electrical chassis ground screw broken

The screw was into the I beam of the chassis rail. I installed another screw near the original.

Is that broken screw into what's like formed sheet metal forming the frame, or heavier duty material like angle iron or square tubing? Those have more thickness to hold onto your broken screw (or to resist drilling). The tip of the screw probably estends on the back side. Using penetrating oil, maybe heat, it's possible you could take vise-grips and continue to "drive" the screw till it came out the back side. If it's into tubing, no. Just drill/tap a new hole.

In my case the old bolt was sheered off flush with the chassis rail.

j-d wrote:
Jayco used ST screws with drill point tips. I've found them through the chassis of our Ford E450. Once IN, they break off at any attempt to back OUT. They must have spun them in with an air tool going about a million RPM.

Most of them do it this way. Those bolts may loosen but it's a royal pain to take it out. You have to keep on pulling it out, rotating at the same time. Had to remove and put back in about 30 of them recently, when doing cleaning and repair of plastic sheets of trailer belly.

Mex - are you suggesting driving threaded bolt with tooth lock washer into the old threaded hole?

I used the tip of the self tapping screw to make the starter hole, then my battery drill to open it up just enough, then tightened with ratchet wrench.

Done

Jayco used ST screws with drill point tips. I've found them through the chassis of our Ford E450. Once IN, they break off at any attempt to back OUT. They must have spun them in with an air tool going about a million RPM. I'd drill and tap as noted above. Make a stop for the drill bit that allows it to just get through the chassis rail material.

MEXICOWANDERER wrote:
I asssssume the broken or missing screw is on the chassis frame rail?

If yes, that frame rail might prove to be a little to thick for a self tapping screw to work well.

Be sure whatever part of the frame you tap into to hold the ground wires that that frame member is not a separate piece of the frame which is riveted to the main frame rail. The ground wire must be connected directly to frame material: that is either the original large frame or a cross member that has been welded to the frame.

I picked up the habit of tapping holes in a frame rail with SAE threads from a tap I only use SAE thread bolts when connecting anything to a frame. Put an external tooth lock washer under the ground terminals then use the SAE bolt on top of that. then gob atop the bolt and the wire terminals or use undercoating spray.

Voice recognition works great if your vocabulary consists solely of "Hwang chow wah kee shan a day kong may fang toy". It sure as hell doesn't work worth ten cents with Inguish.

correct, the broken screw was into the main chassis rail. I have tap & die sets so can use one of those.. just wondering how much clearance I have on the other side of the chassis rail for drill and tap.

Yes a self tapping screw will work just fine. The frame is soft steel !!

I asssssume the broken or missing screw is on the chassis frame rail?

If yes, that frame rail might prove to be a little to thick for a self tapping screw to work well.

Be sure whatever part of the frame you tap into to hold the ground wires that that frame member is not a separate piece of the frame which is riveted to the main frame rail. The ground wire must be connected directly to frame material: that is either the original large frame or a cross member that has been welded to the frame.

I picked up the habit of tapping holes in a frame rail with SAE threads from a tap I only use SAE thread bolts when connecting anything to a frame. Put an external tooth lock washer under the ground terminals then use the SAE bolt on top of that. then gob atop the bolt and the wire terminals or use undercoating spray.

Voice recognition works great if your vocabulary consists solely of "Hwang chow wah kee shan a day kong may fang toy". It sure as hell doesn't work worth ten cents with Inguish.