Pressing carriage bolt through aluminum

[ligito]

I want to press a couple of 1/4-20 carriage bolts into 1/8 to 3/16 aluminum flat bar, to use as through the box mounts on an ATV box.

What hole size should I drill, to make it start through and stay fixed but not turn?

I'll press through the aluminum from the inside bracket but it will mount through steel under the box. where it attaches to the rack.

[lynnl]

Since no one else responded I'll offer my thoughts, for what they might be worth. Going through only 1/8 or 3/16" aluminum, I'd think the aluminum will deform to the point where just a little interference would hold about as well as more.
In short, I'd grab the first drill I had smaller than the bolts, and try that.

Oh wait... you said carriage bolts. I assume you want the shoulders to bit into the aluminum.
I'd probably shoot for about a 1/16th smaller that the diagonal measurement across those shoulders, and then pound or press them in.

[Don Young]

The square sholders will press into a 1/4" hole just fine.

[Arcane]

Since it's thin aluminum, it would take very little to use a small square file to rough out the hole slightly undersized and square to boot. You'd have a very nice snug fit that way.

[darryl]

A 5/16 hole would work fine also, and won't take as much force to put in, nor distort the material. It will offer all the resistance to the bolt turning that you'll need. In any event, don't try to draw them in using the bolt itself- that might be fine in wood, but in aluminum or steel you run the risk of wrecking the threads. Hammer them in, and use a backup piece. My choice would be a chunk of steel rod about 5/8 or 3/4 diameter, with a 1/4 inch hole for the bolt to fit through. Either lay the bolt head on an anvil or whatever, then pound the backup piece, or hammer the head with the backup piece on something solid.

[JanvanSaane]

I don't know about availability but on delivery trucks that use a rear roll up door some of the bolts that go through the door have a spline at the base. Would kinda look like a wheel lug stud. All that is required is drilling a ¼ inch hole and pull the bolts in with the nut. The doors are made by a company called Whiting Door. The bolts I have seen are longer but maybe someone makes a shorter version. Jan

[Mike Burdick]

ligito,

Carriage bolts are usually made of the lowest grade of bolt material and pressing them into the aluminum usually results in an unsightly fit.

Perhaps you might consider this rather inexpensive alternative if your project would allow: Farm mowers use sickle sections and these can be bolted into place using section bolts. These bolts are very hard and are ribbed near the head for holding. Most farm equipment supply stores sell them. The nuts are slightly oval so they will not vibrate loose and the ribs will cut cut into the material when the nut is tightened

For example:



http://www.cfcdist.com/shopping/inde...roducts_id=941
.

[SGW]

I'd drill a 1/4" hole then square it up with a narrow pillar file with safe edges, as Arcane suggests.

Or use those that are designed to be pressed in. Mike shows one version. Check McMaster-Carr and see what they have.

[J Tiers]

I agree with Mike B.....

The steel used is often soft buttery stuff that harder aluminum will deform.

The only problem is that SOFT aluminum won't take the splined bolts well, they may spin out ...

So maybe for harder grades, use splined, for softer grades drill and file.