Thread: Need to make large holes in steel

Do you need the holes? Or do you need to make the holes? If you merely need the holes, I'd suggest a chat with a local metal fabricator to establish a ball-park cost estimate, and necessary logistics. You might be surprised, one way or the other.

Cheers,
Joe

Hi

Buy a BIGGER drill.

You will use it again - sometime - and be pleased you have it

BTDT

Triangular holes result from the wrong drilling speed and/or the lack of clamping of the material being drilled. In most cases incorrect sharpening of a drill results in a larger hole than the drill bit size.

Maybe you should consider a new drill press too

Kind regards

Peter

when i first started doing metalwork i had a Kmart drill press went way to fast to drill 1 inch diameter hole so to my favorite hobbit hole ( the worlds best tool shop ) got 1 inch bit cost $15 dollars took the pieces to the fabrication shop did the job for $5 dollars

The quickest and best way is to use a 25mm drill. If you can get the speed of your drilling machine to 300rpm or less then the rest is easy. Sharpen the drill correctly and use the "folded rag" trick to drill the holes. Drill a pilot hole about 10 or 12mm first then open the hole to size. The correct form of the newly sharpend drill is to back off the front clearance to a minimum. Make sure the cutting edges are the same length and same angles, this is essential for good results. Use lots of soluable oil coolant or whatever you have or prefer. A 5/8 drilling machine will handle the 25mm drill with ease but you must have slow revs and use the folded rag. Using the folded rag you can actually drill the hole to 22mm dia and then finish with the 25mm dia. Yes, the rag works that good. You can also move the position of a predrilled hole that has to be opened up with a bigger drill by using the rag. I have repositioned a drilled hole by over 2 and even 3mm. It's a piece of cake to do but I suggest you use cotton rag, it works the best. The top edge of the drilled hole will be perfectly circular, have sharp square edges and be exact size. Dont forget to reshape the drill or it wont work as good or as safe as it will/can be. Easy job!

Kody

Originally Posted by DJ's Timber

If you're up for a short drive, I have bits in that size here if you want to bring them here and drill them

Thanks, DJ, I have sorted it out albeit slowly with a file, not pretty but should work.

Kody "folded rag trick" as Pauline would say... Please explain?

I find step drills fanatastic no jamming.
Yeah what is this folded rag business.?
Is it to stop the bleeding when a conventional drill jams in metal?

The folded rag trick, you put a piece of cloth between the drill and the work, and drill through the rag. Stops the drill bit from grabbing/chattering and cuts a cleaner hole. I have never heard or seen an explanation of how or why it works, if some whiz-kid out there knows how it works I for one would love to hear it.

Regards
Ray
.

How well do these step drill do with thick steel, I thought they were only for thin metals like tin?

I been using sutton hole saws to do bigger holes in 3mm mild steel, cut a pair of 4" holes the other day very slow(about 5min each) and even with a 2hp 20" JET DP it was a struggle!

Step drills are really designed for thin materials which often tear + grab conventional drills as they cut thru but are good for thicker steel as again they dont grab if you go slowly .
Obviously if its thick you need lubricant + can probably only use the biggest step but if its the size you want no problems.

hate to rain on the parade of all these great ideas but post #2
Buy a bigger drill = dollars from your pocket
File it bigger = time from your life
What can you best afford
I have looked at some of the posts here, when all the guy wanted was to spend the least dollars to produce the desired result with the least effort
Do any of you bother to read the origional post

Mr Ashore get on your boat you are no fun.
what is the point of a forum is if you cant ######## on about stuff.
He doesnt want the simplest cheapest answer he wants to know how to go from Melbourne to Sydney via Darwin.

Get a superdrill thing.

I have two and use them all the time for bigger holes, especially in heavier plate. They run on a 1/2" and 1" shank.
You can sharpen or make your own cutting tools the same as a lathe tool.
Not sure where you buy them now but mine were only about $15.

Ian

Originally Posted by Tiger

I need to make 25 mm holes in 2 bits of 5 mm plate. The biggest drill bit I have is a 16 mm bit. Anyone know of a way to make these holes and they don't have to be perfectly circular with your basic run of the mill items found in a typical workshop? I am considering using a file to make the hole larger but that will be slow. Other option is to buy a bigger drill bit but it would only be used for a one-off job.

If you aren't to fussed about it being perfectly round I'd just lace drill the size hole you need using a say 3mm bit, then chisel it out and file it up.