Spax Screws

Do these things really work? I'm interested in knowing whether I could drive them through the face of 1/2" plywood into the edge of

3/4" plywood without splitting. (Assuming I'm reasonably near to the middle of the edge.)

JP

Reply to
Jay Pique
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I've done that. I like Spax screws. Of course you do have to use the right size. A #12 X 2 1/2" may split it. Ed

Reply to
Edwin Pawlowski

Jay:

Yes, Spax screws really do work. They come complete with threads and everything! ;-)

However, more to your question, and following my rather flipant answer, the real issue when using a screw as you propose is the fact that all screws act as wedges. Splitting can be avoided by removing the material that the screw shank would ordinarily displace (drilling a pilot hole), or by placing the screw far enough away from the edge of the board that the material's interfiber strength is not exceeded. Small screws obviously displace less material, so they tend to cause fewer splitting problems.

Spax screws, as well as the many variations of sawtooth screws on the market (including our own ProMaster screws) all work basically the same way - the saw teeth are designed to cut the fibers as the screw is driven. This does little to reduce the material displaced by the screw shank. It does seem to make the screw drive more easily, and it does seem to reduce splitting under certain conditions.

Unfortunately, the edge grain of plywood is quite different than the face or edge grain of solid lumber. Plywood is easily de-laminated, and because of the cross grain laminations, a screw is threading itself into both edge grain and end grain. Thus, plywood is especially suscepitble to splitting when a screw is drive into edge grain.

There are several solutions to this:

  1. Predrill the hole in the edge plywood edge grain. Use a bit slightly smaller than the screw shank, and use an extra-long screw to maximize the thread contact. Also, unless using our ProMax screws with their Optimized Thread Length, it is a good idea to drill a clearance hole in the first board so that the screw can not cross thread.
  2. Excavate a recess in the plywood edge grain into which you glue a block of wood, which you can then drive a screw into using your preferred method.
  3. Drill a 1" to 1-1/2" diameter hole in the face of the plywood, about 3/4" to 1" from the edge, but only about 3/4 of the way through the plywood. Then glue a matching sized dowel into the hole (make sure you orient the grain so that the face grain is parallel to the edge of the plywood). Drive the screw so that it threads into the dowel for a very strong joint.

Hope a bit of this helps.

Jim Ray, President McFeely's Square Drive Screws

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Reply to
Jim

Not wanting to sound flippant, but wouldn't "Square Drive" be more accurately referred to as "Robertson"?

Or does that violate a trademark of some sort?

I have built furniture for family in the US (I'm in Canada), and I always use the Robertson (Square Drive) screws. They had to fix something their son broke, and I had to send them a screwdriver to do it because they couldn't buy a Robertson where they live!!

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Reply to
Robert Wein

I doubt that you will find a more qualified guy to respond than Jim but..

P.L. robertson invented the them in 1908.

The namesake company is still in business:

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suspect that Robertson is a trademark of the Robertson screw company, not unlike "Kleenex" is to "facial tissue"

FWIW, Mcfeeley's site (Jim's) does cite the inventor

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Reply to
Stephen M

Yeah - I was skeptical but the lil' buggers are nice. I keep a box of #8 by

1 1/2" around. And I don't bother with pilot holes.

Easy..

Hard... Don't think Spax brings anything to the table when it comes to screwing into the edge of anything. Think you'd still be doing pilot holes.

Reply to
mttt
[snip]

Jim, you are way to helpful to be real. I just wanted to let you know that your knowledge and contributions to this group are greatly appreciated.

Tim Douglass

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Reply to
Tim Douglass

ISTR that someone on this ng said that square drive are straight sided whereas Robertson are slightly tapered.

Is this true? I know the Robertson are tapered and like them that way (easier to put the screwdriver tip in), but know nothing about the US Square Drive brand.

Mike - who always buys Robertson wood screws.

PS - Pre NAFTA, all (almost all?) electrical stuff in Canada used Robertson or Robertson/Slot screw heads. Now a lot is Philips or Philips/Slot, which sucks - you can't get a Philips to stay on the end of the screwdriver and it takes two hands to put in a screw or bolt!

Reply to
Michael Daly

Hi -

You're correct - it's a trademark. You can't use "Robertson", unless you buy the product from Robertson...

Cheers -

Rob Lee

Reply to
Robin Lee

Michael:

This is one I have answered before, but I'm just too lazy to search for my prior postings, so here goes again. You can probably Google it though.

The Square Drive recess is an Industrial Fastener Institute (IFI) standard, and calls for 1.5 degree taper to each face of the recess (3 degrees total). To my knowledge, no manufacturer purposely makes the recess non-compliant. One of the major obstacles the inventory overcame was developing a basically parallel sided recess that was manufacturable. Providing a slight taper to the recess allowed for easy removal of the "punch" that forms the recess. The reason for the taper is thus one of manufacturability, not trademark (and of course, the patents expired long ago).

