The Bool Audio Blog

April 2023 — Finally making parts 

With the enclosure complete, the next task was getting the coolant system properly sorted. We had originally planned to run neat cutting oil as a flood coolant, but after about a month of everything in the workshop coated in a fine oily mist — and bills of around £130 for 25 litres — we admitted defeat and switched to a water-based semi-synthetic, Qualichem Xtreme Cut 250C. An inline filter was added to the coolant pump output shortly after to stop metal particles being sprayed back into the cutting tool.

Next is some finishing touches to the enclosure.

With coolant sorted, one significant problem remained before the machine was truly production-ready. Changing tools on a manual drawbar means repeatedly tightening and loosening a bolt above the spindle by hand — slow, repetitive, and hard on the wrists. For a single part requiring fifteen or more tool changes, it simply wasn't viable. 

The solution was a pneumatic power drawbar — a compressed air system that releases and locks the tool at the press of a button. We designed and built the entire system in-house using a combination of the CNC machine and the manual lathe. The cylinder is a three-stage design, all parts machined from EN24T steel. Once it works, it changes everything about how the machine feels to use. 

We also adopted the TTS tool holder system, sourcing holders from Emvio Engineering in the UK. A 12-position tool rack was designed, laser cut, painted with epoxy, and fitted to the side of the machine — though 12 positions filled up faster than expected. With some parts requiring more than 15 tools, a second rack is already on the list.

By the end of April 2023, the machine was fully operational and we could finally turn our attention to what all of this had been building towards — the tonearm itself.