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Full thread v. partial thread wood screws.


epsilonGreedy

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I am struggling to find Spax stock for 4x30 and 4x35 countersunk partial thread screws in stainless. Amazon can supply full thread equivalents which has got me thinking what type of fixing jobs require partial v. full thread wood screws?

 

At the start of my build I purchased a full set of 2400 Spax screws supplied in a mini suitcase draw ranging in size from 3.5x16 to 6x120. The 16, 20 and 25mm long screws were full thread and the rest were partial thread.

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I ordered 4000+  (A2 SS, 50mm deck screws)  from Klokow ( as above)   Article number SPAX-0537000500503 , postage 24 Euros.  2 or 3 days (then - might be longer now)

 

Quote

 which has got me thinking what type of fixing jobs require partial v. full thread wood screws?

 

Cladding (my hands won't take the recoil of a nail gun, and the sheepdog goes mental.)

Edited by ToughButterCup
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14 minutes ago, Onoff said:

A mate bought Spax from here. Cheaper than he could in the UK even factoring in shipping:

 

https://www.klokow-gmbh.de/

 

 

Looks good and unlike the Amazon site the parts are sensibly described whereas on Amazon the Spax screw product database must have been setup by someone who has never picked up a screwdriver in their life.

 

The German site also offers "Amazon Pay" which I hope will remove some of the financial risk of dealing with an overseas retailer.

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Full thread screws are convenient for general use but are significantly weaker in shear and bending due to the metal removed to form the helix. Also straight shank screws will pull pieces together (floor boards etc.) while full threads leave any gaps and simple pin the two parts where they are

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11 minutes ago, SteamyTea said:

partial thread is a bolt.

Not in a “wood” screw it’s not ?
 

to pull bits together with full thread requires a clearance hole in the top piece.

Edited by joe90
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4 minutes ago, joe90 said:

to pull bits together with full thread requires a clearance hole in the top piece.

They all do, that is how bolts work.

 

This Screw or Bolt debate has been done before.  It is material independent and is all to do with what is being joined together and why.

 

Bolts need washers as well.

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1 hour ago, SteamyTea said:

It is material independent and is all to do with what is being joined together and why.


I disagree, it is material dependant.  With metal or wood you have bolts and screws, screws have thread the whole length, bolts do not. Both require clearance holes in both pieces (and washers).  With wood you can have full threaded screws or partial threaded screws ,  clearance hole in one or not. To clamp two pieces of wood tightly you need either partial threaded or a clearance hole in the top piece. There are special wood screws made with a different thread pitch near the head specifically for pulling pieces together.

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2 minutes ago, joe90 said:

screws have thread the whole length, bolts do not.

Yes, isn't that what I said.

 

3 minutes ago, joe90 said:

To clamp two pieces of wood tightly you need either partial threaded or a clearance hole in the top piece.

Yes, that is what bolting is.

 

4 minutes ago, joe90 said:

There are special wood screws made with a different thread pitch near the head specifically for pulling pieces together.

Are they screws or bolts, or hybrids.

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There doesn't seem to be a consistent definition on the internet although the fact that a screw has a self tapping thread and a bolt has a machine thread is often mentioned. So the length of thread on the shank seems irrelevant.

 

"Although coach bolts and coach screws are distinct components in their own right, the two do share a number of similarities. The most notable similarity is the head shape, which is domed, or mushroom-shaped, in both instances. Both coach screws and bolts are also best suited for use with wood."

"However, a key difference is that coach screws feature a self-tapping thread. This means that these screws can create their own threads in timber, ensuring a more seamless installation. On the flip side, carriage bolts have a machine thread, meaning that they always need an adequately-sized pilot hole to be drilled into the material before installation."

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When I did engineering in college (back in the dark ages?) we were always taught bolts had a plain section which fitted the thickness of the materials held together and screws were threaded all the way. The difference is  bolts had a bigger diameter plain section than the thread to be a snug fit in the material, wood screws with a plain section is a smaller diameter than the thread.

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20 minutes ago, joe90 said:

When I did engineering in college (back in the dark ages?) we were always taught bolts had a plain section which fitted the thickness of the materials held together and screws were threaded all the way. The difference is  bolts had a bigger diameter plain section than the thread to be a snug fit in the material, wood screws with a plain section is a smaller diameter than the thread.

Just to really liven this thread up....

 

 

Bolts that have the shank threaded are called set screws....???

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This place have thought long and hard about this problem and just call them both:

M12 Hexagon Head Set Screws Bolts, High Tensile Grade 8.8 Galvanised, DIN 933

https://boltworld.co.uk/collections/m6-bolts/products/m12-hexagon-head-set-screws-bolts-high-tensile-grade-8-8-galvanised-din-933?variant=32061282451549

 

At least nobody will be confused now ?

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