Milling and jimping

REK Knives

REK Knives

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Any tips how to mill fine jimping? Not even sure what end mills to use or how to go about it - use a vise that tilts? Tilt the head and use an edge of the end mill?
 
There are a number of ways to do this. Tilting the head and using a regular endmill limits you to 90 degree jimping profile, but is probably the easiest way to do it on a vertical mill while avoiding head clearance issues. I would avoid trying to do it in a way that requires you to center cut the root of a profile, as the surface speed prevents any actual cutting at the point and the tools are fragile.

Honestly I think it's faster and easier to do with a checkering file, if you're going to do it across the thickness of a blade. If you're going to do it on the side and the cuts are longer it might be worth the setup. I could jimp an inch by hand faster than you could tilt your head to 45, then tilt it back and tram it level again, not including the time you spend milling.
 
kuraki said:
There are a number of ways to do this. Tilting the head and using a regular endmill limits you to 90 degree jimping profile, but is probably the easiest way to do it on a vertical mill while avoiding head clearance issues. I would avoid trying to do it in a way that requires you to center cut the root of a profile, as the surface speed prevents any actual cutting at the point and the tools are fragile.

Honestly I think it's faster and easier to do with a checkering file, if you're going to do it across the thickness of a blade. If you're going to do it on the side and the cuts are longer it might be worth the setup. I could jimp an inch by hand faster than you could tilt your head to 45, then tilt it back and tram it level again, not including the time you spend milling.
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Ok, to date I have tried both ways to an extent - although with a checkering file I just did it on a scrap piece of steel - it looked really good but it seems like this would be hard to get perfectly 90° and going around contours like the curved end on the butt of a fixed blade. but on my mill, while very precise, I am getting a chattered/rough surface effect which seems to be minimized with climb milling though. In this pic I am using a 1/2' carbide end mill from lakeshorecarbide at max rpm, dry with chips being blown out w/ compressed air - milling g10 and annealed steel all at the same time. Any tips?

i-K2ssVKw-X2.jpg
i-c4HmgQP-X2.jpg
 
You might try a high RPM slightly more than spring pass climb milling to get a better surface finish.
 
kuraki said:
You might try a high RPM slightly more than spring pass climb milling to get a better surface finish.
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I understand climb milling in reference to the direction of the cutter and the direction of the feed. Can you explain spring pass?
 
KnuckleDownKnives said:
I understand climb milling in reference to the direction of the cutter and the direction of the feed. Can you explain spring pass?
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When making a cut at depth the tool and work deflect from each other. Even in very rigid setups, it can be minimized but not eliminated. A "spring pass" refers to making the same cut without additional feed, you've allowed the tool and work to spring back to their unconstrained state and are making a cut at the same dimension with whatever is left over.

When I say "a little better than a spring pass" I mean if he was making a .060" depth of cut, then, on the spring pass, possibly advance .001 or .002" to climb mill back. Just enough to match the depth of the surface roughness he's trying to eliminate, but not enough to create a significant amount of deflection.
 
I have never jimped anything, but wonder why you would run a square end mill at 45 degrees rather than just running a 45 degree end mill at 90 degrees? At least that way you don’t have to re tram the head.
 
Jonathans said:
I have never jimped anything, but wonder why you would run a square end mill at 45 degrees rather than just running a 45 degree end mill at 90 degrees? At least that way you don’t have to re tram the head.
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A 45 degree cutter has zero surface speed at the center and drags its way through the cut. Hard to get a decent finish.
 
I use my Fordom Flexshaft with a 3/32” Carbide burr. About a inch of burr. ——- Mark it out with black marker and slowly work in the notches. It takes a while to get the hang of the torque pulling you forward, you’ll get the hang of it!
 
No, I was thinking a 45 degree chamfer type cutter and being the machining noob that I am wasn’t considering that the center of the cutter lacked any surface speed regardless of spindle speed. Thanks Kuraki.
I had thought of one of the smaller double angle cutters with the blade held vertically, but there you couldn’t get clearance from the tool holder
 
kuraki said:
When making a cut at depth the tool and work deflect from each other. Even in very rigid setups, it can be minimized but not eliminated. A "spring pass" refers to making the same cut without additional feed, you've allowed the tool and work to spring back to their unconstrained state and are making a cut at the same dimension with whatever is left over.

When I say "a little better than a spring pass" I mean if he was making a .060" depth of cut, then, on the spring pass, possibly advance .001 or .002" to climb mill back. Just enough to match the depth of the surface roughness he's trying to eliminate, but not enough to create a significant amount of deflection.
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Thank you for the detailed explanation.
 
Like this.
kuraki said:
A double angle cutter? That's possible but would be a tough setup depending on where the jimping is on the knife.
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This is what I used to use to cut my nail nicks.
 

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Yeah, a double angle is similar. There's just not enough spindle clearance to jimp with a cutter like that.

One thing a little horizontal mill would be great for, if you did enough to justify it.
 
autogateman said:
Like this.

This is what I used to use to cut my nail nicks.
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Not to derail the thread too much but that's interesting! What size do you recommend? Looks like since it's solid carbide it would work on doing a blade even after ht
 
What size do I recommend for using it for nail nicks? I used to use a 1" and it did a decent job if you dont have a fly cutter.
 
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