Driving sheet-metal screws into 4130

Greetings, all.

I'm restoring a Champ, and have a question about driving screws into a
drilled 4130 tube.

If I drill the proper sized hole, the screws refuse to 'take'; they simply
give up their threads to the harder metal of the tube. If I over-size the
hole, then the screw won't hold diddley (that's a technical term).

Do I just keep driving fresh screws until one finally makes it in? I've
tried both stainless and cad-plated 'pk' types.

Another related question: These screws are going into a structural tube -
the windshield pillar, in this case. The original design from Champion
appears to have been thus. Is there a danger here, other than opening the
tube to moisture and corrosion? I am making an 'extra' hole, by the way.
And, unfortunately, I can't weld it up, since the fabric and interior are
done, and the hole is through the fabric, and right next to the headliner.

Jon B.

"Grandpa B." never.mind wrote in message
...
Greetings, all.

I'm restoring a Champ, and have a question about driving screws into a
drilled 4130 tube.

If I drill the proper sized hole, the screws refuse to 'take'; they simply
give up their threads to the harder metal of the tube. If I over-size the
hole, then the screw won't hold diddley (that's a technical term).

Are you tapping the holes? As in, with a tap and die set (preferably that
is made for working on 4130).

"Jim Carriere" wrote in message
...
"Grandpa B." never.mind wrote in message
...
Greetings, all.

I'm restoring a Champ, and have a question about driving screws into a
drilled 4130 tube.

If I drill the proper sized hole, the screws refuse to 'take'; they
simply
give up their threads to the harder metal of the tube. If I over-size
the
hole, then the screw won't hold diddley (that's a technical term).

Are you tapping the holes? As in, with a tap and die set (preferably that
is made for working on 4130).

Where did he get the screws and what kind are they?

On Fri, 23 Jan 2004 12:05:08 -0500, "Jim Carriere"
wrote:

"Grandpa B." never.mind wrote in message
...
Greetings, all.

I'm restoring a Champ, and have a question about driving screws into a
drilled 4130 tube.

If I drill the proper sized hole, the screws refuse to 'take'; they simply
give up their threads to the harder metal of the tube. If I over-size the
hole, then the screw won't hold diddley (that's a technical term).

Are you tapping the holes? As in, with a tap and die set (preferably that
is made for working on 4130).



He did say "sheet metal screws". You would use machine screws in a
tapped hole of course. The problem is that the tubes he refers to are
pretty thin walled and would not accept much of a real thread. Might
it easier to run PK screws in though.

O-ring

"O-ring Seals" wrote in message
...
On Fri, 23 Jan 2004 12:05:08 -0500, "Jim Carriere"
wrote:

"Grandpa B." never.mind wrote in message
...
Greetings, all.

I'm restoring a Champ, and have a question about driving screws into a
drilled 4130 tube.

If I drill the proper sized hole, the screws refuse to 'take'; they
simply
give up their threads to the harder metal of the tube. If I over-size
the
hole, then the screw won't hold diddley (that's a technical term).

Are you tapping the holes? As in, with a tap and die set (preferably
that
is made for working on 4130).



He did say "sheet metal screws". You would use machine screws in a
tapped hole of course. The problem is that the tubes he refers to are
pretty thin walled and would not accept much of a real thread. Might
it easier to run PK screws in though.


Bob...........

The tube frame for the Emeraude canopy uses rivnuts (metric thread of course
)) which work well. Harbor Freight has a nut rivet kit for $13.00 which
might work for occasional use.

Rich S.
O-ring

On Sun, 1 Feb 2004 14:07:40 -0800, "Rich S."
wrote:



He did say "sheet metal screws". You would use machine screws in a
tapped hole of course. The problem is that the tubes he refers to are
pretty thin walled and would not accept much of a real thread. Might
it easier to run PK screws in though.


Bob...........

The tube frame for the Emeraude canopy uses rivnuts (metric thread of course
)) which work well. Harbor Freight has a nut rivet kit for $13.00 which
might work for occasional use.

Rich S.
O-ring



Rich,

The area where he is placing the screws is in structural fuselage
tubing. I feel that the hole size required for rivnuts might
compromise the integrity of the tubing. He is adding a new set of
holes as it is. Best to get some number sized drill bits ( 1/64" one
way or the other may not work ) and practice on some scrap tubing to
find the one that works.

O-ring

Just a caution on the Harbor Freight rivnut tool. I found the #6 mandrel
included with mine was undersized, and would not engage the threads of
the #6 rivnuts well enough to crimp them. The #8 worked fine*; I haven't
tried the other sizes. Just something to look out for if you're planning on
using #6s.

*By working fine, I mean it pulled some righteous brand-name RivNuts.
The #6 didn't work with either the HF or brand-name ones. A dial
caliper vs a screw checker revealed the undersizing issue. It just pulled
the thread out of the rivnut. Actually, just pulled the crest of the
thread,
since the mandrel didn't reach all the way to full thread depth.

Henry Bibb

Rich S. wrote:

The tube frame for the Emeraude canopy uses rivnuts (metric thread of
course
)) which work well. Harbor Freight has a nut rivet kit for $13.00 which
might work for occasional use.

Rich S.

"O-ring Seals" wrote in message
...

The area where he is placing the screws is in structural fuselage
tubing. I feel that the hole size required for rivnuts might
compromise the integrity of the tubing. He is adding a new set of
holes as it is. Best to get some number sized drill bits ( 1/64" one
way or the other may not work ) and practice on some scrap tubing to
find the one that works.

Gotcha, Bob. Mebbe he just needs one those rare "sheet metal screw" taps???

Rich S.

"Henry Bibb" wrote in message
ink.net...
Just a caution on the Harbor Freight rivnut tool. I found the #6 mandrel
included with mine was undersized, and would not engage the threads of
the #6 rivnuts well enough to crimp them. The #8 worked fine*; I haven't
tried the other sizes. Just something to look out for if you're planning
on
using #6s.

*By working fine, I mean it pulled some righteous brand-name RivNuts.
The #6 didn't work with either the HF or brand-name ones. A dial
caliper vs a screw checker revealed the undersizing issue. It just pulled
the thread out of the rivnut. Actually, just pulled the crest of the
thread,
since the mandrel didn't reach all the way to full thread depth.

I'll watch for that, Henry. I bought one a couple years ago when they were
on sale, but it's still in the package.

Rich S.

On Mon, 2 Feb 2004 17:14:34 -0800, "Rich S."
wrote:

"O-ring Seals" wrote in message
...

The area where he is placing the screws is in structural fuselage
tubing. I feel that the hole size required for rivnuts might
compromise the integrity of the tubing. He is adding a new set of
holes as it is. Best to get some number sized drill bits ( 1/64" one
way or the other may not work ) and practice on some scrap tubing to
find the one that works.

Gotcha, Bob. Mebbe he just needs one those rare "sheet metal screw" taps???

Rich S.



Rich,

Now that you mention it, a self-tapping sheet metal screw of some type
might work.

Bob