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My 51 GMC 1/2 ton has some wierd shaped screws holding some parts together like voltage reg, fuse block, fenders, where can I find the tool to use on these and what type of screw is that??
Thanks !!!

"Clutch head"

http://www.classicparts.com/1947-66-Clutch-Head-Screwdriver-Set/productinfo/98-001/

Great, thanks for the link to !!!!

Also try http://www.mcmaster.com/ page 2773.

I always wondered why clutch head screws were used. Were they part of a mechanised screwdriving machine of some sort?

They seem to hsve been a dead end in the world of screwdom.

The clutch head screws were actually used at least through the 1970's, maybe later. When I worked at a Chevrolet dealer in the late 70's-early 80's I had a late 70's Chevrolet custom van that I had to replace a quarter panel on. The rear floor was carpeted & stapled to plywood,and the plywood was screwed to the van floor with clutch head screws. I had no idea what they were and one of the older bodyman in the shop had a set of clutch head drivers he let me use.

Back in the fifties most mechanics had a set of clutch-head screw drivers, as most GM cars had some of the screws, as 51 GMC 100 discovered. At the time, I could never get one of the old-timers to tell me why. They seem to have been used on tractors, also.

Hoyt

UNITED SCREW AND BOLT CORPORATION

Clutch Head Screw - for lower cost, efficiency, speed, and safety

Now that is an interesting ad Tim, where do you come up with this stuff? That's the first time I've seen that a flat blade screwdriver will work in the clutch head slots. And that sure answers the age-old question about why they ever used them in the first place.
Sure wish United Screw and Bolt Co. was still in business and producing the screws and tools.
Denny Graham
Sandwich, IL

Denny,

I use flat-head blades all the time with clutch-head bolts, even though I have various sets of clutch head drivers and bit-heads.

The interesting thing about clutch heads is the self-centering aspect of the head. This characteristic is like a Phillips head, but the clutch head has a much more positive "feel" and a stronger "grip" than a Phillips. Good for efficient assembly lines - human assemblers when our trucks were built.

By the way, I get a kick out of people who say they dislike the clutch head bolts because they rust so badly and are so hard to remove. That is foolishness - any steel bolt that sits on our old trucks for 40-70 years is going to be quite rusted (unless the truck has lived in an arid environment). It just so happens that most of our bolt heads are clutch head; they are rusted; they are therefore hard to remove. Do not blame this on the clutch head.

Tim

If you buy one of the cheap security screwdriver bit sets they have three different sizes of bits that will work on clutch head screws. I got mine at harbor freight for 7.99 on sale

Early on I noticed that the clutch head tools fit very sloppy in the original clutch head screws on my truck. I just thought it might be because the slots were wrung out by previous removal and installation.
But being the curious type that I am and a nit picker on top of that I've noticed some little details that stand out when I look at the original advertisement from “UNITED SCREW AND BOLT CORPORATION” that Tim posted. The reproduction screws and screw drivers aren’t the same shape as the originals.
The screws that are on that "tractor" John Deere site really don't have the original hour glass shape and looking at reproduction screws that I've gotten from several of our vendors the same thing hold true with their screws. Also all of the drivers sold today are also wrong, whether they are those sets of four screwdriver handle bits or the individual hex drive bits that McMaster sells or the SnapOn and hardware store square drive choices. None of them have the original shape. For ease of manufacturing all of the drivers today are simply cut using standard end mills, which gives them a butterfly/bowtie shape. If you have a mill you can duplicate this very easily, I’ve made a couple my self.
The original shape is perfectly clear in Tim’s advertisement, there is a large outer diameter and a small inner pilot diameter and the straight lines. These lines are very crisp and will defined in the original screws. The matching drivers are cut using a form tool not an end mill, which is also quite clear when you look at the end of the machine cut on the bit.
As the literature states, all of this gives a positive “lock on” of the screw and driver which I have yet to see with any of the reproduction screws or drivers.
So I guess this explains why this is just one more of those poorly executed attempts at reproducing an original part or tool.
Oh if I only had Jay Leno’s money and could afford to design and manufacture some decent American Made high quality reproductions!

Denny Graham
Sandwich, IL

I for one am glad GM did away with the clutchhead screws.I have replaced most of mine with regular 6 point socket head bolts.One type screw I have started using in my woodworking shop are the Mc Feeley square head screws. You can really put the torque to them and the heads will not strip out like the phillips and slotted head screws.

