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.

[Darnell Hagen]

On a table saw, the pins are cut by angling the mitre gauge with the blade at 90°, the tails with the gauge at 90° and tilting the blade, the stock flips back and forth to do both sides. Although it would be convienient to have a blade ground, it is unneccesary if you use a fret saw to clear the waste. The fret saw will clean up the low corner easily, it's only 1/8" wide.

It is much easier to do a machine cut dovetail on the bandsaw (http://thewayiwood.blogspot.com/2010/04/bench-making-top-dovetails.html).

[Salem Ganzhorn]

I have cut the pins on a table saw using a sled like this one: http://lumberjocks.com/projects/22450

Works great. Perfectly clean pins. I then use the pins to layout the tails and cut the tails on the bandsaw. Yes you have to clean up the tails with chisels but it isn't that bad :).

[Bob Smalser]

Machine Cut Through Dovetails
http://www.sawmillcreek.org/showthread.php?t=13905


http://pic20.picturetrail.com/VOL12/1104763/5732475/73537166.jpg

[keith jensen]

Sounds like Bill and Larry could trade blades and be back in the table saw dovetail business....

[Bruce Wrenn]

Mark Dugenskie does dovetails using both the table saw, and band saw. His video "Mastering Woodworking Machines" shows cutting the tails and pins on table saw, and removing waste using band saw. His video on the band saw shows using just the band saw.

[Leigh Betsch]

Here's a few pics of how I do it on a tablesaw. I don't like to eyeball up to a line so I built a fixture that I can accurately index from one cut to the next. Because the workpiece is angled to cut the pins and since my fixture only makes moves in the 90 degree direction I wrote a few formulas in an excel worksheet to do the trig calculations when I index from one cut to the next. The excel program also calculates the tail moves. To avoid a line to line fit I had to add in a offset so I can allow clearance for glue. By using a thin kerf blade I can cut a pin as narrow as about .100". I use a 10 degree dovetail which leaves very little waste with a .100 pin left to chisel out of the tails.
I wouldn't say that this is the simplest way to make dovetails but it does avoid eyeballing to a line and the tablesaw blade leaves a nice crisp cut. Oh yeah my fixture is mounted to my Euro slider saw but I think you could make one that would slide in the miter slots of a cabinet saw also.

[Charlie Stone]

Leigh,

That is great, that seems to be pretty much on track with what I had in mind. Could I trouble you for a few more angles on how that jig works. If I am seeing it right, the board being cut is resting against an angled backer board, is that right? Also, does that angled backing move with the rest of the section it is in when the handle is turned, as 1 full unit sliding across?

What brings all this up in the first place is, Very much like the original video I referenced, I have some double hung windows (close to 40 sets) which need to be either repaired or replaced with exact duplicates (the originals were made in the late 1860s-early 1870s (most likely on a machine exactly like the one in the video). The top section of each window is put together with a roughly 3 inch long dovetail. I would like to have a reliable jig that could make repeatable cuts.

[Leigh Betsch]

Leigh,

If I am seeing it right, the board being cut is resting against an angled backer board, is that right? Also, does that angled backing move with the rest of the section it is in when the handle is turned, as 1 full unit sliding across?


Yes that's right. The 10 degree fence (angled baker board) is screwed to the sliding jig fence and moves with it. The angle fence is unscrewed and turned over and re-screwed to the jig fence to make the cuts on the opposite side of the pin. Then the angled fence is removed and the tail board clamped to the jig fence, a 10 dovetail blade put in the saw, and the tail cuts indexed. My pics just show a 5/16 piee of scrap being cut, 1/2" thick stock makes a muh better looking dovetail at 10 degrees.

I watched that y-tube video. Man that place looks dangerous. I don't know why anyone would restore that to operating condition. Maybe for a museum but never to earn a living. OSHA would never let him have employees!

[Brett Robson]

After reading this thread yesterday, I decided to give table saw dovetails a shot. I knocked together a simple jig after work and gave it a try this evening. The angle on the jig is set at a 1:6 which I think is somewhere around 8 degrees, although I didn't measure it.

Here is my very first attempt. Not too shabby for the first try I think! Total time spent from freehand drawing the pin locations to tapping the parts together - about 15 minutes.

I sawed the tails out entirely on the band saw. I just left my basic combo blade in the table saw for the pins.

I could have made the pins even thinner, the only restriction there is leaving just enough room for the band saw blade to enter when cutting the corresponding tails.

[Larry Heflin]

Just noticed that Fine Woodworking dot com has a new video series on building a cherry bookcase. Video #1 is an almost 9 min. video on tablesawn dovetails. It incorporates use of a jig on the table saw for the pins and a band saw for the tails. Lots that is similar to what has been mentioned here. Very interesting and timely in view of this thread. Not sure if you have to be subscribed to view it.

Larry

[Steven Green]

The new video in Fine Woodworking online is a guy that's building a bookcase and the first video in the series shows him cutting tails and pins on a tablesaw. Uses a shopmade jig and a bandsaw. Not bad at all

[Kim Howarter]

That article is by Jeff Miller who runs a furniture woodshop in Chicago. I took a class from him on doing dovetails by hand and using the tablesaw/bandsaw method. It does work nice. We spent the first 4 hours learning how to cut a dovetail by hand with a dovetail saw and chisels and then the last hour was spend doing it with the fixture on the table saw and bandsaw. Much quicker method.

[glenn bradley]

I built a quick version of Jeff Miller's sled to see how I liked it. It does work well and is pretty simple to do. I'm not a big DT guy but when they fit the style of the piece, they sure look nice.