Drilling/Cutting Holes in Stainless

[Inigo]

I'm trying to fit a Webasto heater to a camping trailer that is made of fairly thin stainless sheet TIG welded together.

I need to cut assorted holes in the base (4 x 7.5mm, 2 x 26mm and 1 x 90mm) to bolt down the Webasto, let air in and out and let exhaust out.

My first thought was for carbide tipped drills in a portable drill and I found these carbide hole saws http://www.steelworkerstools.com/sm26-26mm-tungsten-carbide-tipped-sheet-metal-hole-saw.html that might be useful.

But to cut stainless I need to push hard and cut slowly which might be difficult trying to cut in situ. Perhaps I could jack up a sheet of ply from underneath?

I got to thinking about a plasma cutter. There are cheap chinese ones on Ebay for not an enormous amount more than a set of carbide drills and hole saws.

What are the chances of a novice not making a complete pigs ear of it?

Any other suggestions?

[Big.Mike]

You could try a laser cutting company, don't know where you are in the country.

A 90mm hole is the one you'll have a problem with. A tank cutter might do it, they are really hard to use on sheet, you need to put ply both sides of the steel and try to use a pillar drill.

The 7.5 not a problem. Use a centre punch then use a 2mm, 4mm, 6mm then 7.5mm drill. Because it's thin you need to have more steps.

Do the same with the 26mm hole using a stepped cutter http://www.tooled-up.com/product/3-piece-titanium-step-drill-cutter-bit-set/187480/

Cheers,

Mike

[Big.Mike]

Oh, or get a sheet metal company to knock another one up for you... it might not be much money, especially if you can leave it with them.

[Les Brock]

We drill holes in stainless stuff all the time on site, slow speed/high torque, plenty of cutting paste and a normal hole cutter up to 100mm, even with battery drills ! (24V)

[Inigo]

The part that I need to cut holes in is the base of an enclosure within the trailer. It seems to be welded construction so I cannot easily dismantle it to get the sheet on the bench and I can only take it to someone else if I take the whole trailer there and not sure how easy it would be for them to cut inside the box either.

Another alternative would be to cut a great big square hole and bolt down a mounting plate - so I can drill some smaller holes around the edge and jigsaw a square-ish hole in the middle.

[Big.Mike]

We drill holes in stainless stuff all the time on site, slow speed/high torque, plenty of cutting paste and a normal hole cutter up to 100mm, even with battery drills ! (24V)

Les, what thickness though, inigos post makes me think it's thin, which is hard to drill without tearing or worse getting the bit stuck!

[Big.Mike]

The part that I need to cut holes in is the base of an enclosure within the trailer. It seems to be welded construction so I cannot easily dismantle it to get the sheet on the bench and I can only take it to someone else if I take the whole trailer there and not sure how easy it would be for them to cut inside the box either.

Another alternative would be to cut a great big square hole and bolt down a mounting plate - so I can drill some smaller holes around the edge and jigsaw a square-ish hole in the middle.

It would be useful to have a picture.

It's not hard to drill holes in stainless, you just need good bits and a bit of a feel for it. Have you got any scrap you can practice on?

[Bowie69]

For the 90mm, I'd get a jigsaw out, fine blade and some ply clamped underneath.

[Inigo]

I'll take some photos this evening.

[gsr341]

7.5mm hole is easy just use a drill , and for the others would use a hole saw , ive cut 6mm stainless with hole saws lots of trime , last one i cut was a 6" hole for a flue , using a hole saw from screwfix , just take it easy , with some cutting oil and you will wizz thru it even with a battery drill

[simonr]

For Hole-Saws, I'd recommend a Plaster Mixing Drill. It's just like an ordinary mains drill, but geared very low. I've used it on hole saws up to 160mm and use it regularly for Notching tube. Mine came from eBay and was only £20 - but is exactly the same as this: http://www.toolstation.com/shop/p24985?utm_source=feed&utm_medium=googleshopping&utm_campaign=googleshopping&mkwid=5EGGNONU&pcrid=26798537543&gclid=CLDf7eXP7LkCFQZZ3godEyQAkQ

It has a top, no load speed of about 800 rpm but will run happily all day at about 100 - so no chance of burning out the hole saws. You need to hang on to it though - it doesn't half have some torque!

Si

[Inigo]

Nice idea with the mixing still, my problem with my handheld variable speed drill is that it is difficult to hang on tight, push down hard and yet squeeze the trigger only lightly.