Screw types

jyang949 | Posted in General Discussion on September 25, 2009 07:16am

I just read that the shank of a wood screw is always unthreaded at the head end. What are ones that are tapered like a wood screw, but threaded all along the shank?

Janet

Replies

SARGEgrinder47 | Sep 25, 2009 07:20pm | #1
Machine screws.. Spax screws.. ab assortment under other names and head types that are sold at WW supply stores.

Sarge..

Woodworkers' Guild of Georgia
RalphBarker | Sep 25, 2009 07:22pm | #2
There is an amazing array of different types of screws that can be used in wood. You might find it helpful to poke around on a hardware site like McFeely's (http://www.mcfeelys.com/) to get a sense of what is available.
MikeHennessy | Sep 25, 2009 09:18pm | #3
"What are ones that are tapered like a wood screw, but threaded all along the shank?"

Another poster said "machine screws", but those are definately NOT tapered.

Drywall screws?

You may also be thinking of a type of sheet metal screw. See the second type pictured here, tho' they are not really tapered along their whole length:

http://hardwareaisle.thisoldhouse.com/2008/09/screw-universit.html

Then there's this. See No. 5:

http://commons.wikimedia.org/wiki/File:Screw_types.jpg

Now THAT clears it up! They are "wkrêt monta¿owy, ³eb z naciêciem" screws. Of course!

For a dizzying array of info regarding screws/bolts:

http://en.wikipedia.org/wiki/Screw

Edit: The reason the top end of a wood screw is unthreaded is to help allow the screw to pull the held item tightly against the substrate. If it was threaded all the way, there would always tend to be a bit of space between the two parts, since the two pieces would be somewhat threadbound.

Mike Hennessy
Pittsburgh, PA
Everything fits, until you put glue on it.

Edited 9/25/2009 2:22 pm ET by MikeHennessy

SARGEgrinder47 | Sep 26, 2009 01:09am | #4
Opps.. that was me that mentioned machine screws and meant sheet metal. My bad as I was in a hurry to get back to the shop. BTW... I prefer to use all threaded to give more bit in lieu of the wood screw. If you drill a proper pilot hole the pieces will mesh together with no problem what-so-ever.

Have a good week-end Mike...

Sarge..

Woodworkers' Guild of Georgia

MikeHennessy | Sep 26, 2009 05:39pm | #5
"I prefer to use all threaded to give more bit in lieu of the wood screw. If you drill a proper pilot hole the pieces will mesh together with no problem what-so-ever"

Don't let the guys over at breaktime hear you say that! You may even suffer the slings and arrows of <gasp> sarcasm! ;-)

For the OP (since you already know this): If you can clamp the top piece tightly before screwing, no real problem with full threads. But if not, the top piece may not get as tight as you want it unless you either manage to strip the threads in the top piece, or you drill an oversized pilot in the top piece (which should work fine). With a standard wood screw, the non-threaded part of the screw ideally goes all the way through the top piece, thus allowing the screw to simply spin in the top piece and continue to sink and pull the top piece tight as it is driven into the bottom piece. The threads of wood screws are also generally coarser, so you'll generally get a better hold in wood vs. a sheet metal screw. That said, a sheet metal screw should hold just fine for most applications. Mike HennessyPittsburgh, PAEverything fits, until you put glue on it.

SARGEgrinder47 | Sep 26, 2009 08:57pm | #6
I don't have any reason to go over to Breaktime Mike but... I would stand behind the statement as I have been using fully threaded for years and mainly in oak... hickory.. ash.. etc. Sarcasm or no sarcasm... a spade is a spade IMO. ha.. ha.. I doubt very seriously the guys at BT would take the time to drill a proper pilot hole as I mentioned as they have dead-lines to meet and time is money to them?

I would guess (?) most there use battery operated drills to drive them.. the majority of time into softer materials for the most part. So.. I believe we might be comparing apples to oranges in reality. You get into black locust or similar and I can see an advantage the wood screw would have in mating the two pieces but again... with a proper pilot hole (not under-sized) I find fully threaded to have more bite and I haven't noticed gaps when I do use them.

Regards... Sarge..

Woodworkers' Guild of Georgia

MikeHennessy | Sep 26, 2009 10:55pm | #7
"I would guess (?) most there use battery operated drills to drive them.."

Most (tho' not all), me included, wouldn't be caught dead using a drill to drive screws in most circumstances. Drills are for making holes (like those pilot holes!); impact drivers are for driving fasteners. ;-)Mike HennessyPittsburgh, PAEverything fits, until you put glue on it.
nazard | Sep 27, 2009 05:26am | #8
Drills are for making holes (like those pilot holes!); impact drivers are for driving fasteners. ;-)

I once remember watching an old codger hammering screws into a packing crate. He told me "the slots are for taking them out".
Jammersix | Sep 28, 2009 08:54am | #11
Fully threaded screws are for applications other than wood to wood.In my opinion.