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SHARPENING

QUESTION: Using the glass and wet dry paper applied, which grits seem to be the most commonly used? Additionally, someone once wrote in about glue that allowed easy removal and replacement of the worn paper. I do a good bit of sharpening with oil stones in the winter months and stay away from the water(ice). This sounds like a good solution. DO 11/26/02

REPLY:  I glued the sand paper to my glass plate once. After that, I just started putting the paper on the glass and holding it with one hand and sharpen the blade with the other. It's a little harder, but not as time consuming as gluing, removing and changing the paper. You can get by with one 12 X 12 piece of glass also.

Also, I keep all my sandpaper on a clip board. It's easy to store by hanging it up and it doesn't curl as badly when the humidity goes up. I've also used the clip board instead of the glass when sharpening. (or my drill press table) I can't tell any difference. It's worth a try, a clip board costs about a dollar. Good luck! BG2 11/26/02

REPLY: I have a 3/8" glass plate about 5" x 20" On the most used side I have 220, 320, 400, 600, 1000 grits. On the other side for starting on badly pitted blades I have 3 coarser papers. I also have some 2000 loose to put a final polish on stuff. The backs of chisels and blades only need to be put through the course once and then for most resharpenings I just go back and start with the 320 or 400. I just use some spray adhesive to hold things down, most of the paper peels off when it needs to be replaced and a quick swipe with a razor blade gets the rest. Using this system the backs of blades etc. are a flat mirror polish in less than 4 minutes.and touch ups take 30 seconds. There is no water or oil slopping around. I always thought I got tools sharp before but there really is no comparison. There are a few articles floating around on this. Dunbar called it scarey sharp and it is. JT  11/27/02

REPLY: Grit size "depends". If you're starting from scratch, you begin with 60 or 80, and will wear the first one out long before you proceed on through the progression. For the touch-ups, you only need the finer grits, and the finer grits are "used up" quicker than the others.

3M makes a aerosol product called "Spray Mount Artist's Adhesive". Its got a short shelf life and the nozzles get clogged easily. There is also a spray-on solvent used for clean up. If you've got room for one of each grit on your glass its nice to glue it down, but as BG said, its not necessary. GB 11/27/02

REPLY:  I use 220-320 grit on glass, with a 3M spray adhesive called Super 77. I've had the same can for 2 years now, and not a clog yet. When the paper is kaput....I scrape it away with a painters razor blade holder/scraper.I also rely heavily on a buffing wheel for final touch-ups. MT 11/28/02

REPLY:  I use a hard felt wheel charged with emery compound and a soft sown wheel charged with tripoli. I agree this method gets you back to work in a hurry, but I've always thought it was a deal with the devil. There's really no way to keep from rounding off the edge a tiny bit and eventually you have to resharpen. I have noticed that the Norton Waterstones I mentioned not only produce an incredibly sharp edge but the edge lasts through many more trips to the buffing wheels than the glass on sandpaper and ceramic stones (very fine sandpaper grit permanently baked in ceramic) I used before. How fast does the white compound cut? BG 11/28/02

REPLY: BG, I agree, sharpening on a wheel postpones going to the stones or sandpaper. The cutting rate of the white polishing compound is indistinguishable to me. I bought a four bar set of polishing compounds at a motorcycle rally. The white compound bar is the finest grit, however, the manufacturer doesn't indicate what the grit is, only that it is the finest grit used for a high polish. I don't spend much time on the wheel so as to minimize any round over. BG2 12/2/02


QUESTION: After reading the relatively thorough comparison in last month's Fine Woodworking about sharpening methods I decided to try Norton's waterstones. I am not disappointed. I bought the economical 2 stone combo set with 220, 1000, 2000, and 8000 grit. They quickly put an incredibly sharp edge on my chisels and planes. The only complaint I have was excessive wear or dishing when I sharpened a gouge. I see in the letters to the editor on this month's Fine Woodworking that two new Japanese synthetic stones, brandnamed Bester,and Shapton are claimed to cut faster and wear less than the Norton stones. Does anybody have any experience with Bester or Shapton, especially on curved tools such as gouges? BG  11/24/02

REPLY:  When I used waterstones I didn't sharped curved tools on them for this reason. Although it sounds like the stones I had didn't wear anywhere near the rate of yours. Mine are japanese but don't know the name, the boxes are long gone. You might want to have a set of oilstones for the gouges etc. Or do what I did, chuck the whole works for a piece of plate glass and sandpaper. It's much less messy, sharpens as good, I think better and is much faster. JT 11/25/02

