FlyBoy8

FlyBoy8

Active Member
The plans call for a #28 drill for the AN507-6R6 screws that attach the W-822 access plates to the spar platenuts (K1000-06).

I have a #27 drill in my tool kit from Cleaveland and the cleaveland cheatsheet shows a #27 drill for fiinal size for an AN509-6 screw.

Is it OK to use the slightly larger (.1440) here in place of the #28 (.1405)?
 
I went to my local Ace HW. They had numbered bits, but were out of the #28 of course. Thankfully Aircraft Spruce is only 20 minutes away. They had them.

Never tried a reamer. Sounds complicated. :)
 
FlyBoy8 said:
I went to my local Ace HW. They had numbered bits, but were out of the #28 of course. Thankfully Aircraft Spruce is only 20 minutes away. They had them.

Never tried a reamer. Sounds complicated. :)
Click to expand...

Reamers are basically precise bits. The flutes run along the shaft. Since there's several cutting edges, they make perfectly round holes exactly to dimension.
Most standard drill bits make a triangular shaped hole slightly bigger than spec. I drill a size under and run a reamer through for all holes if possible.
 
FlyBoy8 said:
The plans call for a #28 drill for the AN507-6R6 screws that attach the W-822 access plates to the spar platenuts (K1000-06).

I have a #27 drill in my tool kit from Cleaveland and the cleaveland cheatsheet shows a #27 drill for fiinal size for an AN509-6 screw.

Is it OK to use the slightly larger (.1440) here in place of the #28 (.1405)?
Click to expand...

YES!! Use it!!
There is no way that 0.0035" larger diameter on the body clearance diameter for a flat head screw is going to make your plane fall out of the air.
 
For a panel cover, I would not sweat it but you'll need the #28 again and why not use the right size, if you don't live in the middle of Alaska where it takes dog sleds to get tools. :D
 
In case you wanted to see it written twice: #27 work just fine. That's all I used for mine. I also pulled out my RV8 manual and no where does it mention the need for #28 drill, but does have # 27 drill referenced as required and many 6 screws used.
 
Yep, Like the pros said - - #28 is perfect for one hole that will be threaded, but when there are many, it often takes a #27 to allow all the screws to insert and start nicely. If you were using a structural screw without threads at the shear area (like and AN bolt) then yes, maybe it would make a difference, but the vast majority of screws we use have threads to the base, i.e. not using the shear loads anyway.

Now you can use your judgement.
 
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