Good Screw Sizes fo General Use

[JamesCH95]

We've standardized to 10-32 as much as possible. Generally SHCS style. Rivnuts, t-nuts, and nylok nuts. It has made life suck a whole lot less to standardize everything.

[GeeTwo]

Last year, almost everything we had was 10-32, allen-drive cap screws and nylon nuts (all steel). This worked out quite well for us; we might change to a different size or two this year (I'm mentoring programming this year, so not on top of the discussion), but we'll definitely have a small set of sizes for anything that we're building. When you do pick a standard size or sizes, STOCK UP ON TOOLS IN THOSE SIZE(S)! You'll never seem to have enough, since (for 10-32) everyone wants the 5/32" Allen and the 5/16" hex wrench at the same time.

[mman1506]

Originally Posted by Chris is me

Socket head cap screws basically every time.

What's the advantage of using socket head over button head?

[Jared]

Originally Posted by mman1506

What's the advantage of using socket head over button head?

Socket head typically has a deeper hex, so it's harder to strip out.

I like 10-32's over 10-24's because it's harder to break the 10-32 tap. As a rule of thumb, I try to get more than 6 threads of engagement in a tapped hole in aluminum. With a 10-32, that works out to 6/32 = 0.1875", but a 10-24 requires 6/24 = 0.250".

Once you've used both for a while, it becomes easy to identify the different threads on bolts, and you can check to see if your nut threads easily on a known bolt.

We've used 1/4-20's as axles for flywheel shooters and pivots for catapult shooters, as well as gearbox mounts.

3/8-16 or 3/8-24 is our favorite for dead axles.

[Michael Hill]

Originally Posted by Jared

Once you've used both for a while, it becomes easy to identify the different threads on bolts, and you can check to see if your nut threads easily on a known bolt.

You must not have "determined" kids that will get that 10-24 nut on the 10-32 bolt. Yeah sure, it'll go on...with enough torque.

[Oblarg]

Originally Posted by Michael Hill

You must not have "determined" kids that will get that 10-24 nut on the 10-32 bolt. Yeah sure, it'll go on...with enough torque.

Quoting for truth. As mentioned earlier in the thread, our solution to this problem is to just not buy 10-24 anymore, which removes the potential for the error in the first place. On a team as large as 449, it's just not worth the hassle for the few places where it's nice to have coarser thread.

[Chris is me]

Originally Posted by mman1506

What's the advantage of using socket head over button head?

Biggest advantage is the deeper hex, but you can also turn it with pliers if you're desperate which is nice. Also lends itself to counterboring.

[Chief Hedgehog]

Originally Posted by Nemo

What we stock:

8-32
10-32
1/4-20

Socket head cap screws from 1/2" length up to 3" or so.
Also lots of nylon insert lock nuts and flat washers. Black oxide preferred over other materials.

Same. We actually cleaned out our old hardware organizer as we make room for these sizes in differing lengths and the accompanying washers, lock washers, nylock nuts, nuts, and acorn nuts.

[Mr V]

Originally Posted by Jared

Socket head typically has a deeper hex, so it's harder to strip out.

I like 10-32's over 10-24's because it's harder to break the 10-32 tap. As a rule of thumb, I try to get more than 6 threads of engagement in a tapped hole in aluminum. With a 10-32, that works out to 6/32 = 0.1875", but a 10-24 requires 6/24 = 0.250".

Once you've used both for a while, it becomes easy to identify the different threads on bolts, and you can check to see if your nut threads easily on a known bolt.

Not only does the socket head have a deeper tool engagement the tool size is usually larger for the socket head making it less likely to damage the tool or bolt. The button head is also weaker than the socket head.

Because the fine threads are not as deep (the reason it is harder to break the tap) you need more of them to have the same strength. If you look at standard nuts you'll find that their height is equal to the diameter of the bolt they work with regardless of the pitch. In other words 4.5 10-24 threads will give you the same or greater strength as 6 fine threads. The fine thread bolt will be stronger but in both cases the threads will pull out well before the bolt fails since you need 2x bolt diameter in aluminum to make the tapped threads roughly equal to the bolt strength.

It is true that once you've worked with threaded fasteners for a while it does become second nature for many people. The problem is that there are a new group of people added every year many of whom are experiencing using threaded fasteners for the first time. Because there are many new people every year that is another reason to not use fine thread fasteners because they are mush easier to cross thread.

[Chief Hedgehog]

In the case of wire - stranded black and red. DO NOT USE White (correct Stratis - a la 2013 FRC 4607 @ North Star)...

Be sure to check the manual and the proper usage.

We try to keep plenty of 10, 12, 14, 16awg Red and Black on hand.

Care to chime in 4607 captain?

[artdutra04]

Another great suggestion for helping to avoid stripped Allen screws is to ONLY use high-torque Allen keys (from Wera).

I've used these since I was in college, and even for small sizes like 3/32" or 5/64" I've yet to strip one of these Allen keys. I've also been able to use these to remove "stripped" screws that regular Allen keys couldn't get out. They aren't much more expensive than regular Allen keys, so it's basically a no brainier.

[MrRoboSteve]

Once you make the switch to hex head machine screws, you'll need to get some real hex keys.

We have a couple sets of the Bondhus HTX10/S T handle hex key sets, and they're great. If you're buying something like this, make sure that the metal of the key shaft goes all the way into the T handle. There are cheaper sets than the Bondhus that just have the hex key set into a plastic handle, which won't hold up.

$33 each on Amazon.

[iggy_gim]

Thank you guys so much. We are going to use 8-32, 10-32, and 1/4-20 with nylocks (Keps just don't appeal to me...). We have a sponsor that will buy them for us for free off of Grainger.

By the way, I was looking on Grainger's website for wire too, I don't get teh difference between the different types of wire. What type of wire is best for our applications (I need to get this order in by Sunday and my coach doesn't know too much about materials as organization...)

LINK to GRAINGER Website

[GeeTwo]

Originally Posted by iggy_gim

.. I don't get teh difference between the different types of wire. What type of wire is best for our applications

LINK to GRAINGER Website

If you're building a house (no motion except in the occasional earthquake), go solid-core with THN insulation. If you're building a robot or a car (something that moves), go stranded, especially for anything above about 20 GA, and a more flexible insulation. If you want to buy local (vice online), go to the local auto parts shop, not the home improvement warehouse. All of their stuff is also for 12V, great for robots. Buying the red/black "zipcord" pairs really helps layout as well. Though honestly, for 6GA (battery to main breaker to PDB) you can probably do just as well buying a nice pair of HD jumper cables at the auto shop and cutting them up as trying to find the wire. One thing to watch when buying auto electrical though -- be sure you don't buy stuff that depends on a chassis ground -- this is specifically illegal for FRC, at least in recent years.