Jump to content
I Forge Iron

tips on shaping with files and sandpaper

Recommended Posts

I posted this question on another site, but I hope it's OK to post it here, too. I'd like to get input from as many experienced folks as possible.

After forging, pretty much all I do on a blade is done with files, stones and sandpaper; in other words, I don't have a belt grinder (and no other power tool I've tried is even close to suitable). I'm still very inexperienced, and one of my biggest problems (a common one, I know) is getting crisp grind lines. Or rather, not getting them! I just seem to have a heck of a time maintaining a consistent angle during draw-filing and sanding. It's especially a problem where blade geometry changes in a way that requires me to change the angle of the file or sanding block -- where the bevel gets wider or narrower, along curved portions of the blade, or where the thickness of the blade changes due to distal taper (which requires me to change the angle of the file or sanding block). If all I had to do was put a forty-five degree bevel on a straight, 1/4" thick bar, I think I could do a half-decent job of that. But the geometry of knife blades really complicated things.

On the attached picture, which is a rough representation of a blade I'm working on now, the geometry is changing in multiple dimensions in the area I've circled. I'm having a heck of a time establishing a recognizable "grind" line there, let alone anything remotely crisp.

Having said all that: tips? Techniques? Suggestions? Book recommendations? I realize what I really need is practice, but I'd feel better if I had a plan to guide that practice; right now I'm sort of groping around in the dark. For whatever reason, the books I've read all seem to sort of glide over this subject without going into much detail. I dunno; maybe I'm just one of the few who's dumb enough to need help with this.


Link to comment
Share on other sites

- how is the blade positioned and clamped while filing?

Clamped flat on a board, which is in turn clamped to the table of a drill press. (Just as a matter of convenience, not because I need to use the drill press during this process!)

- what height in relation to your body is the blade while filing?

Mid-torso level.

- are you draw filing?

Yes. I started with more conventional filing to knock down isolated high spots, but I'm well past that point now.

I'll try to provide photos when I get a chance.

Edited by MattBower
Link to comment
Share on other sites

Hi Matt
Have you used a straight edge to check your work? Hold it on the bevel and hold up to light to check.

Use a felt pen to cover the blade in ink, then check to see where your file is cutting.

I found that I could keep things flatter when using the file in the conventional way.

Crisp grind lines on shallow angles are hard to maintain with file and sand paper get it as flat as you can with the file.

Hope this is of help.

Link to comment
Share on other sites

Have you looked into filing guides? Often used to file the tang/blade transition even and consist of hardened strips of metal you clamp on the blade to provide a straight edge to file up to (and no more!)

How many hundred blades have you done? Practice is a big part at getting good for most of us.

Link to comment
Share on other sites

Not even close to a hundred, Thomas. Like I said, I know a lot more practice is really the key. But practicing bad habits only reinforces them, so I'm trying to learn as many good habits as possible.

I've seen filing guides used for tangs, as you mentioned. It had occurred to me to try a similar sort of thing for bevels, but I've never seen it done before and haven't gotten around to trying it myself. I've also seen some nifty filing jigs, like the ones shown here: filing/grinding jig Building something like that might go a long way toward solving the problem in the short term, but then I'd never learn how to do it by hand.

Link to comment
Share on other sites

Only one thing not covered here so far is files. You must have good files to file well. Old cheap or clogged files are your enemy. I pay more for files than it seems right but they work well for me. Anneal your blank before filing. Establish all lines then but leave the blade thick enough that after heat treat when you clean it up again if will not be too thin.

Link to comment
Share on other sites

Another thing not mentioned is pressure. A file can flex if pressed too hard, use a light touch and let the file do the work.

You might consider making a filing horse. This is basically the same thing as a shaving horse, a narrow bench you straddle with a wood pylon and foot clamp. For blades your pylon and clamp could be quite narrow. Most importantly the height should be comfortable and what I call "indexed" to you. This is the same idea as setting your anvil to YOUR working height.

What I prefer for filing is elbow high. With my arms hanging at my sides I lift my forearms to horizontal and where my grip is is where I want my work held. This would be the blade in the case of a knife.

This allows you to work sitting down which makes you more stable and is far less tiring. Being able to index your elbows against your side really helps keep strokes consistent. Having your elbows indexed against your sides removes the need to keep your upper arms and shoulders working in the same plane. Sitting down removes the need to keep your back, legs, feet and everything in between in a consistent position.

