dovetails on a table saw

[Charlie Stone]

I was watching Roy Underhill yesterday: first season, show title "Old woodworking machines" (http://www.pbs.org/woodwrightsshop/video/2600/2612.html) and at about 18:00 mins in there is a machine built in the 1800's used to cut dovetails with essentially a fixed circular blade and an adjustable sliding jig. Has anyone made anything similar to this jig adapted to be used on a table saw?

[Wally Alexander]

One of the magazines awhile ago, had an article about a jig to do dovetails on a tablesaw. I think it was Shop Notes, but not sure. I bought it but was a little disappointed. You had to have your blade ground to the same degree as your dovetail so you would get a flat bottom. I didn't want to go through the hassle. Wally

[Roger Jensen]

I read the same article and had the same reaction - why would I dedicate one blade ground to the angle of my dovetails? I woudn't even know where to take a blade to have a custom angle cut on the carbide tips, let alone trust they would do it correctly.

Has anything in woodworking inspired more magazine articles, tools and jigs than dovetail joints? You can pretty much bank on FWW having an annual article on a better way to cut them. Haven't we figured this out yet?

[Philip Rodriquez]

Forrest makes a specialized dovetail blade, for the TS. I've never used it... but they sell it.

[Charlie Stone]

Okay, well, this is why I included the video link and time stamp. The machine cuts the dovetail perfect (sq bottom) with a straight blade. The idea being, the blade is fixed and the jig moves the work piece to modify the angle of attack against the blade. Almost like a tenon jig, but rather then doing 90 degree angles to the blade it would be 2 offset angles. It seems to be nearly impossible to describe in text.

[Jim Galvin]

I believe the article was in Fine Woodworking issue 152 written by Steve Latta. He used custom ground sawblades by Forrest

Jim

[Peter Quinn]

Okay, well, this is why I included the video link and time stamp. The machine cuts the dovetail perfect (sq bottom) with a straight blade. The idea being, the blade is fixed and the jig moves the work piece to modify the angle of attack against the blade. Almost like a tenon jig, but rather then doing 90 degree angles to the blade it would be 2 offset angles. It seems to be nearly impossible to describe in text.

I don't think it matters how you orient the work relative to the blade, a square tooth blade will not make a proper dovetail. The cutter must be ground to the proper bevel angle for it to work. Same reason you can't make a router dovetail with a straight bit applies to the TS.

[Charlie Stone]

Okay, here is a picture of how I think it would work.

A jig (similar to a tenon jig) would hold the work vertical and offset by X degrees to the blade making the exit point of the blade wider then the entry. A pass though the table saw (possibly with a dado stack for width) would establish one side of the cut and remove some of the central waste. The work would be passed back across the blade (running or not), the jig realigned to postion 2, where the blade enters at or near the same entry hole, however the backend would be reoriented to expand the exit hole as the blade passes though. This would allow a square blade to create a flat top/bottom to the dovetail ... The sides would be parallel on the horizontal but with a thicker exit point as apposed to the entry point.

If I were better at sketchup I would have created an animation.

[Ryan Eldridge]

I always liked Mr. Underhill but I watched a couple of minutes on that video and was scared half to death. Him and the gentleman he was doing the show with were comparing a couple of the items they ran through their cope and stick machine, and were about an inch away from the machine while it was running.

A little nerve racking to say the least.

[Charlie Stone]

I just watched it one more time and noticed what everyone is talking about. This method would work for the pins, but not the tails, and of course, they didn't show how the tails were cut.

[Lee Schierer]

I was just out in South Dakota and Leigh Betsch showed me a jig he is working on to do just that. The sample dovetails I saw looked pretty good. I don't know if he is quite ready to share his design with others though.

[Steve Wurster]

Taunton's "Jigs and Fixtures" book by Sandor Nagyszalanczy has a jig for doing dovetails on the table saw. See page 99 of the 2006 printing.

It's basically a sled with fences on the front and back. One is mitered 8 degrees away from perpendicular (left and right), while the other uses ramps to basically make 8 degree bevels (again, left and right). This way the blade doesn't have to be specially cut. The sled is designed to cut about 90% of the joint. You still have to do some work manually.

I've never built it, so I don't know how easy it is to use in practice.

[Leigh Betsch]

I was just out in South Dakota and Leigh Betsch showed me a jig he is working on to do just that. The sample dovetails I saw looked pretty good. I don't know if he is quite ready to share his design with others though.

I'll take a couple of pics tonight and post them here. I just bought a cheap HF digital caliper to mount to it so I don't have to use my digital table saw fence to read the positions.

I bought a Forest WWII dovetail blade but you could use a chisel to square up the bottom of the tails if you don't want to spend the $'s for a specalty blade. I use a standard WWII to cut the pins.

[Bill Bukovec]

I have cut dovetails on my tablesaw using a custom ground blade.

I used the instructions in Fine Woodworking, article by Mark Duginske,

The blade was a Vermont American that I bought for $20.00. I took it to a sharpening shop and had the bevels all ground to the same angle. That cost me another $20.00. At the time (1990) I had a right tilt table saw.

The blade worked very well. Since I didn't use the blade for anything but dovetails, it stayed sharp.

The dovetails were nice and clean in the inner corners of the tails. The pins were cut with a regular or dado blade. I was able to get a nice tight fit. This method allows you to vary the width of the pins.

I no longer use this method because I have a left tilting saw. Guess I will have to post it in the classifieds.

Bill

[Larry Heflin]

I bought one of those custom ground blades from Forrest years ago after reading an article mentioning them. In the reverse of the situation stated above, I had a left tilt saw and shortly after replaced it with a right tilt rendering the blade unusable on the new saw. It's a such a beautiful blade that I've been thinking for years that I'll have it reground into something I can use. In the meantime, however, I've been gravitating to hand cutting dovetails.