[CAUT] S&S hammer flange rail material

[Fred Sturm]

On Aug 20, 2008, at 8:56 PM, Chris Solliday wrote:

> even with the panheads the non uniformity of the threads can throw  
> it of if
> you tighten down even alittle too much. I use the washers even with  
> the
> pans.
> Chris Solliday


Hi Chris,
	I'm not following you. As far as I can see, a washer will spread the  
pressure of the head over a larger area, assuming it is larger than  
the head. But it would apply pressure to the flange in exactly the  
same alignment, it wouldn't change the direction in which the screw  
head was bearing on the flange. The washer is flat and acts as if the  
screw head was that much thicker, or at least that's how I think of it.
	In my mental picture, the only thing that will cause the flange to  
tip on the rail (assuming the rail is flat and clean, and the flange  
bottom is too) is a screw hole drilled off center (fore or aft) or at  
an angle. I don't see how any difference in the screw threads could  
affect this, or could cause a flange to tilt when over tightened.
	I can see potential benefits to adding a washer. The wood won't be  
crushed as much, for one (the washer protects the wood from the  
twisting action of the screw, and if it is larger, spreads the  
pressure over a larger area). OTOH, if there is a small discrepancy in  
the angle of the hole, the screw head tends to dig in and crush the  
related side of the flange, which in my mental picturing, helps to  
adapt things and level the flange. I see flanges where one side of the  
screw head has made a bigger indentation, and assume that is what is  
happening.
	Maybe the esteemed Mr. McMorrow had it all figured out as Alan  
reports, and I've been missing out on the answer all these years  
because I was a cheapskate and didn't buy his book. Anyway, I can't  
say as I have seen a really clear analysis of what goes on and why  
(hence my earlier post giving my own take on it).

Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu