Pluunge Cut Grinding Jig

etp777

etp777

Joined
Aug 12, 2002
Messages
2,259
OK, I decided I needed one of these, so remembering one picture posted(by rlinger, I think), started making one. had 8" or so of extra 5/32" O1(not sure what happened to the other 4-16", but oh well) sitting around, so I cut it in half, and ground off rough ends. Plan on drilling holes in them wide enough for 2" or so blades(if I ever make anything wider than that I'll make a newjig). Plan on doing a full quench, then triple temper at 300 or so(think that'll give me 63RC off top of head, if the O1 is fully hardened). Will pick up a coupla bolts, some washers, and some butterlfly nuts from wally world tomorrow.

ANyways, does this sound like it'll work? IE hard enough, big enough, etc. THink the O1 is 1.25" or 1.5" wide, can't remember off top ofmy head(at work right now). Have some small skinners drawn up though that I'd like to flat or hollow grind, and don't want an ugly plunge like I've had on previous pieces. Any input will be greatly appreciated.
 
If it was me I would use 1/4" steel an
drill & tap one side. But I`m lazy so I
would just buy one, about $20.00 Just
my $0.02
 
Just go practice some more.................nothing can beat the skill of two well trained hands.
 
I should work, mine is 3/32" O-1 given a 400 deg. draw. I used self taping screws and pre-drilled one side and screwed it together before harding. works pretty good to. When one side or the other gets a little worn from the belt I just true it up with my disc sander. I doesn't replace a steady hand, but it does speed up grinding for me a good bit.

I've done them free hand and with the jig, and both ways I usualy have to do some fileing to true it up right. But it is nice to use the jig as part of the lay out and speeds up rough grinding. I have file guide that is 3/4" wide that works out perfectly when I want to do a Fowler type smooth ricasso.
 
Tom's right. You can just mark the plunge cut with a magic marker, or like I do, just wrap some masking tape around the choil, right where you want the plunge to end. It's really not hard.:eek: :D
 
I tried using jigs for things early on... Never could make them work right.. I agree with Tom, nothing like blades under your belt to give you the ability you want...
 
RLinger built me one. Because of the platen design I can only use it on one side. However, I found I can set the plunge cut on one side by grinding edge down.

In any case it's not a cure-all, comes-out-perfect-every-time kinda deal. It still takes a steady hand. I use it on and off. For example, I had an uneven cut (both on alignment and angle). I used to straighten every thing back up then I took it off and finished up.

I also use it alot for making lines on blades so they are even on both sides. Just a handy device to have around.

FWIW

Steve

BTW Thanks again Roger.
 
I built the same kinda thing out of 3/4" angle iron, threaded one side for 1/4-20 bolts and viola! even plunges every time. I only use it to establish the grind, once I move to 220 it comes off so I can radius the plunge. I like it because it makes it easy to get the angle and position of the plunge right from the start. But I call it my "Cheater" because I do think it's cheating just a little bit... :D

Dave
 
I figure I'll go both ways on this one, as y'all do make some good points. I will make myself the jig(and plan on using my disc grinder to true it back up, as necessary), but I will work on freehand grinding too. I have 5-10 pieces of O1 and 440C in a couple of thicknesses that I had precut to 4" or so for neck knives. I've decided not to make these now, and was just going to use these to practice my flat grind, and to learn how to do a hollow grind. I'll still do this, but will also use it as an opportunity to practice a nice even plunge.
 
Originally posted by etp777
I figure I'll go both ways on this one, as y'all do make some good points. I will make myself the jig(and plan on using my disc grinder to true it back up, as necessary), but I will work on freehand grinding too. I have 5-10 pieces of O1 and 440C in a couple of thicknesses that I had precut to 4" or so for neck knives. I've decided not to make these now, and was just going to use these to practice my flat grind, and to learn how to do a hollow grind. I'll still do this, but will also use it as an opportunity to practice a nice even plunge.
Click to expand...

You can also get some lathing strips from the lumber yard. Those wooden strips make for cheap practice. Just lay out your pattern like a real knife, profile, and grind the bevels. You dont have to go beyond a course belt, and it will last forever grinding those strips.
You can practice contouring your plunge cuts with a finer belt also.
 
Sound good to me. I like mine. Do like Sylvester says though and tap one of the pieces so you don't have to mess with nuts. Hex head bolts make it easy to tighten up too and helps to keep the jig from slipping out of place while tightening it. So far mine is working fine and is wearing well (only two knives using it so far though).

Your HT sounds okay too. Just give it enough temper so it won't brake on you as you tighten it around narrow ricasso blades. It will bow a little but straightens okay (your temper sounds okay. I may have done mine at 350 F.) I too used O1.

Roger
 
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