Washers and screw shank size

[mhorowit]

Well, I'lve succeeded in putting the aluminum leading edge on the final aileron.
In the process, I had to 'move'(enlarge/elongate) several holes in the LE so I could get to the screw hole in the rib. To make up for the removed metal, I"d like to place a washer between the #4PK screw and the LE. A #4 washer extends the width of the PK screwhead only a little; a #6 is what I want to use, but now the size of the hole in the washer and the diameter of the screw shank are significantly different. Is that a problem? - MikeH

[Robert Lees]

Re: Washers and screw shank size

Why not just use a #6 PK screw (I did). After covering, you can't tell the difference. I'd rather have the screw head wider, than sticking out more, with a washer.

Rob

[astjp2]

Re: Washers and screw shank size

Just leave the enlongated hole and just cover it with chaff tape, you will never know the difference under the fabric. Tim

[mhorowit]

Re: Washers and screw shank size

Just leave the enlongated hole and just cover it with chaff tape, you will never know the difference under the fabric. Tim

I was thinking about replacing some of the bearing surface that I had removed by making the hole in the LE larger.

[VictorBravo]

Re: Washers and screw shank size

You can make your own custom washers easy enough. Go to the hobby shop and get very thin stainless sheet (.010 or .012 or something). Drill the hole for the screw. Cut out the shape of the washer to cover the elongated hole. Hold the washer in place with some tape or a drop of super glue. The .010 extra that it sticks up will not be visible. No need to put a 1/8" thick washer under a screw that's only holding down .016 sheet metal...

[high time cub]

Re: Washers and screw shank size

http://www.aircraftspruce.com/catalog/cspages/washers.php

[Robert Lees]

Re: Washers and screw shank size

I was thinking about replacing some of the bearing surface that I had removed by making the hole in the LE larger.

That won't work, Mike. The load-carrying is in the flange of the rib, not the LE. Unless I misunderstand you.

Rob

[mhorowit]

Re: Washers and screw shank size

That won't work, Mike. The load-carrying is in the flange of the rib, not the LE. Unless I misunderstand you.

Rob

I'm probably explaining things incorrectly. Here's an example. Assume the head of the PK screw is 1/4" in diameter and I've removed metal on the LE (attempting to locate the hole in the rib) equal to 3x the size of the original hole in the LE. The PK screw will still grip the rib, but the undersurface of the screw has much less metal to clamp, making it much easier for the LE to rip out from under the PK screw. Not very likely considering all this will be covered with fabric, but I'm trying to think like an engineer. I'm trying to replace that bearing surface with a washer. Thoughts as always are appreciated - MikeH

[mhorowit]

Re: Washers and screw shank size

You can make your own custom washers easy enough. Go to the hobby shop and get very thin stainless sheet (.010 or .012 or something). Drill the hole for the screw. Cut out the shape of the washer to cover the elongated hole. Hold the washer in place with some tape or a drop of super glue. The .010 extra that it sticks up will not be visible. No need to put a 1/8" thick washer under a screw that's only holding down .016 sheet metal...

Bill - you wouldn't happen to know of a quicky way to punch out 3/8" washers?
My first thought is to sharpen some of this tubing I have and punch it like a leather tool - MikeH

[flybikefarm]

Re: Washers and screw shank size

What you need is a shim punch. Most machine shops or tool and die shops have them. George

http://www.precisionbrand.com/