What considerations apply to material selection for cartridge mounting bolts?

RB, off the top of my head I am not sure you’re correct regarding horizontal effective mass for an LT tonearm, because there is still a distribution of mass between stylus tip and the air bearing such that mass near the tip is more readily moved than mass at the bearing. I think it would still depend upon the distribution.As you said most of the mass is at the distal end. I have not looked it up on ChatGPT or even the internet in general. Just guessing.

@lewm  outer tube

On the Holbo, as opposed to servo-driven tangential arms, the entire arm assembly including the air bearing outer tube acts as a single rigid mass.  The bearing outer tube is about 70-mm long, while the business end of the tone arm is just a tad over twice that, forming a rigid T.

The cartridge end really only has two degrees of freedom, because of the T-shape and 10-micron tolerances.  It can only pivot precisely vertically, and it can only slide precisely horizontally, on an essentially friction-free air-layer.

When the stylus moves sideways, it has to act on the entire mass, no matter how distal or proximal each bit is.  There is no need to even introduce the artificial concept of effective mass.

One consequence of the design is that there is virtually no fore-and-aft movement at the cartridge so nasties in the groove like scratches and dust don't set off sympathetic rattles.  The cartridge cannot rotate in any plane except vertical, which it has to do to ride warps.

No matter how closely I look, I cannot see any jerkiness or stiction whatsoever in the sliding motion. Quite brilliant design, in my opinion

@lewm 

I never thought of asking ChatGPT but since you mentioned it ...

I started with "what is the effective mass of a holbo tangential tone arm" and got the textbook answer for vertical effective mass.

Then I tried "what is the effective horizontal mass of a holbo tangential tone arm" and got a better answer, though a bit waffly:

Holbo tangential tonearm has a very high effective horizontal mass, which is characteristic of air-bearing linear trackers, as the entire moving carriage assembly contributes to the inertia in the horizontal plane. 

While the exact effective horizontal mass is not a single published specification number, it is generally considered to be: 

• Significantly higher than its effective vertical mass of 7.5 g.
• Closer to the total tonearm mass of 31.6 g (which is the mass of the moving part, including the arm wand, counterweight, and carriage).
• In some similar air-bearing designs, the effective horizontal mass can range from 40 g to over 100 g or even more, as additional weights are sometimes added to achieve a specific low-frequency resonance point. 

Then I put my original question in again, and got a refinement as ChatGPT added the horizontal component.  It learns:

The effective vertical mass of the Holbo tangential tonearm is 7.5 grams. This places it in the low-mass category, generally suiting it for high-compliance cartridges. 

In tangential (linear tracking) tonearms, the effective mass is typically specified differently for the vertical and horizontal planes. 

• Effective vertical mass: 7.5g
• Total tonearm mass: 31.6g 

The effective horizontal mass of linear tracking arms is generally much higher because the entire arm assembly moves horizontally, which can be in the range of 40-100g for some models. However, the Holbo design has a very small effective mass for the sideways (horizontal) movement, which is cited as 31.6g before adding the cartridge and mounting hardware. 

For optimal performance, this low effective vertical mass is best paired with cartridges that have high compliance to achieve the ideal resonant frequency range of 8-12 Hz. However, the manufacturer claims it works well with a range of cartridges, including some lower-compliance moving coil options. 

My titanium bolts arrived eight days after I ordered them, and two months earlier than expected.  The slow boat from China must have been a hovercraft, at least. 

Because the pack did not include nuts, I have to wait for the next boat, bearing aluminium bolts and nuts, before I can try either.

Cut long bolts shorter

put a pair of nuts on first, use the top of one as a guide to cut the bolt

when you back off the 1st nut, force it using pliers, whatever, it will straighten the threads for you, 

file anything loose

now the threads are straight and the other nut is undamaged