So I see an advertisement for an SDS Max rotary hammer that is "1 1/4 in" , and another (that is apparently more powerful?) at "1 9/16 in", and yet another at "2 in".

What does that dimension (1 1/4, 1 9/16, 2 in) actually signify?

2 Answers 2


That's the chuck size.

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It tells you the maximum size shank that the tool will accept. A larger shank size allows more power to be applied to the bit without breaking it. That is why larger chuck sizes usually have more amps.

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  • I don't mean to be argumentive, but that seems odd. An SDS Max bit is just one size, isn't it? So the chuck size for one SDS max drill should be the same size for any other SDS Max drill. Commented Aug 17, 2021 at 18:29
  • @KerryThomas SDS, SDS-Plus, and SDS-Max are shape descriptors. Each shape supports a range of shaft sizes; SDS-Max is supposed to be 0.5"-1.75" but apparently Makita blazes their own trail per my screenshot? 2" could be a typo. See en.wikipedia.org/wiki/Drill_bit_shank for more information.
    – MonkeyZeus
    Commented Aug 17, 2021 at 18:47

So I contacted the tech support department at Milwaukee Tools. The gentleman I spoke to (who knew the answer right away, and did not sound like some offshore support guy reading from a script) said that this dimension refers to "The tested maximum size of the twist bit that may be safely used with the tool."

From our conversation, I was given to understand that:

This is a twist bit: twist bit

As opposed to a hole saw: hole saw

  • 1
    "This inch rating refers to the solid drilling diameter capacity or basic power of the drill" beltsandboxes.com/sds-vs-sds-plus-vs-sds-max-vs-spline-drive - Mine does 4" cores; no idea what the other number is, prob 2". Doesn't matter though, I have nothing between 1-1/8" drill bit and a 2" core.
    – Mazura
    Commented Aug 17, 2021 at 23:24

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