How to Sharpen a Dovetail Saw

First, find out whether your saw can be sharpened at all. If the teeth are dark blue or black at the tips, they are impulse-hardened and no file will touch them — that saw is a replaceable-blade tool, not a sharpenable one. If the teeth are the same bright steel as the plate, it is filed, and you can keep it cutting for the rest of your life with a 4 in extra-slim taper file, a saw vise and twenty minutes.

This site has the general routine on how to sharpen a hand saw, and if you are sharpening a 10 ppi panel saw that is the page you want. A dovetail saw is a different job in four specific ways, and each of them is a way the general advice goes wrong on a fine backsaw.

The four differences

1. The teeth are much smaller, so the file must be too. A dovetail saw runs somewhere between 15 and 20 points per inch. The 6 in slim taper file that handles a panel saw is physically too large: its corner radius is bigger than the gullet you are trying to file, so it rounds the gullet instead of deepening it and the teeth lose their points. You need a 4 in extra-slim or double-extra-slim taper, and for anything above about 18 ppi a needle file is the realistic option.

2. It is filed rip, not crosscut. A dovetail saw cuts down the grain through the thickness of a board, which is a ripping action, so the teeth are filed straight across at 90 degrees to the plate with no fleam angle at all. That is good news: a rip file is the simplest filing there is, because you hold the file square and push. The rake — how far the front of each tooth leans back — is where the character lives, and we come to that below. Rip vs crosscut teeth has the geometry.

3. It wants almost no set. Set is the alternate bending of teeth left and right that makes the kerf wider than the plate so the saw does not bind. A dovetail saw's whole value is a narrow kerf, and the plate is thin enough that very little set is needed — a few thousandths of an inch per side, which is less than most saw sets will deliver on their lightest setting. Many dovetail saws are sharpened with no new set at all, because the existing set is still there.

4. There is less room for error. On a 10 ppi saw a tooth filed a little too far is cosmetic. On an 18 ppi saw, one heavy stroke takes a tooth below its neighbours and that tooth stops cutting. Light strokes, counted, identical on every tooth.

What you need, and what it costs

An honest note on supply before the list: we have no saw file, saw set or saw vise in our product registry with a listing we can verify, so none is linked on this page and none is recommended by name. The rule here is that we only link to products we have checked are live. The sizes below are what to search for.

A taper file sized to the pitch. For 15 to 16 ppi, a 4 in extra-slim taper. For 17 to 20 ppi, a 4 in double-extra-slim, or a needle file at the top of that range. Buy two or three: a saw file is consumable and a dull one skates and glazes the tooth instead of cutting it. Bahco and Grobet are the names worth looking for.

A saw vise, or a wooden substitute. The plate has to be held rigid with only the teeth and a sliver of plate above the jaws, or it will chatter and the file will skip. A proper saw vise is the comfortable answer. Two pieces of hardwood with a slight bevel on the top inside edges, clamped in a bench vise, is the free answer and works.

Magnification and light. This is not optional at 18 ppi. A cheap head-worn magnifier and a bright raking light are what let you see which tooth you are on, and more sharpening jobs are ruined by not being able to see than by bad technique.

A fine mill file for jointing. Only if the tooth line is uneven. On a saw that has been used rather than abused, you skip this.

A saw set, probably not. Most dovetail saws do not need resetting at a sharpening. If yours genuinely binds after filing, a fine saw set on its lightest setting, applied to every other tooth from each side, is the tool — and be aware most sets are designed for coarser pitches and will overdo it.

The sequence

Step 1 — test the teeth with the file. Before anything else, take a file and draw it once across a few teeth with light pressure. If it bites, the saw is filed and you are in business. If it skates with a glassy feel, the teeth are impulse-hardened, and no amount of technique will change that. Stop, and buy a replacement blade or a filed saw instead.

Step 2 — clamp it low and rigid. Teeth plus about an eighth of an inch of plate above the jaws, no more. If you can hear a ring when you tap the plate, it is not clamped tightly enough.

Step 3 — joint the tooth line, only if it needs it. A mill file held flat on the teeth, run along the length until every tooth shows a tiny flat on its tip. This makes every tooth the same height and it also makes them all temporarily blunt, which is the point: the flats tell you how much to file each one. Skip this if the line is already straight, because jointing removes tooth height you cannot put back.

Step 4 — file every gullet, square across. Place the file in the first gullet, hold it level and at 90 degrees to the plate, and take two or three light strokes on the push only — never drag it back under pressure. Move to the next gullet. Same number of strokes, every time. Work along the whole saw in one direction.

Step 5 — watch the flats disappear. If you jointed, the shiny flat on each tooth tip is your gauge. File until the flat on the tooth in front of the file is gone, and then stop on that tooth. When every flat has gone, every tooth is the same height and sharp.

Step 6 — decide the rake, once. Rake is how far the front face of each tooth leans back from vertical, and it is set by how you tilt the file. Zero rake — the front face dead vertical — is the most aggressive and the hardest to start. Relaxing the rake to about 10 to 15 degrees makes the saw dramatically easier to start and a little slower, which on a joinery saw is almost always the right trade. Pick one and keep it consistent along the whole plate.

Step 7 — stone the sides lightly. One light pass of a fine stone flat along each side of the tooth line removes any burr and evens out set irregularities. It also takes the saw from cutting a slightly ragged kerf to cutting a clean one.

Step 8 — test in scrap and wipe it down. Cut a kerf in softwood end grain. It should start without jumping and track straight. Then oil the plate, because a plate you have just filed is bare steel — cleaning and waxing hand tools covers what to use, and rust removal and prevention is the fix if you have left it too long already.

Which saws can be sharpened at all

This is the buying decision the topic forces, and it is why the four saws in the table above are the ones on this page: every one of them is filed rather than impulse-hardened, so every one of them can be sharpened by the routine on this page indefinitely.

Lynx 10 in tenon saw, 15 TPI— made by Thomas Flinn in Sheffield, and the only saw here whose maker publishes how it is filed. Sheffield spring steel, folded brass back, beech handle on brass button screws. The best-made saw on the page.

Footprint 256 10 in, 15 TPI— a brass-backed Sheffield saw whose listing says the plate is re-sharpenable repeatedly, with three brass handle screws you can replace. The most explicitly renewable saw here.

Crown 187 Gents Saw 8 in— the small filed backsaw most people actually use for dovetails, and the cheapest route on this page to a saw you can keep forever. Straight handle rather than a pistol grip.

Spear & Jackson 12 in, 15 PPI— a filed western backsaw at a sane price, and the longest here, so it covers tenon shoulders as well as dovetails.

Everything else — the dozukis, the razor saws, every impulse-hardened pull saw — is a replaceable-blade tool and belongs on how to replace a Japanese saw blade instead. That is not a criticism of them; it is a different ownership model, and Japanese saw types explained sets out which is which.