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Silver & Deming (Reduced Shank) Drills

Silver & Deming drills are large-diameter twist drills with a shank turned down to a size a common drill chuck can grip. This sheet covers how to recognize them, what options to stock and where they fit against taper shank drills.

Ref CT-0007ANSI B94.11M

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

A Silver & Deming (S&D) drill is a straight-shank twist drill whose shank is smaller than its cutting diameter. The most common shank is 1/2 in, so a drill press or heavy portable drill with a 1/2 in chuck can run a hole well over 1/2 in. Reduced shank drills with a 3/8 in shank are also sold for smaller chucks. S&D drills are general-purpose tools for fabrication, maintenance and farm shops. They are covered with other twist drills in ANSI B94.11M, but overall and flute lengths vary more between makers than they do for jobbers.

How to identify

The body is large and the shank steps down sharply behind the flutes. The shank is usually 1/2 in round, often with three flats so it does not spin in a three-jaw chuck. S&D drills are shorter than a taper length drill of the same diameter. A large drill with a Morse taper and a tang instead of a round shank is a taper shank drill, not an S&D.

Comparing large-hole drill options

Option	Shank	Best fit	Watch for
Silver & Deming	Reduced round, often 1/2 in, often 3-flat	Drill presses and heavy portable drills with a 1/2 in chuck	Chuck slip at high torque without flats
3/8 in reduced shank	Reduced round, 3/8 in	Smaller portable drills	Limited torque for the larger sizes
Taper shank	Morse taper with tang	Machine spindles and sleeves	Needs the matching taper and a drift to remove
Annular cutter	Weldon or quick-change	Magnetic drills in plate	Not a twist drill; needs its own arbor
Step drill	Small round or hex	Thin sheet only	Not for thick material

Key points

S&D is a shank style, not a length series. Confirm the shank size the customer's chuck accepts.
They come in fractional sizes, usually in 1/64 or 1/32 steps through the common range, and in sets.
HSS is standard. Cobalt versions are available for stainless and harder steels.
Run large drills slowly. Surface speed rises with diameter, so a large drill at a small-drill RPM overheats quickly. See the SFM to RPM chart.
A pilot hole reduces thrust and helps a large drill start on location.
Exact flute and overall lengths come from the maker's catalog.

Common mistakes

Selling an S&D to a customer whose chuck is only 3/8 in.
Running an S&D in a light cordless drill and blaming the drill when it binds.
Confusing a reduced shank drill with a taper shank drill when the customer has a Morse taper spindle.
Assuming every maker's S&D has the same length.

Governing standards: ANSI B94.11M (twist drills). Manufacturer catalogs for shank size, flute length and overall length.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

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