Regrettably not, Andrew

This has long been a gripe of mine … Grrr!!

The proportions of the metric ones simply don’t do justice to Imperial cap-heads.

MichaelG.

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Edit: __ Well-found, Peter

Our Tool-Makers used to grind their own, by modifying a drill-bit

MichaelG.

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Edit: __ Like wot Vic illustrates !

I start the counterbore to nearly full depth with a normal drill then finish with a flat bottom drill, much easier to grind than the stepped arrangement

Make your own custom size counterbore from silver steel.  These are easy to make and sharpen and suitable for occasional use.

https://gadgetbuilder.com/CounterBore.html

Making a step drill.

https://youtu.be/wxrf4TJvygA

On 6 January 2026 at 06:51 Paul Lousick Said:

 

That’s quite an odd design for a countbore?

These are some of the four teeth ones I’ve made from silver steel. I harden but don’t bother to temper them, I just leave them glass hard. I’ve not had one chip yet. The angle of the teeth is easily cut for whatever material you intend to counterbore.

I make my own too. For tempering silver steel tools, lately I have been giving them about 15 mins in the air fryer at 200°C. It hardly changes the colour or hardness at all, but does considerably improve the toughness.

On 5 January 2026 at 18:14 Andrew Tinsley Said:
“I would like to have a few Imperial counterbores, as I often work on older equipment. The cheapest I can find seem to be at least £35 each and very much upwards of that figure. Does anyone know of a source of cheaper counterbores?”

Andrew, I have two of these:

https://www.ebay.co.uk/itm/371695786775?var=640675509787

The name may be incorrect, but the items I received are counterbores like in the pic.

On 5 January 2026 at 18:43 Vic Said:
“In my experience counterbores produce aesthetically over size looking holes”

Look for the Chinese sellers selling 5 piece sets M3-M8. They are definitely not oversized. Many of these sellers give the dimensions. Don’t know what they’re like on tougher materials but they work great on alu, copper alloys and mild steel. I bought two sets for £8.50 each about three years ago. Still on the first set.

These are the measurements of a typical set:

M3: 5.9 (blade diameter) * 3.2 (boat) * 6 (shaft diameter) * 45 (full length)

M4: 7.4 (blade diameter) * 4.2 (boat) * 6 (shaft diameter) * 48 (full length)

M5: 9.5 (blade diameter) * 5.2 (boat) * 6 (shaft diameter) * 51 (full length)

M6: 11.0 (blade diameter) * 6.2 (boat) * 8 (shaft diameter) * 58 (full length)

M8: 14.0 (blade diameter) * 8.2 (boat) * 12 (handle diameter) * 67 (full length)

“Blade” =  bad translation of “cutting flutes” or similar.

”Boat = bad transl. of “pilot”

“Tracy Tools have them in 3/8 7/16 and 1/2 inch sizes at £8 each”

When I inquired about six months ago their site suggested they had them, but when I contacted them they said they didn’t have any, hence my purchase from Spalding Fasteners.

I’d be inclined to say that a lot of the home made cutters being shown here are more in the style of spot face cutters. off the shelf Counterbores tend to have longer flutes so can clear the swarf at typical cap head depth or deeper. The cutters here would clog if not retracted several times and they are just like spot and back spot facers in this respect.

But in a hobby workshop the only real difference is how far in you feed them.

Probably the most useful commercial counterbores I’ve seen are those with replaceable pilots, they were quite expensive though the last time I saw them.