Your Guide to Buying an Adjustable Reamer

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Your Guide to Buying an Adjustable Reamer

Reamers fine-tune the sizes of holes and leave the sides much smoother than any drill. Adjustable reamers add flexibility so that machinists can work with odd-sized holes, but they also require special care and use because they are more delicate than other reamer types. Understanding adjustable reamer sizes and features helps machinists choose a high quality set for all their odd-sized reaming needs.


Adjustable Reamer Sizes

Each adjustable reamer works in a small range of sizes. In a reamer set, the largest size of one corresponds to the smallest size of the next largest reamer so that theoretically they all cover any size hole.


Adjustable Reamer Size

Approximate Size (inches)

Approximate Size (mm)


.25 to .28

6.35 to 7.14


.28 to .31

7.14 to 7.93


.31 to .34

7.93 to 8.73


.34 to .37

8.73 to 9.52


.37 to .41

9.52 to 10.32


.41 to .44

10.32 to 11.11


.44 to .47

11.11 to 11.91


.47 to .53

11.91 to 13.49


.53 to .59

13.49 to 15.08


.59 to .66

15.08 to 16.67


.66 to .72

16.67 to 18.26


.72 to .78

18.26 to 19.84


.78 to .84

19.84 to 21.43


.84 to .94

21.43 to 23.81


.94 to 1.06

23.81 to 26.99


1.06 to 1.19

26.99 to 30.16


1.19 to 1.34

30.16 to 34.13


1.34 to 1.5

34.13 to 38.1


Reamer Features

Adjustable reamers differ in terms of their shank shape, blade number, and materials. Most adjustable hand reamers have square shanks to fit a hand spanner, rather than a machine. This is because their straight flutes and adjustable blades are too delicate for machine speeds. Smaller reamers have four blades, while larger ones may have five, six, or even seven blades. The most affordable are made of hardened steel, but carbide reamer blades come at a premium price.


Reamer Accessories and Parts

Metalworkers should budget for pilots, blades, and cases when buying a hand reamer or a set. A pilot helps guide the reamer into the hole at the right angle, which is arguably the trickiest part of using a hand reamer. Blades, another expense associated with adjustable reamers, are notoriously delicate. However, machinists should appreciate the fact that the blades are replaceable, unlike regular reamers, which cannot be sharpened without losing their size once they become dull. High quality adjustable reamer sets often come with wooden cases that insulate each tool.

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