slamdunk
11th February 2012, 05:10 AM
Hi Guys,
Any advice on how to drill 12mm holes in 8mm galvanised steel angles? Which drill bit to use and any paint required to touchup new holes?
Ben Dono
11th February 2012, 06:45 AM
I'm surprised this has not been answered yet! Normally there are heaps of guys on these forums and answers come real fast. I think there must be an issue with the net.
I will give a short answer to get you started! This is my way and there are many ways to do it. There are a lot of senior members here that will post some better info for you soon I'm sure.
Simple way is to centre punch a mark where you want the hole so your drill starts where you want it and not wander everywhere.
I'm guessing your using a cordless or a powerdrill so you can do this in 2 drills
Start with a 4 or 5mm drill bit with a reasonable speed at the trigger and pressure. Use a coolant/lube!!!!! Wd40 or the likes is fine for a few holes in a hurry but if you have a lot of holes get the proper stuff.
When you drill, your aiming to have curly springs come out as chips
If they are turning blue it means your going too hard and fast.
Next jump up to 12mm. Back of the speed of your drill and use more lube/coolant. Your looking for curly chips that are not blue! If they are blue it means you should back off a bit as you are heating you drill bit.
Breaking through the hole is the tricky bit as it's easy to chip the cutting edges of your 12mm drill. There is another thread here where I ask about this problem and I got a lot of good answers!
Buy good drills! Sutton or bordo are good.
Cold gal spray paint works a treat. Give them a damn good shake before you spray and clean off all the lube on your steel.
How many holes are you drilling?
What is it for?
The speed you drill is pretty critical. If you have not drilled mild steel before you might be surprised on how slow the drill rotates. YouTube it so you can have a look but start out with about half the speed you would use when your drilling timber and go from there. The guys here will prob explain that a bit better.
pipeclay
11th February 2012, 06:55 AM
If the location of the holes is important use a centre punch to give a locateing point for the drill to start.
Use good quallity drill bits (pay $5 to $20) per drill,they maybe less,dont buy the sets of drills from the discount stores.
If you think you will be using drills a lot and of varying sizes you can get good quallity sets that will cover ranges 1 to 10mm or ,5mm to 13.
If you are using a hand held drill you will need to use at least one smaller drill than 12mm to start with,you may need to use two.You could start with a 5mm drill then try the 12mm,if this was no good or you found it a bit hard you could try 5mm,8mm then 12mm.
A variable speed hand drill would be best if you have one.
If you are using a Bench or Pedistal drill it would be easier,still drill the pilot hole,(you may even find you dont need the pilot as you can apply more force with the bench drill) then just run the 12mm drill through.
You will need to run the bench drill at around 500/600 rpm for the 12mm drill,if the drill was quick and easy to change speeds you could run your pilot at say 750 to 1000 rpm,but if its time consuming just run both drills at the slower speed.
If you have a lot to drill you could drill all the pilots first the finish with the 12mm.
If there are a lot of these holes to drill you may need to buy extra drill bits if your not able to resharpen them.
Some type of cutting oil/compound is also a good idea if you have a lot to do.
After you have drilled the holes and cleaned any burs you can give them a coat of Cold Galvanising paint,comes in either a spray or can.