Nail nick grinding

I've been using a die sinker to burn in match strikers on liner locks recently. Not really economical unless you happen to own a sinker EDM, but it gives the flexibility to stick any shape you want into hardened steel.
 
I've been using a die sinker to burn in match strikers on liner locks recently. Not really economical unless you happen to own a sinker EDM, but it gives the flexibility to stick any shape you want into hardened steel.


Haha, funny you should mention that. I just came home with a Sinker EDM. ;)
 
I just did a couple blades and used a steeper angle, i like it ok. It isnt perfect. Not sure how i feel about the top of the nick being slightly curved, not sure how that is happening. It is solid though, that chewed up left thumb nail of mine can grip it hard and not let go. Welding angle iron to the heavy plate did help with chatter but i noticed my cut off wheel is getting a bit unbalanced and so it wobbles a bit. It still cuts decent though.

oh0zvN8.jpg
 
Randy, dust the top off and it'll look better, however, the most likely reason for your top being curved, is that there's a little radius from the sharpest point of the edge, to the top of the wheel. In a perfect world, you want it as straight to the point of your angle as possible. However, even with the stones I use on a surface grinder, I have to redress it every so many blades, or it'll start showing less sharp ends, and curvature.

With your method, you're going to likely have to dress it more often, maybe every knife.
 
It's a Hansvedt 150B, got an incredible deal on it, which do you have?
I've got an sm-150b as well, mine was Steve Schwarzers old machine. Great little die sinkers. If you've got any questions about them feel free to ask. I'm not the biggest edm expert, but I've had it running for a month or two and went through servicing and setting up.

Manual calls for rustlick edm30 oil, but Im running rustlick edm250 with good result. You'll need 6 pails to fill it, if you got a good enough deal the fluid could cost as much as the machine.
 
I've got an sm-150b as well, mine was Steve Schwarzers old machine. Great little die sinkers. If you've got any questions about them feel free to ask. I'm not the biggest edm expert, but I've had it running for a month or two and went through servicing and setting up.

Manual calls for rustlick edm30 oil, but Im running rustlick edm250 with good result. You'll need 6 pails to fill it, if you got a good enough deal the fluid could cost as much as the machine.

Guy I got it from has been running it, he just upgraded to a slightly newer, 3 phase unit.

Yeah, I paid less than the costs I'm googling for the oil, at 5gal prices. Looks like the smart move is to go ahead and invest in a 55 gal drum, but I have a friend with a large outfit that runs a lot of high end EDMs, that may be able to hook me up with fluid.
 
Randy, dust the top off and it'll look better, however, the most likely reason for your top being curved, is that there's a little radius from the sharpest point of the edge, to the top of the wheel. In a perfect world, you want it as straight to the point of your angle as possible. However, even with the stones I use on a surface grinder, I have to redress it every so many blades, or it'll start showing less sharp ends, and curvature.

With your method, you're going to likely have to dress it more often, maybe every knife.

Yep, that's what it is. I should of checked between blades.
 
Guy I got it from has been running it, he just upgraded to a slightly newer, 3 phase unit.

Yeah, I paid less than the costs I'm googling for the oil, at 5gal prices. Looks like the smart move is to go ahead and invest in a 55 gal drum, but I have a friend with a large outfit that runs a lot of high end EDMs, that may be able to hook me up with fluid.
I ordered mine from KBC out of convenience (and free shipping) and it was around $900-1000 Canadian to fill it. But at the level of use a knifemaker gives it, rustlick edm250 will last upwards of 20 years from talking to my machines previous owner.

Also, I'd recommend pulling the covers off and checking the hoses and wiring. Even though my machine was in use until shortly before I bought it, there were a number of things that really needed replacing. And the filter on the inlet side of the servo valve that the manual says never needs replacing, does need replacing after 40 years. Standard aircraft part, I paid $8 from a Cessna dealer.
I'm assuming you have the manual for it, if not I'd highly recommend picking it up. As much how to run edm machines as a manual.

