A common method of making strong threaded holes in aluminum is with
Helicoils. If you're not familiar with them, they're spring looking
objects, wound from trapezoidal wire, usually stainless steel. In
practice, the hole is tapped oversize with a special "STI" (Screw
Thread Insert) tap, the insert is screwed in, its driving tang is
broken off & the job is done. In addition to being common in the
aviation industry they're also widely used to repair damaged threaded
holes.
Roy
--- In 7x12minilathe@..., "rancerupp" <rupps@...> wrote:
Thanks Ron. So how about using threaded inserts in an aluminum
block?
First downside I see with an insert it creates an additional place
for possible lost rigidity. I've seen Pem Nuts for 6-32 screws in
1/16" alum. pate. Has anyone seen similar for 3/16 or 1/4 inch
bolts?
T-Nuts come to mind, but those are for wood. If the threads are the
only forseeable problem, then I'd prefer to use alum.
As for rigidity, my toolpost is 2 3/4 square and 1 5/8 high. Top
lip
is a bit over 1/2, the middle slot is about 3/4, the bottom lip is
a
bit over 1/4. The middle slot is about 1/2 in from the outer edge.
With that, the shortest threaded insert would be for the bottom
(1/4").
Good point about shimming the sides. I have some ideas on that but
I'll wait before introducing those.
Anyone know of sources for threaded steel inserts? Thanks.
Rance
--- In 7x12minilathe@..., <trainguy_347@> wrote:
Hi, Rance. Aluminum (aluminium) is strong, but it has been my
experience that threaded holes are easily stripped or deformed with
twisting motions. Steel would probably be best. As for the
stability,
try using a shimming block against the inside vertical surface of
the
tool, between it and the tool post. Good luck, Ron.
---- rancerupp <rupps@> wrote:
Thanks Ron, and to Clint for posting the pics.
Ron, others, would you think that al. would be sufficient for
this or
does it have to be steel? The toolpost that comes with the 8x12
seems
huge. I would think that an alum. one of the same dimensions
would be
fine.
Also Ron, did you have any problems with the mounted tool bit
twisting while using your set screw configuration? Clint had
expressed concern of rigidity.
Rance
--- In 7x12minilathe@..., "Ronald Durbin"
<trainguy_347@> wrote:
I have done this with a smaller post, except that
I used set screws (or grub screws, as our British brothers
and
sisters
call them) comming up from the bottom. To adjust, just undo
the
retaining nut on top, lift up the post, back off the top
screw
slightly, engage (run further in) the bottom screw tightly,
and
replace the post as per normal. This sometimes take a few
tries,
but
once the height is achieved, all is well. Great drawings, by
the
way!.
Ron.
