Screw Size Usage?

[Kent A Bathurst]

Just occurred to me that I don't really know the criteria for choosing between, say, a #6 wood screw and a #8. My on-hand inventory tends to influence my choice, but that seems rather inelegant. So:

I'm in a situation where I'm going to use your basic Philips flat head wood screw, 1-1/2" long. I have both #6 and #8 from which to choose. I will do the appropriate countersink with a tapered bit [like the Fuller gizmo], and wax the screws.

Is there any what you might call "science" that influences the choice between #6 x 1-1/2" and #8 x 1-1/2"?

In case length plays a role, then same question for 1" and 2".

[George Yetka]

Which one "Feels Right"? I feel 6 is more prone to snapping 8 is the point at which they very rarely break on me. I will use 6 on the shorter sizes in conjunction with glue and get tighten the joint "Enough" to set the glue. Aside from that make sure you pair the countersink appropriately. Beyond 1" I dont use #6. and beyond 1-1/2" I dont think I ever use #8

[Edward Weber]

Length is easy to factor. You typically want 2/3 the thickness in the secondary piece. If there is no limit, twice the length of ht primary piece.
Gauge usually depends on usage, will there be stress on the fastener. Is it being used as a structural fastener or simply holding a panel in place.
Also hardwood vs softwood may change the size of the pilot hole and thread pitch. Finer threads for hardwood, coarse threads for softwood.
You might like this
https://www.rockler.com/learn/wood-screw-buying-guide

[Kent A Bathurst]

Beyond 1" I dont use #6. and beyond 1-1/2" I dont think I ever use #8

You're more conservative than I am. I'll take #6 up to 1-1/2" without a second thought, and #8 to 2". But that's why I asked - to get a sense of proper limits.

[Kent A Bathurst]

Length is easy to factor. You typically want 2/3 the thickness in the secondary piece. If there is no limit, twice the length of ht primary piece.
Gauge usually depends on usage, will there be stress on the fastener. Is it being used as a structural fastener or simply holding a panel in place.
Also hardwood vs softwood may change the size of the pilot hole and thread pitch. Finer threads for hardwood, coarse threads for softwood.


The 2/3 rule was new to me - good, objective guideline - thanks. I think I've generally been under that - more towards just longer than 50/50

I don't tend to have only screws in places that will be subject to significant shear loading, so that issue of stress doesn't concern me too much.

I'm in-process on a couple of end tables where the design leaves short apron tenons into the leg mortises. So I go from the inside through the tenon with a couple screws to reinforce the glue joint. For Arts & Crafts, I might peg the joints, as part of my "amateurish" predilection toward "ridiculously over-decorated joinery".

[George Yetka]

You're more conservative than I am. I'll take #6 up to 1-1/2" without a second thought, and #8 to 2". But that's why I asked - to get a sense of proper limits.


Kent I use screws to guide me. I buy the GRK r4 screws in 1-1/4 up to 2-1/2 they are #8 up to 2-1/2" and at 2-1/2 they have #9 as well I use 9 in the 2-1/2. For 1/2" to 1" I use Mcfeely black screws which are available 6-10. But I have no real knowledge of whats appropriate. I do know I dont like SS screw

[Malcolm McLeod]

A little engineering…??
Screws can fail in 3 ways: 1)shear, 2)pull out(tension), and 3)pull over(tension).
#1 - a side load breaks the shank.
#2 - the thread pulls out of the ‘base’ material.
#3 - the head pulls thru the ‘fastened’ material.

I think a quick Giggle for “screw shear strength” or “screw holding strength” should yield a table of recommended screw size. (You’ll have to estimate/calculate the expected loads.)

Or just grab something that feels ‘right’. And is already in the shop screw cabinet. (My preferred method.)

[Michael Burnside]

Malcolm brings up a good point. Are you picking a screw for something that is going to be structural, hold people, require sheer or pull strength? Or are you building a cabinet or other type of furniture? If it's the former, you better look up the code and make sure you're using the right screw for the job, or in fact, if screws are even allowed. Sometimes nails (or very specific types of screws) are required for their higher sheer strength. I would never assume or go by gut in those situations.

That said, if it's a cabinet or something that won't really see huge forces, hold people, etc., I'm with the "feels right" crew, usually by order of indoor/outdoor, length and diameter.

