View Full Version : Smoothest mill file

02-24-2015, 12:48 PM
Hello All,

I'm looking for a source for a mill file to do the smoothest possible job of filing the edge of woodworking "card" scrapers. Mine are .025" X 3" X 5", hence the name "card". Sharpened to a highly polished edge these simple hand scraping tools are one of the most useful tools in a guitar maker's shop.

The problem comes when re-sharpening. The process of burnishing the edges at a 10 angle to produce the burr that does the cutting makes a small bevel. I use a couple of DMT diamond stones---45 micron and 9 micron---to polish the edges and faces of the scrapers, but it takes a lot of time to hone down past the bevel created by the burr making process.

Draw filing with a 6" smooth mill file---the finest toothed file I have---leaves quite a rough edge that still needs a lot of work to bring it to a nice crisp polished corner, ready to be burnished. I'm willing to spring for a high quality super smooth mill file (a Grobet?), I just need to know what to ask for, and where to buy one.

Many thanks,

Brian Burns

02-24-2015, 01:02 PM
Maybe try some wet/dry paper of an appropriate grit on a flat surface?

02-24-2015, 01:36 PM
There is a dead smooth file

02-24-2015, 01:54 PM
Maybe try some wet/dry paper of an appropriate grit on a flat surface?

Hello Rich,

The idea of filing is to remove stock quickly. I can work my way down through the bevels in about 10 minutes each of sweating, using my 45 micron stone, where a file will get me through them in 30 seconds. I have a 120 micron (closely 120 grit) stone that does it fast enough, but leaves a lot of work left to do on the finer stones. The scraper steel is Rockwell 48-52.

By the way, for years I've used 60 grit wet or dry silicon paper on glass to flatten my soft Japanese water stones. As a sharpening medium it wears out really fast. Diamond honing stones are the only practical thing for a woodworker trying to make a living at it.



02-24-2015, 01:58 PM
There is a dead smooth file

Hello Mark,

Yes, I've read of the existence of such a beast, but I'm at a loss as to where to find one.



02-24-2015, 02:04 PM
This method wouldn't cut it? http://www.liutaiomottola.com/Tools/Scraper.htm

02-24-2015, 02:07 PM
Try "Bahco" for the dead smooth, may have to go via Europe.

Just looked, about half of their offered needle files can be got in "dead smooth" (nothing that I could see in the regular hand files was dead smooth)

02-24-2015, 02:30 PM
Hello Rosco-P,

R.M. Mottola is a friend, but I hadn't thought to check his website to see his scraper sharpening method. I don't do his initial drawing out the burr somewhat by burnishing the face of the scraper first. That step might be a workaround to avoid producing the bevels in the first place. Thanks for the tip (:->)...

I have a point-and-shoot camera coming tomorrow that will focus very close-up. I'll see if I can take some photos at various stages, and blow them up to see what's really happening.



02-24-2015, 02:35 PM
It came up in a search, near the top by the way. I'm no fine woodworker, but recall reading in FWW long ago that sharpening cabinet and card type scrapers was supposed to be quick and easy. Having to stone the edge just seems too time consuming for a commercial or production shop.

Paul Alciatore
02-24-2015, 03:06 PM
I may be missing something here, but it should not take that long to sharpen a card scraper. At least not one with a straight edge.


Perhaps you are going at it too aggressively. If the previous burr was only a few thousandths wide and at a 10 degree angle, then you should only need to remove a few ten thousandths of metal to get down below it. That would go fairly quick on almost any stone or abrasive paper. Or just a few light strokes with a file.

02-24-2015, 03:26 PM
So called "pivot files" are the finest, smoothest cut files I've ever seen, and I think would leave you with a surface that would easily burnish. The potential issue is that I've never seen a pivot file longer than 2.5" or so. They can be difficult to find, I'm not sure if they are still manufactured but old ones are out and about if you keep your eyes peeled.

02-24-2015, 05:07 PM
Hello Roscoe, Paul and Max,

Sharpening a card scraper to a high polish raises its usefulness to a much higher level. I make classical guitars, and I can scrape hardwoods to a surface ready for French polishing---no sanding required. And it's fast. Guitars are mostly curved surfaces, and scrapers will follow curves.

Softwoods don't like to be scraped, though cypress is hard enough that it will scrape Ok, if I'm not too aggressive.

