How to add clamp note for datum slot.

[DIMGUY]

I am using a slot with rounded end as datum -B- , Dia 10 MM and my -C- datum is a target point on a trim edge. I would like to add a clamp note on the opposite side of part so -B- datum pin will not slide within slot. Basically i want the pin to stay nested in 10 MM rounded end of slot.
Do i just mark an "X" on the trim edge and note a clamp pressure? Thanks, Neal

 

[ctopher]

I would not indicate this on a drawing, it is a process. It should be on some type of job traveler.

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 08
ctopher's home (updated Aug 5, 2008)
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[DIMGUY]

Are you saying that if one degree of travel is open on a datum feature, it's a gage process / standard to automatically add a clamp to restrict said range of free motion?

 

[drawoh]

DIMGUY,

Is your part flexible?

Your datums must be sufficient to immobilize your part. The only reason to specify clamping would be if your part is flexible.

If your part is flexible, your clamping specification is valid. Read ASME Y14.5M-1994, Section[ ]6.8 on Free State Variation.

JHG

 

[KENAT]

DIMGUY, can you put a sketch as I'm having trouble seeing how this set up constrains all 6 degrees of freedom.

KENAT, probably the least qualified checker you'll ever meet...

 

[DIMGUY]

Let me try to explain this a little easier for you.

I'm working on a convertable top assembly.(lots of links and clevises) I have to attach the main pivot bracket, (5mm steel plate.) to the rear wheelhouse inner LT and RT. In each wheelhouse inner there is a weld pin fixture set for my main pivot bracket location. The bracket has a U/D F/A slot to load the assembly on the first plp, once the pin bottoms out in the slot, the convertable top stack is set on another U/D pin that contacts the trim edge of my main pivot bracket. They attach the top at the headder/windshield with pins and a latch system then go back and screw down the main pivot bracket on the left and right sides of the wheel house.

Now for the detail main pivot bracket fixture:

So, once i locate the detail pivot bracket on the pin for the slot, (-B- datum) - then rotate the part to the edge, (-c- datum) while resting on my -A- datums. the part would still be able to slide Aft out of the open slot. Not if i add a clamp to hold it while guaging.
What is the proper way to call out the trim edge i would like a F/A clamp to keep the part nested in the slot while gaging? Thank you in advance.

 

[KENAT]

So really the b datum is the end of your slot, effectively a single point of contact.

I'm wondering if you should just effectively switch B & C. Can your 'C' datum feature be used for 2 points?

KENAT, probably the least qualified checker you'll ever meet...

 

[DIMGUY]

That wouldnt' work.
The round ended slot is 10mm +0.1/-0.0, my pin is 10mm
The end of the slot is my secondary datum, datum -B-.
I'm just going to add a clamp to apply 5 lbs of pressure to hold my pin in the radius of the slot F/A and call it that. Thanks for your help.

 

[KENAT]

Yeah, I see now that what I suggest might not give you what you need.

What is the tolerance on your pin? An undersize (albeit only a little) pin in a hole/round slot, pushed to one extreme effectively has a near line contact. So assuming the hole/slot is perpendicular to A this effectively gives you only 1 DOF that you are constraining.

To make sure the pin hits the 'end' of the slot it is also implicitly centered on the width, correct?

Can the width of the slot be your B and the 'end' of your slot be your C?

KENAT, probably the least qualified checker you'll ever meet...

 

[ctopher]

It would be very helpful and less time consuming if you post a pic.

Chris
SolidWorks/PDMWorks 08 3.1
AutoCAD 08
ctopher's home (updated Aug 5, 2008)
ctopher's blog
SolidWorks Legion

 

[KENAT]

Any of these look promising?

KENAT, probably the least qualified checker you'll ever meet...

 

[drawoh]

DIMGUY,

Is your B[ ]datum the slot, or is it the radius at the end of the slot?

A slot datum allows movement along the slot. Your subsequent datums must restrict that movement. Actually, slots are a good tertiary datum.

An alternative is to call up the slot radius as your datum[ ]B. Now, your datum[ ]C prevents rotation around datum[ ]B.

Your fabricators and inspectors will have to clamp on the side opposite your slot. This is implied. There is no need to call this up. Detailed clamping specifications are only for flexible parts.

JHG

 

[JMarv]

Detailed clamping specifications are only for flexible parts

Wouldn't a convertible top assembly be considered a flexible part?

Joe
SW Office 2006 SP5.1
P4 3.0Ghz 1GB
ATI FireGL X1

 

[KENAT]

Jmarv, the assembly may be but I believe the OP is about dimensioninag a part of the assy. One of the fundamental rules of 14.5 para 1.4n is that dims & tols apply only at the drawing level they are specified.



KENAT, probably the least qualified checker you'll ever meet...

 

[JMarv]

Kenat,

I misunderstood the intent of the OP. Thanks for the clarification.

Joe
SW Office 2006 SP5.1
P4 3.0Ghz 1GB
ATI FireGL X1