1. Senior Member
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Mar 2008
Location
Kent, U.K.
Posts
2,351
Originally Posted by winchman
"...but I bet the first few I made would come out wrong"

How would you know they're wrong?
I wouldn't have to. I'd bet they'd be wrong whether I knew it or not

2. Member
Join Date
May 2002
Posts
46

More on Compound Angles

Here is the answer I was looking for. It has been great revision for me and I have had considerable help from a mathematics forum.

The problem was to find the set-up angles required to make a skewed milling cut in a rectangular block following given angles on three of its surfaces.

The desired angles are A, B and C in planes YOZ, XOZ and XOY respectively. This is a right handed coordinate system with angles X -> Y, Y -> Z and Z -> X being +ve.

1. Align vice jaws // X.

2. Set block in vice so that line at angle A is // to XOY

3. Tilt vice by angle D to XOY. Where

D = atan(cosAtanB)

4. Rotate vice by angle E from XOZ. Where

E = atan(cosAsinC/(cosCcosD-sinAsinCsinD))

John.

3. Member
Join Date
Nov 1999
Location
SE OZ
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3,964

3-dimensional set-up

Mark out the OP's job (as per his pic - here):

Put it in a 3-axis vise like this:

Put the vise on a flat plate and use a surface guage or a height guage
- like this:

http://i200.photobucket.com/albums/a...faceguage4.jpg

Or a variation like this:

and set the three axis until the lines on the job are parallel to the mill table.

4. Member
Join Date
Nov 1999
Location
SE OZ
Posts
3,964

Theme

More variations on a theme (no maths needed here either):

5. Member
Join Date
May 2002
Posts
46
Thanks for the many ways to do it if you have the equipment.

6. Senior Member
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Jan 2010
Location
Kansas City area
Posts
5,117

Compound Angle

You can leave the base of the vise flat on the mill table. Turn the vise to the first angle and clamp to the table. Put an angle block of the correct angle under the part to tilt it sideways in the vise jaws and then tilt the vise for the final angle.

7. Senior Member
Join Date
Oct 2007
Location
Demokratik Republik of Washington
Posts
278
Originally Posted by winchman
"...but I bet the first few I made would come out wrong"

How would you know they're wrong?
Darn... now I have to clean coffee off of my key board........ I have done that before... and had inspection make the same mistake... only on assembly did they find out it was wrong....

There are only two angle to figure... Tilt and rotate. Use a common leg, the angle you are cutting as the lenght of 1 and work from that. It really is simple.

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