Gallery, Projects and General > How do I??

boring a compound angle in a block?

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shipto:
I need to bore a hole into the end of a aluminium block which is 85 x 65 x 40 but it needs to be 25 degrees one way and 33 degrees the other way. I have a 4 jaw chuck and a faceplate to play with but not a clue how I am going to hold the block securely enough to bore the hole.
would appreciate any ideas.

awemawson:
You need a 'compound sine table' like the one illustrated below.

Now that one is a fairly expensive bit of kit - perhaps you can jury-rig something similar

An alternative is the compound vice also below

Lew_Merrick_PE:
It sounds as if you wish to bore this hole using a lathe -- which is almost certainly a non-starter.  However, as Awemawson suggests, a compound sine plate would normally be the preferred method.  My approach would be to set-up the (say) 33° angle on my tilting table (using a precision machined triangle to dial in that angle) and support it on a pair of precision machined triangles to set the 25° aspect.

What I do is to make triangles out of 6 inch X .250 inch bar stock.  I drill & ream PF holes for (ø.1875 inch) dowel pins at 5 inches on one (.250 offset) "edge" and a third hole at (6.000, 6*tan(angle) and then mill my (.250 offset) edges from the dowel pins.  I make them in pairs, steel stamp the angle on them and store them in a box/rack for re-use.  I then have a number of lengths of ø.500 bar that are reamed SF for my dowel pins such that I can coordinate the pair when necessary.

Does this help?

philf:
Much easier to set up in a milling machine with a tilting vice set to one angle and the work tilted in the vice at the other angle. (Or a compound vice like Andrew suggested)

I can't see how a 4-jaw would help.

In the lathe a tilting angle plate fastened to your faceplate set to one angle then clamping the work to the angle plate at the other angle could do the trick.

Phil.

shipto:
I agree setting it up on a milling machine would be best unfortunatly I dont have a mill yet. maybe I could set it up on the works pillar drill if I can find a reamer the right size i need? will have to look into that.

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