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What considerations apply to material selection for cartridge mounting bolts?

I have found myself needing some longer bolts to relocate a Shure V15 Type 3 cartridge to a Holbo air-bearing system.

The Holbo tone-arm is a tangential tracker with a rigid rectangular 'launch pad' for the cartridge.  The pad is 3-mm thick which is much more than the fixed SME head-shell my dad bolted the Shure to some 45 years ago.  If it was supplied with longer bolts, they disappeared decades ago!

I will most likely have a similar issue with my Audio Technica VM540ML cartridge which is probably a better fit for the Holbo.  It was supplied with a head-shell 4-mm thick, but the bolts slots are recessed by over 2-mm.

A quick internet search turned up bolts made of stainless steel, titanium, aluminium, brass, plastic and nylon.  Some brass bolts are gold-plated (for corrosion resistance presumably).  As a one-time metallurgist, I know that stainless steels can be non-magnetic, or magnetic.

Plastic and nylon are lightweight insulators and immune to electro-magnetic effects like induced eddy currents.

The lower the material density, the lower effective mass of the cartridge.  Here brass is clearly the worst, being denser than steel and weaker than the other metals.

I presume that the main engineering requirement is to firmly couple the cartridge to the tone-arm but I have no idea how firmly.

The Funk Firm has an opposite view with its Houdini coupler which in effect splits the bolts in half, with an elastic suspension between the cartridge body and the tone-arm.  It seems to allow the cartridge body to swing easily to the left or right side.  Does anybody here use these?

richardbrand
richardbrand's avatar
richardbrand OP
1,374 posts
 

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.

elliottbnewcombjr
7,711 posts
 

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

richardbrand's avatar
richardbrand OP
1,374 posts
 

@elliottbnewcombjr 

Good advice, but I needed to cut mine longer!

All my boats have now arrived from China.  One had aluminium bolts with washers and nuts, another titanium bolts and the last one titanium nuts.

slaw's avatar
slaw
26,469 posts
 

For wood bodied carts such as ClearAudio, that have no mechanical receptor, plastic cartridge bolts may be considered.

lewm
14,658 posts
 

RB, Your quoted responses from ChatGPT suggest that it does not know what it does not know. Which is to say that it ought to understand the concept of effective mass, but it does not seem to.  I would say that the same reasoning applies to the calculation of the effective mass in the horizontal plane as it does to the effective mass in the vertical plane, which is related to the distribution of the mass, from the stylus tip to the joint between the arm wand and the track upon which it moves. Plus for horizontal EM, perhaps there should be a fudge factor for any friction in the air bearing, which of course is likely to be very low in magnitude. I welcome any objections to my non-answer. (There is on the internet a formula for vertical EM.  Distribution of the mass seems like a problem in integral calculus, to me.)

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