Drilling larger holes in aluminium, or any metal

[Neeves]

I want to drill 15mm aluminium plate to produce a 20mm - 25mm diameter hole. Later I might want to drill stainless or steel. I have a large and powerful variable speed bench drill but it has a limited chuck size of 12/13mm.

I know nothing about the terminology of describing drill bits and I know even less about drill bits themselves!

My drill bits are maximum of 15mm and my larger drill bits have a 'stepped' design, the portion held in the chuck is of a smaller diameter then the working part of the drill. My drill bits are simple, cheap, steel, no coatings.

What do I need to search for to source to drill 20/25mm. Do I need 'special' bits, fancy coatings. What is the term for the stepped bit (with the portion held in the chuck smaller than the bit itself (or do I need a bigger chuck).

Or is my objective inaccessible.

Jonathan

 

[Yellow Ballad]

I think you're after a holesaw, I would look for a colbalt jobbie like below.

http://www.screwfix.com/p/bosch-cobalt-holesaw-25mm/95168

And you'll need this to go with it

http://www.screwfix.com/p/bosch-powerchange-holesaw-hex-arbor-pilot-drill/55830

 

[Neeves]

Thanks Tom,

I have hole saws (looking somewhat as your link), various sizes upto about 120mm diameter, which I use on fibreglass and wood, but never metals. I cannot believe mine are cobalt (I think they were described as being locksmiths hole saws).

Are mine too toylike - or will they work with lots of lubricants?

Jonathan

 

[Jaguar 25]

I want to drill 15mm aluminium plate to produce a 20mm - 25mm diameter hole. Later I might want to drill stainless or steel. I have a large and powerful variable speed bench drill but it has a limited chuck size of 12/13mm.

I know nothing about the terminology of describing drill bits and I know even less about drill bits themselves!

My drill bits are maximum of 15mm and my larger drill bits have a 'stepped' design, the portion held in the chuck is of a smaller diameter then the working part of the drill. My drill bits are simple, cheap, steel, no coatings.

What do I need to search for to source to drill 20/25mm. Do I need 'special' bits, fancy coatings. What is the term for the stepped bit (with the portion held in the chuck smaller than the bit itself (or do I need a bigger chuck).

Or is my objective inaccessible.

Jonathan

A simple way of producing large diameter holes in metal plate is to mark out the required hole size and drill a series of small, interconnecting holes (5 or 6mm dia), saw them where there is no interconnection and then file the peaks until you reach the marked out diameter. Particularly easy using a pillar drill.

 

[Yellow Ballad]

Unfortunately (for me) I'm not an engineer so I'm not sure. 15mm is quite deep but they say they will cut SS so aluminium should be ok, I've found in the past aluminium clogs up files quite easy but I imagine taking it easy and lifting it out each mm or so would keep the teeth clean.

Colbalt drills are fantastic compared to anything else, it's all I buy now.

I think anything beefier would really require a mill with a cutting head.

 

[pete]

I agree with the hole saw I use these http://www.builderdepot.co.uk/starr...MIlOz_ivWc1gIVxcmyCh1RLAXXEAQYBCABEgKdXfD_BwE and have used them up to 10mm thick stainless steel.
I think I was using a 38mm or40mm saw and from memory got about 3 to 4 cuts from one saw. Usual story - slow speed, lubrication, keep it cool, sharp saw and make sure it keeps cutting, if it starts to skid stop and change the saw.
Starrett is a good make don't try a cheapy.

 

[Neeves]

Pete,

Mine are like the ones in your link, except blue.

I'll try tomorrow,

Thanks for the replies - most educational.

Jonathan

 

[colhel]

A blacksmiths drill. For example;

http://www.nutandboltshop.com/black...u3azCyctqaXbRqgWjnXHIBaNQ7pVMCuEaAnrIEALw_wcB

 

[DinghyMan]

Easiest way is probably to use a RotaBroach in a holder in the chuck of your bench drill or use a morsa taper adaptor holder and temporaily replace the chuck.

As they are hollow the force required to drill is way less than a normal drill and no pilot hole is needed.

Loads of oil plus a bit of load and they will go through 15mm ally or stainless no problem.

 

[rogerthebodger]

I want to drill 15mm aluminium plate to produce a 20mm - 25mm diameter hole. Later I might want to drill stainless or steel. I have a large and powerful variable speed bench drill but it has a limited chuck size of 12/13mm.

I know nothing about the terminology of describing drill bits and I know even less about drill bits themselves!

