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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
faustuss's avatar
faustuss
791 posts
 

@audphile1 

"I really like the Riverstone Audio gauge. You should check it out."

I've seen good reports about it previously elsewhere I'm sure but if I was going spring for "digital" I'd probably go with the Rega Atlas and get it right the first time.

@lewm 

"In my several decades of experience with it, the SFG was imprecise and results were often not repeatable. Plus it could damage a cantilever if one were not careful. These days it makes no sense not to use a digital scale, just making sure that the one you choose has its weigh pan in the plane of the LP surface."

Well maybe you're rather fumble fingered and just don't have the touch but I've found the SFGII to be exactly how I described it upthread. If it ain't broke...

If any of you lived nearby and had the privilege of hearing my systems playback I seriously doubt, if you evaluated it honestly and unbiased that you could be critical of the sonics in any way! 

It should be obvious which coast I live on if you consider reaching out.

richardbrand's avatar
richardbrand OP
1,362 posts
 

@faustuss 

It should be obvious which coast I live on

Seems like we are both on the East Coast.

Just half a world apart ...

richardbrand's avatar
richardbrand OP
1,362 posts
 

@rsf507 

The masses of those bolts are very informative, even though they are way too short for my needs. 

The stainless-steel pair weighs as much as my cartridge!

My Holbo tonearm has an effective vertical mass of 7.5 grams, The Shure body is 6 grams and the screws are 6.3 grams.  Wow.  Nylon bolts are just 1 gram.

For completeness, with the Holbo's tangential arm, the stylus has to shift the entire tone arm assembly sideways.  Its mass is very small at 31.6 grams before you add the cartridge and bolts.

In this application at least, lightweight bolts probably do matter

tonyptony
634 posts
 

Soundsmith sells some

I have three packages of these. They’re great but they don’t work on unthreaded carts. 

lewm
14,649 posts
 

31.6 g plus weight of cartridge etc, would be the horizontal mass (maybe not "effective mass"; I don't know how to calculate that in the horizontal plane).

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