Compound angled holes

[Frosty Thunder]

OK I'm stumped. I'm trying to get a set of leg's in a stool I'm making. The two front legs are pitched 10 deg out to the side and 20 deg out to the front. My drill table rotates right and left (need deg) and what is my degree of rotation of the work pc? Perhaps someone has a formula. The back legs are 10 deg both ways.

Thanks George Yoder

[David Anderson]

Ah ha! same problem for Windsor chairmakers. I once wrote a small program to figure the complex angle, but I find it easier to adjust the drillpress table right or left (10-deg in your case) and put a temporary platform plywood on top of the cast iron table with two wedges glued to the underside. In your case, the simple angle of the wedges would be 20-deg. No calcs needed. Dave

[Woodworm]

I'd make a pair of wood blocks with the correct angles (on the TS, RAS or MS) and use that to either:

-align the drill press table with a level

-keep the drill table level and use the block to rest the work upon.

[heyscott]

I came up with some formulas for you using trig:

Let a be the angle to the front Let b be the angle to the side

Angle to rotate piece on table: theta = atan(tan(a) / tan(b))

Angle to tilt the drill:

phi = atan(sqrt( tan(a)^2 + tan(b)^2 ))

If a and b are 10 and 20, then theta = 25.85 phi = 22.02

If a and b are 10 and 10, then theta = 45.00 phi = 14.00

Scott

[Preston Andreas]

George,

The easiest way I found to do it is to tilt the drill press to 10° (in my case, 6°) to the left and later to the right. I found out that a degree or so off makes a big difference to the footprint of the legs, so I used a long drill bit and machinist protractor for a more accurate setting. (see -

)

I then tilted the seat up (20° for you) using a 20° wedge. To make an accurate wedge, I rough cut a 4" x 4" piece of cedar to nearly the angle. Then, using a sled, I ran it through the planer for an accurate wedge. For instance making a sled 6" long on the horizontal leg and 2 3/16" for the vertical leg gives a 20° wedge. I believe I have a pic or two of the setup if you want it.

For the other two legs, use a 10° shim. Just curious, why the difference in angles between the front and rear legs?

If I read you right, you want to use one angle. Figuring the resulting angle of the diagonal of a plane tilted 10° one way and 20° is straight forward, given the seat dimensions, but setting up a jig with one angle to hold the seat in the proper orientation is not. I tried this first and found later it was easier to tilt the table and then the seat. The only caveat is the fence on the drill press table must be 90° to a line through the center of the drill press column and the chuck. That is easy to achieve. Once I figure it all out and set it up, I drilled a handful of seats in no time.

Preston

[Kurt]

[e-mail] (heyscott) wrote in news: [e-mail]:

Those of you with kids, remember to save that description in the folder of examples you whip out in answer to the perennial question, "When would I use this in real life?" (Some items are more difficult to answer... for history, the only one I've gotten them to accept is "Those who ignore history are doomed to never get jokes based on it.")

Thanks for the numbers, Scott.

[Tchswoods]

On 7/21/2004 "Frosty Thunder" [e-mail] wrote

Even lower tech might be a hand drill with two sliding bevels set to the appropriate angles. If you are only making one piece, it seems to be a lot of set up for each hole. Lots of set up = lots of potential for error. (IMHO)