Drilling a lot of 1/2" holes, best method

Paddy · Aug 25, 2011

I'm building a hand rail that has 1" square tube with 1/8" wall thickness. I have a bunch of copper ground rods I will cut to length and sit in the 1" tube, 4" on center. The tubes need to be drilled on just onside, not all the way through.

I called a water jet cutting outfit but they can't do just one side. So drilling is my only option. I friend has a some what large drill press, (Grizzly). So what I know is slow RPM and use lots of oil. The issue is when you drill a hole, the oil just isn't doing much. I thought I might use a small pump with a sump tray and provide constant lube.

Any sugestions on the perfect drill bit, RPM and pumpable lube? There are 450 holes to drill so I need to get it right. I have a drill doctor so re-sparpening will be in my future!

Patrick T

Lloyd_E · Aug 25, 2011

Slower is better. I have a 16" delta drill press floor model. I use the slowest setting - I think it is around 700rpm. I would tape the side to be drilled and put layout marks on the tape and remove tape after drilling. Find the best bit(s) money can buy and go at it. Will the railing be at an angle when installed? If so you may have to drill a pilot hole first than make a jig with the correct angle and drill final holes. When marking lay your top and bottom rail side by side and mark. You may want to drill side by side too... just to keep an eye on the process.

Good luck... show pics...

psj12 · Aug 25, 2011

Most ground rods are steel with a heavy copper plating. The may develop rus on the cut ends.

jonyyuma · Aug 25, 2011

Unless the rods are very old they are Copperclad,, as stated above. I had to assume you will be painting the finished product.You might want to clean the rods well with scotch brite pads or steel wool prior to painting..

PapaPerk · Aug 25, 2011

One option is to have a machine shop do the work. A CNC mill will knock it out in no time. That's what I would do if I had to drill 400 holes!

TonyF · Aug 25, 2011

Paddy said:
I'm building a hand rail that has 1" square tube with 1/8" wall thickness. I have a bunch of copper ground rods I will cut to length and sit in the 1" tube, 4" on center. The tubes need to be drilled on just onside, not all the way through.

I called a water jet cutting outfit but they can't do just one side. So drilling is my only option. I friend has a some what large drill press, (Grizzly). So what I know is slow RPM and use lots of oil. The issue is when you drill a hole, the oil just isn't doing much. I thought I might use a small pump with a sump tray and provide constant lube.

Any sugestions on the perfect drill bit, RPM and pumpable lube? There are 450 holes to drill so I need to get it right. I have a drill doctor so re-sparpening will be in my future!

Patrick T

Go to McMaster or Enco and get cutting fluid, TapMatic, ReLion etc don't make the mistake of using engine oil or similar. Engine oil is designed to prevent friction and allow things to slide, when cutting you want the bit to grab, the cutting fluid keeps the chips from welding to the bit. Some folks use kerosene or WD40 - YMMV. I'd get a quart or so and just apply it with an acid brush, no need for anything fancy, just a dab will do ya.

With a 1 inch bit the RPM will be very low, ~ 400 RPM...

Cutting speed (CS) X 4
-----------------------
Diameter of cutter (D)

Figure around 90-100 for the Cutting Speed using steel.

Clamp the workpiece down good, and/or position it against the drill press column, a 1" bit may grab and fling the entire bar around like a weed eater string.

I would probably use a 1" bi metal hole saw, get a couple and use the cutting fluid. You may have to experiment with the size, 1 " hole saw will cut a hole a little larger than 1".

Good luck

TonyF · Aug 25, 2011

PapaPerk said:
One option is to have a machine shop do the work. A CNC mill will knock it out in no time. That's what I would do if I had to drill 400 holes!

Ditto!

PapaPerk · Aug 25, 2011

TonyF said:
Go to McMaster or Enco and get cutting fluid, TapMatic, ReLion etc don't make the mistake of using engine oil or similar. Engine oil is designed to prevent friction and allow things to slide, when cutting you want the bit to grab, the cutting fluid keeps the chips from welding to the bit. Some folks use kerosene or WD40 - YMMV. I'd get a quart or so and just apply it with an acid brush, no need for anything fancy, just a dab will do ya.

With a 1 inch bit the RPM will be very low, ~ 400 RPM...

Cutting speed (CS) X 4
-----------------------
Diameter of cutter (D)

Figure around 90-100 for the Cutting Speed using steel.

Clamp the workpiece down good, and/or position it against the drill press column, a 1" bit may grab and fling the entire bar around like a weed eater string.

I would probably use a 1" bi metal hole saw, get a couple and use the cutting fluid. You may have to experiment with the size, 1 " hole saw will cut a hole a little larger than 1".

Good luck

He's drilling 1/2" holes. The metal is 1" wide.

om21braz · Aug 25, 2011

You're not going to like this, but I'd drill lead holes first (approx. 7/32" dia. @1000-1200rpm). The smaller bit hits a punch mark easier and will prevent the larger bit from leading off. The big task for you is not drilling the holes - but is laying them off properly.

sal64 · Aug 25, 2011

Paddy said:
I'm building a hand rail that has 1" square tube with 1/8" wall thickness. I have a bunch of copper ground rods I will cut to length and sit in the 1" tube, 4" on center. The tubes need to be drilled on just onside, not all the way through.

I called a water jet cutting outfit but they can't do just one side. So drilling is my only option. I friend has a some what large drill press, (Grizzly). So what I know is slow RPM and use lots of oil. The issue is when you drill a hole, the oil just isn't doing much. I thought I might use a small pump with a sump tray and provide constant lube.

Any sugestions on the perfect drill bit, RPM and pumpable lube? There are 450 holes to drill so I need to get it right. I have a drill doctor so re-sparpening will be in my future!

Patrick T

you need to set a stop on the drillpress c clamp a piece of steel to drillpress to set the center distence then if you dont need it to be to precition draw a pencile line at 4 inches use a good high speed steel drillbit slow speed and applie little oil with an acid brush on drill tip four each hole.