What sort of shank is this?

[Crey Guy]

Hi all,

Feel like bit of a rookie question, but I bought this step drill bit from Screwfix thinking it was a normal hex shank. It has three flat sides but the rest is circular if the images don't show that.

It fits in my drill fine obviously but I need ~150mm extension. I've got this for a hex bit, but this doesn't fit that.

What is this type of shank? Google has been useless so far. Additionally, what sort of extension or adapter could I use to be able to use this?

Thanks

[Dave54]

This looks like one of those shanks with 3 flats 120 degrees apart.
It gives the normal drill chuck a way of holding the bit so it won't rotate. You engage the jaws of the chuck on the flats,

[etaf]

you could take back and get these from toolstation,if they give the size range you are after
https://www.toolstation.com/hss-titaniu ... hMQAvD_BwE

If you already have an extension have a 150mm extension that works with that type of fitting

[Dave54]

That's the best idea that etaf has above.
I hadn't read about needing an extension.