One of the frequently asked questions about Hard Part Turning we’re asked here at B&B Precision is about coolant. One of the selling points of Hard Part Turning is often that you won’t have to use any coolant, and yet considering the speed and heat being generated can this really be best practice?

Don’t Use Coolant because…

As the chip removes the vast majority of the heat away from the work piece, you simply won’t need coolant in most cases. This is great for both your back pocket and the environment. Speaking in general terms it would be best not to use coolant wherever you have an interrupted cut. When your insert enters and exists your work piece it gets exposed to fluctuating temperatures. First heating up as it cuts through the metal, and then obviously cooling from the use of the coolant. This can result in thermal shock, which is why we recommend not using coolant.

Coolant for Depth

If your work piece has a tight tolerance, then it may be necessary to use coolant. Tighter tolerances often need a smaller depth of cut, which means smaller chips and therefore not enough heat is being transferred away. Using coolant can extend the insert’s life and benefit the surface finish, but generally the advantage of using Hard Part Turning is that you can go without.

Kind of Coolant

If you do use a coolant, then it must either be water based or polymer style. This is because the extreme heat generated by the turning can easily reach 1500°F and a chip could actually ignite an oil-based coolant. Another safety notice in regards to extremely hot chips is that they can easily injure an operator. Be sure that the proper guards are in place before you start turning.


If you are going to use coolant then the challenge is in getting the coolant as close as possible to the work piece. This is because due to the speed and heat, coolant may actually vaporise before doing its job!

The team here at B&B Precision have had a lot of questions about Hard Part Turning and its benefits against Cylindrical Grinding. If you’d like to find out more about the results that HPT can achieve or are looking for a fast and efficient outsourcing company, then look no further. Email us at or call 01484 866386

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