I read through a 1967 paper by Shure’s Chief Engineer James Kogen on the topic of tonearm skating. I was able to discover some interesting findings that the turntable/tonearm manufacturers didn’t get quite right in designing effective anti-skating mechanisms.
• Skating is the result of the friction generated between the stylus tip and the groove wall.
• The greater the friction, the greater the skating force.
• Skating is not the same as the centripetal force that is generated by the tonearm and the rotating record. (see Centripetal Force Graph)
• Using a blank record to set the anti-skating will result in a 5% error since this action is a demonstration of centripetal force and not skating.
• The skating force decreases as the tonearm travels toward the spindle. Skating is greatest at the lead-in groove and curves downward to its lowest about 15 mm before the lead-out groove. This is the opposite of centripetal force since that force increases as the tonearm gets closer to the spindle. (see Skating Graph)
• Most turntable mechanisms calibrate the anti-skating force to counteract the centripetal force of the tonearm: Increasing anti-skating as the arm travels toward the spindle. This includes mechanisms using springs and weights. So, for most tonearm designs, too little anti-skating is applied at the lead-in groove and too much force is applied toward the spindle.
Centripetal force increases as the tonearm moves toward the spindle. This is how anti-skate mechanisms also behave.
Skating forces behave the opposite of centripetal forces: The force decreases and reaches its minimum just before the lead-out groove where it ramps up as it moves toward the label.
Other variables that affect skating:
• Highly polished tips will decrease the amount of friction between the tip and groove wall thereby decreasing the skating force.
• Stylus Shapes*
Most Skating Elliptical (0.2 x 0.7mil): Narrow area of tracing
^ Elliptical (0.4 x 0.7mil): Wide area of tracing
^ HyperElliptical: Narrow tracing, spread over a large area
^ Micro Edge Type: Very narrow tracing, spread over a very large area
^ Shibata Type: Narrow tracing, spread over a very large area
Least Skating Spherical: Very wide area of tracing spread over a large area
*Most anti-skating settings are calibrated for elliptical shaped tips. Some have separate scales for spherical and elliptical
Anti-skating for cartridges with brushes:
I found a 1979 article asking the question on what would be the proper anti-skating setting for cartridges with stabilizer brushes (Stanton, Pickering, Shure).
For a 1 gram stylus tip tracking force (For Stanton and Pickering, the total VTF would be 2 grams; for Shure the VTF would be 1.5 grams), both Stanton and Shure recommends an anti-stake setting equal to the total VTF tonearm setting.
Note: The actual unit of measure for anti-staking is about 12% of the VTF. So a “1” setting of anti-skating is about 0.12 grams of force.
Stanton gave the following setting procedure:
Set the VTF such that only the brush rides the surface of the record but the stylus does not touch the record. When the record is turning, the tonearm should skate toward the spindle. Adjust the anti-skate dial such that the tone arm remains stationary. Now you can increase the tracking force to 1 gram and add an additional unit of measure to the anti-skate dial. What you are doing is setting the anti-skating for the brush first, then adding the tracking force and anti-skating for the stylus.
BUT, In 2016, Shure made a complete 180 on their recommendation:
Since skating is the result of the friction between the groove wall and stylus tracing edge, the anti-skating setting should be set to match the tracking force at the stylus tip (1 gram).
Most of the brush bristles only ride on the surface of the record and those few that manage to get into the groove wall are too soft to create any significant amount of skating.
Oh well, kinda makes sense, but so did the original recommendation.
Summary:
• The blank record test shows the centripetal force of the tonearm which does not reflect the actual skating force. Stylus shape has no effect on centripetal force but radius size does.
• The stylus must be tracking in a record groove to create skating. It is depended on stylus shape as well as radius size.
• Centripetal force increases as the tonearm moves toward the spindle.
• Skating force decreases as the tonearm moves toward the record label.
• Tonearm anti-skating mechanisms are designed to counteract the effects of centripetal force; increasing as the tonearm moves toward the spindle.
• It is not known how the mechanism is calibrated: Is it an average, minimum, maximum value? What stylus shape is it optimized for?
• Assuming the setting is the average force across the record; the initial setting will be lower than the optimum force and higher as the tonearm moves toward the spindle.
• Re-adjust (lower) anti-skating settings is necessary as tonearm bearings become worn and dirty.
• If “less is better than more”, use a line contact stylus and set the anti-skating amount ¾ to ½ of the VTF amount. Anti-skating will be insufficient at the beginning but will be a closer match as the tonearm approaches the middle of the record. This could be totally off base depending on the design of the tonearm mechanism.
I’m not a perfectionist and I’m not going to lose sleep over this. I suppose it’s the best tonearm designers can do. It’s like cartridge alignment: There are only two points on the record where the alignment is perfect and we just live with imperfection for the majority of the record. With anti-skating there is probably only one point were the forces are perfect; and that lasts for less than a second.
