Drilling through 2” of steel

T

Talber8

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Hello, drilling a new hole for a hitch pin in a hitch extension on drill press. 5/8” hole through 2” steel

Is it best to start with a small pilot jump right to a 5/8 twist? Or should I start with a pilot and slowly increase drill size?

Im using a drill press that only goes down to 650rpm
 
Annular cutter is another option.....The gurus will chime in on the drilling procedures.
 
If you have to purchase a tool to make this hole I would agree with @Aukai and go with an annular cutter. If you already have the 5/8” twist drill then I would probably use a 1/4” pilot and then go to the 5/8” using a good amount of cutting oil. Others might approach it differently.

BTW, Welcome to Hobby-Machinist, glad to have you onboard.
 
Annular cutter would be my first choice, recently made a spider out of 2.5" 1045 an used a 1.25" annular cutter to core out the center which was 2" from either side. Took about 2 minutes per side with cutting fluid. Problem in this situation, is first the expense if you do not have a means to hold the cutter and second is the speed. Annular cutters need slow steady pressure, I was told to always keep the RPM below 400 RPM and that was with 1/2-3/4" range. Prior to using annular cutters, I just sequentially went up in size with drills, so something like 3/8", 1/2" and then 5/8" (might be able to skip the 1/2"). I have seen bigger mills go straight to a large bore drill, typically they have a lot more mass/rigidity and slower speed. Drill speed for a 5/8" is around 400-600 RPM for steel. Might be too much for a drill press unless it is a heavy duty model. I have a set of reduced shank drills in the 1/2-1" range, but I usually drill a smaller pilot hole for most metals.
 
I would go with a 1/4 or 5/16 first, then chew through it with the 5/8. Assuming a 5/8 pin I would recommend 41/64 or 21/32 drill bit. You need a little clearance, the drill bit might actually drill on size. Makes it a bit hard to install the pin.
 
For mild steel speed is 670 rpm for 5/8
No need to pre drill,only if it is critical that the hole is i the right possision or you drilpress is to weak..
 
Is there a need for a solid extension ?
 
Only problem with the classic "pilot first" approach is that small drills are far more prone to wonder in deep holes - not least of all because they have limited chip clearance ability - and once they've done so will guide bigger drills down the same path. I've drilled an 8mm hole through a 75mm (3") block of steel recently, simply by spotting then punching straight through with an 8mm split point drill. 5/8 is not an impossible task with a reasonably rigid drill press and a sharp split point drill. 640rpm is right on the money for 5/8 in steel, so you're good there.
 
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