In the 1960's I was first taught to sharpen a scraper by draw filing with a mill file (single cut), and then burnishing out a hook with a hardened steel rod used just on the edge. That worked fine for rough work, but always left a surface requiring a good deal of sanding because the filing scratches appeared in the burr.

Some 30 years ago I developed a sharpening system for hand plane irons called "Double Bevel Sharpening", and was teaching a class in it at the Japan Woodworker in Alameda CA when a student asked about sharpening scrapers. I said I didn't use them much as they were pretty crude tools. I went home thinking that I had given a pretty poor answer to the student's question, and that perhaps I could come up with a better sharpening system for scrapers.

I developed a couple of tools for polishing the edges and faces of scrapers to a 9 micron (1200 grit) finish. Then I've been using my burnisher only on the edge to roll out a burr. The resulting wood surface is both crisp in appearance and very smooth. The problem comes when re-sharpening, and it's just a time problem.

My Veritas edge burnishing tool is set to a 10 angle, and working on a crisp square corner it not only forms out a burr, but makes a small bevel. If I work long enough with my edge dressing tool, I can get back to a crisp square corner. My thought about filing with a really smooth mill file is that I can cut the time down for getting back to a crisp, square corner.

The suggestion that I look at R.M. Mottola's scraper sharpening method has brought out a possible way to avoid making the little bevels that need to be gotten through when re-sharpening. He burnishes the faces of the scraper first, which I had seen done before, but he does it at a very slight angle so as to form out a burr that is vertical to the edge. I had not noticed the very slight angle. He then burnishes from the edge, turning the burr down parallel to the edge---no bevels, if his drawings are an accurate representation of what is actually happening.

If this all seems like a lot of huffle and kerffufle for a small reward, I can assure you that working with a really sharp scraper is one of the more pleasurable things in woodworking (:->)...Now, if I can just speed up the sharpening process...

Thanks for all your helpful suggestions,



02-24-2015, 05:27 PM
Just throwing out ideas. If you could touch up the edges to a perfect 90 via a surface grinder might that work? Honing machines typically used with scissors wouldn't give the accuracy or surface finish needed?

02-24-2015, 05:48 PM
Hello Roscoe,

I would LOVE to have a surface grinder! But I took the vows of poverty when I decided to be a guitar maker, and it's well beyond my means...

I took a wonderful machine shop course at Mount San Antonio College in Pomona, CA back in the 1960's, and the surface grinder was one of my favorite machines top use.

BTW, I learned a lot about woodworking in that class. Feeds, speeds, cutting angles, chip load per tooth, heat dissipation---they have all been useful in woodworking. In fact, my sharpening system is based on the understanding of the importance of cutting angles that I got from that class. Google "double bevel sharpening" and you will get a link to my youtube video on it.



02-24-2015, 05:49 PM
the finest cut files I have used are #6 cut Swiss files.

02-24-2015, 06:12 PM
I follow William Ng's method. It works beautifully for me. I also use the Shapton "Professional Series" ceramic stones, I've never had great success with DMT's products.


02-24-2015, 06:45 PM
I see your problem, I did not realise a dead smooth or no6 was so rare!.

Paul Alciatore
02-24-2015, 07:02 PM
I am curious about these files myself. Please do post any source that you find.

02-25-2015, 04:34 AM
Just throwing out ideas. If you could touch up the edges to a perfect 90 via a surface grinder might that work? Honing machines typically used with scissors wouldn't give the accuracy or surface finish needed?

Can he? Maybe. If he had a surface grinder.

02-25-2015, 05:52 AM
I know I'll get shouted down, but have you tried using a piece of broken glass. I have used it and was pleased with the result. For curves you can break a bottle.

J Harp
02-25-2015, 09:06 AM
Broken glass works very well for smoothing axe handles and such, but I'm not sure it would be ideal for a guitar top because it sometimes loses tiny chips in use.

Edit, This is not meant to be shout down...

Steve Steven
02-25-2015, 09:28 AM
MSC seems to have the best selection of files I know of, heres a link to a catalog page of Swiss files. However, #4 cut seems to be the finest offered:



02-25-2015, 09:50 AM
Quote from a popular woodworking hand tool forum (http://www.forums.woodnet.net/ubbthreads/showflat.php?Cat=&Board=handtools&Number=6955142&page=2&view=collapsed&sb=5&o=&fpart=all):

Get them from Harry Boggs. Sharp and ridiculously under-priced. Friendly people too. Tell him what you want to accomplish, and he'll select the right files.

