Q.I need to attach some simple padded clamps to my frame to hold brake lines. They need to attach to 2x4-inch rectangular tubing. What is the best way to do this without having to tap the frame? I read in an earlier column that you had attached an entire stainless floorpan using machine screws, so I imagine my problem can be solved. J.P. MachadoVia the Internet
A.To begin with, I don't know why you don't want to drill and tap the frame; that's the most straightforward way to attach brake line clamps, and it's not very hard to do, especially if you use a cordless electric drill. If you can hold the drill very steady, it's possible to both drill and tap the holes with the cordless drill. 10-32 screws should be strong enough for the job, and holes this size are quite easy to drill and tap, even in 1/8-inch wall steel tubing. If you go to a machinist's supply house, you can get thread-rolling taps, which have no flutes, and they are much stronger (and therefore less likely to break) than standard fluted taps.
These taps require a slightly larger drill size than the ones used for a fluted tap, so be sure to find out the proper size hole to drill before you attempt using a thread-rolling tap. This is exactly how I tapped the dozens of screw holes for the stainless floor you mentioned! One more thought on this: The taps found in most auto parts stores, hardware stores, and "big box" stores are made of carbon steel, and although they are relatively inexpensive and have their place in the world, the taps sold at machinist's supply houses (both fluted and thread-rolling) are made of high-speed steel, and they are much stronger! Trying to remove a broken tap from a hole is usually a difficult and frustrating job, and should be avoided at all cost!
If you absolutely can't (or choose not to) tap the holes, your options are more limited. There are stud-welding guns that can weld a stud onto steel tubing or plate. I'd suggest going with a 1/4-inch thread size if you choose this option.
One last possibility is to bond attachment plates to your frame. You can buy little plastic mounting tabs about 1 1/4-inch square with a pressure-sensitive adhesive backing that can be adhered onto a framerail, and they are designed to hold components using a zip tie. Although I've never used them for holding brake lines, I believe they would be strong enough for this application if you spaced them together closely enough.
Q.Boy do I have a big problem! I put a minivan roof on my '31 Model A Tudor sedan (you know, the type with ribs going front to back). I welded it all around the edge and supported it well underneath. I have a support brace every 8 inches, which I bonded to the roofskin with automotive-grade adhesive. I used some plastic filler on top of the bonded areas to make it perfect.
Boy, was it perfect ... until my first outdoor show, when the sun hit it and for some reason the metal moved and it looked like the ocean. It got all lumpy and wavy! I immediately took it inside to let it cool, and it went back almost to where it was, although I can still see some slight waves. What is causing this problem, and what can I do to correct it? If there is no easy fix, please spread the word so none of my follow street rodders make the same mistake!RichardVia E-mail
A.I'm very sorry to hear about your problem, since I know what a big job it is to fill a sedan roof. As I understand it, you put in braces going across the roof insert from side to side, and these braces are bonded to the roofskin with adhesive. The problem here is that the roof metal expands when it is heated, and the braces try to prevent the roofskin metal from expanding, pulling low spots into the roofskin wherever they are attached.