What size screws do you stock up on?

Ken from ontario said:
Alright,the reason I ask about the size/type of screws is a bit deeper , but let's keep it simple so I understand.you see I know many of you design and fabricate parts/ tools etc , so when you design some part from scratch , how do you determine what type of screw to use, or whether to use socket , button or flat head cap screws(or any other type of screws), I can imagine how the length is determined but what formula do you use for the thickness and type of the screw? or how many screws, what the location ? corners ? center? both?
I do understand bolt come in variety of strength, and are used based on the amount of stress they would be under but could you use more weaker screws opposed to a few but more heavy duty ones? i.e, 10 pcs of 1/4"-20 opposed to 4 X 3/8"-16?
I ask because right now I use what I have in stock but I'm a hobbyist, how do the pros choose their screws?
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As a Mech and Aero Engineer, I would hazard a guess that only a small percentage of bolt patterns and bolt selections are actually engineered based on loads.Instead many are designed by "TLAR method" (meaning That Looks About Right). I am including everything ever built in that statement. Certainly, there are cases that demand careful design such as pressure vessels and some places on aircraft but its a waste to spend a lot of effort to design a sheet metal cover attachment. In order to get a complete understanding of bolted systems, there are a number of physics and materials calculations that need to be learned. However, you may be able to find some books or reference material on the web with somewhat 'canned' answers for sample situations.
 
markba633csi said:
I dislike certain sizes with a passion; 6-32 for example and 1/4-20. Those two I try to avoid. They strip, they shear off, more that other sizes in my experience. And industry uses them everywhere. Aack! 8-32 and 10-32 are fine. 1/4-28 I like too. Metrics are all good. I like fine threads in steel and coarse threads in aluminum. Did you know an 8-36 is nearly identical to a metric 4mm? Just a hair larger IIRC.
I don't have a good system for storage, so I try not to keep too many fasteners on hand. Life is too short to sort. You dig?
Mark S.
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Yes, Mark, I dig(mostly in my parts bin). Not to be disagreeable but I kinda like 1/4 x 20. On small screws and nuts, I usually
locate the bolt I want and then look in the nuts bin for a "fitting" nut. If I want pairs or more of matching hardware, well, that takes
a little longer. On the small bolts and nuts, I'm sure it is a mix of imperial and metric. Sometimes a magnifying glass helps
on real small stuff or maybe even two pairs of 3.0 reading glasses for small parts or electronic circuit board soldering! It's
also handy to sharpen tiny drill bits or look at the cutting edge on end mills or lathe tooling when fine tuning an edge.
Yesterday, I was reefing on a bolt that holds on the front wheel on a riding lawn mower. It turned out to be 5/16 x 18
and left hand thread. Is was on the left side of the mower. How sinister is that? It's on an older mower. On something
new, the wheel is probably held on with a cheap springy washer like thing and covered up with a chrome plated plastic
pretty looking widgit. That's where the disdain comes in for me. What else is cheap on the machine? Probably everything!
One thing I don't like is when they make a casting and there is just bearly enough meat on the aluminum casting for the threads
making it almost impossible to thread the hole to the next bigger size...Now, that's disdain, probably metric to boot!
Most of the world is metric but we in the states get to enjoy a mix of metric and imperial and have to lug around TWO sets
of toolage cuz you never know what you might need! Gotta love Crescent wrenches and Vise Grips...;):)
 
I have a lot of different fasteners, mostly imperial because most of the equipment I work on uses that system. I have bolt bins set up by size, each horizontal row is a given size then as you go across from right to left the fasteners increase in length by either 1/4" or half inch increments depending on size. Size ranges from 0-80 through 1 1/8". Various types of washers and nuts are on the right side. My biggest problem is having an employee grab several handfuls of something and then put away what is left over incorrectly. : SIGH: In the winter during our slow season someone usually gets to resort the bins. I also keep several fastener black books around, plus several catalogs, McMaster, fastenal, and Tacoma screw. It is very useful to occasionally thumb through these just so you know what is available.
My problem today is more and more metric fasteners, so I need to get set up for that, but a good selection from 4mm up to 25mm in all the different thread pitches is a lot of bolts.

