Twinning

[johnoisamanc]

Hi.

Could someone please explain twinning to me please? Is it the same as the cutterhead lifting due too much stereo being cut against depth of cut.

Cheers.

[Steve E.]

Where have you heard the term? I'm unfamiliar with it.

[opcode66]

Quantum entanglement is sometimes referred to as twinning or the twin effect.

Twinning in the urban dictionary is defined as having sexual relations with twins.

Twinning in the world of crystals is when two separate crystals share the same geometry (have the same points).

Never heard this with relation to vinyl records. Maybe it is some term referring to the electroplating and/or pressing process????

[Techie]

Robert K Morrison uses the term in his book when describing visual patterns on a cut disc. Different patterns can indicate signs of trouble, for instance a moire pattern can indicate a low frequency rumble, etc.

Again, from memory (I'm at work) I believe twinning indicates a feedscrew that is not in perfect adjustment. He doesn't elaborate on what twinning looks like, but I imagine it would appear to be grooves that are grouped in pairs, if the head is not being drawn across the disc in a consistent manner due to having too much play between feedscrew and cutter carriage. Just my guess.

[Jccc]

Is this considered "twinning"?

When i changed the feedscrew to my 6n i noticed it started cutting wiered patterns on my lathes sometimes even messing up the whole acetate. And then found out i did not have the feedscrew completely dialed in.

[THD]

What is twinning?
- When two grooves overlap or touch as a result of overmodulation. Twinning is also caused by improper groove-to-land ratios or defective lead screw.

[tragwag]

oh I see!
We call that "overcut"

[emorritt]

Hmmmm... I guess two overcut grooves would be "conjoined twins"

[Techie]

I just found this on the web.

http://www.charm.rhul.ac.uk/history/p20_4_2.html

extracted from above:

4. Twinning is a result of the faulty operation of the traversing gear carrying the wax blank when being recorded upon by the cutting tool. The grooves, instead of being uniformly spaced about 0.01 in. apart, are in pairs slightly less than 0.01 in. apart, the pairs being separated by a correspondingly greater distance as shown in Figure 35. Presumably the friction on the guides is excessive, causing a portion of the carriage to hold back, thus flexing the structure. The energy stored up in this manner supplements the force operating at the point of retardation, and is periodically expended in overcoming the friction. The rate at which the table carrying the wax moves along under the cutting stylus is thus non-uniform. This variation of the speed of translation of the wax has, of course, nothing to do with its rate of rotation. The explanation given here is confirmed by the fact that in one case where the trouble was experienced acutely, it was overcome, after every expedient had been tried without success (including dismantling and rebuilding the recording machine), by the substitution of a lubricating oil having a different viscosity from that recommended by the makers of the machine. Several cases of twin grooving have been found among Worldecho records, one of which is shown in Figure 35. The defect is of little consequence in itself but may lead to a breakdown of the partition between two contiguous grooves for reasons which will be explained later.