Tip: Drill Index Chart

[osaleh]

Originally Posted by Rick6a

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.

Hi.

I am working on my training project currently, soon to start 7A. This chart that you provided, will this tell me what drill size to use for a specifid rivet size provided by VANs instructions? In my training project, Vans specify for example rivet size AN426AD3-3. I know this is a 3/32" diameter. so How do i know the drill size? #30 or #40 etc...

[Rick6a]

Originally Posted by osaleh

Hi.

I am working on my training project currently, soon to start 7A. This chart that you provided, will this tell me what drill size to use for a specifid rivet size provided by VANs instructions? In my training project, Vans specify for example rivet size AN426AD3-3. I know this is a 3/32" diameter. so How do i know the drill size? #30 or #40 etc...

As a technical counselor, I always try to acquaint the builder to the many benefits of referring to a drill index chart. Just yesterday, a builder stopped by my hangar to borrow a reamer and asked what size drill bit he should use to first prepare the hole with prior to making the final full size pass with my borrowed reamer. I encouraged him to tape a drill index chart on a wall somewhere in his shop and refer to it often.

To answer your specific question, a #40 drill (or #41) drill bit is standard for preparing a hole to accept an AD3 rivet. But really, your question is just scratching the surface. You are going to run into many situations in which you need to figure out what size drill bit is appropriate for the hole diameter required of any given fastener. You can quickly determine that important information using two tools. One is a drill index chart. The second tool is a micrometer or dial calipers. The two tools go hand in hand. If you seek optimum hole quality as routinely expected in aircraft production facilities, use em.

[az_gila]

Originally Posted by Rick6a

As a technical counselor, I always try to acquaint the builder to the many benefits of referring to a drill index chart. Just yesterday, a builder stopped by my hangar to borrow a reamer and asked what size drill bit he should prepare the hole with. I encouraged him to tape a drill index chart on a wall in his shop and refer to it often.

A #40 drill (or #41) drill bit is standard for preparing a hole to accept an AD3 rivet. But your question is just scratching the surface. You are going to run into many situations in which you must figure out what the hole diameter for a given fastener will be. You can quickly determine that with two tools. One is a drill index chart. The other is a micrometer or dial calipers. The two tools go hand in hand. If you seek optimum hole quality, use em.
...

...the micrometer if you buy one of these. Made by General tools and in most good hardware stores -

http://www.generaltools.com/Products...o-60)__15.aspx



If you want to know what drill to use for your rivet/screw, just poke the rivet/screw through the holes in the gauge...

It also helps you check that the drill you just picked up for the #8 screw clearance hole is really a #19 and not the #21 you bought to drill stock for a 10-32 tapped hole...

It also helps you skip the tap drill chart previously mentioned since it is engraved right on the face of the gauge.

PS The micrometer is still good to have, but the "hole gauge" is probably easier for drill bits, even if it is a bit lower-tech than the 6 digit precision of Rick's micrometer.

In this case, simpler is better....

[DCat22]

Originally Posted by Ironflight

....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

This book?