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?
18mm! Yes, that is a bit long but not unobtainium. I think some of the ones I bought in Tokyo are that length. I will take a look at my stash. If I have any, I will send them on to you. Otherwise, if we can both remember for that long a period of time, I am slated to visit Tokyo again in the early spring (northern hemisphere). I know exactly where to buy them in Akihabara. This eBay vendor has M2.5X16mm, if that length could possibly work.Here
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@richardbrand on mounting problems The SME 3009 improved and Shure V15 mk3 was right up my street in the 70s, along with the Garrard 401 and SME plinth system. The whole rig was quite the standard go to front end. I found the V15 mk2 was more forgiving with vinyl imperfections. SME offered as an upgrade at the time, nylon nuts and bolts to cut down mass just after the “improved” arm launch. I went down that road which was against the bolt everything up as tight as possible norm. I never noticed a difference to be honest. I tried recently to put my V15 mk3 back into service and had the same problem with needing longer bolts. The cartridge is not very strong laterally as metallic nuts and bolts can distort the shell as washers larger than the bolts don’t fit. There’s no spare diameter to ensure a more secure fix. The nuts can slip sideways (as not captive) out of the mount. The plastic is then compromised forever. l never thought the cartridge worked anywhere near spec using compatible after market styli. The Shure “trackability” was just not there. The new stylus would not track their test record at the highest modulations like before. Good luck with your quest to get this classic cartridge up and working again. My cartridge ended going back into stock. After l first retired the V15, l started using a Goldring G900IGC that runs to this day, having a spare NOS stylus in reserve.. |
And these people sell M2.5X20mm, a bit longer than you need for around 20 bucks US. Here |
I posted a big thank you a bit earlier, but Audiogon swallowed it! Your offer is extremely generous, and much appreciated, but I am in operation with two overlong and over-skinny bolts my local dealer gave me. When I went to the website page you first recommended, I discovered some hex socket bolts in 20-mm and 25-mm lengths, so I ordered 10 x 20-mm ones for just over AUD-20, delivered next year. Alas, not gold plated. Now I am wondering if the 20-mm includes the head or not. Emails will be going to China. By the way, Chinese exports to Australia jumped 35% last year, due to the t-word. Now if you happen to spot any DS Audio cartridges and equalisers in Akihabara ... ;-) |
For stuff like DS Audio, you have to speak very good Japanese and gain the respect of the sales people who typically speak zero English. My son can do that; I cannot. With his help I was able to score the Koetsu Urushi about 15 years ago, but the days I go shopping are days he has to go to work, so lately I shop alone. I cannot discuss T without risking a cardiac death. |
