I guess I should have been more yakkity about the screws.
If anyone hasn't seen or noticed these cussed things, here are a few details about them
The threads are the problem area.
They are roughly triangle shaped with rounded "corners". [image 2555]
The first few turns into the metal displaces (tears usually) the metal of the hole and, roughly, forms the threads in the hole.
Problem is, Aluminum & and magnesium act sort of "gummy".
So the threads end up mostly tearing out of the part and as a result are weak.
The shreds of metal tend to foul in the relief areas of the screw and sort of hold it in place.
Problem with that is the shreds,(being soft metal), tend to be compacted by vibrations.
So the screws slowly get lose.
Has anyone found any lose, bottom pan screws, on clamshell saws??
Now you know -one- part of the reason why.
Weak, half torn out, threads are most of the rest of the problem.
Secondary problem is IF the screws are oxide finish.
Oxide finishes are horrible for a sliding across another part (abrasive actually).
(remember that grinding wheels are typicaly made from oxides).
The tri-lobe screw thread is designed (in theory) to have the thread slide across the metal as it displaces.
Except the oxide finish just galls and tears out most of the soft metal.
If my photos aren't too terrible, you might can see where the screw pushes the first few turns (outlined in blue) [image 2558]
Then the load sits on the three lobes up the length of the screw (outlined in red) [image 2558 again.]
As you might suspect, this is another part of why these screws work lose.
We're putting all of the load on a very, very, small region of the screw threads
and when you combine that with the ragged threads in the work piece or part,
you can see why we find lose pans, covers, etc.
This is why I wanted to know if Tri-Lobe screws were used in the transfer covers.
Combine 'em with any gasket issue and we're looking at a good chance for a leak.
A "bright finish" cadmium(?)or something else shiny would help, a little,
with the tearing of the hole.
But.... We still have the problem of all of the load being borne by the small area that the lobes present.
Here are a couple of links to vendors of them.
Their drawings show it better than I can photograph it.
http://www.abs-metal.com.tw/tapping-screws-series/tri-lobe-thread-pt-thread-screws
https://d2t1xqejof9utc.cloudfront.net/screenshots/pics/ae1403bdc11c201c460fde20113d5446/large.JPG
But I'll still post a couple of quick snaps of a tri-lobe from my hoardings.
I might try to set better lighting and see if I can get better pics later.
Now do y'all see why I say to toss them out and re-tap the holes for a proper screw?