Sutton 2.5mm Chucking Reamer DIN212 - Cobalt Steel

The Sutton R102 is a chucking reamer in cobalt HSS (HSS Co), listed to DIN 212 / ISO 521. It is a machine reamer with a parallel shank that finishes drilled or bored holes to an H7 tolerance, for toolroom and workshop use, with a bright finish (uncoated and polished) and 10° left-hand flutes.

There are 42 sizes from 2 mm to 16 mm, including the common fractional-inch sizes from 1/8 in to 5/8 in, with 3 to 8 flutes depending on size (3 flutes at 2 mm, 5 flutes at 2.5 to 3.572 mm, 6 flutes at 3.969 to 13.5 mm and 8 flutes at 14 to 16 mm). Each size lists its own shank diameter (d2), so check the holder or collet you plan to use. This cobalt reamer is rated 'optimal' in more materials than plain HSS reamers: as well as non-alloy and low-alloy steels and grey cast iron, it adds quenched and tempered low-alloy steel (to about 275 HB) and ferritic nodular and malleable cast irons.

Where this product is used

• Machine finishing of small to medium drilled or bored holes to H7 where the reamer is held in a chuck or holder.
• Toolroom, workshop and production reaming of dowel, pin and bush holes.
• Jobs in tougher materials, where the cobalt grade is rated 'optimal' across a wider set of steels and cast irons than plain HSS reamers.

Getting the best results on the machine

• Leave enough stock to cut. The starting guide for machine reaming is 0.20 mm for a 6 mm hole, 0.30 mm for a 12 mm hole and 0.50 mm for a 50 mm hole. Too little stock makes the reamer burnish rather than cut.
• Run slowly. The most efficient reaming speed is often about two-thirds of the speed you would drill the same material at, and the rule is that speed must not be high enough to permit chatter. Drop the speed again when you need close tolerance and a fine finish.
• Keep the feed up. Reaming feeds are usually much higher than drilling feeds: 0.038 to 0.10 mm per flute per revolution is a suggested starting point. Too low a feed can cause glazing, wear and chatter; too high costs accuracy and finish.
• Use straight cutting oil. In reaming the lubricant is chosen for finish rather than cooling, and that usually means a straight cutting oil.

Recommended starting surface speeds for reaming:

If it chatters or the finish is poor: Speed and feed that are wrong (too high or too low) are linked to all four problems: breakage, wear, chatter and poor finish. It also lists lack of rigidity (fix: improve rigidity), entering the work too fast (fix: slow the approach feed), oversize or undersize guide bushes and a badly drilled hole (fix: replace the drill).

Fit and tolerance

H7 is the ISO 286 hole tolerance: never smaller than nominal and never larger than nominal plus the IT7 band (10 µm up to 3 mm, 12 µm over 3 to 6 mm, 15 µm over 6 to 10 mm, 18 µm over 10 to 18 mm). Sutton holds the cutting diameter of its parallel reamers to M6 limits (BS 122 Part 2), chosen to produce H7 holes. For example, a Ø5 mm reamer has cutting diameter limits of Ø5.004 to Ø5.012 mm and the finished hole is held within Ø5.000 to Ø5.012 mm (H7); a Ø12 mm reamer has cutting diameter limits of Ø12.007 to Ø12.018 mm and the finished hole is held within Ø12.000 to Ø12.018 mm (H7).

Key specifications

Related reaming tools

For larger holes on a Morse taper machine, the R101 machine reamer runs from 6 mm to 50.8 mm, and for hand reaming see the R100 hand reamer. If you want to ream a bigger range with one tool, the R109 adjustable hand reamer adjusts across a size range. The AIMS Reamer Guide explains allowances and fits in more detail.

Having reaming problems? Our Cutting Tool Troubleshooting Guide covers reamers alongside drills and taps.