SMD Replacement 301 Spindle

SMD Acoustics Garrard 301 Spindle

Made in the UK this spindle is dimensionally an exact copy of the original Garrard 301 spindle. It is manufactured from a high carbon, high chromium tool steel grade offering very high wear resistance and toughness. After the spindle is CNC machined it is vacuum hardened to HRC 55 - 60.

Once hardened the spindle is precision ground to the original diameter a nominal 0.4825"  +0 - 0.0001" (12.255mm +0 - 2.5 microns) that's an incredible tolerance to achieve (see below "Making Sense of Microns"). Finally the spindle is subject to ceramic polishing to give that polished look of the original.

The materials, the number of processes and accuracy required make this a relatively expensive item but it is at the heart of your 301 and a cheap spindle will give poor results and worse still may cause expensive damage to your 301.

If you are considering buying a replacement spindle from any supplier you need ask a few questions to make sure you get a quality product that won't wear out quickly, it won't be poor mechanically and consequently poor sonically and that it will not damage your existing bearing housing:-

• Are you sure it is made to the original sizes and tolerance and is it parallel?

• Is it made from a suitable steel that can be hardened and won't wear excessively, corrode or seize (beware of stainless steels) in the Oilite bushes?

• Is the spindle correctly hardened on the base of the spindle and on the diameter where it rides in the bushes?

• Is supplied with a smooth ground finish, not a turned finish that will be rough and may damage your bushes and be mechanically noisy?

Note: We have stripped down countless Garrards 301 and 401's and have measured the spindle diameters many, many times when evaluating the condition of a turntable. With the odd exception of a rogue spindle the process spread across Garrard originals in good condition suggests a nominal spindle diameter of 0.4825" (See photo Below) and this varies very little typically +/- 0.0002".

 

Making Sense of Microns

The tolerances Garrard worked to over 50 years ago are similar to the best required for present day aerospace and nuclear applications, that and the interesting facts below put into perspective how tiny the tolerances are we are talking about and how specialised the engineering is to achieve these tolerances.

Did you know?

A 100mm (4") steel gauge block increases in length by 11 microns (0.00043") as its temperature changes from 20 degrees C to 30 degrees C.

Particle of dust = 4 microns (0.00016")

Particle of cigarette smoke = 2.5 microns (0.0001")

Cross section of human hair = 75 microns (0.003")

Approximately the smallest object visible to the unaided human eye = 40 microns (0.0016")

Should I replace my spindle?

If your spindle looks like the one below then its time to replace it as performance will be suffering. Another area to check is around the diameter of the shaft where the shaft is in contact with the bushes, this is also worn on some spindles we see. Check with a calibrated micrometer and if the diameter is less than 0.4822" (12.248mm) we would suggest it might be worn although this may not be visible to the naked eye, see above on the smallest object visible.

How did my spindle get damaged?

Has the base of the bearing been "upgraded" ? If so maybe this has used an unsuitable thrust pad or bearing and possibly this has worn the base of the spindle.

Has the bearing has been re-bushed (Damage to the outside diameter)? If so the wrong tolerances may have been selected for the bushes (very difficult to achieve without honing).

Has the bearing has run dry of oil? This may cause wear.

50+ years of heavy use may well wear the spindle.

Key Features SMD Replacement 301 Spindle

• British Made
• Manufactured from the finest British tool steel (Don't buy mild steel spindles you can't harden the material sufficiently and they will have a very short life).
• Vacuum Hardened to HRC 55-60.
• Precision ground to 0.4825" diameter+/-0.0002"
• Ceramic Polished