I've got a Unisaw that I want to attach an extension table to the rear of.
There's two holes (approx 3/8" diameter) already drilled in the rear flange
of the cast iron top (it came from the factory that way), but they're not
tapped; just through-drilled. They're a little too small for clearance of
a 3/8" bolt; it would be nice if they were whatever the tap drill diameter
for a 3/8 UNC is supposed to be, but I haven't measured them exactly, so
I'm not sure.
I suspect the easiest way to attach something would be to tap those two
holes and bolt on a piece aluminum angle, to which my plywood table would
get attached. How difficult will it be to tap these holes? I've tapped
holes before, but never in cast iron. Does it go easy? Is there any risk
that I'll damage the top? What if I end up having to drill some additional
holes in the flange?
Because it's danged near impossible to get to the back side of the flange
to hold a nut in place. The sheet metal cabinet is in the way. I tried
reaching in from the throat opening, but I'm not enough of a contortionist
to get my arm where it needs to go.
5/16-18 NC is F (.2570"/6.528mm)
8-1.25mm is H (.2660/6.756mm)
5/16-24 NF is I (.2720"/6.909mm)
8-1.00mm is J (.2770"/7.036mm)
5/16-32 NEF is 9/32" drill hole size
9-1.25mm is 5/16"
3/8-16 NC is 5/16"
9-1.00mm is O (.3160"/8.026mm)
9-0.75mm is 21/64"
3/8-24 NF is Q (.3320"/8.433mm)
10-1.50mm is R (.3390"/8.611mm)
10-1.25mm is S (.3480"/8.839mm)
10-1.00mm is 23/64"
from kbctools.com catalogue, not double checked/verified. Letter equiv's
from Machinery's Handbook. If you want to know if, consult it. If you need
to know how to make the tool to make the tool, consult it.
If you screw up you can use a heli-coil, etc.
Cast iron taps fairly easy, but it clogs the tap, so back it out to clear
the chips, then tap anouther 1/4 - 1/2 turn or so.
DAGS comes up with this site for drill sizes:
Using Opera's revolutionary e-mail client: http://www.opera.com/mail /
Those are designed "exactly" for that purpose. Those holes
match the Biesemeyer back rail, which an outfeed table can
The Biesmeyer rail is attached with thru bolts and nuts.
Go here for detailed instructions on how to build the
outfeed and bolt sizes....
No drilling required......
Roy Smith wrote:
Maybe I'm not understanding this question very well. You want to attach an
extension to the BACK of your Unisaw? For use as an outfeed? If you do,
the miter slots will be useless, unless you have a way to cut them through.
Either way, drilling and tapping holes in cast iron is easy and explained in
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