One last note to save you possible trouble (which I very nearly did myself) the hydraulic system takes iso32 turbine oil (shell turbo T for example) NOT HYDRAULIC FLUID. It may not cause problems, but with how cheap the right oil is and how expensive that servo valve is, I wouldn't risk it.

Hopefully your machine has capacitor discharge (which was optional) as its boarderline a requirement for nail nicks. And forget no wear mode for nail nicks. Without really good flushing (which you won't have) it literally cuts a few thou per hour.

Anyways, I've probably told you enough you already know. Feel free to message me if you have any questions.
 
I ordered mine from KBC out of convenience (and free shipping) and it was around $900-1000 Canadian to fill it. But at the level of use a knifemaker gives it, rustlick edm250 will last upwards of 20 years from talking to my machines previous owner.

Also, I'd recommend pulling the covers off and checking the hoses and wiring. Even though my machine was in use until shortly before I bought it, there were a number of things that really needed replacing. And the filter on the inlet side of the servo valve that the manual says never needs replacing, does need replacing after 40 years. Standard aircraft part, I paid $8 from a Cessna dealer.
I'm assuming you have the manual for it, if not I'd highly recommend picking it up. As much how to run edm machines as a manual.

One last note to save you possible trouble (which I very nearly did myself) the hydraulic system takes iso32 turbine oil (shell turbo T for example) NOT HYDRAULIC FLUID. It may not cause problems, but with how cheap the right oil is and how expensive that servo valve is, I wouldn't risk it.

Hopefully your machine has capacitor discharge (which was optional) as its boarderline a requirement for nail nicks. And forget no wear mode for nail nicks. Without really good flushing (which you won't have) it literally cuts a few thou per hour.

Anyways, I've probably told you enough you already know. Feel free to message me if you have any questions.


Yes, it does have capacitor mode.. Fortunately, the PO refurbed this machine after it sat for a while, and he's pretty meticulous. All new filters, many new hoses, a new control board, etc., and yes, came with a manual.

Thanks, it'll be a few weeks before I get to setting it up, but if I run into any snags, I'll let you know.

As far as the "No Wear Mode", don't worry, I've already got a source for electrodes cheap/free, and have spent the last week wrapping my head around how to make most of the electrodes I'd want to use for this sort of task, that can easily compensate for electrode wear.

I'll still likely use this machine only for rare, one-off, or complex, nail nicks, as I still believe the other methods are king for this in most cases. I actually got the EDM for more interesting embellishment and construction ideas, plus general fab use, and it's just damn cool. ;)
 
They are cool alright. I've taken to burning opening holes in my liner locks with it as I hate thumb studs.
I mainly bought it for complex integrals and interframe folders, I just haven't had the time to play with it for that yet.
I'm looking at picking up a Gorton 3U pantograph to go with it as a companion machine. Those two together should open up some really cool possibilities.
You got a great deal if its already been gone over. Its a lot of time and a good bit of money to go through a die sinker.
 
They are cool alright. I've taken to burning opening holes in my liner locks with it as I hate thumb studs.
I mainly bought it for complex integrals and interframe folders, I just haven't had the time to play with it for that yet.
I'm looking at picking up a Gorton 3U pantograph to go with it as a companion machine. Those two together should open up some really cool possibilities.
You got a great deal if its already been gone over. Its a lot of time and a good bit of money to go through a die sinker.


Yeah, a pantograph has always been on my list also, I've turned down a few, mostly because I just don't have room until I get into my new shop.
 
I don't have room for half of my tools, I've still got a surface grinder in a uhaul locker. I think I've got space in my basement for the Gorton, provided I disassemble it and get a few people to help carry it in. Not looking forward to that one bit.

But between cutting matching electrodes and inlay pieces for interframes, handle inlays, and various other tasks, it should be worth the trouble. The price is right too.
I very much have a tool problem lol
 
So while i have been making mostly two overlapping blade knives, i made a single blade the past couple days for a confidence booster after messing up two knives in a row.

