HS - Match drilling spar cap into spar flange

Caribbean10 · #1 02-21-2021, 07:39 AM

So the RV-10 build instructions tell you to match drill the HS spar caps into the spar flanges using a 3/32" drill (Not a #40 drill). In a later step, you come back and final drill some of those holes using a #40.

My tool kit didn't come with a 3/32" bit. So can I match drill these holes using #40 or do I have to use a 3/32"? And if I do have to use a 3/32, would I be fine using my regular Home Depot Dewalt multipurpose 3/32" bit or do I need to get something better?

flion · #2 02-21-2021, 08:27 AM

Depends how exact you want to be. Best practice is to drill 3/32" and ream to #40 later. Home Depot (or other local places) will sell cobalt bits in fractional sizes. You should also consider investing in a complete drill set with extras in #30 and #40 plus 6" and 12" drills in the common sizes and reamers, too. Good tools make a difference. That said, many RVs have been built without reamers, etc. There is a certain tolerance, so it will be up to you whether you can accept 'good enough' over 'best'.

No_0ne · #3 02-21-2021, 09:03 AM

https://www.amazon.com/Viking-Norsem...3919200&sr=8-3

Buy a really good set of drill bits. Add some extra #30 and #40, in short and long lengths.

hillc95 · #4 02-21-2021, 05:27 PM

FWIW it took me one kit to swap over to using a reamer anytime I final "drill" any holes.....Vans put out a video highly recommending reaming over drilling as well

No_0ne · #5 02-21-2021, 05:48 PM

Quote:

Originally Posted by hillc95

FWIW it took me one kit to swap over to using a reamer anytime I final "drill" any holes.....Vans put out a video highly recommending reaming over drilling as well

Agreed on the reamers, I keep examples of all the commonly used sizes. You still need a quality set of drill bits though, which is why I recommended the set above. In the scheme of what tools are most useful, versus what they cost, having a good selection of bits is a wise investment.

hillc95 · #6 02-21-2021, 05:53 PM

Agreed. IF I have to get a bit from the hardware store I learned the hard way you need to buy the premium ones they have. Getting a regular bit (even if it says it's rated for metal) ends up chattering on the aluminum rather than actually drilling.

Caribbean10 · #7 02-22-2021, 06:28 AM

Quote:

Originally Posted by flion

Depends how exact you want to be. Best practice is to drill 3/32" and ream to #40 later. Home Depot (or other local places) will sell cobalt bits in fractional sizes. You should also consider investing in a complete drill set with extras in #30 and #40 plus 6" and 12" drills in the common sizes and reamers, too. Good tools make a difference. That said, many RVs have been built without reamers, etc. There is a certain tolerance, so it will be up to you whether you can accept 'good enough' over 'best'.

Yeah I have the kit from Cleaveland that contains all sorts of drill bit sizes and reamers, but it didn't come with 3/32, which is why the question. Wasn't sure if it was optional or recommended or what. Luckily I do already have a nice set of Cobalt fractional bits that I can use for this.

Quote:

Originally Posted by hillc95

FWIW it took me one kit to swap over to using a reamer anytime I final "drill" any holes.....Vans put out a video highly recommending reaming over drilling as well

So you're saying that I should match drill using the drill bits but final drill using an appropriately sized reamer?

Taltruda · #8 02-22-2021, 09:38 AM

There are mixed feelings about using readers. Yes, a reamer makes a more perfect hole, but a rivet expands to fill even an imperfect hole. It may be better to have an imperfect hole filled in by a rivet, as it grips or bites better into the imperfections. Does it really matter? Will a plane fall out of the sky because your holes are too smooth? Will it not win Grand Champion because your holes are rough inside where the rivets expand?

Mckay · #9 02-22-2021, 10:40 AM

There are no mixed feeling on reaming holes in primary structure.

Taltruda · #10 02-22-2021, 10:54 AM

Quote:

Originally Posted by Mckay

There are no mixed feeling on reaming holes in primary structure.

Holes for bolts, pins, ect.. reamed holes are ideal. Want even better surface finish? Why not hone holes? But for rivets, a drill makes a perfectly acceptable hole. If you ever had to drill out a rivet in a reamed hole, the rivet shank is more likely to spin, while in an imperfect drilled hole, they don’t spin and are much harder to push out the shank. I am perfectly content drilling my rivet holes as opposed to reaming, unless it’s in a place where I can’t access between sheets to deburr, then I’ll ream to minimize the burr that’s created by a drill. Thousands of RVs are flying around with drilled holes, many more other planes, so to the person (Caribbean10) who asked if they NEED to drill undersized then team to final size, the answer is no you do not.