How much difference if the tonearm is mounted 5mm

Raul, read the opening post.  A tone arm was bought.  Should he drill the mounting hole at the given dimensions per the manual?  You say yes.   Why?  Because the manual says so?  Sorry but mistakes often get made on drawings.  I'm a Aerospace engineer and I have correct hundreds.  Who said that the arm in question actually measured what the manual says they all are expected to measure?  To drill a hole in your arm board because some stranger says that is where most of the arms he has manufactured should be located is just plain wrong!  That arm should be measured. S2P determined.  Then drilled.  It is not rocket science. It is just plain common sense.  We are not talking text book geometry here.  We are talking about one particular tone arm. 
Regards,

ds, Have you really observed such errors?  I am putting myself in your shoes.  In my thought experiment, I have a new tonearm, and the manual says to mount it so as to achieve a pivot to spindle distance of 215mm (for example).  What measurement would I make of my sample of said tonearm in order to know that following this instruction would be a mistake?  I guess that could be distance from pivot to center of headshell slots, for one example.  But manufacturers don't often even supply that spec.  So how did you know that you had a "bad" sample of any particular tonearm?  I respect that your training and life experience may have equipped you to detect and solve such problems better than I.  In my imagination, badly made samples would be more likely to have out of spec bearing friction, much more likely than to be significantly (could define as +/-0.5mm???) longer or shorter than specification.  As I noted above, there is also the case where thorough analysis of the geometry might lead one to prefer a different P2S for a given tonearm from that which is recommended, but that still assumes all of the samples of that tonearm are alike.

Hi Lewm,
I am confused. On my Feickert protractor, there are 3 different geometries for alignment, S, B, and L. Could i use it to align with Stevenson or the tractor is only acurate for only the Baerwald?
Thanks,
Calvin

Dear Dangcao: Sure that Lewm ( Hola! ) will give you a precise answer about your protractor.

In the mindtime you have to know that the Stevenson geometry alignment is the worst one of the 3 you mentioned because is the one that gives you the higher distortions/errors all over the LP recorded area but the last few indide mm. and I'm sure that other 

You can read it and see it through the link I posted and gave to you. I hope this time you really read it, is very important to understand the why's on this critical alignment issue.

http://www.vinylengine.com/tonearm_alignment_calculator_pro.php?arm1=Arm+1&l1=ps&a1lv=207&am... 


Regards and enjoy the music,
R.

Lewm,

  If you are given a spindle to pivot distance mount point of 215mm, then there must be a arm length that was used by the person who approved that 215mm position.  Measure your arm and verify that it measures what is assumed to be its length.  If it doesn't measure that length, and I have one that didn't, then that mounting hole you are about to drill (using that 215mm dimension), is going to be in the wrong place.
  My JVC UA 7045 tone arm is the arm that has convinced me to do the critical check and not just 'blindly trust' those printed templets.  
  On the templet for the JVC 7045, the spindle to pivot dimension is 130mm.  The templet shows that the head shell arm lift (which btw, attaches to the cartridge), would then be in the center of the slots.  I drilled my dummy plywood armboard as stated.  130 mm from center of spindle to pivot point.  The cartridge when mounted in the Technics head shell, when set-up using the Mint Tracker curve device sat in the most forward locating of the slots.  This is and of itself would not be a problem if I only used one cartridge and had only this one head shell.  But I own 80+ cartridges.  All mounted on various head shells.  What I discovered is that this particular Technics head shell has its slots are not only longer, but are also positioned 50mm farther to the rear than any other head shell I own.  Its most forward cartridge location position is to the back side of some of my other head shells and beyond the slots on most others.  I even have other Technics head shells who's slots do not even come close to this original head shell that came with this tone arm.  
  Now ask your self.  What is it that you want to do?  If you are using a curve checking device to set up cartridges with, then is that not what your goal is?  To set the cartridge so that it traces that curve.  
  I wanted to know why no other head shell will work with this arm except the one provided by Technics if that is, I drilled my arm board where I am being told to drill my arm board via their templet.
  What I discovered is that my arm does not measure in length what it states it to be on that templet.  It is slightly long.  How long?  By close to 5mm.  I thought about removing the head shell collar and machining the end of the arm tube to shorten it by this 5mm.  (The company I worked for has a rather large machine shop so I could have pulled in a favor and had this done for free).  But why take that route. Why chop up the arm when it was obviously the numbers on that templet were not representative of what my arm measured.  Why not just take the arms current measurements and reconfigure that spindle to pivot distance so the the hole I drilled actually is where is should be in reference to my actual arm length.  Not where I am being told to drill it.  My arm hole currently measures 135mm from spindle to pivot.  5mm more from the spindle that stated on the templet.  All my head shells, now are usable.  Even that original Technics allows the cartridgde to be mounted closer to what is depicted on the templet.   When I state ''are usable'', I am referring to setting them up correctly with the use of the Mint Tracker.  If the stylus tip deviates from that curve line anywhere on that line, whether it be near the spindle or near the records edge, then it is not set up correctly.
I have a picture taken of the original Technics head shell sitting along side a Sumiko head shell.  Give me an email address and I will gladly send it to you so that you can see for your self.  Once you see it, then picture in your mind if a cartridge was mounted in the center of the slots on the Technics, where would it be in the Sumiko which is sitting right along the side of it.  
   Now put yourself in my place at the time I was trying to figure out where in the hell to drill this hole.  At that moment in time, where did the actual error lay?  Was it the arm length?  It might be correct pertaining to the drawings being used to actually manufacture the arm.  Then Is it the drilling templet that is wrong?  Would you have just blindly gone ahead and drilled that S2P distance hole as stated by the experts who included this templet with the arm?  Well there is an error here somewhere and it certainly wasn't going to be the hole that ''I'' drilled!
Any other questions?  Just ask.  
BTW:  You have resurfaced memories of this experience that I had sincerely tried to forget!  (gran)
Regards,