I have a part being machined that calls for 2 captive studs to be
inserted and thought I'd try to put the studs in myself. They're
stainless, 8/32 about an inch long and require a .163 pocket
(partially drilled hole).
I thought that maybe I could build some sort of jig to keep them
straight and then tap them with a hammer?
Is there a small accessory or something that maybe I could use with an
arbor or vise? Any ideas?
Need to do them myself to save some time and money.
Not sure this is the same stud, but it probably is similar to some I have
used. I took a piece of steel and drilled a hole that would barely clear
the threads. I faced it on the lathe so it was flat and at a right angle.
I place the material with the stud in it on a flat surface, stud sticking
up through the material, and place my driver down over the stud. I then
whack it with a hammer until the stud is flush on the back side. This was
done to put 4-40 studs in aluminum sheet, and worked quite well.
If you're using the stud I think you are, the hole diameter is pretty
important. It should have a shoulder that is knurled, and below that, a
circular dovetail-like feature. The shoulder cold forms material into
this dovetail for pull out resistance, while the knurl keeps it from
rotating. If the hole is even a few thou too big, the stud won't hold
securely. You want the smaller diameter to -just- fit the hole.
They also take a fair bit of pressure, even for a #8. But a length of
1/2" CRS faced square, with a center hole just big enough to take the
stud, is the tool you need. An arbor press will be needed, or if the
holes are close enough to the edge, you can use a vise. I've done plenty
of PEM inserts with my Kurt vise.
Hope this helps.
Hammering directly on the stud doesn't consistently work well unless
you have unusually good aim and control. You could hammer on a smooth-
faced steel block placed over them. As mentioned an arbor press or
milling vise is better. You can pull them in part way with a nut to
keep them from shifting in the press fixture.
The common fixture is a drilled steel block attached to the arbor
**Something similar I do: **
I set alignment pins in molds now by drilling the press fit and the slip fit
in both plates and using the slip fit side as a guide for starting the pin.
Then I just smack it with a hammer to start the pin. (Usually 18-8 into
6061) Since I cut the molds on the little CNC mill I usually cut a short
pilot hole and chamfer before throwing them on the drill press, but I could
drill and chamfer on the mill quickly enough if I had a different machine
with a tool changer. For me its faster and accurate enough to hand drill
(on the press) those features. ** A possible solution for what you do: **
I think for a threaded stud (I assume half threaded and half press fit from
your description) I might make a thread on bushing for the threaded half.
Then drill a hole in a piece of plate that is a nice slip fit for the outer
surface of the thread on bushing. Make the bushing longer than the
thickness of the plate. Use a plate substantially thicker than the press
fit portion of the stud. Chamfer the edges of the press fit hole in the
work piece to assure proper starting of the stud, also to prevent ridging
around the pin. Smack, press, or clamp as needed. When the face of the
bushing meets the work piece remove your guide plate, and unthread the
bushing. ** Comments: **
It's a pretty simple concept, but if you like I'll make you a quick sketch.
Refine of course for desired level of precision and accuracy. Variations on
the theme could be used for a stud that is only partially threaded on the
exposed end etc.
If you have multiple studs you might make your guide plate as a template for
all of them instead of just one at a time. Obviously not practical for
multiple studs going into planes at different angles or surfaces at
different levels. Possible though if production numbers are high enough to
justify a special jig.
For a little ease of removal cut a bolt head on your drive bushing. For
work piece protection if necessary pad work piece face with leather or
rubber. Glue to drive bushing maybe? Maybe machine an acetal or HDPE
bushing for the work piece face of the drive bushing?
By drilling and threading your drive bushing all the way through you might
be able to use a set screw from the drive end (hammer side) to set and/or
adjust your drive depth easily.
I fit root nuts & press in studs using a cheap air chisel/air hammer from a
I take a standard chisel and turn down the end in the lathe to suit the
It works really well, very quick and they bind in much better than hitting
with a hammer.
Way Back in the lat 1970s I pressed thousands of 8-32 pem studs into .
1/8" aluminum plate using a drill press in place of an arbor press. It
didn;t require much force - certainly no more than drilling a 1/2"
hole - and it worked fine.
Not turning at all. You can make a tool to put in the chuck that fits
the stud, or if you only have a few to do, you can thread a spacer
onto the stud to protect it. I used a simple tool - a piece of round
stock with a clearance hole for the stud drilled into the center.
For pressing in threaded inserts, I just used a hex bolt chucked in
If you have a slow speed (emphasis on slow) reversible drill press... how
about a threaded rod coupler the size of the stud threads?
Chuck up coupler, thread in stud, press in, reverse off, thread in the next
It should maintain as much accuracy as your drill press has. Wouldn't do it
on mine, but might work great of a decent quality drill press.