Need a Professional Opinion

[byalexandr]

So I am working on my 5.5L chassis, which is constructed mostly of 22 gauge zinc plated steel. I am tapping the threads by hand (just as I am doing the entire project by hand) and I thought I'd experiment on the material since it is relatively thin. Now, normally on a decent quality steel chassis, the thin steel is sort of punched to make a tunnel that's the right diameter, and then it is threaded so there are several threads and the screw has something to hold onto, as seen here:

Well, I can't exactly do that by hand, unless I spend hours finding and perfecting a technique to get the punch process just right and still have working threads. So, I decided I would test it with just the threads through the thickness of the steel, as seen here:

There is only one or two threads actually holding it, but the screw still functions fine and I can still tighten it without it stripping. I also tested it on some 3/32" high carbon steel since I had it lying around, and of course it works but I can't make a chassis out of that stuff. This is what it looked like, obviously it had the most robust threads:

 

So, all you engineers and people with fabrication jobs (actual professionals, not the regular users on here, sorry), is this joint going to be bad? I mean, it holds and all, and I'm not crazy on tightening the threads, and I'll be the only one using and maintaining the case (unless I sell the design, then the company can do whatever with it). I'm just worried about how easily it will strip in the long term and how difficult it would be to repair since there is already so little material.

 

Any thoughts? Should I just go ahead with that or do you have a suggestion as to how I can punch the sheet metal like the first photo? Perhaps I could make it thicker with some high tensile strength epoxy or something, but I think that would be quite time consuming to fill up the pilot holes first and wiat for it to cure before I tap it, not sure if it would even leave a nice thread.

 

Thanks, @byalexandr

[byalexandr]

I talked to my dad, who's a control systems engineer and in engineering management, he says it'll be fine as long as I don't over tighten it, even though it's a bit loose if it's not tight. I can still get it very tight without stripping, but I don't know how easily it can come loose. Perhaps some Loctite will do the trick, but for now I think it might work.

 

I'll wait for some replies, I know it's pretty delicate but it looks like it will work okay, just need to see what others think before I start threading everything up.

[W-L]

27 minutes ago, byalexandr said:

I talked to my dad, who's a control systems engineer and in engineering management, he says it'll be fine as long as I don't over tighten it, even though it's a bit loose if it's not tight. I can still get it very tight without stripping, but I don't know how easily it can come loose. Perhaps some Loctite will do the trick, but for now I think it might work.

 

I'll wait for some replies, I know it's pretty delicate but it looks like it will work okay, just need to see what others think before I start threading everything up.

What they do for the first kind is usually a friction or flow drill and tap giving it that extra backing or threading material, not something that can be easily done without a heavy drill press or milling machine usually but requires tooling:

http://www.trick-tools.com/Flowdrill_Roll_Form_Tap_6_32_6_32_Flowtap_4473

 

 

 

It looks like your material is of relatively good thickness so it shouldn't have any problems as long as your not torquing it super high.