The term "Square Drive" is one that we have been using for almost twenty years, not because we were trying to establish a new standard or anything, but because we wanted a descriptive name for the recess when trying to promote them to woodworkers in the USA. There were already enough "vanity" recess names (Frearson, Phillips, Reed-Prince, etc) that meant nothing to the user not having prior knowledge of the recess shape (quick now, what is a Frearson recess?). Identifying the screws as "Square Drive" in our catalog helped the woodworker know what the screws looked like without research. I can't tell you that we coined the name "Square Drive", but the screws certainly were not in common use 20 years ago.

Your comment about the pre-NAFTA Robertson recess use on electrical parts is interesting. Most of the electrical stuff I work on now has Robertson recess screws, and much of it is of Canadian manufacture. Please don't tell me that the US market is starting to see the light just as the Canadians succumb to the sometimes illogical demands of the US market. Ironic, and rather tragic.

HTH

Jim Ray, President McFeely's Square Drive Screws

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Reply to
Jim
    • P
  • Vote on answer
  • posted

Where's Mr. Phillips when you need him?

Jon~

Reply to
P©WÉ®T©©LMAN

I'm most interested in the ability to dispense with the drilling of pilot holes. Would anyone care to do a bit of experimenting with a few 1.5 inch sixes and eights to see if the splitting issue is significant? Hmmm...maybe I should just break out the crowbar and buy a few myself!

JP

********************* Now accepting donations of Spax Screws.
Reply to
Jay Pique

There are two versions... IIRC, Robertson is tapered slightly while square drive is not.

djb

Reply to
Dave Balderstone

Dave:

Actually, a popular myth. Not sure how it got started, but it sure does make the rounds. See my response to Michael Daly above.

Jim Ray, President McFeely's Square Drive Screws

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Reply to
Jim

"Robin Lee" wrote in news:JDAfc.27201$ snipped-for-privacy@news20.bellglobal.com:

I find that to be "a good thing". I don't know how many "square drive" tools I have thrown away over the years, but I still have every screwdriver with the Robertson name on it. That name on a tool (or a box of screws) really means something.

Reply to
Murray Peterson

Okay, but are there not two versions, one tapered, one not?

djb

Reply to
Dave Balderstone

Dave:

I can't say that every Square Drive screw ever made has been made according to the IFI standard, but those that are made to the standard have tapered sides. As I mentioned in my earlier posting, parallel sides make the screws almost impossible to manufacture because the punch that forms the recess becomes difficult (if not impossible) to extract. The slight taper provided in the IFI standard is virtually imperceptible, it's the key to Robertson's original patents, and it's the thing that makes the recess both functional (stick fit) and manufacturable. There are two versions only if the manufacturer doesn't know what the heck they are doing. I guess when it comes right down to it, there may be two versions: one that works and one that doesn't! ;-)

So friends, that is why it is important to deal with a supplier that stands behind their product. (And for what its worth, I can assure you, our Square Drive Screws have recesses with tapered sides!!!)

Jim Ray, President McFeely's Square Drive Screws

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Reply to
Jim

Maybe not in common use but square drive screws as we called them were certainly used many years ago. In high school in the mid 60's I worked at a trailer & camper mfgr, Fleetcraft in DT Seattle and we used them for that. The only problem really was the bit to drive them in. It wore out (rounded end) very quickly unless your air drill was exactly parallel to the screw, which took a few extra seconds. Since time was money you had to work fast and that made for a lot of worn out tips which you had to buy, they were not supplied at company cost. Of course the worn out bit meant a worn out screw head too so buyer beware

- back then.

Jim wrote:

Reply to
Grandpa

Grandpa:

I probably should have been more specific when I said they were not in common use. Industry was starting to adopt them, especially the mobile home and recreational vehicle industry. Adoption was also fairly regional for some reason - probably word of mouth or cross-pollinatio as employees moved from one company to another. What I was trying to say was that they were not in common use by recreational woodworkers, even though there were in fact a few mail order catalogs selling asmall selections, even back then.

I really didn't mean to imply that they were unknown - heck, they were invented in 1908 in Canada, and have been the preferred recess type there for many many years. (In fact, the Canadian magazine "TODAY" initiated a subscriber survey in 1982, which resulted in the Robertson screw receiving the number one ranking of the best things about Canada. It even beat out the newfoundland dog, and the Canadian flag!

Jim Ray, President McFeely's Square Drive Screws

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Reply to
Jim

I'm a confirmed McFeely's man now - 'cept for that one box of Spax (?spaxes? spaxies?).

C'mon sing along with me! "I'm a McFeely Man now, now. I'm a McFeely Man now, now. I'm a McFeely Man now, now. I'm a McFeely Man now, now.

Bangity, bang. Bangity, bang.

I'm a McFeely Man now, now!"

Reply to
mttt

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