10-32 or 10-24?

[MrForbes]

We haven't really standardized on any particular size of hardware, because different things need different sized hardware. For example, mounting SMC solenoid valves requires 2-56 hardware, while mounting one end of our roller uses 1/2-13 hardware. We use several different sizes in between, too....5/16-18 for bumper mounts, 1/4-20 for several things, lots of #6, #8, and #10 screws to attach stuff to the plywood belly pan....and rivets in 1/8, 5/32 and 3/16" sizes of various lengths.

[Alan Anderson]

TechnoKats standardized on M3 and M5 for a year or two. It made finding the right tools trivial. We had a couple of plastic storage boxes with all the right drill bits and taps for the proper-sized holes. We had other storage boxes with a variety of bolt lengths.

I miss the simplicity of those days. I don't know what happened, but now we've got 10-32 and 1/4-20 and lots of other stuff all over the place.

[Phyrxes]

This is a transition year for us on a fasteners, as we have our first sheet metal frame. We went with a 3/16 rivet (using a number 11 wire gauge drill bit) which is slightly smaller than a clearance hole for a 10-32 bolt so we can drill out the rivet and bolt it if needed.

[AdamHeard]

#10-32 and 3/16" rivets.

1/4"-20 and #4-40 are stocked for places that need them, but we minimize there use.

Vex forced us to use some #8-32's.

Standard hand tools is nice, and lets us get a huge variety (L's, Ball end screwdicers, t handles, powerbits, etc...)

[FrankJ]

I would suggest that you pick & stay with one thread for each size screw. The day will come that some helpful person will dump the 10-32 nuts in with the 10-24 nuts, and then you will go nuts.

The nice thing about 1/4 is they have a broader range from acceptably tight to broken.

[JamesCH95]

Originally Posted by FrankJ

I would suggest that you pick & stay with one thread for each size screw. The day will come that some helpful person will dump the 10-32 nuts in with the 10-24 nuts, and then you will go nuts.

That happened to us... prompting the standardizing of 10-32.

[Matt C]

1/4-20 almost exclusively, all button heads unless the applications does not allow. We have a drawer filled with the correct sized T-handles and a bunch of 7/16" wrenches. Also have the same set-up for 10-32, but do not use them as often.
You still have the occasional student that has issues tightening stuff up only to realize that they grabbed a metric wrench from places unknown...

[theawesome1730]

We use 1/4-20, 10-24, 10-32, 8-32, 6-32, and 4-40. Typically 10-24 are used in aluminum that we have tapped and 10-32 in steel or other harder materials. Keeping the two separate is somewhat challenging

[tim-tim]

We typically use 10-32, 8-32, 6-32 SHCS and 3/16" and 1/8" rivets.

For the most part, #10's are used for COTS items, everything else is riveted of #8 or #6. Even #10's are overkill in most applications.

[magnets]

10-32's!!!

Easier to tap (saves money with fewer broken taps), stronger, get a tapped hole in thinner material.

We don't use too many on our robot. We find that for structure, welding is way lighter than 1/4-20's. For prototypes, we use 1/4-20, and (unfortunately) 1/4-28's, as we have thousands of these stupid things.

On things that I work on, I don't usually end up with too many 10 sized hardware. I find that 99% of the time, something else will fail before that bolt, so I go with 8-32's for weight.

[Mr V]

Originally Posted by DampRobot

10-32. All the things others mentioned, plus you can tap them into thinner material and still get the required six threads of engagement.

Originally Posted by magnets

10-32's!!!

Easier to tap (saves money with fewer broken taps), stronger, get a tapped hole in thinner material.

There is no magic universal number of threads to have in the tapped material, it depends on the diameter of the bolt and the relative strengths of the fastener and the material that is being tapped.

The general rule of thumb to ensure that the strength of the tapped hole is similar to that of the bolt you are threading into it is to have the thickness of the tapped material equal the diameter of the fastener when the materials are similar in strength. When the tapped material is not as strong as the bolt you are threading into it such as a steel bolt into aluminum you want the thickness of the material to be 2x the diameter of the bolt.

So using a 10-32 instead of a 10-24 does not mean that you can universally tap into thinner material. With either fastener if you are tapping into aluminum to accept a steel bolt you'll want the material to be 3/8" thick. So for a 10-32 you want 12 threads while using a 10-24 you would only need 9 threads to achieve similar strength of threads in the tapped material.

Head to your local hardware store and take a look at the different sized nuts and you'll find that the height of the nut gets larger as the size of the bolt does and you will find that a fine and coarse thread nut has the same height. If you have a store that also stocks aluminum and/or nylon fasteners you'll find that the height of the nut is the same for those made of steel, since they are intended to be used with bolts made of the same material.

That being said the Socket Head Cap Screws that many FRC teams use is way overkill for most applications, so tapping into material that is thinner than the rule of thumb suggests will work just fine.

Here is a good discussion of coarse vs fine and the benefits and drawbacks of each. http://www.katonet.com/article/coarsevsfine.html

Coarse threads are more durable and have greater resistance to stripping and cross-threading.

The part I put in bold is exactly why I insisted that we standardize to 10-24 after my first season with my team, since for many of our students being on our FRC team is their first experience with assembling things with nuts and bolts. As mentioned above the bolts are usually overkill so the greater strength of the fine thread bolt is not necessary. Using nylock nuts or thread locking compound means that the fact that fine threads are less likely to loosen isn't necessary either.

[Michael Hill]

Our team uses both. #10-24 is nice for speed, but sometimes #10-32 are used for things like fine grain control or needing to get as many teeth in mesh as possible. I believe this year, our chain tensioning system uses #10-32 into a helicoil for these reasons. For our drive system, we typically rivet everything since we typically use a sheet metal base. We really try to determine what the right screw is for the job.

[Dan.Tyler]

We standardize to the extent possible on 1/4-20 and 10-24, shcs or fhcs. The only exceptions are motors that require specific threads, or situations that demand a larger fastener (specifically a larger size, rather than higher strength)

The reason? Cost. In high strength fasteners, coarse threads are slightly cheaper. I doubt you could find a well designed FIRST bot where you need the strength of more than a quality 1/4-20 fastener. And the course threads give us the option of tapping into wood, polycarb, aluminum or steel without much issue.

Two box wrenches and two allen keys will take the bot completely apart and put it back together.

[JamesCH95]

We just standardized (mostly) to 10-32 this year and love it.

We have also started to use 10-32 riv-nuts for connecting thin materials and 10-32 t-nut inserts for connecting to plywood. Basically we wanted to have as many bolts as possible be removable with a single tool. It's worked out pretty well so far.

[Dan.Tyler]

It's shocking how well the metric wrenches fit in 5/32 and 3/16 hex heads...