Anatomy of Keys

Anatomy of Keys

Our customers are surprised and delighted when the keys we send them work better than their original keys.

Copies are usually worse than originals, right?

Are we engaging in baffling feats of magic? No. There’s a technical reason our keys often work better than the original: Instead of just replicating a key, we make deductions about the locks they operate, and cut a key to fit that lock.

The Differences Between Keys

There are thousands of varieties of keys on the market. A typical hardware store carries about 150 types of blanks. What sets apart one blank from another are the grooves on the side of the key:

Keyway grooves determine whether a key can slide into a lock

The shape and the placement of these grooves determines whether the key can slide into your lock. Markings on the head of the key sometime make it easier to identify the blank, but that’s just a courtesy on the part of the manufacturer. The shape of the head is another courtesy, but also not a reliable indicator. The person who copies your keys at a hardware store becomes very skilled at matching up the grooves of your keys to the right blank by sight.

It’s easier to identify the keyway groove if you look down the blade

Just as the grooves determine whether the key can enter your lock, the key’s teeth determine whether it can turn your lock. Most locks tolerate variations in the width of the troughs and the heights of the peaks. But locks are very sensitive to the depth of the troughs.

The depths of the troughs determine whether a key can turn its lock

The teeth are cut in increments of .38 mm (0.015”) on most Schlage locks. A key will turn the lock if every tooth is within 60 microns of the cut depth specified by the lock.

The troughs are cut in discrete increments. Not all cut depths are valid.

When Good Keys Go Bad

Bad keys are either difficult to insert into their lock or need to be jiggled to turn their lock. The first problem usually means that the peaks are too sharps or that the troughs aren’t spaced according to specification. The second problem usually indicates that the troughs are too deep or too shallow.

How We Make Bad Keys Good Again

A traditional key copying machine follows the contour of the original key and grinds the same contour on the copy. This process introduces tiny errors that accumulate over generations. Our process measures the depth of the teeth of the original key. Instead of cutting the new key with those depths, it instead cuts them at nearest cut increment of the lock. Each tooth is also cut with the width and spacing specified by the manufacturer of the lock instead of the spacing and widths of the original key. By not following the contour of the original key, we avoid propagating the errors of the original key.