Mess-up installing my andair fuel pump.

some time ago I bought the Andair PX375-TC boost pump for my RV-7.
I'm was now at the point that I installed the pump on the cabin cover but made a stupid mistake during drilling and I'm wondering how to solve it.
I accidentally reamed the holes in the feet of the pump to #12 for 10-32 size fasteners. They should have been #19 for 8-32 socket head SS screws (MS16995-27).

I believe that installing the 8/32 screws is not an option as the whole pump may wobble after a while with vibration in the oversize holes.
So I started looking for some possible screws that would be 10-32 in size and would fit in a K1000-3 nutplate.

Does any of you have an idea for 10-32 size screw that fit a K1000-3 nutplate which have the smallest head possible ?
I was thinking of the MS16996-11 (which is the upsized 10-32 5/8 version of the prescribed MS16995-27 8/32 but wonder if that still would work.

I tried putting an AN3 bolt in or a 10R12 SS screw but the head of these interferes with the little socket head screws in the pump itself.

any advice would be greatly appreciated.

Jurgen---you could make a bushing to fill the hole.

Tom

Thanks for the reply Tom.

Would that be possible ? a bushing that fills the gap between #19 and #12, that sounds like awefully thin for a bushing. I'm also wondering what the size of the bushing would need to be in terms of height. Butting agains the nutplate and extendin to the hole in the fuel pump feet ?

JurgenRoeland said:

Thanks for the reply Tom.

Would that be possible ? a bushing that fills the gap between #19 and #12, that sounds like awefully thin for a bushing. I'm also wondering what the size of the bushing would need to be in terms of height. Butting agains the nutplate and extendin to the hole in the fuel pump feet ?

Click to expand...

If you give me the dimensions I can make you some bushings…
I mean the envelope to Belgium can`t be that expensive (will ship from Switzerland)

Cheers Yves

Just checked that a #19 hole would be 4.2mm and the #12 4.8mm means a bushing with only 0.3mm wall thickness… I can try to do that but if you could open it to 1/4" (or 6mm) it would be easier. The height should be Maybe 0.1-0.2mm less than the thickness of the base.

Let me know if I shall switch on my lathe tonight And tell me the dimensions and material...

Why not just use #10 screws?

DIY Fillister or Pan Head Screws

The cross width of a #10 Phillips screw head is (approx.) .169", the head diameter of an (AN) #8 FH screw is .269". With those dimensions, there is almost a .050" "edge" distance between the screw slot and the outside diameter.

If you would machine turn #10 screws down to a .269" head diameter, you would have a (de facto) #8 fillister or pan head on a #10 screw body.

If you don't have access to a lathe suitable for such small work - the screws can be (carefully) ground down by hand on a belt sander, or equivalent.

YMMV.

You can do the same thing with socket head Allen screws, but the edge distance gets pretty small.

HFS

Just use 10-32 socket head cap screws and be done with it. Any GOOD hardware store will have them in their fastener section,,,,and they are usually black oxide hardened steel.

I made some investigation and the socket heads of the 8-32 screws is between 0.262 min and 0.270 max. The 10-32 version of these has a head of 0.303 min and 0.312 max inches. the 0.303 is already too large. also the height of the hex head is 0.190 which interferes with the screws in the pump.
I posted a message to Andair to see if I can replace the feet on the pump. This just seems to be two support angles screwed to the pump. So that might be another option I found out.