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How to Buy a Chuck Key for a Hand Drill or Drill Press

I had just bought a second-hand drill press, but the chuck key was missing. No problem I thought, chuck keys are easily found. Just type in chuck key in google, and thousands of results will appear…

That’s the problem, thousands of results do appear. But which size chuck key do I buy?

Old Chuck Key (1/2
An Old Worn Chuck Key (1/2″ or 13mm)

Getting the correct size chuck key, helps with tightening the drill chuck and reduces wear and tear.


What Size or Measurements do I use, to Buy the Correct Drill Chuck Key?

Topics:

Generic Chuck Keys:

There are multiple makes of drill (and drill types) out there. They can come with a variety of different size drill chucks…

Various Chuck Keys (6.5, 10 & 13mm)
Various Chuck Keys (6.5, 10 & 13mm)

Typical drill chuck sizes:

Inches Metric
1/4″ 6.5mm
3/8″ 10mm
1/2″ 13mm
5/8″ 16mm
3/4″ 20mm

Obtaining a chuck key via the drill chuck size tends, to relate to a drill chucks fitted to mass-produced ‘generic type’ hand-held drills.

For example – A generic 1/2″ (13mm) drill chuck key fits a generic 1/2″ (13mm) drill chuck. Some generic chuck keys may be a bit loose, some may be a perfect fit.

For the more specific drill type (non-generic), this isn’t always case…

Chuck Key Size Measurement:

There generally appears to be four methods of measuring a chuck key:

And a combination of the above, which may also include:

  • Length x Width x Height (L x W x H).
  • The Number of teeth.
  • The outer diameter of the gear teeth.
  • etc, etc.

Drill Chuck Size:

The drill chuck size is very relevant to non-generic drill chucks (see the section above on “Generic Chuck Keys“). For non-generic chuck keys, it is one of two or three criteria for selecting a chuck key.

The Manufacturer’s Reference Number:

Do you Know the Make of the Drill Chuck?

  • Is it marked on the drill chuck?
  • Is there a reference number?
  • Does the reference relate to a chuck key?
  • Do you know the make of the drill and the model number?

The drill chuck markings can mean many things (see the image below), but they can lead you to the answer:

13mm Drill Chuck Markings
13mm Drill Chuck Markings. 1/16 – 1/2 relates to the drill capacity, 1/2 x 20 is the Drill spindle connecting thread size.

Go to the drill or drill chuck manufacturer’s website and see if there are any data sheets with the drill specifications detailed. Hopefully, it will tell you which chuck key you need?

Note:

  • A drill will sometimes have a drill chuck supplied by another manufacturer.
  • The drill chuck markings usually refer to just the drill chuck. Use these details to work out what chuck key you may need.
16mm Pillar Drill Chuck Markings
16mm Pillar Drill Chuck Markings

Some of the drill chuck brands:

Measure the Drill Chuck, Chuck Key Pilot Hole Size:

This appears to be the most reliable method of sizing a chuck key (other than knowing the specific chuck key reference number). However, you should cross-reference / combine this measurement with the other data / measurements you have.

I used a caliper to measure the hole size. Don’t forget to take account of any flat edges on the calliper measuring jaws, as this will give you a slightly incorrect (under-sized) reading. Or, you could use a drill bit to find the size of the pilot hole.

Note that many of the pilot hole sizes are often quoted in inches as a fraction. Use an online conversion tool if needed.

The physical chuck key size (measurements):

Some suppliers will provide general measurements for you to compare, such as:

  • Length x Width x Height (L x W x H).
  • The Number of teeth.
  • The outer diameter of the gear teeth.
  • etc, etc.

This is just a case of measure what you can on the original chuck key (if you have one), and the chuck itself and see if you can match anything up with the supplier’s information?

Not always the best solution, but sometimes all you’ve got?

Hope this helps…