[Kent A Bathurst]

Kent I use screws to guide me. I buy the GRK r4 screws in 1-1/4 up to 2-1/2 they are #8 up to 2-1/2" and at 2-1/2 they have #9 as well I use 9 in the 2-1/2. For 1/2" to 1" I use Mcfeely black screws which are available 6-10. But I have no real knowledge of whats appropriate. I do know I dont like SS screw

I get it - not familiar with the GRK, but they make part of the decision for you based on product offering. That's actually pretty cool.

Oddly enough, I'm building some stuff for outdoors, so SS screws are the game here. :)

Thanks for the input George.

[Thomas McCurnin]

I'm with you--i reach for Number 6 90% of the time. Number 8 when there is some serious structural issues, and then move to 10-14 for door hinges and Number 10 construction screws with a square head for most serious outdoor stuff that needs to be solid.

[Edward Weber]

I can't/wont recommend a number or length of fastener like others, without first seeing it's application.
Yes there are some basic guidelines you can follow but "it depends" is always part of the equation.
Too many variables to consider.
This is just one selection of screws I have.
507006

[Tom Bain]

I get it - not familiar with the GRK, but they make part of the decision for you based on product offering. That's actually pretty cool.

Oddly enough, I'm building some stuff for outdoors, so SS screws are the game here. :)

Thanks for the input George.

FYI … You probably won’t even find a lot of options for #6 SS screws. Most SS are geared toward decks, siding and such so they tend to start at #7 or #8. However, you can get trim head SS screws if you want to make them less noticeable. I just repaired the soffit of my barn/workshop and used a ton of #7 x 1 5/8 trim heads for that.

[Jim Becker]

The majority of the screws I use for project fasteners are #8 square drive with some #6/#7 trim head square drive thrown in. I buy these from McFeeley's. If I need something longer than 2", since I don't usually need that, it's typical T-25 head construction screws...usually #9.

I avoid Phillips head anytime I can unless I'm hanging drywall. Square/Robertson and T-xx (star) are the only one I pay for unless there's no other choice.

GRK makes excellent fasteners and they are the bee's knees for structural construction needs when using a hammer or a gun isn't practical. (I can't really swing a hammer much due to wrist issues)

[Edward Weber]

FYI … You probably won’t even find a lot of options for #6 SS screws. Most SS are geared toward decks, siding and such so they tend to start at #7 or #8. However, you can get trim head SS screws if you want to make them less noticeable. I just repaired the soffit of my barn/workshop and used a ton of #7 x 1 5/8 trim heads for that.

I get my SS screws and other supplies from Albany County Fasteners

https://www.albanycountyfasteners.com/

They have a wide selection, even in #6
https://www.albanycountyfasteners.com/Category/Screws_And_Bolts?Per_Page=40&Sort_By=bestsellers&f_diameter=%3Cspan%20style%3Ddisplay%3Anone%3B%3E0 40%3C%2Fspan%3E%236

[andy bessette]

In the work I do #8 sees a lot of use. But the job dictates appropriate screw size. And I regularly use #6 through 14, with the occasional #16.

[Kent A Bathurst]

I get my SS screws and other supplies from Albany County Fasteners

https://www.albanycountyfasteners.com/

They have a wide selection, even in #6
https://www.albanycountyfasteners.com/Category/Screws_And_Bolts?Per_Page=40&Sort_By=bestsellers&f_diameter=%3Cspan%20style%3Ddisplay%3Anone%3B%3E0 40%3C%2Fspan%3E%236


Thanks - always looking for a new source.

My SS screws are basic Phillips flat head wood screws. Bolt Depot and McMaster-Carr. Bolt Depot sells any qty, with price breaks. McM-C sells quantities like 25-50-100, depending on the item. In quantity, McM tends to win the "delivered ptice" game.

[Kent A Bathurst]

I can't/wont recommend a number or length of fastener like others, without first seeing it's application.
Yes there are some basic guidelines you can follow but "it depends" is always part of the equation.
Too many variables to consider.
This is just one selection of screws I have.
507006

OK - tell me about the containers - size and source?

[Lee Schierer]

Typically, I use #8 screws for assembly purposes. Length depends upon the thickness of the piece being attached. The smooth shank should gon most of the way through the piece being attached. You can use full threaded screws is you first drill a clearance size pilot hole in the piece being attached. With the decline in quality of the typical zinc plated wood screws in the big box and most hardware stores, I've switched over to SPax screws in # 8 and #9. The torx head drives better and allows removal if needed.

