think hey, maybe there's a widget on the net.
There always is...
 
I've tried dove tailed cutters and a couple sizes of fly cutters. The fly cutters need to have the tip shaped just right. Both work if the blade is soft. My best nicks are done after heat treating and grinding with a knife edged 4 1/2" wheel on the surface grinder. The same thing can be done on the milling machine. The real trick is to hold the blade still and not move around. The stone needs to be redressed with a diamond file for the final touch. Experiment and practice on scrap steel until you get the confidence to touch a finished blade.

Most all the factory nicks are/were pressed in soft. Try creating the match strike nicks any other way. Anybody have a picture of that process? I'd love to try that.
 
Last edited:
Fellhoelter said:
Fly cutter diameter is kind of arbitrary, as is wondering about the width of a nick cut by one.

I have several fly cutters I made while in school.

The actual cutting diameter is dependent on how far out you stick the bit.

I can get the same cutting diameter from a 1" fly cutter as I can from a 3" cutter, just stick the bit out further.
Now the 3" cutter will support the bit better, and give you better results, but both cutters can achieve the same cut.
Click to expand...

I realize the bits can be moved in and out, but I wanted the most stability for the given diameter. As for sizes being arbitrary, I think a 1/2" nail nick would look kind of silly on the 4" blade of a grandaddy barlow, but not so much on a 1.5" pen knife blade. Vice/Versa with a 1" nail nick.

Then of course, there is the changes per depth as you mention.

Thanks for the info Brian.
 
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