Cannot drill fat steel?

I'd been having problems drilling 1/2 inch thick steel on a drill press. Only about 1/4 inch deep the 1/2" HSS drill bit
would seize or glaze the steel and will cease to drill any further.
The drills were sharpen with diamond disc and sharpen keen to the tip finishing with a 400 grit diamond. Should I be using cutting oil, coolant or a different type of drill bit?
Thanks
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You should clamp it between two pices of metal or hardwood of about 1cm thik.
Johnny Verhoeven

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You may be drilling the steel at too high of a spindle speed. Yes you should use a coolant. It may also be the steel you are using. If it is 4130 it may be hardening because of spindle speed and the heat that generates.

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