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Who has drilled/cut into frame rails? Installing bolts question....

HenryKrinkle

NAXJA Forum User
Location
WI
I'm trying to find the right hardware for mounting rock rails into the frame rails. So far I know they need to be 3/8x about 1 1/2" and "self - threading". There are about 3 types of self-threading screws I've found. I'd like to get the strongest mount possible. Here's what I've found:

1 Thread-Cutting: Cuts its own threads. For thicker material. Weaker threads. Hardware not graded.

2 Thread-Rolling/Thread-Forming: Displaces material into thread. For thinner, less brittle material. Stronger hold, can remove and install without damage. Hardware not graded.

3 Drilling and tapping: I could pre-drill and then tap the hole to use a grade-8 screw. Little more expensive, but would likely be the strongest option. Depending on the thickness of the frame rails I'd either cut or form the threads with the appropriate tap.


So, who has seen how thick this material is? Would you consider it soft, hard, brittle, malleable, etc?

I'd like to roll/form the threads for strength- anyone think they'd need to be cut in instead?

Thanks...
 
if you want to do it right.
drill holes and sleeve them, then use regular bolts/nuts/washers.
I used the self tappers for my rails, they tear out under hard abuse.

drill and sleeve, especially if you want to take them off easily.
 
The frame rails are pretty thin. Something less than 10 guage I'd say. Probably not enough to take threads. There are holes in the rails already, crawl under there and form your own opinion. If you were to do stiffeners then I'd say drilling/tapping is feasible
 
I know that the self-tapping screws seem weak, but that's what AJ's and other companies send for hardware. Many people say the AJ's rail hold up well too.

Anyway, I guess I'll sleeve the horizontal holes (to avoid crushing inward) and will use thread-forming bolts for the bottom holes (no access to top).


Thanks for your inputs^^
 
All my rails are held on (at the framerail) with nutcerts(1/4"-20).Haven't come loose in over 10yrs!
 
I used the self tappers for my rails, they tear out under hard abuse.

Wrong. I've beaten my rock rails so hard that rockers ended up into my doors. The self-cutting bolts never backed out once. I even crappily installed them.

drill and sleeve, especially if you want to take them off easily.

Wrong. If you live in a rustbelt, they WILL seize to the bolts. Even with antiseize. Trust me.
 
I'm trying to find the right hardware for mounting rock rails into the frame rails. So far I know they need to be 3/8x about 1 1/2" and "self - threading". There are about 3 types of self-threading screws I've found. I'd like to get the strongest mount possible. Here's what I've found:

1 Thread-Cutting: Cuts its own threads. For thicker material. Weaker threads. Hardware not graded.

2 Thread-Rolling/Thread-Forming: Displaces material into thread. For thinner, less brittle material. Stronger hold, can remove and install without damage. Hardware not graded.

3 Drilling and tapping: I could pre-drill and then tap the hole to use a grade-8 screw. Little more expensive, but would likely be the strongest option. Depending on the thickness of the frame rails I'd either cut or form the threads with the appropriate tap.


So, who has seen how thick this material is? Would you consider it soft, hard, brittle, malleable, etc?

I'd like to roll/form the threads for strength- anyone think they'd need to be cut in instead?

Thanks...

Drilling & tapping sheet metal to use a 3/8" grade 8 bolt? The bolt is WAY stronger than the sheet metal. Home Depot Grade 2 bolts would be stronger than the sheet metal.
Think about it this way - under load, the slider is pushed UP into the rocker. The bolts are only there to keep it from falling off on the highway, as far as I can tell.
Throw some self tappers in and call it a day
 
Wrong. I've beaten my rock rails so hard that rockers ended up into my doors. The self-cutting bolts never backed out once. I even crappily installed them.

I tore them out, 3/8" self tapping screws, and this was an MJ frame, so twice the metal thickness of an XJ frame.


Wrong. If you live in a rustbelt, they WILL seize to the bolts. Even with antiseize. Trust me.

I live in NE Ohio, I know about rust, never seize is great on threads, if you want to keep sleeved bolts from rusting, cover them in grease before you install them, or don't cheap out and buy zinc plated bolts and actually do maintenance.
Just my experiences, personally I'd not use self tapping screws ever agin, they look nasty, they wallow the holes if you take them on and off a few times, and, as I stated, I tore some of them out of the frame.
 
what size self tapping screws? the 'self tappers' that come with jcr sliders are more of a self tapping BOLT. its not a screw in anyway. i think its 3/8 16tpi.

NO, self tapping screws are not the right thing to use here... self tapping bolts however are basically the industry standard. if you broke them, please say so, as the screw bit is confusing.
 
what size self tapping screws? the 'self tappers' that come with jcr sliders are more of a self tapping BOLT. its not a screw in anyway. i think its 3/8 16tpi.

NO, self tapping screws are not the right thing to use here... self tapping bolts however are basically the industry standard. if you broke them, please say so, as the screw bit is confusing.

I suppose they were bolts, hex head, with the flanges on the bottom of the head. Needed pilot holes drilled, as they didn't have a pointy tip. I did not break the bolts, I tore them from the frame, the rock rails were attached to my frame in 4 places,two bolts per leg, and attached to the pinch seam with about 8 self tapping screws (MJ cab).

I break things. If it were a mall crawler or light trail wheeler I would use self tappers, if it's a serious trail rig, just sleeve and bolt them, cause you're going to want to attach something else structural to them at some point.

Eventually I ditched tje rock rails, they robbed too much clearance, and I really don't care about the sheetmetal anymore. It's all going to get boatsided and ex caged anyway.
 
what size self tapping screws? the 'self tappers' that come with jcr sliders are more of a self tapping BOLT. its not a screw in anyway. i think its 3/8 16tpi.

NO, self tapping screws are not the right thing to use here... self tapping bolts however are basically the industry standard. if you broke them, please say so, as the screw bit is confusing.


3/8-16 x 1 1/2" is the size I'm going for. All the hardware catalogs still consider them "screws" even though they are big and "bolt" seems to fit better in my head too.
 
Guys clarify between self tapping and self drilling. Self tappers are generally for thinner gauge sheet metal & theoretically do not require much of a pilot hole, I havent seen may bigger than 1/4". Now self drilling screws look like a wood lag bolt, but are coarsley threaded full length & come in much heavier duty sizes & require a pilot hole & I have used them in the frame rails so far with success.
 
Self tappers work great.
I have aj's rails, and I had to take them off, and reinstall them when I did my stiffeners.

The holes are all fubar'd but the still work. (I did tack weld the legs on however.)
 
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