Surface Finish marks

[metL4mr]

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

 

[ctopher]

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
ctopher's home (updated 06-21-06)

 

[powerhound]

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

 

[metL4mr]

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?)

 

[drawoh]

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

 

[ctopher]

I agree with drawoh.
faq559-1100


Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 06-21-06)

 

[KENAT]

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.

 

[ctopher]

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
ctopher's home (updated 06-21-06)

 

[ewh]

OK, Chris, you're starting to sound like an engineer.

 

[ctopher]

oh noooooooooooooo....!


Chris
Systems Analyst, I.S.
SolidWorks 06 4.1/PDMWorks 06
AutoCAD 06
ctopher's home (updated 06-21-06)

 

[KENAT]

This is our standard note:

SURFACE ROUGHNESS TO BE ____ RMS PER ASME B46.1.

I think Ctopher may have been correct....