With the two overlapping blades, the nail nick came out and consistent on each blade, and those blades were flat ground on the side facing outward where the nail nick was.

For this single blade, i ground the nick, tapered the blade, and then beveled. I noticed the nick came out asymnetrical, the bottom of the nick shifted slighted away from the thin tip towards the thicker base. It makes sense geometrically. The question is, does this bother you? After thinking about it, the only way to prevent this is to taper and then do the nick.

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The asymmetry is more obvious than I would expect, I would suspect something maybe wasn't quite square/centered when you ground it.

Bear in mind that I cut mine after it's already finish ground, so it's laying on the surface grinder chuck at an angle (laying flat across the opposite side's bevel) but it's not enough to make it obvious to the eye. Most people cut them before beveling the blade using a fly cutter or similar, and of course, with a strong distal taper, that would show a slight asymmetry also (as you're bevel is ground futher on the more tapered end, into the nail nick), but it's not typically apparent to the eye in that case either.



Looking at yours, I'm wondering if what we're seeing isn't just a bit more chatter on the "high" (less ground into the nick, on the tang side) side, washing out the nick some, that you're cleaning up on the low side (toward the tip) after grinding more there. FWIW, the low (tip) side, looks more defined.


Either way, for doing this "by hand" with what you're using, you're getting good results. I'd practice a bit more, but what you may simply need to do is find a better stone that'll hold an edge better, and maybe have a precise mandrel machined to mount the stone. You may be getting close to the limit of quality you can expect with the tools you're working with.


Also, you're making real good progress over-all on slipjoints. I'd try to focus on getting the choil notch refined/clean next, and then general fit-and-finish.
 
Thanks javand, i do feel like i am getting there one knife at a time. What's wrong with the choil? Fit and finish will be the death of me haha. I cannot, to save my life, get the bolsters sanded perfectly even on both sides. I am still working on the bolsters right now as we speak.
 
Thanks javand, i do feel like i am getting there one knife at a time. What's wrong with the choil? Fit and finish will be the death of me haha. I cannot, to save my life, get the bolsters sanded perfectly even on both sides. I am still working on the bolsters right now as we speak.


Bolsters are tricky, especially if you haven't had anybody to "school you on it". One thing many of us have learned, be it for sculpting handles, or bolsters, or anything else where you've got to cut two symmetrical opposites, is to do it by "faceting" in steps. You can make this easier, by scribing a line (I do it by eye, but this will help until you're confident), with the liner inside laying flat on a surface plate, and with a height gauge scribe a line where you want the bottom of the bolster contour ground, on each piece. Then, rough grind the corners off the bolster almost to that line, at a sharp angle, around, on both pieces, basically cutting the corner off. Then cut the top corner of that angle you made, cutting the radius by "facets", this way you're just holding an angle, and cutting the high spots off, once you've got them all cut down and the basic shape right, the last step is to "blend" those facets to a consistent round. If you repeat the steps for each bolster on both bolsters at the same time, you should have no issue getting symmetry.

Trying to cut a full radius at once, is what makes it very difficult to get symmetry across both pieces. Although eventually, you'll be able to, and you'll skip some of those faceting steps, but even still I knock the corners off at a steep angle to the point I want the radius to terminate, then blend in the tops of the bolsters. Also, I recommend grinding the bolsters to the thickness you want first, flat, so that you're not trying to remove equal amounts of the top of the radius on each bolster, this is very difficult to keep symmetrical. In a perfect world you want to blend radiuses to the point that you're just "barely kissing" the apex of the radius on the top of the bolster.



As to the choil, well, I personally would like to see a nice sharp corner on the inside of the notch, and of course, try to have your bevel grind plunges terminating right at the notch, not running past onto the ramp. I cut my choil notch with a half-round needle file, with the half-round side toward the tip of the blade, before HT, but you can use a knife edge file or similar also for a different effect, or cut it with a stone.
 
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