REPLY: I use sandpaper on glass all the time, and often follow up with ceramic stones, but I don't think I ever got the level of sharpness quickly produced by the Norton 8000 grit stone. I have to agree, it is messy. But the mess is kind of fun, like jumping in a mudpuddle. BG 11/26/02

REPLY: For carving tools, I have wrapped wet dry sand paper around dowels of different sizes to touch up the inside edges of gouges. Additionally, I have found the leather strop to be very useful for getting rid of the "wire edge" after sharpening. Some carvers like to charge the leather with compounds - I like the straight leather. If you haven't used the cloth buffing wheel with [white-stainless steel]compound, you might like it. I use the slow speeds on my old 1750rpm motor and gear it down with pulleys. I must confess, I go to the wheel these days more than the strop when I am in the shop- it takes 3 seconds and you're back carving. DO 11/26/02

REPLY: I agree with DO on the buffing wheel. I bought a non-stitched polishing wheel ($6) mounted it on a 5/8 bolt and chucked it in my lathe and turn it about 600 rpm with the white compound after honing with 1500 grit sand paper. If you think the sandpaper put a mirror finish on the blade, you won't believe what buffing will do. It doesn't take long and really works well for irregular surfaces like gouges. BG2 11/27/02


Tip: I've been a convert to Mike Dunbar's sandpaper on glass sharpening method for a long time (but after 400 grit I still go to my ceramic stones for finishing). The annoyance with the sandpaper on glass method, however, is removing the sandpaper. I tried regular 3M adhesive, PSA (adhesive backed) sandpaper, and still suffered theannoyance of wasting time scraping the darned sandpaper off the glass after the paper was spent. Then I found the answer: Artists Spray Mount by 3M. It has a very weak tack. Plenty to hold the sandpaper on the glass, but weak enough that you can just grab the paper by the corner and peel it right off clean. Try it. You'll be as excited about it asI am. Anybody interested in some Klingspor PSA rolls? WKG 1/31/00

Reply to WKG: I too swear by the sandpaper on glass. I normally start with 320 grit wet/dry and progress through 400, 600, and 1000 grits. Some folks continue to 1200 and 1500 but I have not found that to be necessary. The paper has been available from Home Depot in my area or from auto body paint and supply stores. I do not use any adhesive at all; which seems to work just fine.

Thank you for the tip, as I was contemplating the use of PSA paper. I also had been told that the 3m spray adhesive works well. For those people out there who are confused with all the choices (natural water stones, ceramic water stones, oil stones etc.) sand paper is a great way to get started sharpening with very little investment. It works great and it portable also.

When traveling I bring a half sheet of each of the paper grits noted above along with a leather strop mounted on a piece of wood and some aluminum oxide. The piece of wood has leather on one side and laminate on the other side. Simply place the sheets of sand paper on the laminate side and when complete turn the board over to the leather side, apply some aluminum oxide and final hone. PB 1/31/00


Sharpening Spoonbits

I learned that spoon bits are sharpened using a burnisher drawn toward the outside of the rounded cutting edge.  This pulls the metal to the outside to form the cutting edge.  There is a good disucussion of spoon bits in  an article by David Sawyer in the Fine Woodworking book on hand tools.  The original article was in the November 1983 Fine Woodworking, 43:70-72.  I have found one of the most useful "tools" for sharpening has been a ten power magnifier.  If any cutting edge is not cutting properly, whether it's a plane blade, gouge or spoon bit,  the magnifier reveals all.  I' m sure that charimakers with more experience could give you a better explanation about sharpenign spoon bits.  PE 12/29/00

QUESTION:  My question is regarding spoon bits. I've aquired some older, "vintage" bits. How do I go about sharpening them and when are they worn out? Is there a recommended repair method when bits are seriously worn? DGK 1/22//03

REPLY:  Dunbars book has a section on maintaining spoon bits. I bought some from Fred Emhof and he refers to the same for sharpening. Dunbar also had another book on restoring old tools that also covered spoonbits. Basically you want a nice round smooth tip and a sharp cutting edge on the inside. I shape the outside on sandpaper on a flat surface, the inside can be sharpened using carving tool stones, sandpaper on a dowel, I think Dunbar used a machinist scraper. You can also use other bits to get going and save the spoon bit thing until you get comfortable with the rest of the process. JT 1/24/03

