We have the harness ran on the unibody build, now I'm trying to decide on the best way to go about attaching the harness to the frame. I found some nice rubber insulated holders that clamp around the harness. Wondering on the best way to fasten them down. Use self tapping type screws, drill through the frame and use small bolt/lock washer/nut ... or drill and tap the frame? The problem with the latter is that I don't own a set of taps. My other question is what is the school of thought on how far apart should the attachments be down the frame. Maybe I'm over thinking this part. I just don't want any problems down the road. We want to drive this truck, not be continually working on nit picky stuff.
I used the same holders -- drilled a proper size hole in the frame and used self-tapping screws. edited to add -- I put the wires in split loom, and I think the holders are about a foot apart.
"Self threading bolt" delivers a better mental picture of what you want. Self tapping screw brings ideas of little gutter screws.
Most call them a sheet metal screw, Grainger says self-piercing screw. http://www.grainger.com/Grainger/Self-Piercing-Screw-1MB47?Pid=search As I recall I used #10, the ones with a hex head. The trick is to drill the hole the right size so the screw gets a good hard grip.
http://item.mobileweb.ebay.com/viewitem?itemId=130890410353 Any GM truck at pull a part should get you about 10-15 easy to get at of these out of the frame.
I assume you mean a unibody Ford pickup? There should be some holes along the frame where the clips for the original wiring harness went, why not reuse those holes.
I did the rubber insulated clips with self tappers on my recent build. No set distance, as sometimes they need to be closer when they change direction with the frame over the axle, and in straight lengths they can spread farther apart. You'll be able to decide as you attach the harness and see how it droops, or doesn't droop. On my Austin I used a piece of 3/4" EMT tubing from the firewall to the rear bumper, and bent it to match the frame. Then I strapped it in 3 places with EMT straps to the inside of the frame. Simply pushed the wiring through it, and it worked great. Easy to add wires if I ever need another circuit back there for whatever reason. I pulled a spare, so it works as a lead wire to pull more in later if needed.
get yourself a # 21 drill bit , a 10-32 tap and a T handle tap wrench..shouldn't set you back more than $20. if you build any cars you will use them many times
Both are for light gauge, like steel studs, ductwork and of course gutters. Not really frame thickness but ought to work on the unibody Use what you want, or what you have. I have the right stuff because its what I want. I figure if The Big Auto manufactures make special bolts for this kind of stuff , well a builder can never go wrong using them for the same purpose.
This is why I ask questions here on the board. Most of you guys have more experience doing things the correct way. I dont want to cut corners and have to deal with this again down the road. Run the wires, clamp em down correctly and be done with it =) If I have to buy more tools and special this and thats Im cool with it ... Ill have them for next build. I really appreciate all the input.
All the screws pictured so far are for thin material. You can use these in thicker metal, but you will have to pre-drill the holes. I don't like these because you'll have heads snap off if you miss the hole size a bit small, and if too big they'll loosen up. There is a screw available though. I was unable to find a pic, but what you want is a self-drilling and self-tapping screw designed for thicker metal (1/8" to 1/4" range). The drill part of the screw is very nearly the same diameter as the threads, and those are fine like a fine-thread metric. I think they only come in two sizes, #12 and 1/4". Not everyone will have these, so you will have to hunt a bit. If you decide to drill/tap for a smaller machine screw, ask for a 2-flute tap rather than a 'standard' 3 or 4-flute version. On material 1/4" or less thick, they can be used with a drill and are much less likely to break. Again, you may have to hunt for these.
For the frame, use 10-32 machine screws and a bit of Locktite. Different size and type clamps are available depending on size and number of wires in the bundle. if I have a lot of wires they will be nylon tied together frequently and they will be fairly stiff as a unit, and I can space out the clamps further.
I keep as much of the harness as possible inside the car out of the weather. I use self tapping screws but do not get crazy over spacing just space as necessary.
I was unable to find these from any of the above in their catalogs. The closest I found was the 'thread-forming screws', but these don't have the self-drilling feature. Here's a crummy pic of one from my screw bin... This a #12 size, about 3/16" in diameter. You can get shorter sizes.