file/grinding guide idea

Discussion in 'Knife Maker Shop Talk' started by Smallshop, Mar 8, 2017.

  1. Smallshop

    Smallshop KNIFE MAKER

    Hey guys,

    I'm thinking of making a file guide. After looking at some I think I don't want flat carbide inserts. I think precision ground carbide rod (silver soldered on to stainless body). I think a rod has a couple gets behind the belt and does not exert any influence on the length-wise blade taper when you get close to the stop a flat could possibly be doing that. rods merely stop the blade . here's my design. It will handle a blade 2.0" wide. I can make it wider if need be.

    Questions..comments...critiques all welcome.

    I made a small aluminum one for my son when he was grinding his was good for that blade...barely. There's four of us making knives I'm thinking of making four and don't want to make four of something to discover my ignorance has everyone in the shop looking at me sideways...:3:

    file guide pic 1.jpg
  2. EdCaffreyMS

    EdCaffreyMS Forum Owner - Moderator

    I've had a couple of file guides with round carbide in the past.....personally I didn't like them, particularly when it comes to using them for finishing out the shoulders on hidden tang blades (when installing a guard on a hidden tang, using a file to finish out those shoulder)..... what most don't realize is that a file has a slight amount of flex..... using the "round" file guide allows for more flex when filing, and most of the time the shoulder you're filing end up with a slight convex to them. It's not enough to visually catch, but when you try to fit a guard, there will often be "gaps" (however slight) on the outboard edges of the shoulders. Some wouldn't worry about it, but I'm anal enough that it doesn't work for me. :)

    Of course the more pressure you apply to a file, the more the file flexes, and the worse the condition. The same thing can occur with flat carbide file guides too, but with lighter file strokes, on a carbide file guide with flat strips of carbide, it's less likely, and much easier to catch.
    In my opinion, the wider and flatter the carbide strips on a filing guide, the easier it is to achieve very flat/parallel shoulders on a hidden tang. You can use a carbide file guide for a lot of different applications/uses, but the most important use for me is the shoulder on hidden tangs..... and for that application I far prefer wide/flat carbide on a file guide.

    I can't really give any good advice when it comes to using a file guide for grinding/plunge cuts.... I've tried it in the past, and found it more productive for me, to freehand.
  3. cnccutter

    cnccutter Well-Known Member

    I don't use mine form belt grinding, but wouldn't the round inserts allow the belt to go in behind the insert thus negating its usefulness as a belt stop?

  4. C Craft

    C Craft Well-Known Member

    Thinking exactly the same thing. Basically the carbide strip is just to protect the side of the file guide. When I am grinding I try to barely touch the carbide strip and off I go across the blade to the point! If the strip was round there is a good chance the edge of the belt is going to go up under it and then you got problems. My O2 on the subject!
  5. Smallshop

    Smallshop KNIFE MAKER

    Thanks guys!
    so, for file want as much planarity as possible....or...wide contact area which necessitates surfaces of carbide are truly in plane. that would mean best if the two halves were surface ground together with dowel pins in place.

    My thought on using it on the belt grinder was that by allowing the carbide to stop on the platen rather than the belt itself would keep the carbide from influencing the belt...allowing just a hint of belt to come around the corner of the platen and and help establish the plunge line. But I think Ed actually has the right idea....learn it freehand.

    I'm going to modify that design and post again to see your of my many year old bad habits is reinventing the wheel....yet sometimes I have come up with helpful thing in the shops I have worked in. as I am getting older I am more careful to not tackle things that don't really need to be

    These are a simple tool and I think a bit of rethink could still make them cheaper to make than buy. I can't afford $400-$600 dollars of outlay for file guides....even though I will have that much time into making them. Right now time is more available than cash. Why do those two never seem to
  6. EdCaffreyMS

    EdCaffreyMS Forum Owner - Moderator

    That has been my experience with carbide file guides. The problems have always been two fold..... the attachment method... when "glued" in place the carbide "moves" ever so slightly with drastic environmental changes. I've never owned/used a guide with brazed/soldered carbide, so can't attest to how that works, but do know that the best/most accurate one I've ever used has 1/8"x1/2" carbide strips dovetailed into the steel fixture, with the carbide being "surface ground" after installation.

    Having said all of that, it took several guards not fitting properly onto hidden tang blades, and a lot of searching for the reason before I realized/discovered that the carbide on my file guide (the glued on variety) were slightly "off" from side to side..... I had one side that was about .006" higher then the other. At first I couldn't wrap my head around that making the difference, but after resurfacing the carbide to within .002", and finding that it solved most of the issues I was having, it proved to me that it was indeed the problem.

    It also made me realize that basically everything we use in metal removal has some amount of flex.... belts, files, end mils, etc. and that I had to be aware of that fact any time I'm building a knife.
  7. Smallshop

    Smallshop KNIFE MAKER

    "It also made me realize that basically everything we use in metal removal has some amount of flex.... belts, files, end mils, etc. and that I had to be aware of that fact any time I'm building a knife."

    Yes! Getting guys in any shop setting to realize this is difficult....EVERYTHING has a modulus of elasticity. That was why I put two sets of clamping holes in my design. If you have a file guide that will throat a 2+ inch wide knife and you are working on a 1+ inch knife those screws are out WAY too far. By the time you have clamped tight enough to stop slippage you have over-flexed the file guide and most likely moved your carbide if it was glued...cracked it if Silver Soldered...and most likely marred the top and bottom edge or the knife (if soft). ANY machine screw exerts more clamping force than we tend to realize...they are "geared down' very much giving a lot of power with little effort.

    The other thing is getting enough surface bearing so you can use the side of a file rather than the flat for cutting in detail. Ed's earlier comment made me realize that a tool that you can file with and grind with also is most likely a compromise. This next design is for filing with no regard to grinding. The carbide is 3/4 wide ($50+ for carbide so gotta make sure it's a a natural advantage to the wider pieces of steel it strength of dowel pin press and less slop on the slip side. Well, not less slop...but if you have a pin in a 1/4 deep hole that is a .0005 slip it will wiggle more than the same diameter hole that is 1 inch deep if the pin is the same length as the hole.(increased bearing surface) It will still move easily yet the quality of fit goes way up.

    Take a look at this one....see what you guys think. I put a small edc I am working on for perspective...under 4" blade, 1 inch wide, 3/32 thick. Obviously I would use the other holes to clamp just didn't move them in the CAD for time purposes. I actually think nice thick angle stock would make the best file guide as you could grind the face that sits on the blade and always force those carbides to be square and parallel. getting more surface on the handle area projects better squareness thus more "free" accuracy.


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