Since finger tight nuts and carriage bolts do a wonderful job anchoring my
drill press vises, I figured that bolts and threaded inserts would be great
way to anchor my plywood drill press table.

I'd like to use blind holes to keep the top smooth.

I bought some 3/8-24 threaded inserts from McFeely's with a 3/4" OD and 5/8"
root diameter.

It seemed logical to treat them like screws, and bore 5/8" holes of suitable
depth with a forstner bit.

Unfortunately when I start threading the inserts in, the plywood starts
to pull apart. Can I make the inserts work, or do I need to do something
else?


--
a href="http://www.poohsticks.org/drew/"Home Page/a
In 1913 the inflation adjusted (in 2003 dollars) exemption for single people
was $54,567, married couples' exemption $72,756, the next $363,783 was taxed
at 1%, and earnings over $9,094,578 were taxed at the top rate of 7%.

Drew Eckhardt wrote:

....
I bought some 3/8-24 threaded inserts from McFeely's with a 3/4" OD and 5/8"
root diameter.

....
Unfortunately when I start threading the inserts in, the plywood starts
to pull apart. Can I make the inserts work, or do I need to do something
else?

Tee-nuts, probably more suited than inserts...

Nope, not appropriate for plywood

Use a t-nut instead to get a threaded insert


John


On Tue, 31 May 2005 13:03:39 -0600, (Drew
Eckhardt) wrote:

Since finger tight nuts and carriage bolts do a wonderful job anchoring my
drill press vises, I figured that bolts and threaded inserts would be great
way to anchor my plywood drill press table.

I'd like to use blind holes to keep the top smooth.

I bought some 3/8-24 threaded inserts from McFeely's with a 3/4" OD and 5/8"
root diameter.

It seemed logical to treat them like screws, and bore 5/8" holes of suitable
depth with a forstner bit.

Unfortunately when I start threading the inserts in, the plywood starts
to pull apart. Can I make the inserts work, or do I need to do something
else?

Drew:

I have used threaded inserts in plywood (hardwood veneer and baltic birch)
with great success (at least for my requirements). The key is to chamfer the
hole where the insert is screwed in. Clamping a guide block to the workpiece
while installing the insert can also keep the veneer from lifting. Note that
a threaed insert in plywood relies somewhat on the strength of the glue that
holds everything together, unlike installing an insert in solid lumber where
the density of the material is the primary contributor to joint strength.

If you need additional advice, or consultation, feel free to call Darin
Lawrence, my technical director, at 1-800-443-7937.

HTH,

Jim Ray, President
McFeely's Square Drive Screws,
www.mcfeelys.com
Festool ISA since 2001

"Drew Eckhardt" wrote in message
...
Since finger tight nuts and carriage bolts do a wonderful job anchoring my
drill press vises, I figured that bolts and threaded inserts would be
great
way to anchor my plywood drill press table.

I'd like to use blind holes to keep the top smooth.

I bought some 3/8-24 threaded inserts from McFeely's with a 3/4" OD and
5/8"
root diameter.

It seemed logical to treat them like screws, and bore 5/8" holes of
suitable
depth with a forstner bit.

Unfortunately when I start threading the inserts in, the plywood starts
to pull apart. Can I make the inserts work, or do I need to do something
else?


--
a href="http://www.poohsticks.org/drew/"Home Page/a
In 1913 the inflation adjusted (in 2003 dollars) exemption for single
people
was $54,567, married couples' exemption $72,756, the next $363,783 was
taxed
at 1%, and earnings over $9,094,578 were taxed at the top rate of 7%.

On Tue, 31 May 2005 13:03:39 -0600, (Drew
Eckhardt) wrote:

Since finger tight nuts and carriage bolts do a wonderful job anchoring my
drill press vises, I figured that bolts and threaded inserts would be great
way to anchor my plywood drill press table.

I'd like to use blind holes to keep the top smooth.

I bought some 3/8-24 threaded inserts from McFeely's with a 3/4" OD and 5/8"
root diameter.

It seemed logical to treat them like screws, and bore 5/8" holes of suitable
depth with a forstner bit.

Unfortunately when I start threading the inserts in, the plywood starts
to pull apart. Can I make the inserts work, or do I need to do something
else?


Pay particular attention to the bore size called out by the
manufacturer.

On plywood, use an oversize drill bit to create a chamfered opening to
the hole.

This will help you with tearout.



Tom Watson - WoodDorker
tjwatson1ATcomcastDOTnet (email)
http://home.comcast.net/~tjwatson1/ (website)

Duane Bozarth wrote in
:

Drew Eckhardt wrote:

...
I bought some 3/8-24 threaded inserts from McFeely's with a 3/4" OD
and 5/8" root diameter.

...
Unfortunately when I start threading the inserts in, the plywood
starts to pull apart. Can I make the inserts work, or do I need to
do something else?

Tee-nuts, probably more suited than inserts...

Doesn't a t-nut need to compress from the opposite side of the material? I
always figured them for a thru fastener.

It wouldn't even be the first time today if I were wrong, however.

Patriarch

Patriarch wrote:

Duane Bozarth wrote in
:

Drew Eckhardt wrote:

...
I bought some 3/8-24 threaded inserts from McFeely's with a 3/4" OD
and 5/8" root diameter.

...
Unfortunately when I start threading the inserts in, the plywood
starts to pull apart. Can I make the inserts work, or do I need to
do something else?

Tee-nuts, probably more suited than inserts...

Doesn't a t-nut need to compress from the opposite side of the material? I
always figured them for a thru fastener.

It wouldn't even be the first time today if I were wrong, however.

No, they are...maybe they won't work well for the OP, I couldn't decide
on his geometry.

On Tue, 31 May 2005 19:13:18 -0500, Patriarch
wrote:


Doesn't a t-nut need to compress from the opposite side of the material? I
always figured them for a thru fastener.

It wouldn't even be the first time today if I were wrong, however.

Patriarch


You ain't wrong.

If the ply starts to delaminate, either the root diameter is wrong, or
the ply has poor lamination strength.

The workaround is to drill a piece of mdf or somesuch, oversized a bit
for the hole, and clamp it to the ply while you're putting the insert.

If the root diameter is correctly drilled, I'd worry about the ply
that I was using.



Tom Watson - WoodDorker
tjwatson1ATcomcastDOTnet (email)
http://home.comcast.net/~tjwatson1/ (website)

I have had good success using threaded inserts in Baltic Birch for exactly
the same type of application of on and off again type fixtures.

Knothead

Take a one inch bit and bore out the plywood, maybe a 64th undersized
(63/64") if you can find it. Then take a slice of a 1" dowel and glue
and hammer it into the hole. Plane it flush, then bore the hole for
the insert in dowel.

John writes:

Nope, not appropriate for plywood

Use a t-nut instead to get a threaded insert

I use threaded inserts with baltic birch plywood just fine.

I build large rockets (20 feet tall and 12" diameter) and the launch
guides are attached via threaded inserts in BB plywood. The rocket weighs
130 lbs and last year the rocket was in a vertical postion for over an
hour while being buffetted by 20 MPH winds.

None of the threaded inserts pulled out. I would suspect that standard
plywood would fare much worse due to the thick veneer layers.

Brian Elfert