Well, this is another reason to use a calculator instead of a rule of thumb. Okay, those numbers are neither 1/2 nor 1/3, though the reamer is spinning close to 1/2 the twist drill, and the reamer feed is faster. Twist drill is 703 rpm (a little less than 2x the reamer), and 1.863 ipm (reamer is feeding a little faster)… Chipload is 0.0015″įor comparison, here is the same cut with a 3/16″ HSS Twist Drill: Here’s what G-Wizard would suggest for reamer speeds and feeds with a 3/16″ HSS Reamer in 300 series stainless, which was the question in the post:Ī 3/16″ reamer going 1″ deep in 304 stainless should run 458 rpm and 2.75 ipm feed. This chip load is a synthetic number for G-Wizard, so don’t try to do too much math on it! 2x the feedrate would be 4x the chip load since we’ve already doubled the spindle rpm relative to a twist drill. Moreover, when we say, “2x more feed”, we actually want “2x more chip load”.
In looking over a number of different manufacturer’s recommendations, we’ve found 1/2 yields results reamer speeds and feeds that are much closer to their recommendations. Some say the ratio to a twist drill is 1/3, while others suggest it should be 1/2. Opinions vary on exactly what that rule of thumb ought to be for reamer speeds and feeds. (Click here to learn what is SFM and how to go from SFM to RPM) Saw this question come up on HMEM. A lot of machinists are taught a rule of thumb similar to this:ġ/3 the SFM, 3x more feed than the same sized Twist Drill What are the best reamer speeds and feeds? More information on how to use a reamer: Optimum Reamer Speed and Feeds Here’s a quick video that shows how to ream a hole on a Bridgeport Mill: If you require more correction for straightness than that, boring may be a better approach. A 1/4″ reamer might improve the straightness of a hole by up to 0.005″, but no more. It can only slightly improve the straightness of a hole if it has front-cutting capability. The reamer is only capable of removing a small amount of material from the hole, and it will tend to follow the hole. Performing reaming correctly depends first and foremost on preparation of the hole.
A PCD reamer can impart a finish as fine as 8 rms in aluminum. The range for cast iron is 50 to 80 rms and 30 to 60 rms for steels.
The surface finish from reaming depends on the workpiece material. For example, you could use our Press Fit Calculator to figure the required hole size and them use a reamer to achieve that size within tolerances.
If you need to hold tolerances tighter than +/- 0.002″ on hole diameter, a reamer is probably the way to go. There are other means to create holes with precise diameters and high quality finish on the walls, but reaming is often the best choice for speed and low cost. Another process, such as drilling must rough out the hole before it can be reamed. Reaming is therefore a finishing operating. Reaming is typically done on a milling machine, a lathe, or a drill press. Reaming is a cutting process that uses a special tool called a reamer to enlarge an existing hole to a precise diameter and at the same to to create a smooth finish on the walls of the hole. Reamer Speeds and Feeds, Sizes, Types, and Tips Guide What is reaming?