[Alan Lightstone]

I mostly use #8 square/Robertson drive screws, like Jim, but also use quite a few #10 square drive. I try to avoid Phillips drive screws like the plague. I used to buy everything from McFeely's but they've not had a number of #6 square drive screws lately that I've needed. So those I've gotten elsewhere. And yes, for construction, the GRX fasteners are great, but Home Depot is often out of the size I need. Lots of inventory of the other sizes, so that could just be me.

[andy bessette]

The screws I use most are stainless flat-head Phillips sheet metal screws. Also use a fair amount of pan-headsfor other purposes.

[Jim Becker]

Interestingly, Alan, when I first bought screws for my then new to me first big shop, I bought a whole bunch of #10 screws because I "assumed" that was the right size for a lot of woodworking tasks. While I do use them when appropriate, I also have a LOT of them left because of that "assumption". LOL I've restocked my most used #8 screws multiple times over the years, but have never bought another quantity of #10 since about 2000.

[Edward Weber]

OK - tell me about the containers - size and source?

They were from Gatorade drink mix.
They were built overkill for holding drink mix powder. I don't think they're used anymore, everything has gone to sensible packaging, like pouches. I've been using them for 20 years or more.

[Kent A Bathurst]

They were from Gatorade drink mix.
They were built overkill for holding drink mix powder. I don't think they're used anymore, everything has gone to sensible packaging, like pouches. I've been using them for 20 years or more.


Count me out. Thanks, though

[andy bessette]

Best way to store/organize fasteners is in these compartmented boxes available at McMaster-Carr. I use the extremely heavy duty, large, yellow, polypropylene #4629T27. Easy to store all common lengths of #6, 8, 10. Separate boxes are used for organizing hex nuts, washers, machine screws (of various head styles) etc.

https://www.mcmaster.com/products/organizers/chemical-resistant-compartmented-boxes-7/?s=plastic+organizers

[Rich Engelhardt]

Normally I use #4 for anything under 1/2" - #6 for anything 1/2" to 3/4" - #8 for anything 3/4" to 1 1/2" - #6 for hanging anything on a wall and #9 Timbermate/Spax/GRK "truss-head" for mid to light-heavy duty.
Once in a while I use lags. Not too often though since screws like Timbermate & Spax claim to be as strong as lags, but, are a lot easier to use with an impact driver instead of putting them in by hand with a socket wrench.

That gets outside the general shop though...


I did recently pick up some GRK #8 "Trim screws"..they are..interesting. The jury is still out on them.

[Kent A Bathurst]

Best way to store/organize fasteners is in these compartmented boxes available at McMaster-Carr. I use the extremely heavy duty, large, yellow, polypropylene #4629T27. Easy to store all common lengths of #6, 8, 10. Separate boxes are used for organizing hex nuts, washers, machine screws (of various head styles) etc.

https://www.mcmaster.com/products/organizers/chemical-resistant-compartmented-boxes-7/?s=plastic+organizers

I'm there for my "overflow" items in the closet, except I use fishing tackle boxes. Same deal - works great.

[andy bessette]

I'm there for my "overflow" items in the closet, except I use fishing tackle boxes. Same deal - works great.

The beauty in these fastener kits is that you have the entire selection right there in front of you when you need them. And can see at a glance when the compartments need refilling. Especially helpful on jobs away from the shop.

[Edward Weber]

Best way to store/organize fasteners is in these compartmented boxes available at McMaster-Carr. I use the extremely heavy duty, large, yellow, polypropylene #4629T27. Easy to store all common lengths of #6, 8, 10. Separate boxes are used for organizing hex nuts, washers, machine screws (of various head styles) etc.

https://www.mcmaster.com/products/organizers/chemical-resistant-compartmented-boxes-7/?s=plastic+organizers



Well, I won't argue what's the Best Way, I just use what I can easily afford and does the job.
This is just small parts/hardware and misc item storage, which is about a third of what I have in containers like this. I couldn't afford the McMaster-Carr boxes for the number I have.
I used to use Plano, then switched to HF. I know they're not as high quality as the ones from McMC but they do the job well enough.
507024

[Kent A Bathurst]

The beauty in these fastener kits is that you have the entire selection right there in front of you when you need them. And can see at a glance when the compartments need refilling. Especially helpful on jobs away from the shop.

