Tip: Drill Index Chart
 

Quick now....off the top of your head....what size would you ream a hole to accept a #6 screw? What is the diameter difference between a #40 and a #41 drill bit, a 1/8" and a #30 drill?, a 3/16" or a #12 drill bit? To what undersize size dimension would you predrill a bolt hole prior to final reaming it to accept an AN4? What size is larger....19/64" or an "N" drill? Could you use a type "V" drill instead of a 3/8" drill bit? Some close tolerance 3/16" interference fit fasteners are inserted into .1850 holes....what reamer size would you reach for? What size drill bit equates to .1850? To be sure, you may not be installing very many precision fasteners into an RV airframe, (I did) but such information is still nice to know or at least have available at your fingertips.

Every home shop should have some version of a drill index chart available for quick and ready reference. In the production shop I came from, such charts seemed to be hanging everywhere. So dependent am I on the chart's usefulness, I must have at least 6 displayed including my basement shop, garage, hangar, and even taped inside tool boxes. The knowledge is free. Take advantage of the drill index chart's unending usefulness and build even higher quality into your dream project.

Drill Index Chart
 

That's a good one. I've taken the one from the back of the Avery Catalog and laminated it. It's also very good, and includes metric sizes, which can be very convenient if you live in a place that has not yet upgraded to the SAE/British/Imperial measurement units. :)

Here's one that I like:

http://www.rvproject.com/drillsize

It's not as printable, but it's great if you have a computer in/near your shop. You can always "Save As..." if you don't have internet in the shop.

And get one of these
 

And... to go with the printed chart, have one of these to make sure that the #36 drill you picked up really is a #36...... :)

Usually available at good hardware stores.



gil in Tucson

Alternate if above pick disappears -

http://www.hardwareandtools.com/Gene...e-u793430.html

and the Little Black Book.....
 

....which, of course, is out in my toolbox at the airport, but is absolutely indespensible for all those quick little shop facts. Dang....what's it called? I have worn out a couple of them over my lifetime..."Standard Aircraft Mechanic's Handbook?"

Paul

I've got one in the shop that is poster size as well as a mouse pad with a Drill Index on it. Can't get along with out them!!

Les Dial
Staff Manufacturing Engineer, F-22A
Lockheed Martin Aeronautical Company

I have several almost just like that that came with orders from the Yard (yardstore.com).

So where is the info about #6 screws and the correct hole size? Is there a guide somewhere that give sizes for different screws?

Thomas

On the drill gage
 

Thomas... it is actually engraved in the General Drill gage pictured above...

6-32 #36 tap, #28 body drill

It's not a complete guide to screw tapping and drilling, but it does 95+% of what we usually need to know for an RV.... :)

gil in Tucson

The 11x14 insert in Cleaveland's catalog does all this plus has edge distance and rivet pitch info, cleco size charts, sizes of the drills to use when tapping a hole, etc. It looks great, is easy to read and, more importantly, it's free. It's been on the wall of my garage my whole project. As Rick said... definitely a necessity and it's amazing how much I've learned from it.

That's funny, I was just lementing the fact that I can never remember what size drill to use for #8 or #6 screws/bolts. I will have to print/make one of those doohickey's.

But how come I can't find a recommended hole size for bolts and screws in the AC 43.13?