Cutting dovetails-Machinery's Handbook and video

[Janderso]

Finally got back on this project.
Tomorrow, I start the 5 degree cuts and the female dovetail.
We just got back from a two week trip up through the Rogue River area of Oregon, Prospect and the camping areas, Bend and the surrounding area.
Caught lots if trout!!

 

[NCjeeper]

Pupper looked like he was having fun.

 

[homebrewed]

The upper Rogue is one of our favorite rivers. We have stayed many times at a little resort just up the road from Prospect, toward the cutoff to Crater Lake national park. It's rustic but close to a lot of pretty country to explore.

You may have gone down the Avenue of Boulders trail there at Prospect. Pretty impressive, too. We love all the Madrone trees along the trail.

The Rogue river comes from a very large spring inside the park, called Boundary Springs. It goes from nothing to a good-sized creek in just a few hundred yards.

 

[Janderso]

Pupper looked like he was having fun.

Oh yeah, anytime she can be off leash she is a happy girl

 

[Janderso]

The upper Rogue is one of our favorite rivers. We have stayed many times at a little resort just up the road from Prospect, toward the cutoff to Crater Lake national park. It's rustic but close to a lot of pretty country to explore.

You may have gone down the Avenue of Boulders trail there at Prospect. Pretty impressive, too. We love all the Madrone trees along the trail.

The Rogue river comes from a very large spring inside the park, called Boundary Springs. It goes from nothing to a good-sized creek in just a few hundred yards.

The Willamette, The Rogue, Umpqua and Deschuttes are all amazing rivers!
Please excuse the spelling errors

 

[ErichKeane]

So just catching up here... I've been cutting a decent amount of dovetails lately, and have been 'cheating' by using the DRO.

For the male dovetail, If you know the diameter of your cutter at the base, you can just use the offset to cut the 'point to point' size. For the female side, if you know the height, you can do the same with some minor trig.

 

[Janderso]

So just catching up here... I've been cutting a decent amount of dovetails lately, and have been 'cheating' by using the DRO.

For the male dovetail, If you know the diameter of your cutter at the base, you can just use the offset to cut the 'point to point' size. For the female side, if you know the height, you can do the same with some minor trig.

Erich,
I just finished cutting the female dovetail.
I find this very difficult.
I need a math tutor leaning over my shoulder.
I'm using .250 pins. The adjustable parallels show a reading of .586". The depth is .393'
The next step is to cut the male side.
I have no idea how wide it needs to be before I start cutting the dovetails.

Old dog = new trick

 

[ErichKeane]

Erich,
I just finished cutting the female dovetail.
I find this very difficult.
I need a math tutor leaning over my shoulder.
I'm using .250 pins. The adjustable parallels show a reading of .586". The depth is .393'
The next step is to cut the male side.
I have no idea how wide it needs to be before I start cutting the dovetails.

Old dog = new trick

Heh, I'm not that old of a dog, and _I_ gave up on trying the pin method I just did the normal sine-math to figure out where the 'inner points' distance on each one goes, then used the DRO to figure it out from there.

 

[Janderso]

Heh, I'm not that old of a dog, and _I_ gave up on trying the pin method I just did the normal sine-math to figure out where the 'inner points' distance on each one goes, then used the DRO to figure it out from there.

?I have a DRO but don't know your method.
I'll get it

 

[ErichKeane]

?I have a DRO but don't know your method.
I'll get it

Ok, so here's the trick.


FIRST, pick a 'width' for your dovetail, inner-point to inner-point on the 'female' part of the dovetail. Center your spindle, and "know" the width of your cutter.

Say, you chose a 1.250 'width' for the inner points on the female part, and a .750 'cutter' width. Cut down the center (or, more likely, have cleared it out with your roughing mill) and set your depth (lets say, .200" for this), and cut until the 'points' hit their size, just like if you were trying to cut with a normal straight cutter. In this case, 1.250" wide, -.750" cutter, is .500. .500" / 2 (for each side!) is .250", so you cut until your DRO reads .250" and -.250".


NOW to do the 'male' part, you do the reverse when you 'cut', you cut the 'width' of the 'inner points' PLUS 1/2 your cutter width. Calculating the inner point is as easy as just doing the trig.

The inner 'corner' is 60 degrees thanks to your dovetail cutter. You want to find the 'adjacent', so open your favorite right-triangle calc (like this one!) https://www.calculator.net/right-triangle-calculator.html

"Alpha" is 60 degrees. 'a' is .200" (the depth we decided above). We're looking for 'b' here, which ends up being 0.11547. Which means the 'narrow' points on the female dovetail are 1.250" - (.11547 *2), or 1.01906. (1.250" because that was the 'inner width' we chose above, *2 because there are two triangles created by the dovetail cutter, 1 on each side).

SO now you want to cut the 'male' side. Target 'inner point to inner point' is 1.01906" (plus perhaps a touch for a running fit!). Cutter is still .750. Set the cut 'depth' on your part right to the .200" we decided on above. Then, with the DRO centered, cut the 'outside' of the part until the DRO reads DOWN to (1.01906 + .750)/2 (cutter size!), or 0.88453.

At this point, your dovetails should be just about right-on, as long as your DRO was. No measuring over pins, just good-new DRO + a small amount of trig