Arbor Press Modification

I'm using the arbor press method for setting my spar rivets.  I bought the Harbor Freight arbor press.  The general idea is that you add a rivet set in the base of the arbor press and set the rivet upside down in the spar.  A few taps with a hand sledge sets the rivet.

Tony Bingelis (of EAA fame) explains the process here:
http://www.eaa.org/en/eaa/aviation-communities-and-interests/homebuilt-aircraft-and-homebuilt-aircraft-kits/resources-for-while-youre-building/building-articles/metal/metal-spar-assembly-tips

Here are the mods I made:

• Polish the ram that makes contact with the rivet
• Mount a rivet cupped rivet set in the base

I don't have pictures of the polishing, but I removed the ram from the press and sanded it up to 400 grit sandpaper.  You'd be surprised how nice you can get it.  Then I used various polishing/buffing bits on my Dremel tool to get it mirror smooth.  The idea is that you do not want to add any irregularities to the rivet with a rough ram surface because that could become a stress point that might cause the rivet to fail.  Worth the work

Here are some pics of me mounting a .187 universal cupped rivet set (1/8th) in my arbor press base.  The method seemed to work well.

Lowered arbor press on base (sections of base are different sizes.  I chose the biggest one)

Marked the ram outline on the base and found the center.

Drill the hole.  I drilled with a 1/8" bit first to create a pilot hole.  Then drilled out with the 3/16" bit.  I also measured the length of the shank on the rivet set to determine my hole depth.  Not sure how important that is, but seemed like a good idea. (PS this is an old and super cheap drill press I bought over a decade ago.  Still going strong!)

The result...

UPDATE:  After riveting the spars, I realized that the center is not necessarily where you want to mount your rivet set.  the problem is when you go to rivet on the aluminum angle, the arbor doesn't clear the angle.  To fix it, drill the hole for your rivet set closer to halfway between the center and the back of the square you draw.  The good thing is, you can turn the table on the arbor to drill another hole.  If I did it again, I would drill the holes in your spar caps, take some measurements, then drill the hole for your rivet set.  My two cents...

I bought these drill bits at the big hardware store.  Went through it like butter!