3" hole in 6mm plate

[CornishPete]

Hi everyone, as the title suggests I want to drill a few 3" holes in the web of an rsj, approx 6mm thick I'd say. Screwfix have a range of 76mm multi material holesaws which say they'll cut sheet steel. I've only ever cut wood and plasterboard with them, any one used one for mild steel? Leaning towards the Bosch one as I have the fast change arbour thing but any suggestions welcome!

 

[8ob]

3" holesaw means slow which means gutbuster is this off a ladder?

Bob

 

[James1979]

Hire a mag drill!

it will be a far sight easier. Those hole saws aren’t really for that. I’ve abused them through thick stuff with plenty of RTD but they don’t like it. Even the decent brands object.

Also they have a habit of splaying teeth with can give a hole slightly oversized which may be a consideration

 

[brightspark]

yep will cut it no probs. just run on slow speed and use cutting compound i use starret arbours and pilot drills but just use the cheap bi metal hole saws . you can do it with a pistol drill but a pedestal drills better if u can move the metal . i drilled 4 x 3inch holes through a 10mm i beam of a pair of stepladders you need arms like garth

 

[premmington]

Hi everyone, as the title suggests I want to drill a few 3" holes in the web of an rsj, approx 6mm thick I'd say. Screwfix have a range of 76mm multi material holesaws which say they'll cut sheet steel. I've only ever cut wood and plasterboard with them, any one used one for mild steel? Leaning towards the Bosch one as I have the fast change arbour thing but any suggestions welcome!

I have cut plenty of deep holes in steel with "holesaws" - I tend to use Starrett ones.

Don't press too hard on them - and use plenty of cutting oil.

 

[James1979]

yep will cut it no probs. just run on slow speed and use cutting compound i use starret arbours and pilot drills but just use the cheap bi metal hole saws

I’ve never had much joy in thick stuff. Suppose it depends how many he has to do.

 

[CornishPete]

Cheers for the replies. The rsj is on the ground so can hold the drill pretty comfortably. Will probably only be four holes, maybe five, might depend on how long the bit lasts. I'm knocking the garage down whilst I build a new extension so moving my bikes to my work unit. I have a spare 4.5m rsj so was planning to resin fix it to the floor and loop the security chains through the holes in the web.

 

[Hitch]

Done this plenty of times where mag drills wont get in, just need a decent drill that will run fairly slow.


Ive never got on with the QR bosch holesaws, they're too wobbly....i'd get a couple of standard bosch holesaws and an arbour.
Pilot drill first, then screw on the holesaw so it doesnt suddenly bite and snap the pilot drill... or swap the pilot drill bit for a bit of 6mm rod.
Bit of CT90/Rocol on it and keep it slow.

On a side note, 75mm is a pretty big hole to bang through the web... has its location been okayed if its structural?

 

[brightspark]

Cheers for the replies. The rsj is on the ground so can hold the drill pretty comfortably. Will probably only be four holes, maybe five, might depend on how long the bit lasts. I'm knocking the garage down whilst I build a new extension so moving my bikes to my work unit. I have a spare 4.5m rsj so was planning to resin fix it to the floor and loop the security chains through the holes in the web.

they should do a fair few holes with plenty of cutting compound .oil is ok but compound is better

 

[cianh91]

Cheers for the replies. The rsj is on the ground so can hold the drill pretty comfortably. Will probably only be four holes, maybe five, might depend on how long the bit lasts. I'm knocking the garage down whilst I build a new extension so moving my bikes to my work unit. I have a spare 4.5m rsj so was planning to resin fix it to the floor and loop the security chains through the holes in the web.

If I’m not picking you up wrong would it not be easier with a smaller hole or just weld eyes on for the chain to loop around

 

[CornishPete]

Done this plenty of times where mag drills wont get in, just need a decent drill that will run fairly slow.


Ive never got on with the QR bosch holesaws, they're too wobbly....i'd get a couple of standard bosch holesaws and an arbour.
Pilot drill first, then screw on the holesaw so it doesnt suddenly bite and snap the pilot drill... or swap the pilot drill bit for a bit of 6mm rod.
Bit of CT90/Rocol on it and keep it slow.

On a side note, 75mm is a pretty big hole to bang through the web... has its location been okayed if its structural?

It's a spare rsj I have, was the top of a cantilever racking upright I shortened. I'm planning to resin fix it to the floor so not structural!

 

[Paul.]

I've done plenty of these too, starret holesaw and rocol rtd, and a slow drill will be fine, to make it a bit easier mark out the circumference of the hole and drill four or five holes spaced out around it to break up the cutting action and give the swarf somewhere to go.

 

[CornishPete]

If I’m not picking you up wrong would it not be easier with a smaller hole or just weld eyes on for the chain to loop around

The chain links are 65mm so the hole can't really be much smaller. Would there be much difference between say a 50 and 75mm hole? Could do 2 smaller overlapping holes like a venn diagram but would the chain fit through? A holesaw is about 10 quid and all I'd need to take is a drill and no prep work involved. Also if anyone was to cut it they'd have to cut the flange and web of the rsj rather than just the thickness of an eye.

 

[Chris Snow]

Ive never got on with the QR bosch holesaws, they're too wobbly..

Same I was so disappointed in what seemed like a good idea. Starrett next time...

 

[Hitch]

Same I was so disappointed in what seemed like a good idea. Starrett next time...

The standard screw on Bosch type are fine (grey ones). Use them all the time on stainless.

 

[eLuSiVeMiTe]

Done plenty with the Bosch hole saws

About 15 50mm holes through
2 thicknesses of 2x9 then through 10mm I beam and a further 2 timbers

One cutter s
Lasted all the holes

 

[brightspark]

dont ever buy a cheapo screwfix arbour and the cheap pilot drills are total dross

 

[Paul.]

I always replace the pilot drill with a piece of 1/4" dia silver steel, even a piece of mild steel will be more stable than the pilot drill when cutting metal

 

[brightspark]

I always replace the pilot drill with a piece of 1/4" dia silver steel, even a piece of mild steel will be more stable than the pilot drill when cutting metal

yep i have a one with silver steel center that i hardened . stops run off on the larger cutters that snap center drills

 

[bricol]

I've done 6" holesaw through 5mm stainless with a Dewalt battery drill, so it is possible (drill needed a new switch fairly soon afterwards admittedly).

However, if your work has any grinders, or if any thieves carry a battery grinder, then the chain is the weakest, er, link.

Why not just resinfix the chain direct to the floor?