My drill bits are maximum of 15mm and my larger drill bits have a 'stepped' design, the portion held in the chuck is of a smaller diameter then the working part of the drill. My drill bits are simple, cheap, steel, no coatings.

What do I need to search for to source to drill 20/25mm. Do I need 'special' bits, fancy coatings. What is the term for the stepped bit (with the portion held in the chuck smaller than the bit itself (or do I need a bigger chuck).

Or is my objective inaccessible.

Jonathan

For aluminium and mild steel I use a bimetal hole saw in a slow bench drill or a vertical milling machine.

I have also used a hole saw in thin stainless steel with a bench drill but you really need a continuous flow of cooling/lubricating oil

For stainless you need a powerful drilling machine so the saw will cut all the time and not rub or stall.

I an drilling a 4 off 25mm dia hole in 10mm thk 316 stainless at the moment using a reduced shank jobber twist drill with some difficulty but getting the job done slowly

 

[Graham_Wright]

You could try a stepped drill. Cheap as chips on ebay so you need't worry about knackering them.

 

[Aja]

Whatever you end up using to cut, ensure the job is well secured and cannot move.
Donald

 

[DownWest]

Use bi-metal hole saws, as reccommended above. Good make, like Starrett, don't go near cheap Chinese like Silverline. Again, slow and lots of lube. I needed to do a lot in 6mm 304 SS, so adapted my pillar drill to half it's lowest speed to match the listed speed for the 50mm holes. Around 60 holes and used 7(?) saws .
DW

 

[Daverw]

If the part is removable you could take to the nearest engineering works with a laser cutter, you would be surprised how low cost this can be. I've just had two brackets made from 10mm SS plate, with full shopping and various holes, 8mm to 12.5mm for £75 a pair

 

[thinwater]

Common hole saws work fine for aluminum and OK on lower strength carbon steel. Stainless steel is a different matter; never tried it.

Use lots of oil, let the saw cool, and clamp the work tightly!

 

[BabaYaga]

I want to drill 15mm aluminium plate to produce a 20mm - 25mm diameter hole. Later I might want to drill stainless or steel. I have a large and powerful variable speed bench drill but it has a limited chuck size of 12/13mm.

As already mentioned a stepped drill works very well in aluminium. Not sure about thicker steel or stainless, though.
http://uk.rs-online.com/web/p/step-drill-bits/7068606/

 

[nemodreams]

I drilled a 40mm hole in 6mm steel plate x 2 with a 'new' good quality holesaw. On a pillar drill - as said, well held, loads of 'proper' cutting fluid. It spits and smokes and smells - but it does cut. I wouldn't try it on anything harder.

On site - when we had to drill large holes in girders ( like 12mm thick - 25mm hole ) we hired a magnetic base pillar drill - still just a rotary pillar drill, and the bits supplied were very odd !
They worked like a hole cutter - ie one was left with a plug from the middle - but had a sort of moving sleeve. They worked like a dream ! Any hire shop would know what they were. As said - the drill was a normal rotary drill - but may have had a special chuck ?

 

[Neeves]

A blacksmiths drill. For example;

http://www.nutandboltshop.com/black...u3azCyctqaXbRqgWjnXHIBaNQ7pVMCuEaAnrIEALw_wcB

This is what I thought I needed, to buy, but did not know what it was called.

Thanks

Jonathan

 

[Neeves]

Common hole saws work fine for aluminum and OK on lower strength carbon steel. Stainless steel is a different matter; never tried it.

Use lots of oil, let the saw cool, and clamp the work tightly!

My drill has a vice so holding tightly should not be an issue. I do confess I do not use it all the time and when the bit breaks through underneath and jambs - I sometimes have rotating work pieces, not nice!

Jonathan

I've seen the term used - what is a pillar drill, as opposed to a bench drill - or are they one and the same thing?

 

[Neeves]

If the part is removable you could take to the nearest engineering works with a laser cutter, you would be surprised how low cost this can be. I've just had two brackets made from 10mm SS plate, with full shopping and various holes, 8mm to 12.5mm for £75 a pair

I wanted something laser cut, small roughly square shape, 100mm x 100mm x 8mm, a slot half way through and 2 holes - you'd be surprised how much it cost Stg100. I cut it myself with an angle grinder, the holes were only 12mm so not an issue.

Maybe I need to send cutting files to the UK and have the parts posted back - it would be cheaper!

Jonathan