Drilling Steel

[JWB_Machining]

Hey,

I'm trying to drill through a rod of Steel (Rockwell C 30) with a Carbide Tipped Drill bit. I used the Machinery's handbook and I think It's saying I should be drilling with a 1/2" drill bit, after center drilling ofcourse) with an RPM of 2475 and a Feed of 14.8 IPM. Does this seem right? Also when I do drill, I have to go 1.25 deep would a peck of 0.1 be good?

[JWB_Machining]

I'm Thinking it should be more like an RPM of 125 and a feed of 0.5

[Geof]

Rockwell C30 is not particularly hard. If this is just a medium carbon steel 2475rpm and 14.8ipm should be okay; I might go slower but even with HSS I would be around 800rpm an maybe 5ipm with a lot of coolant.

Things can change if it is an alloy steel or stainles that works hardens becasue then you need to take the speed down but keep the feed up a little to prevent rubbing and work hardening. Even so 125rpm and 0.5ipm seems a bit slow.

What is the material?

[JWB_Machining]

Steel with Rockwell hardness C is all I know I just tried RPM 764 with a Feed of 3.0 and that ate the bit up though.

[JWB_Machining]

I'm sorry make that 500 RPM

[JWB_Machining]

Ok Running it at 800 RPM with a Feed of 5 just ruined this Carbide tipped bit. Is it Possible these bits are just garbage?

[davereagan]

Carbide tipped drills are generally not for steel, they are for cast iron. I've killed a couple of them in mild steel. A HSS or Cobalt drill would work fine around 500 rpm and 4 inches per minute. Maybe faster if you have a bunch of holes.

[mc-motorsports]

Cobalt, 500 RPM, 2 IPM and increase the feed if you can. Manual feed or full CNC?

[dertsap]

Originally Posted by JWB_Machining Ok Running it at 800 RPM with a Feed of 5 just ruined this Carbide tipped bit. Is it Possible these bits are just garbage?

possible they are garbage but if they are quality the first speeds and feeds you got from the handbook is about right , actually a lil on the slow side for a 1/2'', what could be killing your drill is the fact you are centerdrilling , thats a no no
best thing is to contact the manufacturer and ask what sfm they recommend

[JWB_Machining]

How does centerdrilling kill my drill? Don't I want to create a spot for it to start bitting into?

[g-codeguy]

Now I know why I never had any luck with carbide-tipped drills the couple times I tried them.

I will spot drill for smaller diameter carbide drills. My understanding is that you should spot drill with the same angle that is on the drill. Unforunately I can't. I suppose this may hurt tool life, but have no way to be sure since I can't test it.

Instead of the drill cutting on the full cutting edge surface, it will start cutting at only one point on the edge with a spot drilled hole. I doubt this is the best thing for the drill. It can cause a notch. At least that is my thinking. Definitely could be wrong! Wouldn't be the first time.

[dertsap]

carbides are generally self centering and do not need to be spotdrilled , carbide does not like starting the cut with the edges of the tool rather than the tip , that initial chatter and slight wander than happens when the drill comes in contact with the spot drill hole is usually the point that a carbide will take a beating