COUNTERSINKS & COUNTERBORES
COUNTERSINKS
Countersink tools are usually a single or multi fluted cutter to machine and leave an angled conical, chamfered recess on the finished job, known as “countersinking”, a tapered head bolt or screw, seats correctly into this angled form. The countersink bit or tool is ideally used for deburring holes as well.
Many types of countersinks are stocked & avail. from Miller’s Tooling, including High Speed Steel countersinks tools & carbide countersinks tools.
Generally in Australia, we commonly use the 3 fluted x 90’ countersink tool for most countersinking & deburring applications. 82’ countersinks tools to suit American screws, and 60’ countersinks tools are used mainly for wheel nut & studs. Other countersink tool sizes & angles are illustrated below. Popular HSS countersink tools go up to 31mm with a ½” shank, larger HSS countersink tools are readily avail. with a Morse Taper shank.
Walter –Titex (German) offers an E6819TIN countersink X 90’, a coated HSS countersink tool, which performs extremely well on Stainless Steels, long life & no chatter.
Walter – Titex also has this tool as a great 5 piece set, TIN coated in a case up to 20.5mm. A must for any machine shops & toolrooms.
Also avail. is the “cross -hole” HSS or cobalt countersink tool, predominately referred to as “Weldon” countersinks in Australia. “Weldon” is a very popular American manufacturer of these cross hole countersink tools & countersink bits. The cross hole type countersink tool is handy in a hand held drill, etc for quick 90’ deburring without the chatter.
Countersink tools with indexable carbide inserts are readily available in several diameters.
Carbide – tipped countersinks can be used for longer life & higher speeds in production & hard materials.
(Also see our “Spotting Drills & Engraving” web page – especially for CNC’s)
It can often be difficult to avoid chatter when cutting with countersink cutters. As usual in machining, the shorter and more rigid the setup, the better. Better-quality fluted countersink cutters sometimes have the flutes (or at least one flute) at an irregular pitching. This variation in pitching reduces the chance of the cutting edges setting up a harmonic action and leaving an undulated surface. This surface ripple is also dependent on the surface speed of the cutting edges, material type, and applied pressure (or feed rate); once started it is hard to remove. Too light a feed tends to increase chatter risk. As in many other machining operations, an appropriate response to the chatter may be to decrease speed and increase feed.
Check out the extensive “Noga” hand deburring & countersinking tools available on our 
“Deburring” (Cutting Tools) page on this website.
Miller’s Tooling Pty Ltd can also offer a “proper” sharpening service of all countersinks & counterbores. (A lot of resharpeners struggle with these tools – you may have already noticed).
General rule for speeds for countersinking & counterboring are half to two thirds that a drill would be recommended to run at, depending on material & rigidity of clamped job.
Chatter is quite common due to excessive speed or uneven feed rate applied.
HSS or brazed carbide “stepped drills” or “sub land drills” with a pilot and countersink or 90’ stepped counterbores lead can be off the shelf or specials made on request, ideally suited for drilling tapping size holes in one operation complete with countersunk hole – try us out.
COUNTERBORES 
The counterbores tool is a 90’ cutting tool, stepped with a pilot to leave a 90’ recessed flat bottomed bore for a cap head screw or bolt to seat in. Counterbore tools are a secondary drill after the pilot drill is produced in a job. A lot of machinist simply grind a step drill by hand or use a slotdrill; however the right tool for the right job, as this can be time consuming, inaccurate, chatter & constant resharpening required.
Many sizes are avail. here at Miller’s Tooling; ideally there is a counterbore tool to suit an individual size bolt. 
Sets from Germany are avail.
Including M3 – M10 x 90’ HSS counterbores in a metal case. (Alternatively Chinese sets up to M12 under $100.00).
We also offer counterbores with interchangeable pilot sizes – very popular with toolmakers.
Reverse & hand countersinks are on our “Deburring” page under ”Cutting Tools”, including all types of hand deburring, etc on this Miller’s Tooling Pty Ltd website.
BELOW IS THE DAINTREE CATALOGUE FOR COUNTERSINKS
Miller’s Tooling Pty Ltd can proudly offer such brands as:
“Walter – Titex” countersinks & cutting tools
“Walter – Prototyp” cutting tools
“Weldon” countersinks
“Daintree” countersinks & cutting tools
“Dormer” countersinks & cutting tools
“Sutton” countersinks & cutting tools
“Capital” countersinks & cutting tools
“Noga” countersinks & deburring tools
”Vargus & Shaviv” countersinks & deburring tools
