C1 Clutch Head Screws - Why?

[Peter M.]

Fascinated by the use of Clutch Head screws on various parts of my 61 Corvette - extreme examples ... the grab-bar (eight of them seemingly for a higher torque application, headlight bucket attachment screws to the front fenders (seemingly light torque application).

CURIOUS
since Phillips head screw was a prevalent fastener throughout the C1's - why did GM select clutch Head screw type in certain areas and not in others - seems like it adds complexity to the assembly process?? Are they easier to use than Phillips in manufacture back in the early 60's? I don't recall clutch head screws on my 1966?

DEFINITION FOUND
"Standard Clutch", resembles a bow tie, with a small circular "knot" at the center. These were common in GM automobiles, trucks and buses of the 1940s and 1950s. Type G resembles a butterfly, and lacks the center "knot".[48] This type of screw head is commonly used in the manufacture of mobile homes and recreational vehicles.[49] The clutch head was designed to be driven with a flat-blade screwdriver as well as a clutch driver."

[Harry S.]

Re: C1 Clutch Head Screws - Why?

They were used on my 63 to attach the Steering Wheel.

[David H.]

Re: C1 Clutch Head Screws - Why?

Peter

Perhaps clutch head is easier to torque to spec?

Dave

[Gary C.]

Re: C1 Clutch Head Screws - Why?

Peter,

Screw application for C1's - Clutch Heads go into metal and Phillips go into fiberglass.

Gary
....

[Michael G.]

[Chris H.]

Re: C1 Clutch Head Screws - Why?

I’ve often wondered the same thing. I’ve wrestled with clutch head screws on Holley metering plates.

[Dan D.]

Re: C1 Clutch Head Screws - Why?

I figured out why they were called "Clutch Head".

They Slip!!!

Dannnnn

[Bill M.]

Re: C1 Clutch Head Screws - Why?

Clutch head screw heads do not strip out as easy as Phillips head screws when using a power driver.

[Dan D.]

Re: C1 Clutch Head Screws - Why?

Phillips head screws cam out. Power drivers help the cam out/ strip out problem on all screw/bolt head designs.

Dannnn

[Leo G.]

Re: C1 Clutch Head Screws - Why?

Recently removed the seats from my 61 to recondition the sliders. Found each rear out board fastener that retained the slider to the seat frame to be a clutch head and the remainder standard hex head fasteners. It’s obvious that Bubba had been there prior to me. Can anyone tell me if the arrangement I found is original or please provide the proper type of fasteners that we’re installed when the seats were assembled.

Thanks to all who contribute and share their knowledge and experience.

Leo

[Michael G.]

[Dan D.]

Re: C1 Clutch Head Screws - Why?

Dan, I’m not sure what you meant by “help”, please edumacate me…

Mike, nothing will guarantee that 'anything' wont cam out. The power driver gives you three different ways to improve (help) your chances is all.

First, the power tool is larger and allows you to put both hands on it to apply more pressure, and you can devote all your energy to keeping pressure on it and not having to devote energy to turning the handle as well.

Second, use a tip that fits the screw head good and tight. A screwdriver may or may not be worn, or fit well even if it is not worn. Power tips are hard, easily replaceable, and you can easily pick a new one, or one that fits better.

Third, use a drill with a clutch/hammer. Set it so the hammer bypasses before it tries to cam. The hammer puts high torque momentarily on the bit, but releases it before it before it cams. And the shock it creates will often break free frozen metal joints as well.

Whatever you do, do not let it cam out. That will wear the head and make it all the easier to cam after that. If using a screwdriver and you feel the screwdriver trying to lift up when attempting to turn it, then stop. You will only make it worse if it slips.

I have been able to remove lots of screws using a battery drill, screws that I could not get out using a screwdriver. For stubborn screws, first squirt it with penetrating oil and let it soak for a while. That sometimes helps. Cold spray is also a possibility that sometimes will work. The next best thing to do is get vice grips on the head, if you can get at it. After that is to use heat, if that is a possibility, as long as the heat will not damage something nearby. The last and final fight is to drill it out.

The above pertains mostly to Phillips head screws. I have a set of clutch head screwdrivers, none of which fit tight in clutch head screws. I have never seen clutch tips for power tools, don't know if they even exist. But I do know that my set of clutch head screwdrivers do not fit well with any of the clutch screws used in my C1.

If someone wants to add to this, by all means do it. This is a common problem with old cars (old anything), and with Corvettes, fiberglass often rules out the use heat.

Dannnn

[Mark F.]

Re: C1 Clutch Head Screws - Why?

...If someone wants to add to this, by all means do it...Dannnn

I remember clutch head screws in several locations on my '49/'50 hybrid Chevy 2-door coupe...

This weblink talks about some of the same things you mention, Dan...and also states GM recognized that Phillips head screws had some deficiencies compared to clutch head screws...I thought it was an interesting read...

http://progress-is-fine.blogspot.com/2016/01/clutch-head-screwdrivers.html