What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Tips on drilling aileron bracket holes through aileron spar?

Draker

Well Known Member
Well, after conferring with the mother ship, I've decided to bite the bullet and re-do both aileron spars on my '7 build. Fortunately I have not riveted the skins on yet. Here's the result of match drilling the bracket through to the spar without properly securing the workpieces:

IMG_0596-L.jpg


This is the left one. The right one is a little better but still way larger than the acceptable diameter for AN3 bolts.

Problem with drilling these is that there are only two holes, so while drilling one hole, there's only a single cleco securing the parts together. I tried additionally holding the workpieces in place with a c-clamp and a small piece of wood, but obviously the bit still walked around unacceptably. Anyone have a good method/tool for match drilling these correctly?
 
I would suggest using a piloted double margin drill.

piloted_double_margin.jpg


http://www.panamericantool.com/double-margin-drills/piloted-double-margin-drills-nas-937.html

•Designed for close tolerance drilling in titanium, stainless, heat treated material and aluminum alloys. When the drill point penetrates enough for the second margin to contact the wall of the hole, the point is stabiized and true cylindrical geometry is established. Smooth accurate holes are produced and reaming can often be eliminated.
 
Last edited:
Drill bushing

Use some sort of drill bushing. Pieces of brass tubing inserted into each other or a true bushing.
Other option is transfer punch. Drill the punch mark small and increase incrementally.
 
I'm not sure if it would work in this specific location but I find that small C clamps can be useful for holding pieces together. The 2" or 3" ones can be found at Lowe's or Home Depot for not much money. I think the ones I have are Irwin. I have about 8-10 of them. I put painters tape on the clamping surfaces to limit the scratching. These small clamps are light weight enough to be useful in many places were a larger clamp doesn't work too well.

Don't worry about this type of mistake. I've ruined several parts by not having them secured well enough.
 
So that is why my ailerons are low! I suggest a 6" C-style vice grip clamp (no feet). Then take the ends and grind down the tips to fit within the hinge. The 6" frame is narrow enough to fit. That's my process for redrilling my hinges for a heavy wing.
 
I can't tell you how I did my bracket drilling because it was too long ago for memory.

BUT.....

For a pre-drilled 2-hole assembly, only one 1 hole needs match drilling. You may choose the 'first' hole and open it up accurately on both parts, one at a time, not as assembly. Bolt it together using that hole. Clamp as appropriate. Match drill the other hole. The only positional error possible is then rotation around the first hole. For an aileron bracket, if you are able to not egg the second hole, position will be essentially perfect.
 
Last edited:
Thanks everyone, I’ll give these tips a try. I remember having to use a lot of force on these holes too, my bits may not be sharp enough.
 
Last edited:
Dull bits

Thanks ever, I’ll give these tips a try. I remember having to use a lot of force on these holes too, my bits may not be sharp enough.

The enlarged hole is a common symptom of a dull bit. I lost a side skin that way. If a but doesn't feel right, toss it. Replace with new, start small and incrementally enlarge. Use light oil on steel.
High speed on aluminum. Low on steel. Let the bit do it's job.
BTW. When you get to stainless, buy several. It will dull a bit quickly. I replaced every 10 or so holes.
 
I would suggest using a piloted double margin drill.

piloted_double_margin.jpg


http://www.panamericantool.com/double-margin-drills/piloted-double-margin-drills-nas-937.html

?Designed for close tolerance drilling in titanium, stainless, heat treated material and aluminum alloys. When the drill point penetrates enough for the second margin to contact the wall of the hole, the point is stabiized and true cylindrical geometry is established. Smooth accurate holes are produced and reaming can often be eliminated.

Neat, but it's a pity the minimum order is for 6 of any one size. :rolleyes:
 
Match drilling anything with a final sized hole already in the piece is best done with a drill bushing/guide. I use my lathe and turn whatever size I need. McMaster Carr carries all kinds of drill bushings if you don?t have access to a lathe.
 
It may be, but if I want reamer quality holes I use my reamer...:D

Yes but final reaming a good hole to size is not the same as stepping up a piloted #30 hole to a #10 in one easy operation. Guess I'm just spoiled :cool:
 
Match drilling anything with a final sized hole already in the piece is best done with a drill bushing/guide. I use my lathe and turn whatever size I need. McMaster Carr carries all kinds of drill bushings if you don?t have access to a lathe.

OK I not a machinest, so how do you match drill to final size both pieces using a drill bushing?
 
OK I not a machinest, so how do you match drill to final size both pieces using a drill bushing?

Sorry Walt, ?match drilling? is probably the wrong term. Since the hole is already final sized in the one piece, the Spar in this example, you are just making a pilot that is certain to be centered. Since the pilot hole is drilled with a small drill size, it takes less clamping pressure to keep things from moving around. You can then use your pilot step bit or frankly the final size drill will typically not drift or wander out of the pilot. Hope that makes sense.
 