I think your missing the point Dale, a lot of us here are doing restorations. The object isn't just simply to keep them running, it's to restore them to their original factory condition and many like me are quite particular about using the original style fasteners also.
The original clutch head screws and drivers fit snuggly and the screws did not cam out or fall off the driver, that's why they worked so well on the production lines. The reprocuction fasteners and drivers are really not up to snuff.
Denny Graham
Sandwich, IL

Dale - those "square head" screws are actually Robertson screws, invented by a Canadian and commonly used up here for ages, much better than clutch for hanging on the driver, and all I use for anything

also GM changed the clutch heads, not the repro guys, my 57 and 58 both had the same clutch heads as the currently available drivers, bowtied

Bill

I still have some of the clutch head screw drivers I bought 50 years ago. They look like the ones in the ad. I keep them in my tool box at home because they can't use them at the shop any way. If remove something like a rear fender on a 50's, I try to save the bolts. Before I ever start, I spray some P oil on the threads usually a day in advance. Before I start twisting, I rattle them a little with a needle scaler. This cleans out the hole for the bit and rattles the rust out of the threads. I'm not into show vehicles, but they just don't look right with hex cap screws where clutch head belong.

No I did not miss the point. I stated that I was glad that GM stopped using them.As for me I replace them with something better.I am not into restoring something back to that much originality.If i were my 55 would have a boat anchor six for power and also my 65.Whereas my 55 has an -ss kicking built up 350 in it, and my 65 is powered by a 500 cu.in. Caddy.Just the way I like em.No offense to you guys who want to retain the original power,but this old guy likes a little get up and go.

red58 I have no idea who first started making the square head screws,but I buy mine from McFeeleys.And I sure enjoy using them.If a Canadian invented them ,my hat is off to him.

Don’t worry Dale, you’ll grow out of that “[censored] kickin’” phase of life as you grow older. Ones ego along with other things tends to shrink with age. (Hope you understand that I’m just pullin your leg Dale, there really is room for the hot rodders and purists in my world).

Hey Bill, take a look at this and see what you think! It’s hard to describe it in words maybe this illustration will help show the difference I was trying to bring out.
http://rides.webshots.com/photo/2605717300098611668cfIpSt
More information from Chevrolet: http://rides.webshots.com/photo/2333611280098611668mpFiEn
The new screws aren’t broached with the offset OD centerline that gives them the “Lock-On” feature. Plus you can clearly see the difference in the cross sectional shape of the reproduction drivers.
Denny Graham
Sandwich, IL

Denny,at 71 yrs. of age I havent grown out of the speed thing. I have my trucks running just the way I like them.However they are treated very good,and I drive them very carefully. Then there are the times when some young punk pulls up beside me at a traffic light and revs up that POS 4 cyl car with a tin can muffler on it and wants to race when the light changes. I always have fun leaving them sitting in the dust.Nothing like a nice well tuned V/8 exiting thru headers and a nice set of Flowmasters,and moving on down the road.I dont see that ever changing with me.

Like I said, with a little luck ya might grow out of it!
Oh I suppose there are times when I wish I could get a little more out of my 93hp 216. But I just kind of smile as I creep away, and in fact I'm begining to enjoy slowing down some finlly.
In my younger days I drove dragsters, midgets, a little bit of sprint car, flew competition aerobatics with IAC and did a little airshow work in my 320ci 750 lb Pitts special and now it's acually nice to kick back and smell the flowers.

Denny Graham
Sandwich, IL

Hey Denny,thats just part of growing old.I used to be a holy terror on the highway,now I too just drive along at the speed limit and enjoy the scenery.Drove truck for a few years and I hate driving on the freeways. So I usually take the backroads and enjoy life.

Hey Denny,sounds like your getting a little older putting around with that 216.Me too. My daily driver is a 2003 Ford Ranger,4 cyl., 5 speed,its not very fast,but it gets great gas mileage.I drive it all over NE Ohio like an old man.But when I back that 55 out of the shop with that well tuned 350 V/8 ,or the 65 with the 500 Caddy something comes over me.I feel like I am 21 again and terrorizing the highways.Guess its that 350 exiting thru those Flowmasters,or the 500 exiting thru the Turbo mufflers.

Speekin' of back roads I really enjoy that route myself but I can't get that young wife of mine to to slow down and enjoy that kind of a ride. The faster we get there the happier she is, if I remember correctly that's the way she was about...... oh, never mind I shouldn't bring that up, the kids might be listening.

Denny G