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?
Getting the correct size chuck key, helps with tightening the drill chuck and reduces wear and tear.
There are multiple makes of drill (and drill types) out there. They can come with a variety of different size drill chucks…
Typical drill chuck sizes:
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…
There generally appears to be four methods of measuring a chuck key:
And a combination of the above, which may also include:
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.
Do you Know the Make of the Drill Chuck?
The drill chuck markings can mean many things (see the image below), but they can lead you to the answer:
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?
Some of the drill chuck brands:
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.
Some suppliers will provide general measurements for you to compare, such as:
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…