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Tips for match drilling into stainless steel

ymc9

ymc9

Well Known Member
Patron
Hi guys,

I just started the flaperon and did a bad job drilling from the skin into the stainless steel counterbalance. The drill bit walked about too much. I think this is the first time for me to match drill into steel. Before trying it again, I'd like to seek tips to do a good job consistently.

My thoughts are:

1. Center punch first
2. Pilot drill with a #40 first then #30
3. Slow speed and more pressure
4. I used WD40 to lubricate but I read somewhere it's not good for steel. Tap magic seems better?
5. Should I try to use a drill press? It's a little challenging to set up a way to clamp the piece.
6. Any drill bit better for steel than the common cobalt split point bits?

What are your suggestions?
 

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Btw, do you guys think the skin piece is savable? Although I've ordered another one from Vans ...
 
ymc9 said:
My thoughts are:

1. Center punch first
2. Pilot drill with a #40 first then #30
3. Slow speed and more pressure
4. I used WD40 to lubricate but I read somewhere it's not good for steel. Tap magic seems better?
5. Should I try to use a drill press? It's a little challenging to set up a way to clamp the piece.
6. Any drill bit better for steel than the common cobalt split point bits?

What are your suggestions?
Click to expand...
All of the above except #5. I used some thin machine oil (worked better than dry Boelube) and dipped the drill bit in it 2-3 times per hole. Really helped to drill the pilot hole with the #40, and GO SLOW! I think I used at least 2 cobalt bits for each flaperon.

And I think that skin is toast……
 
jsalley said:
All of the above except #5. I used some thin machine oil (worked better than dry Boelube) and dipped the drill bit in it 2-3 times per hole. Really helped to drill the pilot hole with the #40, and GO SLOW! I think I used at least 2 cobalt bits for each flaperon.

And I think that skin is toast……
Click to expand...
Thanks! Why is using a drill press a bad idea for this job?
 
ymc9 said:
Thanks! Why is using a drill press a bad idea for this job?
Click to expand...
It's not! After screwing up my first skin, here's what worked for me:

1. Cleco the flaperon skin to the spar to hold the counterbalance weight in the proper position.

2. Using the flaperon skin as a template, mark the position of the holes on the counterbalance weight.

3. Clamp a self-centering drill press jig to your drill press to hold the counterbalance weight and carefully drill in the spots where you marked the holes. If I remember correctly, I started with a 3/32-inch bit and then drilled to final size.

The jig was less than $10.00 at Harbor Freight.
www.harborfreight.com

Self-Centering Drill Press Jig

Amazing deals on this Self-Centering Drill Press Jig at Harbor Freight. Quality tools & low prices.
www.harborfreight.com www.harborfreight.com
 

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ymc9 said:
6. Any drill bit better for steel than the common cobalt split point bits
Click to expand...
I used Milwaukee Red Helix Hard Metal Cobalt Drill Bits, available from Home Depot. Double-checking my builder log, I see I actually started with a 1/16-inch bit, followed by a 3/32-inch bit and a 1/8-inch bit. I then drilled to final size with a common #30 cobalt split point bit. I was able to drill all the holes in both counterbalance weights using one of each bit mentioned above. I used liquid Boelube as a lubricant.

www.homedepot.com

Milwaukee 3/32 in. Cobalt Red Helix Twist Drill Bit 48-89-2303 - The Home Depot

Provide optimum strength and protection against breakage while drilling by choosing this Milwaukee Cobalt Thunderbolt Drill Bit. Offers durability.
www.homedepot.com
 
rv12iS-builder said:
It's not! After screwing up my first skin, here's what worked for me:

1. Cleco the flaperon skin to the spar to hold the counterbalance weight in the proper position.

2. Using the flaperon skin as a template, mark the position of the holes on the counterbalance weight.

3. Clamp a self-centering drill press jig to your drill press to hold the counterbalance weight and carefully drill in the spots where you marked the holes. If I remember correctly, I started with a 3/32-inch bit and then drilled to final size.

The jig was less than $10.00 at Harbor Freight.
www.harborfreight.com

Self-Centering Drill Press Jig

Amazing deals on this Self-Centering Drill Press Jig at Harbor Freight. Quality tools & low prices.
www.harborfreight.com www.harborfreight.com
Click to expand...
Awesome. This looks perfect!
 
Get drill bits from Rodman. https://rodmandrill.com/ I picked up a set at Oshkosh a few years ago. I used one drill bit for 9 7/32 holes in 3/16" stainless steel for a non-airplane project. And the drill bit was still sharp when I was done. No pilot hole, just center punched and drilled with a hand drill at medium speed. These are the best drill bits I've ever used!
 
Stainless is a royal pain. If you get it hot it will harden and become very difficult to drill. It only takes 1/2 second for it to happen.

Your approach should be completely different than aluminum. Speeds should be 1/10th of aluminum. Pressure at least 2-5x aluminum. Feeds roughly the same. If you aren't making chips immediately you risk hardening the metal. Use lube and don't be stingy. Anchor lube if you can get it otherwise something liquid (not wd40) that will flow into the hole as you drill and carry the heat away as steam or smoke. ATF works fairly well in a pinch.
 
I had the best results super slow and high pressure. Like count rotations slow. I use a cutting oil. Just a drop or two. New bits. #40 for the starter hole then up no more than 10 at a time. Takes forever but a big bit will grab and distort the hole.
 
CRC Trefolex Cutting Paste is my go-to for drilling holes in stainless steel and mild steel as well as tap & die cutting. The paste sticks to the part and drill bit to provide better lubrication. +1 on wirejock, super slow speed and high pressure, you should see some curled chips if you have the right pressure and speed. Good luck finding Trefolex, I am still using the quart I bought 15 years ago.
 
Mel said:
Pet Peeve........WD40 is NOT a lubricant! It is a Water Dispersant.
Click to expand...
While that may be true, it is not really relevant here. When drilling, we are not using the fluid as a lubricant, but as a coolant to pull heat out of the bit and the metal. Lubricantion doesn’t really apply here as we are cutting into the metal with the bit, not sliding across it. While I use sulfur based cutting oils for machining steel, i have found wd40 works better when machining aluminum, so it does have a place in metal work.

Larry
 
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I finally completed the task with the following procedure:

1. Start with a hand drill with 3/32, match drill to make a dent good enough to help center the drill press (but not a full hole)
2. Using the drill press jig recommended by @rv12iS-builder, drill through with 3/32
3. Cleco the skin back then match drill with #30

The result was not bad, although the process was a bit intensive and time-consuming. I ruined about 3-4 drill bits for the two stainless steel tubes. Ruined a reamer too to learn it's definitely not designed for the job :ROFLMAO:

The self-center jib recommended by @rv12iS-builder is wonderful! Drill press works much faster than hand drill.
 
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