Thread: Drilling big holes

for me it would depend on how accurate you require your holes to be,you could allways sharpen your drill sheet metal style for the 1.2 an 1.5,after drilling those holes resharpen your drill for the 5mm plate,just make sure that the outer edges of your drill are cutting before the drill breaks through maybe 140 degree or similar.

There are hole saws designed to cut steel plate "suttons" have a range, as to price wouldn't have a clue but you could try balckwoods they proberly have an on line cattle-dog

Rgds

I believe that you need a drill press, and an 18mm drill bit. They're expensive but it should last you for a long time. Hole saws will battle.

Hi

Originally Posted by Vernonv

Hi All,
Just after some advice. I am needing to drill a few 18mm diameter holes in some 5mm and 1.2 to 1.5 mm steel. What is the best, simplest and cheapest way to do this?

Should I use a normal 18mm drill bit (still have to find one)?
Should I use some sort of hole saw?
Is there some other contraption that would be better?

Thanks in advance.

A twist drill generally has a much longer lifespan than a hole saw, so I would prefer the 18mm drill. You should be able to obtain an 18mm drill reasonably easily. Bunning MIGHT have them, but otherwise Blackwoods can get one in for you if they are not already on the shelf.

To save having to resharpen an already GREAT new drill, drill the 5mm steel first and then if at all possible clamp several of the thinner pieces of steel together an drill as though it was a "thick" piece of steel. With the thinner material and such a (relatively) large hole, it will be important to clamp the thin material as close as possible to the hole being drilled.

Another option to drilling thin material is to use a backing of some other material eg block of wood. Again, if you can clamp the material close to the hole being drilled you can avoid resharpening the drill to a different included angle.

Because drilling such a large hole in thin material tends to pull the material up, if you can place a second block of wood etc on TOP of the hole being drilled you can obtain VERY clean holes.

If you have many items to drill, then making a small jig for this will help substantially. You could possibly use such a jig to position the hole to save time in marking out etc.

BTW you should really use a drill press with an 18mm drill, whereas you could use the holesaw in a hand drill.

HTH

Years ago we used to use a die for this, I think that was what it was called, you drilled a 1/4" hole and attached the cup on the back and the cutter on the front and jsut screwed the two together and out popped the disc, dismantle the thing and start again.
We used to use them for mounting instruments in panels on one off jobs, there were a variety of sizes but I would imagine any decent metalwork supplier would still have them.

Well, it looks like the the punters are leaning towards the 18mm drill bit.
I already have a drill press, so that won't be a problem - and I will try with a backing/topping block.

Just need to source the drill bit - closest Bunnies is more than 100km away. I will try the local M10, building supplies and engineering/car parts places.

Thanks for the input everyone.

G'day.
Depending on how big the item is that you want to drill.
I would mount it on a rotary table on the mill and make the 18mm hole with a 6mm slot drill.

Thanks Iain and Glock.

Iain - I have used one of those die things, a long, long time ago. Works OK on thinnish sheet, but will not work on 5mm stuff.

Glock - I think the cost of the mill would be somewhat prohibitive and uneconomical in this situation . Although, I could try it on the Minister for War and Finance - "... the only way to drill those holes properly is to buy a $2000 mill." ... WHACK!!! .

Was the mid 60's when I last used one, aaahhh, the apprenticeship days, thinking back it was aluminium chassis' we were cutting.

What about a super drill?
You start wuith a 1/2 inch hole then the superdrill will drill any hole up to 2". It's not a gimmick, I own one and use it heaps, you do need a drill press, but that's not an issue in your case.

once again how accurate do you need the holes and how many items are you drilling,and if you know how to sharpen drills its you most cost effective and in my opion easiest way to go

Pipeclay - the holes don't need to be super accurate.

I think I will go with MrFixIt's suggestion of using a backing block. That will hopefully stop the bit from binding and also reduce the chance of a distorted hole.

Make sure you clamp the job to the drill press table. A job spinning on a drill makes a nasty mess of the operator, if it grabs.

In the absence of needing super accuracy I would use a holesaw but it is really six of one half a dozen of the other.

My drill press is not really rigid enough to cope with big bits and as a result the hole ends up with a kind of triangular out of roundness too it (i'm sure some people know what I mean).

A nice gentle touch and plenty of cutting fluid and I have had no problems cutting with some fairly big holesaws (guess 70mm+).

I would guess an 18mm bit is going to be $40 or more and it is a pretty useless thing to have for a one off job.

You should be able to get a holesaw more easily and even though it might cost about the same once you buy the arbor, the arbor itself is a handy thing to have.