20mm hole drilling - mag drill cutter?

[astro_al]

Hi all, any ideas how to drill a 20mm diameter hole in 20mm plate steel?

I'm caught between a crappy but cheapo reduced shank drill (a la ebay), a hyper expensive 20mm drill bit (e.g. Cromwells), a hole cutter, or seeing if I can fit a rotabroach style mag drill cutter into my pillar drill and doing it that way.

What's the best method?

Cheers, Al.

 

[Blackjack]

Not entirely sure why that's a problem...

Buy a Blacksmith's drill set from Machine mart, and as long as your drill runs slow enough and you've got adequate clamping, you shouldn't have a problem.

http://www.machinemart.co.uk/shop/p...iths-drill-bit-set-/path/twist-drill-bit-sets

Drill a 10mm hole, then step your way up to 20.

If you need it more accurate than that, your pillar drill has a morse taper, and again runs slow enough, a second hand reamer with a suitable size morse taper. Probably find that on E-bay.

 

[astro_al]

Its not a problem, I just wondered if cheapo drills would not last long at that diameter, or if a hole-drill would be faster / better.

Thanks for the input. Al.

 

[madkayaker]

holesaw plenty of cutting fluid and slow speed

 

[Blackjack]

Its not a problem, I just wondered if cheapo drills would not last long at that diameter, or if a hole-drill would be faster / better.

Thanks for the input. Al.

The set I've got seems to have lasted pretty well if that's any use.

For the £25 or so, you get a fair range of drill bits, used with care (like any large bit has to be) they seem to last OK, so for home use, I think they're about the best bet.

Critical thing is if your drill runs slow enough.

 

[astro_al]

Thanks, its always good to hear how people get on with stuff.

I think my slowest pillar drill goes down to 75 rpm, which should do the trick.

So, holesaw or machine mart... Hmmm.

Cheers, Al.

 

[madkayaker]

a decent holesaw will last longer and give better cut than a budget drill bit

 

[wyn]

I've used the machine mart blacksmith drills for a while now and they are fine.

Also used holesaws for 20mm plate with not too much hassle, but the 20mm holesaw might give you a 21-22mm hole.

I have also got a morse taper adaptor for broaches......but the quill on the drill has a bit of play so using it usually turns into a nightmare.

 

[Blackjack]

a decent holesaw will last longer and give better cut than a budget drill bit

I'd disagree with that given we're talking about 20mm thick material.

The life of the drill or the holesaw will only depend on how it's treated. Difference being you can resharpen the drill bit...

Hole quality in 20mm material, I'm pretty sure the drill will give a cleaner bore.

And don't forget that for the £25 the drill set costs you're getting quite a few sizes.

That said, if it was putting a hole in 3mm plate, I might be using a hole saw, though 20mm dia is a little small to be thinking about that.

A lot depends on the drill youre using.

 

[astro_al]

Right. Thanks guys.

It does seem inefficient to cut through all the material in a 20mm hole just to remove a 'plug' - better to cut a circle round it?

Thats why I wondered about Mag drill cutters in a pillar drill. Best of both worlds? More accurate / quicker than a hole saw, more economical than a regular drill bit?

Cheers, Al.

 

[madkayaker]

how accurate does it need to be? Hole saws are a bit inaccurate compared to drills nowhere near as accurate as mag drill

 

[wyn]

Is it just a one off job or have you got a few to drill ?

Maybe hire a mag drill for a day if you have a lot to drill.

 

[astro_al]

Not very accurate - just for some bolts.

Yes its one job, but I have a few holes to drill.

Why do I need to hire a mag drill? I mean, its a good idea but can I just use a mag cutter in a regular pillar drill?

Cheers, Al.

 

[wyn]

I got an adaptor from mm for use with broaches.

I think the actual dia of the locating bit on a broach is around 3/4".

Probably my previous post was guided a bit by the poor results i have had, due to the play in my pillar drill.

 

[Hitch]

If your pillar drill goes down to to 75 rpm, get the reduced shank drills. Minimal effort to use.
You have the option of buying an adaptor to take broaches, but expensive unless you wil use it a good number of times. If you have access to a lathe, you could make a basic one easily.

Holesaws, i wouldnt bother with unless its under about 6mm thick.

Another option is to buy the tct holesaws/broaching cutters that will go in a standard 13mm chuck Length wise, 20mm is probably about the limit for a 20mm cutter.
One brand is Alfra, stockists wise, cant remember who keeps them.

 

[chevyman_de]

I got an adaptor from mm

Way too expensive! Look here! The seller is reliable and ships fast.

 

[gavuk]

I'm with Blackjack and Hitch ,i've use holesaws up to 10mm thick material if its a large hole 50mm+,but for 20mm hole in 20mm matl ,i would drill just don't drill too big on the pilot hole ,less than half the finished hole size is what i would use and cutting fluid/oil as well......Gav

 

[hareng]

Same here HSS drill in pillar drill.
http://cgi.ebay.co.uk/LINEAR-FULLY-...3286.c0.m14&_trkparms=66:4|65:1|39:1|240:1318



Decent Starret holesaws wont last long may do two holes with coolant on slowish speed. Would need at least two so it would cost you any way! ****** and unbranded forget it.

 

[astro_al]

Thanks very much guys. I'll go with a drill for now then.

I do have a lathe, so I might buy a broach cutter and make an adaptor if I need lots more holes.

Is that right Gav? Only drill to less than 1/2 the final hole diameter?

Ta, Al.

 

[gavuk]

I wouldnn't go bigger than 10mm for a 20mm hole nomally i go just larger than the chisel centre of the final drill......if u go 16-18mm it will be more difficult than leaving more meat .....more tendency to snag ,i'm sure others will may have a different opinon ,works for me ....Gav