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July 2023 — The VTA system in detail
"Applying downward pressure results in lateral clamping force."
Here is a translucent model of the arm mounting collar showing the internal clamping mechanism for the VTA. When you tighten the hex screw from above it puts force down on the clamp actuator that in turn applies pressure to the support pipe clamp.
A quick update this month — it's been a busy period across several projects, but there's enough progress on the tonearm to share.
The VTA clamping system is worth explaining properly, because it's one of those details that looks simple from the outside but required careful thought to get right. The arm mounting collar uses a hex screw accessed from above, which drives a clamp actuator that in turn applies lateral pressure to the support pipe. The support pipe clamp itself locates against the pipe with a smooth matching radius rather than a point contact, so there's no risk of damage and the clamping force is distributed evenly.
A small batch of clamp actuators and some support pipe clamps.
The adjustment screw is located just under the main body.
The advantages over a conventional sideways grub screw are real. Less torque is needed to lock it securely, the adjustment is accessible without reaching awkwardly around the arm, and the pipe surface stays unmarked no matter how many times the VTA is adjusted. All the clamp components are made from silver steel and heat treated for durability — except the grub screw itself, which is 14.9 grade hardened steel.
Most of the parts have been completed for the support pipe assemblies.
One detail we're particularly pleased with is the plan to engrave the support pipe with 0.5mm or 1.0mm graduations. It means VTA adjustments become measurable and repeatable — you can note a setting, try something different, and come back to it exactly. That kind of precision is usually the preserve of arms costing considerably more.
Work also continued on the support pipe assembly this month. The zirconium ball bearing at the heart of it was chosen over stainless steel for its superior hardness and durability, and the end of the bearing support has been hardened and lapped to a very fine flat finish. The sapphire housing and support screw are both nickel silver — chosen for its durability, corrosion resistance, and the fact that it machines beautifully.
Next month, work begins on the 4th axis upgrade — which has been waiting in the queue for longer than planned.
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