Final Drill using Reamers, pros cons

Jskyking · #1 07-24-2019, 05:11 PM

Getting ready to final drill left wing spar flanges. Is there a difference using a #40 drill bit vs #40 reamer?
Thanks
Jt

Robin8er · #2 07-24-2019, 05:35 PM

Are you talking about the countersink holes for the skins? It's better to use a drill bit. I've read not to use a reamer because a perfectly round hole allows the rivet to possibly rotate with vibration. So in this case it's actually better to use the less precise drill bit.

1001001 · #3 07-24-2019, 05:40 PM

Quote:

Originally Posted by Jskyking

Getting ready to final drill left wing spar flanges. Is there a difference using a #40 drill bit vs #40 reamer?
Thanks
Jt

I use reamers wherever I can. Cleaner hole, less deburring. It doesn't make a perfect hole, but it's better IMO.

Girraf · #4 07-24-2019, 06:49 PM

If Van's thought reamers were really necessary, I figure they would have told us to use them. I stick with drill bits, but what do I know.

Mike S · #5 07-24-2019, 08:01 PM

A double margin drill bit is kinda like a compromise between a reamer and a standard drill bit.

I like them when I need to drill to size, and do not have a reamer of the correct size.

jcarne · #6 07-24-2019, 09:45 PM

I use reamers whenever I can. I will second Mike though, them double margin drill bits are sweet! I'm using them exclusively now for drilling initial holes. Heck I like reamers so much I usually drill to 43 and them ream to 40 (assuming it's not prepunched of course).

swisseagle · #7 07-25-2019, 10:25 AM

I had a lot o micro cracks after dimpling, when using reamers!

Looks like there is a bit of heat generated and this changes the characteristic of the material.

The cracks are visible after dimpling, but you need a magnifying glass.

For sure I was lubricating and was using low RPM.

Had to replace the center section ribs due to this.

terrye · #8 07-25-2019, 12:20 PM

Quote:

Originally Posted by swisseagle

I had a lot o micro cracks after dimpling, when using reamers!

Looks like there is a bit of heat generated and this changes the characteristic of the material.

I used #40 and #30 reamers extensively (but not exclusively) on my prepunched holes. Neither drills nor reamers generated any heat that my fingers could feel and unless the aluminum is way too hot to touch, the temper and material properties are unchanged. I suspect micro cracking after dimpling has more to do with the deburring bit and chamfer than the reamer or drill surface finish inside the hole.

To the OP, do some test holes using a drill and also a reamer and a good deburring bit. Examine the holes with a 16x magnifying glass. I think you'll find the reamer results in a better surface finish.

BMC_Dave · #9 07-25-2019, 05:32 PM

People are reaming holes in sheet metal? Talk about the forest through the trees...

Scott Hersha · #10 07-25-2019, 08:09 PM

I used piloted reamers in most pre-punched holes in all three airplanes I?ve built. No cracks, and the hole was cleaner and easier to deburr without taking too much material off. Never had a crack, holes were clean, results were good. If I wouldn?t have had these piloted reamers, I would have used a drill bit and not thought twice about it. I think some people get in to trouble when they over deburr the holes, hence the reamer requiring less aggressive deburing. I don?t think there?s anything wrong with either method.