Counterbore, suggestions?

[Aukai]

I needed a counterbore yesterday to sink a bolt head. Any suggestions for CBs, and pilots. I am also getting different spellings for the word, which is correct, one word or two? LOL Thank you

The bolt head in the picture is already 1/2 thickness, so I didn't feel good about cutting it down anymore.

 

[Charles Spencer]

I bought these.

https://www.ebay.com/itm/5pcs-M3-M8...-End-Mill-Cutter-Pilot-Slot-Tool/192409434491

 

[magicniner]

I bought a set with a common shank and pilots, all the counter bores fit the shank and can be used with all pilot sizes.

 

[Aukai]

Still looking around, how's this set?

http://www.shars.com/40-pc-3-flute-hss-interchangeable-pilot-counterbore-set-1

 

[TomS]

I bought my set from CDCO a few years back. They've held up well. Current price is $32 for the set.