Are the screws that hold the soft top frame brackets on the roll bar self-tapping?

[roboto65]

I know someone on here will know. Are the screws that hold the soft top frame brackets on the roll bar self tapping or are you supposed to tap the holes out and install. From what I have found it's a button head screw Mopar 6x1.25 is the size. Mine looks like they have never been used the PO had a soft top on it but no brackets.

 

[freedom_in_4low]

Looks intended to self-tap.

 

[roboto65]

Thank you so much ! I guess mine never had a soft top they are not threaded for sure.

 

[freedom_in_4low]

Thank you so much ! I guess mine never had a soft top they are not threaded for sure.

Hard to capture in a photo but the threads actually start like a rounded off triangle near the point and then fill out closer to a circle at the head. They're most often used in sheet and tube and are designed to somewhat extrude thin material and have thread pitch like a machine screw instead of a sheetmetal screw so that they create necessary thread engagement and are less prone to stripping the hole. As a result they don't look like the sort of self tapper most people are used to seeing, but it's super common in automotive since about the 90s. The ones Chrysler was using usually taper all the way to a point but typically the very end is cut off so there's just enough taper to fit into the hole and start grabbing (I believe this is done mostly for worker safety to not have sharp points sticking out, but most of the places they're used on our Jeeps are protruding into inaccessible spaces so the sharp point doesn't matter).

 

[mrblaine]

Hard to capture in a photo but the threads actually start like a rounded off triangle near the point and then fill out closer to a circle at the head. They're most often used in sheet and tube and are designed to somewhat extrude thin material and have thread pitch like a machine screw instead of a sheetmetal screw so that they create necessary thread engagement and are less prone to stripping the hole. As a result they don't look like the sort of self tapper most people are used to seeing, but it's super common in automotive since about the 90s. The ones Chrysler was using usually taper all the way to a point but typically the very end is cut off so there's just enough taper to fit into the hole and start grabbing (I believe this is done mostly for worker safety to not have sharp points sticking out, but most of the places they're used on our Jeeps are protruding into inaccessible spaces so the sharp point doesn't matter).

View attachment 656098

One of the few trivia bits about fasteners I struggle with. I don't know the exact name to find that type of screw. It is in the class of self tappers but it is differentiated from the typical self tapper we commonly use in that is displaces material to form the threads versus removing material to create threads. Essentially the difference between a roll forming tap and a cutting tap or in this case, self forming versus thread cutting.

This gets most of it.
https://monroeengineering.com/blog/self-forming-vs-thread-cutting-screws-whats-the-difference/

 

[freedom_in_4low]

One of the few trivia bits about fasteners I struggle with. I don't know the exact name to find that type of screw. It is in the class of self tappers but it is differentiated from the typical self tapper we commonly use in that is displaces material to form the threads versus removing material to create threads. Essentially the difference between a roll forming tap and a cutting tap or in this case, self forming versus thread cutting.

This gets most of it.
https://monroeengineering.com/blog/self-forming-vs-thread-cutting-screws-whats-the-difference/

I was introduced to them as a "trilobular thread rolling screw". DIN 7500 is the standard that defines it.

 

[mrblaine]

I was introduced to them as a "trilobular thread rolling screw". DIN 7500 is the standard that defines it.

I'm aware of the trilobular stuff but I was pretty sure those aren't them. They are used a few places on the TJ, most common are the panhead Torx that hold the brake line brackets to the frame. I don't recall if those are fully pointed. They may be in use for the exhaust hangers. Have to double check that one to jog my memory.

Almost doesn't matter nowadays with the search terms so diluted.

 

[freedom_in_4low]

I'm aware of the trilobular stuff but I was pretty sure those aren't them. They are used a few places on the TJ, most common are the panhead Torx that hold the brake line brackets to the frame. I don't recall if those are fully pointed. They may be in use for the exhaust hangers. Have to double check that one to jog my memory.

Almost doesn't matter nowadays with the search terms so diluted.

The one I pictured came with a Bestop soft top and it's definitely trilobular, it just has the sharp point instead of missing the tip. It might not strictly meet DIN 7500 but it's the same concept.

 

[roboto65]

Thanks! You guys are a wealth of information keep up the great job. Thanks again!