P

Pman

Active Member
Regarding the two holes that are required to be drilled in the F-445 Flap Bearing Block:
Wondering if someone can explain why the plans and construction manual have us drill a #10 hole for the AN3 bolt. Seems to me, drilling a #12 hole would be the appropriate diameter to accommodate an AN3 Bolt? (#10 hole will obviously result in a sloppy/loose fit?)

Thank you in advance for your replies!

Mike
RV8
 
Pman said:
...Seems to me, drilling a #12 hole would be the appropriate diameter to accommodate an AN3 Bolt? (#10 hole will obviously result in a sloppy/loose fit?)...
Click to expand...

Is this those nylon blocks? Nylon is squishy in a way that makes it unpleasant to machine in any kind of precision way. Holes often come out undersize because the material stretches around the drill bit instead of cutting cleanly.

Thanks, Bob K.
 
Drilling flap blocks

Bob Kuykendall said:
Is this those nylon blocks? Nylon is squishy in a way that makes it unpleasant to machine in any kind of precision way. Holes often come out undersize because the material stretches around the drill bit instead of cutting cleanly.

Thanks, Bob K.
Click to expand...

Yes, it also has a tendency to flex and cause the bit to drill crooked.
I used a #12 reamer and got them to fit pretty good.
 
Larry and Bob have it.
I saw that when I was doing mine and assumed the reason for the oversize was to compensate for the material "shrinking" from the drill size. As an experiment I drilled to #12 and tried it. Bolt would not go through. I did try reaming with marginal success before drilling up to #10 where the bolt fits just fine.

There are some places where you can be suspicious of the plans but this one is correct.
 
Thanks for the reply Gents....
Yes, the "nylon" Flap Bearing material is the item I'm questioning. Specifically, I'm wondering why the plans call for using a (larger than normal) #10 drill for an AN3 bolt hole?
Nominal size for an AN3 bolt hole is .1875----just wondering why the plans call for us to drill using a #10 oversize hole (.1935)?? I'm sure there's probably a good reason, however, before I drill the block I am wanting to determine why I should NOT use a #12 drill??
Thanks again!

Mike
RV8
 
Yep, #10 drills don't leave a #10 hole in delrin. The material seems to stretch around the drill bit somewhat rather than be cut by it. An AN3 bolt will still be a tight fit in a hole drilled with a #10 bit. If you use #12 bit like you would in aluminum, you probably won't even be able to get an AN3 bolt through the hole by hand.
 
Thank you all for the reply & info....
I'll go ahead and drill with a #10 drill bit, greatly appreciate the help!

Mike
 
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