DRILLING INTO STEEL

[Nicetoseeyoutoseeyounice]

I’m trying to drill a hole through a steel plate, approx 5mm thick, I’ve started with a smaller bit and then changed to a bigger one, this went through quite good, but, I need the hole to be slightly bigger, enough to get a 10mm bolt through. I therefore changed the bit to another, slightly bigger but when I try to drill into the hole the drill is literally bouncing off, I’ve given it a few goes but it continues to happen.
Any help where I’m going wrong would be greatly appreciated.

 

[Burnerman]

Use new HSS drill bits and try to reduce the drilling speed with the bigger sizes.
Some lube does no harm and the eventual size hole you need is 10.5mm.
John

 

[Nicetoseeyoutoseeyounice]

Sorry, I should have said but I’m using top of the range HSS bits, I don’t get it, the small bit was great to start me off, the next zipped through, but the final one to make the hole bigger just bounced, I’m baffled.

 

[Burnerman]

There's a chance the big drill got overheated if the speed was too great and then immediately blunted.....I'd use an 8.5mm bit or similar before reaching for the final one - keep a lot of pressure on the drill before you pull the trigger.
John

 

[Nicetoseeyoutoseeyounice]

Thanks for the tip, I’ll try the slow drilling and see if it helps, also some lube.

 

[Munroast]

shouldn't of drilled the first hole all the way through, just started the hole off with say a 4mm bit. Then a 10mm at the slowest speed you can get with a bit of light oil as a lube. (10.5 would be better for M10, but can be achieved with a 10mm)


What to no with your prob .... what are you using a hand held or a pillar drill. Be helpful if you had a big countersunk bit to ream the top of the hole you have, if not try and offer your drill to the bit very gently. Is your big drill true? does the end wobble when you spin it ?

 

[Harry Bloomfield]

I prefer to have the drill running, before offering it to a pilot hole and if its a largish bit, hold the drill very tight.

 

[cdbe]

Try another bit. One false move and they overheat and turn to mush. You know because it's going great and then it just stops.

 

[RandomGrinch]

Post edited to address legitimate safety concerns:

Always use correct PPE for drilling:
Wear safety glasses.
Don't wear gloves.
Tie long hair back etc.

Hi,

I've found this quite usual when I've drilled through steel on a pillar drill.
Even when the setup is perfect, the bit can flex a little, this causes the cutting edge to catch and flick up material; causing vibration. You end up with an oval, or tri-lobed hole (at least to start with)!
As above, lubrication and going slow will help.

I haven't tried it myself, but I have seen it suggested that putting a thick piece of 'emery' cloth (folded 3 to 4 times, into a very small square) over the hole, drilling through it, and letting it spin (at a very slow speed) will dampen the vibrations.
The workpiece must be firmly fixed into place before attempting this.
Keep hands and fingers away from the workpiece when drilling!

Good luck!

 

[Nicetoseeyoutoseeyounice]

Thanks for all your suggestions, I’ll put these into practice tomorrow and hopefully something will work. By the way, I’m just using an ordinary drill, the bit itself dosnt wobble when spinning.

 

[Munroast]

Hi,

I've found this quite usual when I've drilled through steel on a pillar drill.
Even when the setup is perfect, the bit can flex a little, this causes the cutting edge to catch and flick up material; causing vibration. You end up with an oval, or tri-lobed hole (at least to start with)!
As above, lubrication and going slow will help.
I haven't tried it myself, but I have seen it suggested that putting a thick piece of cloth (folded 3 to 4 times) over the hole, drilling through it, and letting it spin, will dampen the vibrations.

Good luck!

that sounds incredibly dangerous, the cloth will wrap around the drill bit and turn into a flail and if the piece of metal also gets caught uo it will be like some sort of mad medieval weapon.

 

[conny]

With the possibility, (no matter how remote), of a piece of the cloth catching on your finger and, ooops! If it's your phone dialling finger you are stuffed.
This is why you don't wear gloves when using a drill or drill machine.

 

[RandomGrinch]

that sounds incredibly dangerous, the cloth will wrap around the drill bit and turn into a flail and if the piece of metal also gets caught uo it will be like some sort of mad medieval weapon.

I should have added 'as long as the work place was fixed in place'.
Yes, I wouldn't fancy a flail around a drill.

 

[RandomGrinch]

For clarity, the person I gained this information from may have been misinformed!
But here is an example of 'Emery Cloth' being used (scroll to bottom):
https://www.askthebuilder.com/how-to-drill-hard-steel-video/

A step drill, may also be easier to use.
If you were drilling a small flat workpiece, sandwiching it between some wood may help.

 

[Old Salt]

Can sometimes help to “smooth” out the hole by running in reverse until it runs smoothly then try drilling through.