Drilling a hole through A500 plate

[Ironworker]

What type of drill bit to drill through A 500,550 steel plate ?

 

[JohnW...ski]

It should be tough but not extremely hard, I looked online and it is rated at about 26 Rc. Any good sharp high speed drill bit should work fine. I would guess about 350-400 rpm for a 1/2 inch drill, double that for 1/4", 1/2 that for a 1".
Good Luck
John

 

[ridgeway]

No problem with carbide.

 

[Stumpy1]

I used the DeWalt Cobalt step drill for a metric crap-ton of holes in AR400 (like 50 holes). I used two drill bits for the entire job (3/8" holes, in 3/8 thick AR400).

https://www.lowes.com/pd/DEWALT-1-4-in-x-6-in-Cobalt-Twist-Drill-Bit/50413704

Cheap and effective in my experience.

Hope this is useful,

Frank

 

[Gappmast]

26RC is quite soft that's about the same as a barrel

 

[tobnpr]

500 Brinell is about 51 Rockwell...

Brinell and Rockwell Hardness Conversion Chart | Rockwell, Rockwell Superficial, Brinell, Vickers, Shore Hardness Conversion Table

Brinell and Rockwell Hardness Conversion Chart - These Conversion Tables presents data in the Rockwell A, B, C, D, E and F hardness range on the relationship among Brinell hardness, Vickers hardness, Rockwell and Shore Scleroscope hardness

www.engineersedge.com

 

[RJTodd]

AR plate work hardens. The trick is NEVER let the bit make a turn without taking a chip. Feed it steady with consistent pressure. Too light and the bit will sweep without cutting. Getting the cut started again is very difficult. Too light is worse that too aggressive.

 

[lb-ft]

Solid carbide. Keep it flushed & cool. Note pressure recommendation above.

 

[Ziabeam]

AR plate work hardens. The trick is NEVER let the bit make a turn without taking a chip. Feed it steady with consistent pressure. Too light and the bit will sweep without cutting. Getting the cut started again is very difficult. Too light is worse that too aggressive.

What RJ said.

Cobalt is excellent.

I’ll add lower rpm than used on free machining steels. The idea is to ensure it’s always cutting, letting the heat depart with the chips. Otherwise it’s like making a fire with a bow drill… spinning in place it will work harden. Only hope of drilling any further after that is very slow rpm, controlled feed, using carbide until the work hardened layer is removed.