Tips for drilling through steel plates?

chim

chim

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L4240HSTC with FEL, Ford 1210
Jan 19, 2013
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Near Lancaster, PA, USA
This past Thursday I needed to drill two 1-1/4" holes in a piece of 4x4 galvanized tube steel at our church. The mag drill wouldn't fit where the holes were going so I took a Morse hole saw and a 20V DeWalt drill/hammerdrill and use it on the drill setting at the lowest speed.

Running it at a really low RPM it went through the 1/4" wall of the tube without getting more than warm to the touch. Went slow enough to be able to count revs of the setscrew that holds the pilot as it went around. Didn't even bother with any lube. In my younger days I'd have burned up a bit or two in my haste to get 'er done. Bit was a nice at completion as it was before starting.
 
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Trapper Bob

Trapper Bob

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L4701, Wicked grapple, 6’ bush hog, pallet forks, 7’ box blade, 6’ Wicked bucket
Jan 17, 2022
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Andover, KS
You can dub your drill point. This will keep the outside edge from chipping when you pass thru the backside of the plate. A split point will decrease the force needed to get thru the material, but can grab as you are passing thru. The step drills are great, working best in thinner material (under 1/4”). There are some combination drills on the market, with the pilot ground on the point. These can be a bit expensive. TIN & TICN coatings are useful. Cobalts & carbides have their place, but do add to the cost. Knowing your material is the best way to choose the right drill. If unknown, experiment a little. Keep your rpm’s down, heat is your enemy. As stated above, lubrication can help.
 
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