REPLY: I agree with JT about using other bits to get started and familiar with the process. The last I checked, you can buy a nice box of Jennings (Stanley) auger bits on ebay. I think auger bits are good to start out on because they are longer and give you a somewhat more obvious visual reference for angles. In my experience there are many things that auger bits do better and faster than spoon bits, and you can make a chair using only auger bits, but there are also a few things which spoon bits do a lot better than auger bits. As far as sharpening spoon bits goes, you might want to buy a relatively inexpensive and new Clico bit from one of the woodworking supply catalogs and follow the instructions for sharpening, which are generally along the lines which JT describes. That way you'll protect your vintage bits while learning. BG 1/28/03


QUESTION:  I am looking for the best method for sharpening spoon bits? I have read conflicting methods. In Mike Dunbar's Make a Windsor Chair book he says to use a slipstone on the nose and never grind the cutting edge. Other information I have read says never touch the outside of a spoon bit and only hone the cutting edge. Any help on this matter would be greatly appreciated. JM 5/22/03

REPLY: I haven't looked at Dunbars book for awhile, but I think he was talking about getting the proper shape by working on the nose. The spoon bits Dunbar was using back then were the cast poorly formed english clico bits and they usually need quite a bit of work. Once you have that done you do your sharpening on the inside or the cutting edge. I use either a piece of sandpaper wrapper around a dowel or sometimes a machinist scraper. I think even Fred Emhoff's spoonbit directions referred to Dunbars sharpening directions. Fred's bits don't need reshaping just the sharpening after they dull. JT 5/22/03


Sharpening a DoveTail Saw

In an Fine Woodworking magazine #121, Dec. 1996 was a great article on refiling dovetail saws. It described how to lay out, refile and reset the teeth for easier cutting and a thinner kerf. It describes filing rip teeth as most dovetailing is actually ripping and most dovetail saws have crosscut teeth. I remade an inexpensive Freud dovetail saw into one that worked incredibly well. I removed the old teeth on a stationary belt sander, just be careful not to overheat it. JT 5/13/02

REPLY:  I've not read the FWW article but I have retoothed several of my saws. Here's how I do it:

I start by filing the teeth off with a bastard file. I usually add a good bit of belly to rip and hand saws. I finish and smooth the edge with a fine mill file.

Backsaws I prefer perfectly flat. So after jointing the teeth off a back saw, I push the edge back and forth on silicone carbide sand paper on glass. Its easy to see when the edge is straight.

When you begin cutting teeth, you must decide what pitch you prefer (i.e. how many teeth per inch). Select a file appropriate for the number of teeth. I've found it helpful to have a saw with the number of teeth I want on hand. That way I can get a feel for which file is the correct one, and roughly how deep the teeth will be.

One word about tooth pitches: (Gee this is a big subject). Lots of guys recommend these super fine toothed saws. They are okay for thin hard wood, but can cut slowly or clog in thicker, softer woods. For cutting dovetails in 4/4 pine or poplar, I prefer a 12 pt saw. 12 pts is my practical limit to cutting or sharpening saw teeth. If you have your heart set on 18 teeth per inch, you may be better off sending it out.

Regarding tooth geometry: I'm assuming you are familiar with tooth geometry such as pitch, rake angle, cross cut v. rip etc. The only thing I'd like to mention is that you can get practically any feel out of a saw by changing tooth geometry and set. Some guys prefer pretty high rake angles on rip saws because they are easy to start a cut. I prefer 0 rake angle (forward portion of tooth perpendicular to cutting edge/bottom or saw). Low or 0 rake angles cut faster which I think is important in dovetails. I figure the fewer times I go back and forth, the less chance for me to screw up.

Anyway, the reason I'm writing isn't to bore you with this drivel- I wanted to pass on a tip I learned long ago:

When you start cutting teeth, you need a good uniformity of depth. The depth will define the consistency of the pitch. Small inconsistencies can be good, big ones cause problems. Some recommend filing to a line, marked in from the jointed edge. This technique has never worked for me.

Instead, I count the strokes with the file. It may take me 4 strokes to cut the first tooth. I'll cut each subsequent tooth with the same 4 strokes. When you start the second tooth, do your best to place it right, but don't sweat it. After the second stroke you'll know if you are too close to the subsequent tooth or too far away. Apply sideways pressure to correct.

Lastly, I've screwed up a bunch of times and started over. Its not that big a deal and the lessons you learn are valueable. I love using a sharp saw and I can't imagine sending out a saw to be sharpened. I would never send out a chisel or a plane!

One more tip. I cut tails first. Before I chop them out I use the saw kerfs to mark the pins with the toe of my saw. I try to make a half tooth in the front of the saw so the saw blade will reach right into the corner. I give it a steep back angle so it will make a good mark. AC 5/22/02

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