Who uses a file guide for plunges? Any Tips?

[J. Keeton]

I recently got a Bruce Bump file guide.... primarily for filing in shoulders. However, I wanted to give a go at using a file guide on the grinder for keeping plunges lined up. I've seen a bunch of people do this. I had a heck of a time getting it to work. I tried an overhang with a J-Flex belt, but was having a hard time getting the belt to bend the way I envisioned.

I was wondering if any of yall routinely use these guides when grinding and if you had any specific tips (belt selection, over hang distance, speed, technique, etc)

Cheers,
JK

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[Hubert S.]

I use mine for the shoulders on kitchen knives. On a small neck (15mm or so), it is difficult to get good clamping pressure, and with my guide being made from aluminum, I was always concerned about flexing the jaws too much and popping off a piece of carbide. On the last couple of knives I made, I used a Kant twist clamp to tighten the guide instead of using the screws. This works great for grinding the shoulders, the clamp does not get in the way.

Edit: I just realized this thread is about tips for plunges, duh. I just skimmed the post and read "primarily for filing in shoulders".

 

[Cushing H.]

I use mine for the plunge all the time - it almost makes it easy...

Mine is home made out of un-hardened tool steel. Yes it does get a little ground away .... but it is just a minutes work to put it against the grinder belt and true of the two sides again.

 

[C_Claycomb]

I use a home made carbide faced guide. Main grind done with 36 and 60 grit Blaze, almost no overhang. Plunge refinement done with 120 and 220 Regalite followed by AO Norax with about 3/16 overhang.
Machine has three speeds, finer belts used on middle speed, about 3750 to 4000sfpm

 

[FredyCro]

Also interested in this. I put a small radius on the corners of my diy D2 platen and hoped that this combined with a carbide file guide and J flex belts will leave me with clean plunges. Still havent tried it yet, but i can picture that the thin j flex belts will conform to the radiused platen. Hope that this will be the case..

 

[Jrmysell]

I use the Bruce Bump file guide for my plunges. I use 984F Cubitron II belts and just do a little overhang. Maybe 1/8" max. Probably less than that and have no issues.

 

[Nriggi1]

James, I have a Bill Behnike type- I use it on every knife- I get in pretty close with the low grits (36 & 60) then get right on the carbide with the higher grits

 

[J. Keeton]

Thanks for the tips yall.

What I think I'm hearing:

1.) Establish rough plunges with low grit belts not hung off edge of platten (maybe up to ~1/32'' away from file guide)
2.) Hang over J-Flex ~1/16 - 3-16 off the edge of the platten (starting around 120 grit)
3.) Run file guide up to edge of platten

All at a ~medium speed

 

[C_Claycomb]

Sounds good. Something I have done with success is to move the guide from where I have it for the coarse belts, where its mainly there to prevent over-shoot, to a point 1/16 or so back on the ricasso and then use it as a guide for actually forming the plunge cut I want using a finer, flexible, belt run off the edge of the platen.
Possibly telling grandma how to suck eggs, but the round-over on the platen can be quite small, it is easy to underestimate the change in radius that results from belt thickness folded over the corner. First platen I made I formed the corner like I would for my hand sanding backing stick, and the plunges it cut were fine on big camp knives, but far larger than I wanted for 3-5" blades.

 

[Londinium Armoury]

I clamp a square of Micarta to the knife and just angle that to set whatever slant or right angle i want the plunge line to be set at.

 

[C_Claycomb]

I clamp a square of Micarta to the knife and just angle that to set whatever slant or right angle i want the plunge line to be set at.

Nice thing about the guides with their double pins is that it helps keep the plunge even on both sides of the knife, as opposed to what you can get with a single block, or even two, just clamped on without pins.

 

[weo]

I don't do many plunges (it's been years and I've only done a few), but I always used the tool as named. Used a chainsaw file against the carbide guide to set the shoulders and radius of the plunge, from the top of the grind to the center scribe line, then to the grinder to clean up the rest of the blade plunge/bevel, then finish by hand sanding using the chainsaw file as a sanding stick.

Because I do mainly thin flat grind kitchen knives, I normally use it to set the shoulders for hidden tangs (2x72 for the top/bottom shoulders, then using files to set the side shoulders).

 

[Travis Talboys]

This is the guide I made. It's just mild steel and two allen head bolts. I grind from 36 to 60 prior to quench, then replace it and finish grinding up to 220. I've been using it like this for close to two years with little deformation. If I ever feel it needs it, a quick pass on the grinder will true up the edges.

 

[AVigil]

Grind about 1/4" away from where you want the plunge. Then put on your file guide and your j flex belt and gently start sweeping in the grind at the file guide at the edge.

always leave a wee bit of the belt overhange exactly the same amount when you do both sides.

Once you have a good transition start to "back up" into the plunge to blend in the grind and the plunge until they meet at the top of the grind.

You literally are "sculpting" that transition from plunge to main bevel.

 

[J. Keeton]

Grind about 1/4" away from where you want the plunge. Then put on your file guide and your j flex belt and gently start sweeping in the grind at the file guide at the edge.

always leave a wee bit of the belt overhange exactly the same amount when you do both sides.

Once you have a good transition start to "back up" into the plunge to blend in the grind and the plunge until they meet at the top of the grind.

You literally are "sculpting" that transition from plunge to main bevel.

Thanks for this... I've never used this method. I generally establish the bevel, then work back towards the desired plunge location using the edge of the platen to "sculpt" the radius of the plunge. I like the idea of being more deliberate.

I've also been messing around with a waterfall top platen to true up the plunges, which has been promising. Thanks for the help yall.