These numbers are all conservative and based on what you can typically get away with on a manual or self-feed drill press or machine using High Speed Steel (HSS) tooling. The numbers for some materials presume the use of appropriate coolant. Higher quality tooling can often allow you to run faster RPM rates and/or more aggressive feed and thrust rates but typically require higher HP for the process as well.
Note that if you are using this chart to estimate the machine requirements for a multiple spindle drilling project, you will need to multiply some of the numbers by the number of holes you will be processing plus add a bit for internal gearing resistance, etc.
Aluminum
Brass
Cast Iron
Low Carbon Steel
Stainless Steel
Plastic / Wood
Fiberglass
A typical drill press often has an RPM limitation of between 2000-3600 RPM. If the chart above specifies a higher RPM than your machine is capable of, it should not cause a problem to run at a lower RPM. For instance, many people drill 1/16″ holes at less than 10,000 RPM with no problems.
The process of drilling holes in metal or similar materials without coolant is possible but not suggested. In most metals, the RPM rate can be decreased to 25% of what is shown above to drill without coolant. However, in stainless, the RPM rate must be decreased significantly more. Stainless steel does not dissipate heat easily. It will almost immediately ruin the cutting edge of your tool. It is often helpful to take a heavier cut in stainless than a lighter one to keep the tip of the tool in “cool” material rather than near the surface that was recently heated up by the last pass of the tool tip. Check with your drill tooling manufacturer for specific requirements and limits.
Reaming generally runs at 2/3 or less the RPM of drilling. AutoDrill suggests the same horsepower rating in case the hole is undersized, etc. The last thing you want is to stall your machine or motor. Check with your reamer tool manufacturer for specific requirements and limits.
Tapping generally runs at around 1/3 to 1/4 the RPM of drilling. We suggests a minimum of 2-3 times the horsepower of drilling for standard tapping processes and higher numbers for flow or roll form tapping. Check with tap your tooling manufacturer for specific requirements and limits.
Why do my tools wear quickly or break?
Note that excessive tool wear or breakage is often caused by:
- Improper surface speeds
- Improper feed rates
- Improper cutting tool type or material (HSS vs TiN vs Carbide, etc.)
- Dull tooling
- Hard spots in the material such as scale, silica, imperfections, etc.
- Improper coolant or lubricant type
- Inadequate coolant or lubricant (overall for chip removal, rubbing, etc.)
- Inadequate coolant or lubricant (at the tip of the tooling)
- The tool is not rigid enough (try drill bushings or guides, guide rods on the drilling machine, etc.)
- Too deep of a cut without proper chip removal – Chip packing (try peck drilling, air blast or coolant through the tool options, etc.)
- Tools that were manufactured or sharpened incorrectly. (watch those clearance, rake and lip angles as well as rough surfaces, etc.)
Calculating cycle time when drilling:
We can help you lower your cycle time when drilling holes in a part or multiple parts. Generally, this is the calculation we use to figure out the time it will take to perform a process:
Depth divided by feed = rotations
Rotations divided by RPM = minutes
Minutes multiplied by 60 = the seconds the process takes.
(Depth = 30% of the diameter of the tool plus the thickness of the material)
Add in stroke up to product time
Add in stroke back to home time
Add in clamp and unclamp time
Add in any human factors, etc.
Add in time for potentially dull tooling, etc.
Add in time for less than adequate machine thrust, etc.
We use the charts above to estimate these numbers.