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General advice on using reamers

Jun 24, 2021
South Jersey
Hi Bob
I know of no stand fast rule (Higher Rpm = x). Perhaps others will.
I will typically do an ad hoc DOE. (Design of Experiment)

  1. Ream some holes using different RPM's per hole and document finished hole size @ what rpm
    • Drill the holes leaving the same amount for reaming in each hole. 1/64 to 1/32
    • Use same cutting lubricant
    • Use the same reamer.
    • Use the same feed
  2. Now change up bit
    • Same as above only keep the RPMs the same for each hole
      • do the math for textbook rpm for diameter
    • Ream some holes using different feed rates and document finish hole size @ what feed
      • On a Bridgeport you only have three feed rates.
  3. You can go further by keeping everything the same and changing up Cutting fluids.
The information you gather from above will tell you a couple of things. What variable has the biggest/smallest impact on size and
any direct correlation the change of a variable and the hole size.

DOE's can be simple to very complex. I have barely scratched the surface but there is a lot of good and free information on the web on their use.

Go make chips!


Cast Iron
Feb 2, 2016
For dummies like me how would each of these factors affect the hole size? Higher RPM = bigger or smaller and such. Handy information to have when a hole needs to be just a little off size. Bob
As far as rpm I have found that increasing RPM decreases hole size a small amount and decreasing increases hole size a small amount. Same with feed. I am just careful not go to slow and burnish the hole instead of cutting.