【转帖】surface finish marks

yang686526

surface finish marks
i have a question with regards to surface finish callouts.
if you had a 24"x24" a36 burnout plate with 2 keyways anywhere on the finished side of the burnout, and the keys are parallel, held to +/-0.001 to eachother with a 0.500 +0.001 -0.000 key width x 0.25 deep. do you need to add a surface finish mark? i personally don't see the point to it, but my new manager does. any information to a link with standards would help.
thanks alot,
metl4mr
can you show a pic of the part. i'm not familiar with burnout plates w/keyways.
chris
systems analyst, i.s.
solidworks 06 4.1/pdmworks 06
autocad 06
  without knowing what your manager is thinking about, it's hard to say whether or not he has a valid point. if i understand what you are describing, my first answer is that a surface finish callout is not required if the key's only purpose is to be inserted into a slot. if the surfaces of the keys are exceedingly rough then inserting them into a slot may be difficult. the clearance between the key and the slot is what will make that difference. another thing to consider is if your manager just wants to ensure a good looking part, which is definitely a valid argument for a surface callout. i sure hope i understood the situation correctly.
regards,
powerhound
the plates edges are plasma cut (burned), there is a slot 0.25 deep that is machined into to ground face of the burnout (24"x24" area) that 1/2" keystock fits into. the surface in question is the sidewall of the slot which is held by 3plc dimension. by the way the plate is 1.50 inches thick. (how do i add pictures to a post?)
metl4mr,
   if your key width is .500+.001/0, then a finish in excess of 1000_microinches uses up your fabricator's error budget.
   my very rough guess is that your fabricator needs to achieve 125_microinches simply to meet your linear tolerance.  i would not specify a finish unless you want something better than that.  
                      jhg
i agree with drawoh.
my place almost always specifes a surface finish, it's one or our standard notes to be filled in.  by default we tend to use 125 unless it needs to be better for performance or aesthetic reasons.
also ... i believe the correct term is "surface roughness", finish is something else.
chris
systems analyst, i.s.
solidworks 06 4.1/pdmworks 06
autocad 06
ok, chris, you're starting to sound like an engineer.
oh noooooooooooooo....!
chris
systems analyst, i.s.
solidworks 06 4.1/pdmworks 06
autocad 06
this is our standard note:
surface roughness to be ____ rms per asme b46.1.
i think ctopher may have been correct....