With so many new people getting into lathe cutting, we wanted to create a quick, concise guide to three essential parts of lathe calibration, no matter what lathe you are using. We won't go into too much detail, various topics are covered in our other blog posts, but for those starting out, here are the three key steps that you must complete to properly calibrate your setup for cutting.
1: LATHE CALIBRATION
Groove Depth
When cutting plastic, a good starting point for an unmodulated (silent) groove is a groove width of around 50 microns (0.05mm), though anywhere between 50 and 70 microns works well. Getting your groove depth right is essential, it directly affects fidelity, stylus longevity, and overall playback quality. Always make sure you're measuring your groove depth; if you're not sure how, we've put together two blog posts to walk you through it here and here.
Rake Angle
Your stylus must be cutting into the material at the right angle to get a clean groove. We recommend 8 degrees back angle, but realistically anywhere between 6 and 10 degrees is completely fine. If you do not know how to measure your rake angle, see here
Stylus Travel To Centre
Your stylus must cut toward the exact centre of the spindle so your grooves end up perfectly centred on the record. You can check this by using a blank disc and drawing or scoring a centreline with a knife and metal ruler, or you can use the alignment tool we make specifically for this task here.
Vacuum System
Ensure your vacuum system is working properly. If there isn't much suction, you've got a blockage or leak that needs sorting. Using a tiny amount of talc powder occasionally can help eliminate static buildup within the tube. Check the vacuum system regularly and make sure the vacuum tube is positioned correctly, a few millimetres from the stylus and blank is a good starting point.
2: PLAYBACK CALIBRATION
The only volume that matters is what's going onto the disc, measured from your VU meter. First, calibrate your playback to 0 VU using a professional test record (we use the Ortofon Test Record). When cutting, monitor your levels from this meter, 0 VU is a good starting point for cutting level, and you can push louder as you gain experience. If your meter only goes to 0dB, remove those markings and treat the end of your yellow LEDs as 0 VU, giving yourself headroom for louder cuts.
3: CUTTING CALIBRATION
It's advisable to get your cutting chain calibrated so the full system works cohesively and as expected. We use a custom cutterhead EQ (for those wanting to learn how to do this, see here), and due to the large high end boost, often 25dB in the high frequencies, headroom needs accounting for.
In our setup, we normalise all audio to -27 LUFS before it hits the EQ. This gives plenty of headroom and means all audio cuts at roughly the same volume. If you're cutting an album, we normalise the first song, then adjust all others by the same dB amount to ensure the audio plays as intended from song to song. Your cutterhead EQ must not clip internally.
These three steps are essential to work through thoroughly when starting out, and doing so will save you a lot of headaches down the line. For those who haven't seen it, see here for 'A Beginners Guide To Lathe Cutting'.