Monday, April 17, 2017

Aluminum Bolts in Aluminum Threads

Looks like galling is taking place.  (Probably two different alloys.)  If there was some way to use through holes in the aluminum, the threading wouldn't be a problem,  Two bolts can indeed be done with through holes and nuts.  But I need to apply clamping force, and nutserts seem to require a tool for installation.  There must be some simple way to do this.  I considered making the threaded part from steel, but you can'get interior right angle steel channel.  At least no one shows such; only radiused internal corners.

There seems to be some agreement that to do steel into aluminum requires a hole depth 2x diameter (which one of told me).  So perhaps 1/16" bolt?  But it won't take the clamping force,  Or perhaps go to 1/2" wall that I am threading?  Not sure if I can find 2.5" 1/2" wall channel.

3x1x14 ga. steel rectangle tube would work if I could slice off one edge.  Don't see any practical way to do that with tools that I have or can afford for a prototype.

As usual, my wife solved the problem while snuggling with me: make my own arbitrary leg width channels.  2" wide steel plate on top, 3" wide plate on bottom probably thinner than the 1/8" aluminum I have been trying to use.  A 1/2" thick, 1" wide steel plate between the edges of the other two plates; through holes on edge of top and bottom plates; tapped holes in side plate.  Bolt it together.  Bottom plate is now wide enough for the caster to bokt directly on; tap holes in bottom plate for clamping bolts which can now be steel pressing against an aluminum compression plate against the wood to be clamped.  Less holes to drill; fewer matching holes required.  Downside: drilling through holes and tapping steel; a bit more weight, but stiff.


  1. Helicoil?

    I used it in an aluminum head for a valve cover bolt that I stripped out. Much stronger than the original aluminum threads.

  2. I have used something like poprivets that might do the job. Instead of the frangible shaft of a poprivet, these have a thread. Screw a stud in the insert and into a devive that looks lime a poprivet gun. Squeeze and the stud compresses the insert. Remove the stud and you have a threaded hole.

    I've used them in thru holes in sheet metal as well as in blind holes.

    I bought a kit about 20 years ago from harbor freight with gun and assortment of inserts for $20 or so.

    Also try msc or mcmaster-carr

    Let me know if you have trouble finding it and I'll track it down for you

    John Henry