Sent from my SM-G930P using Tapatalk
 
What really bugs me is when fasteners are under specd. Like when they use one size too small to save money.
Just like Cathead said: what else are they cheaping out on? BTW the word for left in Italian is "Sinistro"
I like 1/4-20 more than I like 6-32. I like 1/4-28 more than 1/4-20.
According to my Pocket Ref there were more than 15 different 1/4" thread pitches made.
They say you should throw out stuff if you haven't used it for a couple years. Heck I have fasteners from like 40 years ago that I still can't find an excuse to throw out, probably because I still find uses for em from time to time LOL
MS
 
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"TLAR". I agree fully, with the caveat that you need to know what to look for. Threaded sections of the fastener at the joint shear plane is one of my major peeves. Material choice is another. You could always tell the noobs at the race track. They were the ones up late trying to drill out broken off loctite'd grade 8 bolts they thought would make a dandy upgrade for the flywheel.
 
Depends on what your projects will be.
In general, it would be worthwhile to buy a screw assortment of both imperial and metric just to have on hand. (Mostly for repairs.)

I'm in the US, but I use mostly metric stuff since that's what is used at work. (Our products ship primarily internationally).
M3x0.5 is probably my most used screw, its a decent size/strength ratio for the size of projects I work on. I only go smaller if I'm forced to by available material thickness. The imperial equivalent would be 4-40.
I use M6x1.0 for the heavier stuff. M8 is about the biggest I've ever felt was needed.

Plan things out though, its nice if you only need a few tools to get into something for a repair job.
Also if there is going to be adjustable feature(s), try to make it so they can all be adjusted using the same tool.

rzbill said:
As a Mech and Aero Engineer, I would hazard a guess that only a small percentage of bolt patterns and bolt selections are actually engineered based on loads.Instead many are designed by "TLAR method" (meaning That Looks About Right). I am including everything ever built in that statement.
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This is accurate. I haven't seen an review for a bolt pattern since college. A little over-kill on bolt size doesn't cost that much more and it never got anyone fired.
 
I only have access to Menards. Junk bolts. I bought a couple 3/8-24 for my tool holders and they the hex is metric size. That just seems wrong.
 
I have socket head cap screws, set screws, flat head cap screws and button head cap screws in sizes from 4-40 up to 3/8 - 16. Have a small selection of M3, M4, M5, M6, M8 and M10 cap screws and set screws also. Also lots of grade 2 hardware store bolts in 1/4-20 up to 1/2-13. Everything is actually organized, somewhat. I use wall-hanger tubs from HF for the hardware store stuff, still need to label the bins. The rest is in labeled bins in a couple of the multi-drawer plastic organizers. Unfortunately, they're only sorted by thread, not length or head style so the drawers get dumped and sorted if I need something specific. Have my over flow of 1/4", 5/16" and 3/8" cap screws in 1-gallon Ziploc bags.

Bruce
 
I use Allen cap screws if they are going to be adjusted or removed regularly, flat head screws where it needs to be flat, and cap screws otherwise, ideally.

I started by keeping various types of fasteners in coffee cans. Boxes with extras were kept on the shelf and packages hung on a peg board. Then I was lucky enough to find one of the metal drawer units made for that purpose. Also, some smaller units with plastic drawers. And a stack of plastic boxes with dividers. It usually gets me close enough that I can find what I need fairly quickly.

If I need a few screws I go to Klem's, a local place. They charge too much but they do usually have whatever I need. If I need a bunch then I order from Albany County Fasteners online.

My favorite places to get machine screws and bolts are yard sales and the dump. If they have some rust on them I clean them up in a mix of detergent motor oil and milling swarf in a rock tumbler. A bolt sizer usually makes sorting them fairly easy.
 
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