Gotcha. Sitting at my bench in the top drawer is this selection. The most common boxes are 2.5" x 3.75" x 1". The others are what McM-C sent the screws in. Blue Tape = SS. Drive style is drawn on some boxes, so I know which bit insert to grab from lower right gizmo set. Drill and impact driver are in next drawer down.

Stuff who's frequency doesn't warrant a spot "front and center" is in the tackle boxes in the storage closet that's right over there where I'm pointing.

I don't travel for work, but if I did I would definitely set things up as you have described. Makes perfect sense.

507025

[Ron Selzer]

I keep screws in the box they come in, tape a screw to the lid, so I can see what is in the box this is at home
keep screws in Durham 099-95 and other models at work

[Ron Citerone]

As others have said, there are lots of variables to picking screw size. I mostly build solid wood furniture and #8 is my size for most applications. #6 for attaching plywood backs. #10 for attaching solid tops and assembling multiple part furniture e.g. chest on chest dresser. Can’t back it up with engineering, just what has worked for me.

P.S. I have become more and more particular about counterboring/countersinking/clearance holes/pilot holes. When in doubt I test things out on a scrap piece of the species I am working with.

[Jim Becker]

P.S. I have become more and more particular about counterboring/countersinking/clearance holes/pilot holes. When in doubt I test things out on a scrap piece of the species I am working with.
This is actually a really good practice. Not only do things look neater in the end, I think you get a better joint when the screws seat cleanly because of that prep. It's a big reason why I use two drill/drivers for assembly...one setup for the counterbore/pilot and the other for the driving. (I happen to use two Festool CXS D/Ds for this as they are lightweight and easy for "me" to handle)

[johnny means]

I use 6s when the primary function is just assembly, like cabinet sides. I'll move up to 8s or 10s when they might need to resist twisting or racking, like a table leg or chair back.

[Bill Dufour]

For countersinking I use a micro countersink cage. Easy one click adjustment every 1/1000 of an inch. Just make sure the countersink angle is correct since most aircraft countersinks are 100 degree while woodscrews are mainly 82 degrees.
Never seen one but they do make piloted counterbores that will fit into a micro countersink cage. I had no luck with rivet shavers for wood plug flush cutting.
bill D

[George Yetka]

This is actually a really good practice. Not only do things look neater in the end, I think you get a better joint when the screws seat cleanly because of that prep. It's a big reason why I use two drill/drivers for assembly...one setup for the counterbore/pilot and the other for the driving. (I happen to use two Festool CXS D/Ds for this as they are lightweight and easy for "me" to handle)

I have had or used 50 cordless drills/drivers in my life and none are as favorite as the CXS. I wouldnt put a 2" forstner in it but for almost everything I do in the garage and around the house its what I use.

I still have a bank of 24 drawers that are 2-1/4" deep 10-12" wide and 30" deep. Many of them have plywood dividers but 5-6 of them have 3d printed bins in increments of 2"x2"(some 2x2,2x4,2x6,4x4,4x6). They have a tap on top that is labeled and are very easy to take out and bring where needed.

[Kent A Bathurst]

............24 drawers that are 2-1/4" deep 10-12" wide and 30" deep....

That's 60 square feet of fasteners. There must be a 12-step grogram for this affliction, George.

[Edward Weber]

Here is how I have my Nut & bolt hardware and misc.
The first four columns are 1/4", 5/16", 3/8" and 1/2-5/8" nuts bolts washers. Last column is small hardware assortments like clips, set screws, cotter pins and so on.
507180
The hammer is for when I don't have the right size.

[andy bessette]

My principal fastener and hardware inventory is more or less organized in one spot. However I keep the 2 most used fastener kits (flathead and panhead sheet metal screws) handy to my main assembly area.

https://i.postimg.cc/rm11S61Z/IMG-2283.jpg (https://postimg.cc/ZBqvSMD6)
https://i.postimg.cc/3N3g1L98/IMG-2285.jpg (https://postimg.cc/XGDG7kTm)
https://i.postimg.cc/bNNx2BsL/IMG-2284.jpg (https://postimg.cc/Sj32BVLz)

[Jim Becker]

My fasteners are in the bin systems on the wall...all fasteners on the left side and the top one third of the right side. The lower two thirds on the right are all my CNC and router table tooling, etc.

507196

[Steven O Smith]

I've bought a lot of fasteners from this place:
https://www.manasquanfasteners.com/
at very reasonable prices, but not recently.