There's a reason fine work is usually done sitting down at a special bench, horse, vise, etc. The fewer muscles and body parts you have to keep in position the easier and more reliably you can work.


Link to comment
Share on other sites

Matt,Frosty,i'm afraid that i must disagree with some of the above(MOST respectfully.I seem to express meself so poorly in writing that often come off as one intolerant ...,no disrespect ever intended).
In my understanding,flat-filing(a very specific action,in machinist's parlance),relies most heavily on our brain's ability to strike a PERFECT plane.
To allow the body to do so,one's posture must be unrestricted by anything.The classic stance is very much like some of the basic karate ones:Back straight,feet spread to about shoulder wide,the work positioned exactly at the level of the tip of your elbow.
I don't think that it can be achieved sitting down-it'll tend to distort that motion,that(much like a correct hammering),involves ALL the muscle groups,legs/hips included.
The file is held by both hands,left one touching the tip,acting as a sending unit for the orientation of the brain.
In part,the difficulty results,Matt,from the orientation of the work:The knife is positioned in a level plane,while the surface being filed-is not.The brain tries to correct automatically,thus smearing the transition.
That same jig needs to be chucked into something capable of rotation,to situate the surface being filed level(in both axis,as our brain is a gyroscope).
Many a cheap machinist vice has that rotary feature.Or a round stock used as a support for the knife can be chucked into the pipe-jaws.Else,one can scrap something together by using an old axle,say,where the work can be clamped to a flat filed on the horizontal shaft,and a C-clamp or vice-grips controlling the rotation.
There's a good description of flat-filing in the ubiquitous Mr A.Weygers(but again,he can be quoted in just about every post!).
All this in addition to all the very valid info above,not contradiction,and with the utmost respect.
The best of luck,Jake.

P.S.Draw-filing,i believe,is also something that doesn't work as flat-filing,the physiology doesn't seem to want to do it in reverse.It is great for hogging out,however.
P.P.S.Rubbing a welder's soapstone on the file teeth keeps it much cleaner.If the teeth are loading up uncontrollably,then maybe something is not right,too-the pressure is too great,the file is not coarse enough for the softness of material,et c.

Link to comment
Share on other sites

Jake: Good points. You kinda glossed over draw filing there and I think people should learn how to do it properly. As the name implies, draw filing means pulling the file toward you, not pushing it. In order to cut on the pull stroke, THE HANDLE MUST BE IN YOUR LEFT HAND. This is the way I was taught nearly 50 years ago in machine shop training. There is a good video on draw filing here: How to draw file an octagon gun barrel for bluing | Video « Wonder How To

When you have the file at right angles to the work and the handle in your left hand, you'll see that the teeth are oriented to cut on the pull stroke and pushing just ruins the teeth.

Edited by nakedanvil
Link to comment
Share on other sites

One thing I have never seen mentioned about filing is that most files have a slight bend to them, probably warping from heat treatment. When you are doing the final flattening of a large area you should make sure you are using the convex side or you will allways end up rounding things off. I found this out when I worked for a company that repaired a lot of printing press cylinders, we used to go through boxes of files. Because we were fiing a small spot that we had built up with plating in the middle of an area that we did not want to cut we would use the convex side of the file and then throw it away when that side was dull.

Link to comment
Share on other sites

No offense taken here, Jake. I'm a huge fan of Weygers. His was the first smithing book I bought, and it's still my favorite. His description of the stuff he was required to do with a file as a student is flat-out mind-boggling to me. That's an interesting point you made about the brain acting as a gyroscope, and rotating the work instead of the file.

Thanks, for the video, Grant. Looks like I've been doing at least one thing right -- even to the point of indexing the file after each stroke.

Link to comment
Share on other sites

Here are a few things that I do when filing a part. I have cleaned up some badly pitted pistols, and rifles this way.

Draw filing is done with a single cut file-only one set of teeth. The angle that you hold it is somewhat dependent on the material being cut, but you can feel the difference in how it cuts in relation to the angle of the teeth to the part. The file only cuts in one direction forwards, so don't keep the pressure on when retracting the file. It is ok to to slide the file back some as this will help to keep it clean by pulling the chips out. Keep the file constantly clean. It only takes one packed chip to add a lot more work to your project when it causes a deeper scratch.

I have not had a problem with dished files, and most that I have are very flat-no rocking when put on a flat surface.

