I'll need to make a jig for drilling two perpendicular holes(3/8" diam.) in
a delrin rod(1/2" diam.)
Holes are perpendicular to the delrin rod axis and each other. Holes are
also offset so they don't cross.
Holes should be somewhat undersized to pressfit 3/8" steel rods inside.
Can you suggest any jig design for this? (I'll be making hundreds or even
thousands holes with it)
A vice set parallel to the mill axis with an end stop on the bed to locate the
end of the delrin bar hanging somewhat out of the vice, maybe with a shim
underneath the end of the bar to stop it flexing. Drill/ream the first hole.
Push a close fitting rod into the hole, loosen the vice and twist the delrin
bar through 90 degrees until the rod end hits a stop clamped to the bed. Move
the table along and drill/ream the second hole. If I've understood what you are
wanting to do that is.
Dave Baker - Puma Race Engines
I'm not at all sure why women like men. We're argumentative, childish,
unsociable and extremely unappealing naked. I'm quite grateful they do though.
Assuming I understand what you've said, a simple box drill jig fitted with
proper drill bushings would do a bang up job of it. The only fly in the
ointment could be if you can't get Delrin stock that is consistent in
diameter. It would be important to have stock that was consistent if you
desire to keep the holes on center, and to locate properly.
Ah! Something I know how to do.
First, though, a question about the stock. Are you sure that it will be
strong enough? After drilling 3/8 across 1/2, you have 1/16 in the
center, tapering to nothing. How long are the rods that will be
inserted and what loads will they have? I'm thinking that this design
may not carry the resulting torque.
Now, the jig. I assume that you have a drill press only. And let's
assume that the finished piece is 1" long. What I would do is take a
piece of mild steel, or even aluminum 1 x 1 x 3 +-. Drill a 1/2" hole
the long way, centered. Drill 2 3/8" holes perpendicular to the axis,
centered across the 1" dimension and 1" apart. The center the first
hole 1 5/8" from the end of the jig.
With this jig in your drill press vice and the vice securely clamped,
feed the delrin stock into the 1/2" hole and drill a 3/8 hole. Advance
the stock so that this hole in the delrin is aligned with the 2nd 3/8
hole in the jig. Put a 3/8 pin through them and drill a second 3/8
hole. Continue down the entire delrin rod. You now have a series of
3/8 holes parallel to each other and 1" apart.
Then reinsert the delrin, rotated 90 degrees. Put a 6"+- 3/8 rod
through the 2 hole in the delrin and slide the delrin up to the jig.
Adjust this rod parallel to the drill table. It can be done by eye
remarkably accurately. Keep the 3/8 rod tight to the jig and drill a
3/8 hole. Remove the 6" rod, advance and pin the delrin as in the first
Cut the delrin into 1" pieces. Oops - the 3/8 holes in the jig should
be 1" + the saw kerf apart.
Bad ASCII version:
| 1 5/8 |
| O O -----|----- centered
Two square (octagonal) collet blocks and two 1/2 inch collets. A piece of 1/2
inch Delrin. One cube of mild steel, the same size as the collet blocks. A
milling machine. A lathe.
Drill and ream one 1/2 inch hole down the center of the block on the lathe.
On the mill, set up the block, the rod, and the collet blocks on the table with
clamps. Drill and ream one hole. Pin it. Rotate and clamp the setup. Drill and
ream the other hole. Remove the pin. Done.
Not only have you made your jig but your first part, too. Now the job can be
finished to 1000 quantity on a drill press instead of a mill, saving mucho
chabo. Oh, yes, you'll need a 3/8 inch "dreamer" so you can go it in one pass,
ground for undersize.
Or spec drill rod, which comes slightly oversized, or dowel pins, which come a
little more slightly oversized, as the cross members. But since the Delrin is
cheap, make the cross members cheap, and just get the dreamer trimmed down a
Is this the knife sharpener again? I charge fifteen cents each time this
fixture is used.
Doug Goncz, Replikon Research, Seven Corners, VA
The hormones work at different speeds: In a fight-or-flight scenario,
glucocorticoids are the ones drawing up blueprints for new aircraft carriers;
epinephrine is the one handing out guns.