Dovetail Question - Chiseling to the Line

[Mark Roderick]

My biggest problem cutting dovetails by hand is getting a perfect mating surface between the pin board and the tail board - specifically chiseling out the waste between the pins.

I cut out most of the waste with a coping saw, then use a sharp chisel angled at slightly less than 90 degrees to "undercut" at the line left by the marking gauge. Too often, I manage to leave a tiny gap somewhere along that line.

Do you guys use any special techniques or tricks to ensure a perfect match every time?

[Bob Noles]

Well..... I do see my eye doctor often and leave of as much caffine as possible :p

[Robert Rozaieski]

Pare back gradually, not all at once, and don't try to undercut. The chisel will want to undercut slightly anyway because of the geometry of the bevel. The last cut should be in the scribe line, but you should only be removing a wisker of remaining wood on the last cut.

Do you leave your end grain proud to be planed flush later? If so, try shooting for a perfect fit or having the end grain a little low rather than proud of the surface so that you need to plane the long grain to flush up the joint. This way, if you find the fit is too tight, you can plane a little off the inside face of the pin board to adjust the fit. This should help the baseline fit as well.

[Al Navas]

My biggest problem cutting dovetails by hand is getting a perfect mating surface between the pin board and the tail board - specifically chiseling out the waste between the pins.

I cut out most of the waste with a coping saw, then use a sharp chisel angled at slightly less than 90 degrees to "undercut" at the line left by the marking gauge. Too often, I manage to leave a tiny gap somewhere along that line.

Do you guys use any special techniques or tricks to ensure a perfect match every time?
Mark,

I also use a fret saw to remove the bulk of the waste. Then:

I use a 2-inch thick, machined board, aligned up with the depth line I marked prior to cutting with the saw. The first chisel cut I make is very light and vertical, and just deep enough to allow me to lightly pare away at the base. THEN I angle the chisel slightly, to undercut a little, as you do. I go in about half way, then turn the board, and repeat.

Only recently I started doing the hand-cut DTs. And this technique pays off handsomely.


.

[Denis Tranchemontagne]

I am no expert, but I just took a class this past weekend, and corrected the same type of problem that you are having. My dovetails came out much better then my early attempts at home.

The teacher, Steve Marcq, had us do a couple of things.

First using the chisel bevel done pare out a chip to the shoulder. Basically something link a 16th of an inch. Start the chisel near the end grain, tap the chisel a few times and chip should break off at the scribe line, this sets the shoulder. The chisel does not get near the shoulder on this step.

Second when placing the chisel on the scribe line, scrape the chisel from in front of the scribe line (waste side) until it catches in the scribe line. Lightly tap the chisel, still at 90deg, then angle the chisel to undercut. and chop the waste out, about 2/3rds down. When undercuting, you need to force, stear the chisel to undercut. When poping out the waste be careful not to lever the waste out, but scrape the chisel forward as not to dent the shoulder. (this was a flaw in most of my dovetails)

Repeat on the other side.

Denis

[Mark Singer]

The chisel width should be very close to the space between pins if possible. I don't usually use a fret saw. I just chisel on the scribe line very slightly undercutting. Bed the chisel in the scribe and bare down when you are just in the scribe.. Usually the problem is sawing rather than removing waste.

http://www.wkfinetools.com/contrib/mSinger/z_art/teakSofa/0_img/IMG_5611.jpg

[Derek Cohen]

Hi Mark

Rule #1 when cutting dovetails - which you likely know, but needs to be repeated in the context of the issue you raise - is that both boards must be square and flat. If there are any warps, etc you will never get a tight fit.

Lining up the baselines is a matter of paring to the line. You can do this by carefully and slowly paring towards the line. Never start on the line - the bevel will cause the chisel to be pushed over the line.

Whether you saw out the waste or chop out the waste is a personal choice. In the end you have to pare up to the line, and not over it.

A slight undercut at the line is preferred to a slight crown - but it can be difficult to pare square.

If you are not confident of doing this freehand, then I have two jigs for you.

http://www.inthewoodshop.com/ShopMadeTools/AJigforParingDovetailBaselines.html

http://www.inthewoodshop.com/ShopMadeTools/ANewJigforParingDovetailBaselines.html

http://i13.photobucket.com/albums/a262/Derek50/Furniture/Workshop%20cabinet/3.jpg

Regards from Perth

Derek

[Tony Zaffuto]

Jigs such as what Derek suggested are a help, but you can also clamp a "wood screw clamp" on the baseline to assist with paring off the wood. I also undercut a tad, but I only do that after paring to the baseline.

T.Z.

[Floyd Mah]

Try orienting the board vertically when you are ready to pare the waste if you aren't already doing so. The reason for orienting the board vertically are several. You can place the work area at a height that suits your height and stance, instead of being compelled by the height of your workbench and chisel length to work in an awkward position. Work placed on the bench may force you to hold and exert pressure on a chisel which is not in line with the forces which you can exert from your center of gravity. You can use your own body weight to your advantage if the board is clamped vertically. Your weight provides some raw force that you can modulate with your arms and hands to control and do delicate work. You use your dovetail saw with the boards clamped vertically for the same type of control. My elbows always ache after I've done any paring with the work laid flat on the workbench.

I find that it is more natural to find a direction level to the floor than one vertical to bench, so it is easier to maintain the correct direction of the paring knife when I am working.

I use these knives http://www.japanwoodworker.com/product.asp?s=JapanWoodworker&pf_id=15%2E636%2E3060&dept_id=12695 (http://www.japanwoodworker.com/product.asp?s=JapanWoodworker&pf_id=15%2E636%2E3060&dept_id=12695) to do my paring. They are extremely sharp and a very good value in a store with $200 chisels. My experience is that they are as sharp as or sharper than the knife blades that are used in the operating rooms. I use a guide clamped under the scribed lines to direct the cuts. My practice is like Denis' to chip out a shelf to guide the paring chisel, using a sharp knife to deepen the scribed line and then levering up a chip with a sharp chisel blow a short distance away from the line. For paring, you should have an extremely sharp knife. The short handle on this knife work well for this technique. I also use a fret saw to remove most of the waste wood before paring.

[Mike Wilkins]

Get a copy of the latest issue of Fine Woodworking magazine. An article inside is about a gentleman that had lots of problems getting decent results hand cutting dovetails. He visited Gary Rogowski, a well-known craftsman and teacher in the Pacific Northwest for some tips and hints on getting better results with his hand-cut dovetails.
I think you will find some useful info in this article.

[Peter Evans]

If boards are not flat, eg wide boards for a blanket chest, the board can be clamped flat for cutting the dovetails. Clearly the boards need to be clamped together at glue up. This was the case with a big chest I made some years ago that is still in good shape.

Obviously there are limits to the cupping.

Cheers
Peter in Sydney