Drill Press RPM for steel

[easygo]

Hi all,
I have been considering buying a drill press for quite some time. I found a used one near-by but the lowest drilling speed is a bit of a concern. The slowest RPM is 380 and I wonder if that is slow enough. I have been drilling with a rather large variable-speed hand drill and there is no way to know what the actual RPM is. I know that I want it to be slow for larger 1/2-1" holes (in mild steel), but is 380 RPM slow enough? It appears to be an oldie but goodie with vise included.

 

[jimgerken]

Nope, in my opinion.

 

[sandman2234]

I think my Bridgeport goes down to 80 rpms, and sometimes I think that is too fast...
David from jax

 

[k0ua]

Most charts say ok for up to 1/2 in mild steel, but some will show it ok for up to 1 inch, by in my experience it is kinda fast for anything over 1/2 and I would not like it even for up to 1/2. Slower is better.

James K0UA

 

[flusher]

Too fast. I'd keep it around 200 rpm and use a lot of cutting fluid. And get yourself a Drill Doctor to keep your twist drills sharpened.

 

[5030]

Get yourself a Machinery's Handbook with speeds and feeds tables and never guess.

You can get away with a bit higher RPM if you relieve the heel of the cutting edge on the drill or reduce the cutting angle (neither of those a Drill Doctor or any Darex drill jig will accomplish however).

Adjusting the cutting angles and relieving the heel can only be done by offhand sharpening which is an acquired skill. No Drill Doctor here.

 

[LD1]

Yep, that is a bit fast too IMO.

I dont use the charts. I just go with my gut based on experience. With HSS bits, blue chips are BAD. Brownish are ok, but silver chips are the best.

No way you are going to get anything other than blue chips with a 1/2"+ bit spinning @ 380RPM:confused2:

I personally would want something that goes as low as ~50 or so RPM for the larger holes. 1"-1-1/4" holes.:thumbsup:

 

[BHD]

many people make a jack shaft and reduce the speed on shop drill press more than the factory settings,

on large holes that is to fast IMO, but on small holes it will work fine, keep some coolant on the bit,

I have never have over heated a bit using this press,

 

[jbooth]

[I have never have over heated a bit using this press,[/QUOTE]

How about the motor. Does it ever overheat.

 

[SandburRanch]

Hi all,
I have been considering buying a drill press for quite some time. I found a used one near-by but the lowest drilling speed is a bit of a concern. The slowest RPM is 380 and I wonder if that is slow enough. I have been drilling with a rather large variable-speed hand drill and there is no way to know what the actual RPM is. I know that I want it to be slow for larger 1/2-1" holes (in mild steel), but is 380 RPM slow enough? It appears to be an oldie but goodie with vise included.

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You better believe it will work so buy it if the price is reasonable. Those don't come around for sale very often. I wouldn't be without one.

RPM is determined by cutting speeds of various materials and those recommendations are all over the place depending on who's chart is being used.

For mild steel 90 feet / minute was once popular but I see now 100 ft./ min. is being used and even higher.

In the link below is the old formula that don't need no stinken pie to figure RPM.
Simply multiply the material cutting speed X 4 and divide that by your drill bit diameter. Using 100 ft./ min. cutting speed you can readily see your 1" HSS bit can be rotated 400 rpm. A coolant fluid or cutting oil for cutting (NOT LUBRICATING OIL) is always recommended.

Safety Tip - always clamp your work securely to the press table via vise, C-clamps etc.

Machine Shop 2 - Lathe Cutting Speeds - RPM Calculations