Boggs Tool & File Sharpening Company

I would contact them for resharpening your existing files & price whatever they would recommend.

02-25-2015, 12:48 PM
Boggs Tool & File Sharpening Company


"I would contact them for resharpening your existing files & price whatever they would recommend."

Hello caveBob et all,

Well, I just got off the phone with Harry Boggs---what an experience! The man seems to know absolutely everything there is to know about files! But, be prepared to have your ear talked off (;->)...And I thought that I was a world champion motor-mouth!

In short, he has or can get, or will make whatever you are looking for. He also has a method of sharpening files that makes them sharper than brand new---and it's not the acid bath method at all, but a steam pressure plus abrasive method. He was leaving town for a few days, so next week I will send him a couple of files to sharpen, and order one of his super fine mill files. I'll report back on what I find out.

As for glass as a scraper, it was certainly used by violin makers, and probably other fine woodworkers "back in the day". I have heard of one fellow recently who uses microscope slides. I've never tried it myself. Also, I sometimes bend my steel scrapers slightly as i use them. I wouldn't dare with glass.

The beauty of the DMT diamond stones is that they are made on cold rolled steel, and are quite flat, and stay quite flat. They do lose their aggressiveness as you use them, and tend to lose it in the center area of the stone, in spite of my trying to spread out the wear to the edges. But all in all I'm quite pleased with them for rough to medium fine work. I finish off my scrapers on the 9 micron (1200 grit) stone, which is the finest grit of their stones that I have.

I finish off my chisels and plane irons with a Takenoko 8000 grit Japanese polishing stone. It's one of the seven wonders of the woodworking world! It's so fine that it doesn't leave a burr for me to find with a 200 power microscope!

Having accidentally become a sharpening guru as a result of my woodworking teaching, I tried out the Shapton line of stones including their $600,--- 30,000 grit model---no misprint here. They seemed to leave un-polished streaks on the bevels of my tools. I don't get those with the Takenoko.

So, my scraper sharpening method using the flat DMT stones makes a sharp scraper very straight---checked with a Starrett straight-edge on a light table. Not a combination square blade, but a 12" straight edge. Who said "Perfectionist!?" Having a really straight scraper is useful for flattening surfaces, or at least hitting the high spots first.

I suppose that this thread has morphed into "More than you wanted to know about woodworking scrapers", but I hope that there has been enough metal working in it to be of use.



Paul Alciatore
02-25-2015, 02:39 PM

Please do NOT apologize for posting this thread. We all have much to learn and I completely enjoy discussions like this. And I usually learn a lot from them. Thank you for posting.

02-25-2015, 05:14 PM
Hello Paul,

My pleasure! And that suggestion that I try the Boggs company is golden. Harry Boggs is a real resource, and I will be buying files from him as well as using his file sharpening service.



J Harp
02-25-2015, 05:23 PM
Another question, Boggs Tool lists Mill smooth, and flat smooth files. I'm not sure what a flat file is, would someone define it please?

Good to know that fine craftsmen do use broken glass for scraping, I was once laughed at when I was asked what I was looking for, and answered that I was looking for a piece of broken windowpane to smooth a hammer handle with.

02-25-2015, 07:14 PM
Another question, Boggs Tool lists Mill smooth, and flat smooth files. I'm not sure what a flat file is, would someone define it please?

It's all in the shape. Here's an illustration of the end on view. If I can remember where I saw the side views, I'll post that too.


Somewhat blurry, but here are the side views.


There is also a "machinists" file, close to a flat or hand but with one safe edge.

J Harp
02-25-2015, 10:14 PM
Thanks Kevin,

The top illustration seems to show that a flat file, and a hand file are thicker than a mill file. The lower illustrations don't show that. I have a couple of curved tooth files which are thicker, but don't recall a bastard cut with the extra thickness.

02-26-2015, 06:14 AM
Any help?



J Harp
02-26-2015, 07:12 AM
Thanks Tiffie,

Your second link leads to this one which gives a good description of the various types of files.

02-26-2015, 08:38 AM
Based on the files in my toolbox, the mill file has a rectangular end profile and a curved taper to the sides. The flat file is about the same width as the mill, but thicker, and has a straight taper to the sides. The hand file is both thicker and wider than the mill file with no taper (or parallel) sides.

J Harp
02-26-2015, 03:39 PM
Thanks KJ1l,

I have learned something from this thread, I don't recall ever hearing of either a flat file or a hand file before.