• Skating is the result of the friction generated between the stylus tip and the groove wall.
• The greater the friction, the greater the skating force.
• Skating is not the same as the centripetal force that is generated by the tonearm and the rotating record. (see Centripetal Force Graph)
• Using a blank record to set the anti-skating will result in a 5% error since this action is a demonstration of centripetal force and not skating.
• The skating force decreases as the tonearm travels toward the spindle. Skating is greatest at the lead-in groove and curves downward to its lowest about 15 mm before the lead-out groove. This is the opposite of centripetal force since that force increases as the tonearm gets closer to the spindle. (see Skating Graph)
• Most turntable mechanisms calibrate the anti-skating force to counteract the centripetal force of the tonearm: Increasing anti-skating as the arm travels toward the spindle. This includes mechanisms using springs and weights. So, for most tonearm designs, too little anti-skating is applied at the lead-in groove and too much force is applied toward the spindle.
Centripetal force increases as the tonearm moves toward the spindle. This is how anti-skate mechanisms also behave.
Skating forces behave the opposite of centripetal forces: The force decreases and reaches its minimum just before the lead-out groove where it ramps up as it moves toward the label.
Other variables that affect skating:
• Highly polished tips will decrease the amount of friction between the tip and groove wall thereby decreasing the skating force.
• Stylus Shapes*
Most Skating Elliptical (0.2 x 0.7mil): Narrow area of tracing
^ Elliptical (0.4 x 0.7mil): Wide area of tracing
^ HyperElliptical: Narrow tracing, spread over a large area
^ Micro Edge Type: Very narrow tracing, spread over a very large area
^ Shibata Type: Narrow tracing, spread over a very large area
Least Skating Spherical: Very wide area of tracing spread over a large area
*Most anti-skating settings are calibrated for elliptical shaped tips. Some have separate scales for spherical and elliptical
Anti-skating for cartridges with brushes:
I found a 1979 article asking the question on what would be the proper anti-skating setting for cartridges with stabilizer brushes (Stanton, Pickering, Shure).
For a 1 gram stylus tip tracking force (For Stanton and Pickering, the total VTF would be 2 grams; for Shure the VTF would be 1.5 grams), both Stanton and Shure recommends an anti-stake setting equal to the total VTF tonearm setting.
Note: The actual unit of measure for anti-staking is about 12% of the VTF. So a “1” setting of anti-skating is about 0.12 grams of force.
Stanton gave the following setting procedure:
Set the VTF such that only the brush rides the surface of the record but the stylus does not touch the record. When the record is turning, the tonearm should skate toward the spindle. Adjust the anti-skate dial such that the tone arm remains stationary. Now you can increase the tracking force to 1 gram and add an additional unit of measure to the anti-skate dial. What you are doing is setting the anti-skating for the brush first, then adding the tracking force and anti-skating for the stylus.
BUT, In 2016, Shure made a complete 180 on their recommendation:
Since skating is the result of the friction between the groove wall and stylus tracing edge, the anti-skating setting should be set to match the tracking force at the stylus tip (1 gram).
Most of the brush bristles only ride on the surface of the record and those few that manage to get into the groove wall are too soft to create any significant amount of skating.
Oh well, kinda makes sense, but so did the original recommendation.
Summary:
• The blank record test shows the centripetal force of the tonearm which does not reflect the actual skating force. Stylus shape has no effect on centripetal force but radius size does.
• The stylus must be tracking in a record groove to create skating. It is depended on stylus shape as well as radius size.
• Centripetal force increases as the tonearm moves toward the spindle.
• Skating force decreases as the tonearm moves toward the record label.
• Tonearm anti-skating mechanisms are designed to counteract the effects of centripetal force; increasing as the tonearm moves toward the spindle.
• It is not known how the mechanism is calibrated: Is it an average, minimum, maximum value? What stylus shape is it optimized for?
• Assuming the setting is the average force across the record; the initial setting will be lower than the optimum force and higher as the tonearm moves toward the spindle.
• Re-adjust (lower) anti-skating settings is necessary as tonearm bearings become worn and dirty.
• If “less is better than more”, use a line contact stylus and set the anti-skating amount ¾ to ½ of the VTF amount. Anti-skating will be insufficient at the beginning but will be a closer match as the tonearm approaches the middle of the record. This could be totally off base depending on the design of the tonearm mechanism.
I’m not a perfectionist and I’m not going to lose sleep over this. I suppose it’s the best tonearm designers can do. It’s like cartridge alignment: There are only two points on the record where the alignment is perfect and we just live with imperfection for the majority of the record. With anti-skating there is probably only one point were the forces are perfect; and that lasts for less than a second.
