BotusBuild Posted February 25, 2023 Share Posted February 25, 2023 (edited) HELP! I need to drill some 16mm holes in a steel I-beam. HSS drills are not doing it. I have some 8mm bits that are going through no problem, but buggered if I can remember what type they are. What type do I need? Carbide? Cobalt? Something else? TIA Stuart Edited February 25, 2023 by BotusBuild Link to comment Share on other sites More sharing options...
IanR Posted February 25, 2023 Share Posted February 25, 2023 20 minutes ago, BotusBuild said: HELP! I need to drill some 16mm holes in a steel I-beam. HSS drills are not doing it. I have some 8mm bits that are going through no problem, but buggered if I can remember what type they are. What type do I need? Carbide? Cobalt? Something else? TIA Stuart If you are only drilling a few holes then HSS should have been fine, but at Ø16 you should slow the drill down and take your time. Even a little fairy liquid under the drill may help. If you are drilling a lot of holes then you may want to go with a cobalt steel bit or black oxide bit. 1 Link to comment Share on other sites More sharing options...
Jenki Posted February 25, 2023 Share Posted February 25, 2023 Cobalt drills will murder the steel, but at 16mm you have to be careful when, not if the drill snatches, (wrist breaker). Take your time, or save your wrists and rent a mag drill. Link to comment Share on other sites More sharing options...
Mike Posted February 25, 2023 Share Posted February 25, 2023 And, because you'll need to apply a good amount of force, be sure to wear eye protection in case you break the bit. Link to comment Share on other sites More sharing options...
saveasteading Posted February 25, 2023 Share Posted February 25, 2023 There can be a huge difference in bit quality. It is well worth paying for big brands. 1 Link to comment Share on other sites More sharing options...
BotusBuild Posted February 25, 2023 Author Share Posted February 25, 2023 59 minutes ago, Jenki said: Cobalt drills will murder the steel Meaning they'll go through it easily? Link to comment Share on other sites More sharing options...
Jenki Posted February 25, 2023 Share Posted February 25, 2023 (edited) 1 hour ago, BotusBuild said: Meaning they'll go through it easily? Yes. But watch your wrists. Also cobalt can chip quite easily Edited February 25, 2023 by Jenki Link to comment Share on other sites More sharing options...
JohnMo Posted February 25, 2023 Share Posted February 25, 2023 For 16mm you really need a magnetic drill. For what it will cost get your local fabricator out to do it for you, they will provide everything. Likelihood of wandering off centre is high with a hand drill, and if it's powerful it is also likely to grab as you break through the other side. Link to comment Share on other sites More sharing options...
Miek Posted February 25, 2023 Share Posted February 25, 2023 Stagger drill the holes. If you can get an 8mm hole , then go to 10, then 12 , then 14 then 16mm that saves a lot of cutting force but takes a little longer. Good HSS drills should easily drill an RSJ Link to comment Share on other sites More sharing options...
Rishard Posted February 25, 2023 Share Posted February 25, 2023 I use HMT drill bits on steel. Cheaper than a mag drill but more than regular hss bits. I paid about £40 for a bit years ago and it still ploughs through steel beams without much effort. Use a good drill or they even do impact bits. Watch any of their videos to see them in action. I would definitely recommend these. https://holemaker-technology.com/collections/metal-drill-bits 1 Link to comment Share on other sites More sharing options...
Alan Ambrose Posted February 25, 2023 Share Posted February 25, 2023 Look at annular cutters - the go to brand is Rotabroach. I would rent a mag drill if you’ve got more than a couple to do. You need a slow speed, cutting fluid, to clear the chips out regularly (e.g. with compressed air) and to control the drill pressure. The forces are high so be careful as others have said. 1 Link to comment Share on other sites More sharing options...
bassanclan Posted February 25, 2023 Share Posted February 25, 2023 Plenty of lubricant to keep the drill tip cool 1 Link to comment Share on other sites More sharing options...
BotusBuild Posted March 9, 2023 Author Share Posted March 9, 2023 UPDATE: After another attempt with a couple of new Cobalt drill bits, I hired a mag drill and bought the relevant bit for that. Hired it for a days - actually returned it at 11.45am!! 4 Link to comment Share on other sites More sharing options...
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