driling through steel

earthwormjim · Post by **earthwormjim** » Thu Apr 14, 2011 4:45 pm

Anyone got any tips on drilling through steel bar?
Bar is 4mm x 4mm.I would like to drill 10 x 2mm holes and then counersink the holes.I anticipate that the succesfull choice of a suitable drill bit will be the easiest route to a happy Jim.

Anyone have any experience in this field?
Many thanks.

This is for my 5th part built robot that I have started,called Raoul.

josh · Post by **josh** » Thu Apr 14, 2011 4:59 pm

square or round? I would suggest punching a notch before you try and drill anything, much easier to correct than a wonky hole. then mild steel should be okay but maybe a bit of wd40 or thin oil as a coolant/cutting lubricant. should be okay with standard hss bits but nice cobalt ones never hurt! if you're using a pillar drill, or something you can vary the speed on, I'd say a slower rpm and feed rate else you just make a lot of heat and not much of a hole. If the drill is running too fast it can get so hot it fuses to the piece.

earthwormjim · Post by **earthwormjim** » Thu Apr 14, 2011 5:21 pm

Great,thanks Josh.
Square,and a pillar dril. I will spray with wd 40,and slow it down a bit,and look for some cobalt bits.
Great info,thanks

Marco Roberts · Post by **Marco Roberts** » Thu Apr 14, 2011 7:23 pm

Everything that josh said is sound.
I would say however that you should keep the drill quite quick with small holes with very ligh presure put on the bit.

Drilling big holes, slow speed lots of force and lubricant to keep the bit cool

earthwormjim · Post by **earthwormjim** » Thu Apr 14, 2011 7:32 pm

Thanks Marco. I have a spare piece,so will give it a try,once the bits arrive.

widow_twanky · Post by **widow_twanky** » Thu Apr 14, 2011 10:10 pm

if you're going for cobalt drills you can buy single ones of the size you want off ebay. A set from screwfix will cost you ?20 minimum.

You really only need an hss drill for mild steel though.

earthwormjim · Post by **earthwormjim** » Thu Apr 14, 2011 11:05 pm

I found a set of 10 cobalt bits for ?6,and a set of 10 HSS for ?1.60.
I know that they are not going to be the best quality for that price,but hopefully they wil get the job done to a reasonable standard.
I thank you on Raoul's behalf.(He doesn't speak much.)

maddox · Post by **maddox** » Fri Apr 15, 2011 6:42 am

for mild steel and HSS/cobalt bits. speed 20m/min

means
0.002*pi*Xrpm=20m/min

Xrpm=20/(0.002*pi-)=3185 rpm

Feed is 0.1mm/rev , meaning you'll drill trough the bar in 5 seconds.
Taking a tad longer won't hurt the drill tough.

But with such small drills, any deviation from the 90? drilling angle will result in a broken drill. Any side force will snap it.
Overfeeding will result in side forces.
And cobalt drills are more prone to snapping than Carbon steel or HSS steel bits.

Remote-Controlled Dave · Fri Apr 15, 2011 8:37 am

I've been learning to drill steel better recently for the heavyweight. Basically slow and torquey has been best. I've not been using a pillar drill which has made things a little more difficult. I find doing a notch as Josh suggested, then starting with a tiny drill bit and working up has made things a fair bit easier too.

earthwormjim · Post by **earthwormjim** » Fri Apr 15, 2011 9:13 am

Thanks guys.
I will use a small vice,to help hold the pieces square while drilling.
And I will notch each hole.I usually use the end of a screw to notch pieces I need to drill,but I may have to find something a bit harder for this.