What's the proper name for these bits!

[lpeedin]

I bought several of these along with a handful of square end bits for $1.00 each at a flea market.

This one is 5/16” on the small end and exactly what I needed to countersink 5/16" cap screws. I'd love to have several more sizes but can't seem to find them. I tried searching for step bits but the only results were the cone shaped bits for step drilling holes in sheet metal.

Thanks for any feedback.




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[JimDawson]

That looks like a drill / counterbore combo bit, I wasn't able to locate that exact bit in a very quick search.

You can buy counterbores from all of the tooling suppliers. Some have a fixed pilot, some have an interchangeable pilot. If I were going to buy another set, I would get interchangeable pilots.

 

[lpeedin]

Thanks Jim, I just found them on McMaster Carr as counterbore bits. According to their prices, I think I found a deal. .

 

[JimDawson]

Thanks Jim, I just found them on McMaster Carr as counterbore bits. According to their prices, I think I found a deal. .

My pleasure. A deal from Mcmaster? I would go buy a lottery ticket)

 

[lpeedin]

My pleasure. A deal from Mcmaster? I would go buy a lottery ticket)

What I meant was, based on MC's price, I got a deal at the flea market.

 

[Marco Bernardini]

You are really lucky!
Here the flea markets offer mainly things like this one:



These counterbore bits, sometimes called "stepdrill", allow you to correctly place a cap screw, with a flat bottom under the head.
Generally, without these bits (and without an end mill) the hole for the head is done with just a larger bit, and this has two drawbacks: first, to center exactly the head and the screw could be difficult (while with such a bit you can even make it with a hand held drill), and second the head gets an uneven support, limited to the circumference edge.
:nono:

On eBay even Chinese counterbore bits are over $15 each, at least the metric ones I need, so you really made a good deal.

 

[genec]

I have always called them step bits, I came across a box of assorted for $1.50 a pound, so far haven't found a use for them.

 

[Marco Bernardini]

I have always called them step bits, I came across a box of assorted for $1.50 a pound, so far haven't found a use for them.

If they are metric and you find a way to ship them to Italy for a very reasonable price, I offer you $3/lb… a deal

 

[kwoodhands]

I bought several of these along with a handful of square end bits for $1.00 each at a flea market.

This one is 5/16” on the small end and exactly what I needed to countersink 5/16" cap screws. I'd love to have several more sizes but can't seem to find them. I tried searching for step bits but the only results were the cone shaped bits for step drilling holes in sheet metal.

Thanks for any feedback.




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They are called "bullet drills". The box stores and hardware stores carry them in sizes up to 1/2".Black & Decker and maybe Vermont American both manufacture these drills. The point is good for starting the hole.
mike