Sorry Walt, ?match drilling? is probably the wrong term. Since the hole is already final sized in the one piece, the Spar in this example, you are just making a pilot that is certain to be centered. Since the pilot hole is drilled with a small drill size, it takes less clamping pressure to keep things from moving around. You can then use your pilot step bit or frankly the final size drill will typically not drift or wander out of the pilot. Hope that makes sense.

OK, I'm still confused.

If you have a small pilot hole and a large final size hole how does the step drill help?

If the pilot hole isn't exactly centered with the final size hole won't the large portion of the step drill cut an edge section out of the final size hole? If there is no pilot hole how does the step drill help?

I don't see how you get centered if one hole is full size. :confused:
 
Well, after conferring with the mother ship, I've decided to bite the bullet and re-do both aileron spars on my '7 build. Fortunately I have not riveted the skins on yet. Here's the result of match drilling the bracket through to the spar without properly securing the workpieces:

This is the left one. The right one is a little better but still way larger than the acceptable diameter for AN3 bolts.

Problem with drilling these is that there are only two holes, so while drilling one hole, there's only a single cleco securing the parts together. I tried additionally holding the workpieces in place with a c-clamp and a small piece of wood, but obviously the bit still walked around unacceptably. Anyone have a good method/tool for match drilling these correctly?

OK, I'm still confused.

If you have a small pilot hole and a large final size hole how does the step drill help?

If the pilot hole isn't exactly centered with the final size hole won't the large portion of the step drill cut an edge section out of the final size hole? If there is no pilot hole how does the step drill help?

I don't see how you get centered if one hole is full size. :confused:

The OP was "match drilling" the bracket to the spar, this infers that both pieces had pilot holes, hence my original recommdation for a piloted double margin drill would likely have prevented the issue the OP ended up with.

Thats the trouble when we add to a thread but lose sight of the original question.
 
OK, I'm still confused.

If you have a small pilot hole and a large final size hole how does the step drill help?

If the pilot hole isn't exactly centered with the final size hole won't the large portion of the step drill cut an edge section out of the final size hole? If there is no pilot hole how does the step drill help?

I don't see how you get centered if one hole is full size. :confused:

The drill bushing insures a centered pilot hole. All I can say is I have had to do this many times in different applications to match a part to a final sized hole including a very tricky strut repair.
Wirejocks linked article walked thru the process very well if you want to go back and read that.
Hope it helps the OP, but if not, I have often learned as much from a little thread drift.
Remember guys, this is all supposed to be for fun and education.
 
The OP was "match drilling" the bracket to the spar, this infers that both pieces had pilot holes, hence my original recommdation for a piloted double margin drill would likely have prevented the issue the OP ended up with.

Thats the trouble when we add to a thread but lose sight of the original question.

OP here. The spar itself comes with small holes that needs to be enlarged to #12. The bracket already has holes but also smaller than #12. You also make a 0.040" reinforcement plate. The process I followed was:

1. Match drill through the existing spar holes to the reinforcement plate. Add clecos as I went.
2. Attach the bracket to the spar+plate assembly with one cleco
3. C-clamp the rest of the bracket to the spar using a small piece of wood
4. Slowly open up the whole sandwich to #12

Due to the difficulty of getting through the steel bracket, I used a number of bits, progressively getting larger (#28, #21, #13, then #12) but as you can see it still turned out very badly.
 
OP here. The spar itself comes with small holes that needs to be enlarged to #12. The bracket already has holes but also smaller than #12. You also make a 0.040" reinforcement plate. The process I followed was:

1. Match drill through the existing spar holes to the reinforcement plate. Add clecos as I went.
2. Attach the bracket to the spar+plate assembly with one cleco
3. C-clamp the rest of the bracket to the spar using a small piece of wood
4. Slowly open up the whole sandwich to #12

Due to the difficulty of getting through the steel bracket, I used a number of bits, progressively getting larger (#28, #21, #13, then #12) but as you can see it still turned out very badly.

OK, if I'm understanding it correctly similar efforts came up in my non-punched -6A kit.

I would have drilled all of the holes in the steel bracket to #13 (tight fit AN3 bolt) and one hole to #13 in the sandwich pieces.
Insert an AN3 bolt into this single #13 hole as a locator, clamp the assembly up, and then drill the other holes straight to #13 using the steel part for alignment. Keep adding bolts for alignment to each finished hole as you go. Note, bolts as alignment pins only, no nuts involved.
When all done, clean up each hole one at a time, still using the bolts as locators to the final #12 - AN3 slip fit.

The steel part is so much harder that it can be drilled to size initially and used as a guide with regular drills if you keep your drill vertical and use sharp bits.
 
Somebody want to buy a couple of sizes and split them up? I agree it seems overkill to have six of each size. .
 
Thanks for everyone's tips and encouragement. The new spar holes ended up much better. Verdict: Dull drill bits. Upon switching to new drill bits, my troubles were over.

IMG_0616-M.jpg
 
Back
Top