When you grasp the file look at the angle it is at and maintain that angle as you push/pull across the part. Find something to spot the edge of the file with like something on the bench, so when you make the next cut you can return to the same angle. When you make the cut look at the pattern left on the part to see if it is correct, or if you need to adjust your angle. Go slow, this isn't a race. A lot of filing has to do with feel. Once you get the feel right it is easier to get the results that you want. If possible make the longest stroke with the file that you can do correctly, This will help eliminate an uneven look.

As for sanding, I used a lot of various size, and shaped blocks to sand receivers, and barrels in order to keep a sharp line. A lot of shops buff the receivers which rounds edges. On a receiver like a Winchester Model 12, I always hand sanded them in order to maintain the original lines. Do not proceed with the next finer grit until all of the coarser scratches have been sanded out with the current grit. One way to check for scratches is to sand at a different angle to what you have been. By doing this the light is reflected differently, and will show discrepancies in the finish easier.

Link to comment
Share on other sites

Standing when doing close benchwork seems to be a recent development. It's how I was taught in shop class as well. Project #1 was a 12" steel scale and #2 was a pair of dice. Both were done standing at the bench vise and both were a serious challenge.

However, outside of what I've seen in recent shops and photos I'd say almost everybody else does these things sitting at a specially designed bench, vise, etc. Take a look at Japanese bladesmiths for instance, every step except maybe making the iron and striking is done sitting down. Forging, senwork, filing, grinding, honing, polishing, everything, all done sitting.

For a simple exercise try freehand drawing a straight line on a piece of paper on a table. Try it standing up and then sitting down. At the turn of the last century draftsmen worked standing up in this country but sometime around the 20's sitting became the norm. Why? fewer, FAR fewer mistakes.

Jewelers? Watchmakers? Instrument makers? Gem cutters and lapidarists? Engravers? Chasers? Embossers? Tatoo artists even? Any of them work standing up? Virtually all of them use specially designed benches and fixtures to keep themselves as precisely indexed to their work as possible. Do you know of a precise freehand craft performed standing as you describe?

Filing and especially draw filing is precision freehand work and I don't know of any precision freehand craft done standing up unless there's no choice.

You have an excellent point about keeping the face being filed level to the ground, the brain is FAR better at keeping things plumb and level. Work can be wedged to change it's plane. A simple round insert for "V" jaw vise can be made similar to a collet visually.

I'm sure I could be wrong but I haven't seen any evidence for precise work being performed better standing and the only evidence I've seen for it being done standing at all is in late victorian sweat shop type situations.

One last think Jake. I sure wish you wouldn't apologize or express so much regret in disagreement, emphasize your respect, etc., etc. for having and stating a strong opinion. While I may not agree I always find your positions well thought out, thought provoking and informative. Anyone who takes one of your posts as being intolerant has issues of their own unrelated to you. I may have issues but your writing sure isn't one of them.


Edited by Frosty
Link to comment
Share on other sites

  • 5 months later...

I have a question about draw filing.
I'm left handed so should i be holding the file in my right hand? or is EVERYONE supposed to hold it in their left hand?

look at item 15 on the previous page by nakedanvil

Quote--As the name implies, draw filing means pulling the file toward you, not pushing it. In order to cut on the pull stroke, THE HANDLE MUST BE IN YOUR LEFT HAND. This is the way I was taught nearly 50 years ago in machine shop training.
When you have the file at right angles to the work and the handle in your left hand, you'll see that the teeth are oriented to cut on the pull stroke and pushing just ruins the teeth. End quote

The file position is the same, whether you are right or left handed,
Link to comment
Share on other sites

I really can't add much to what's been posted here as far as helping with filing accuracy but I would like to interject with a little discussion here about the desirability (or UNdesirability) of these crisp grind lines. On my own knives I find that the existence of such crisp details tends to preclude the optimal angles/thicknesses for optimal cutting work. Thus (as a very practical sort of maker) I find that I consider such details to be rather impractical frills that detract from optimized performance. For knives that are intended to be used often, such details also (IMO)complicate and/or inhibit re-sharpening processes significantly. I realize that this won't help you to file crisper lines but perhaps it COULD help you to produce even better (from a practical user POV) knives that are not dependent on such skills.

Link to comment
Share on other sites

  • 8 months later...

You all are bringing up some great points about draw filing. I have been making knives for about 20 years and for 98% of the knives I've made I have used simply files and sandpaper after forging to shape. I have found out alot of info in this thread that I was ignorant of. You can learn something new here everyday. Possibly the most important is what celtic forge said, keep your files clean, clean, clean. They cut better and last longer

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...