# What do these symbols mean?



## RogerP (16 Feb 2016)

The ones in the yellow area. Particularly the 1.6 with the triangle?







This is part of a construction sheet. Measurements are metric.

Thanks.


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## NazNomad (16 Feb 2016)

Architecturally, I'd associate that triangle with a revision to the plan of some kind.


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## woodpig (16 Feb 2016)

NazNomad":169aerxs said:


> Architecturally, I'd associate that triangle with a revision to the plan of some kind.



Yes, I've seen reference to notes like that before. The upside down T is I think perpendicularity?


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## Jamesc (16 Feb 2016)

Hi,

The inverted tick with a triangle is a machining symbol. Basically it means this face must be machined. The 1.6 refers the the quality of the finish.

Have a look at http://www.roymech.co.uk/Useful_Tables/Surface_Texture/draw_surfin.html.

Regards

James


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## chipmunk (16 Feb 2016)

So is it the inside of hole that is to be machined to be that smooth? 

The size of the 3mm clearance hole needs to be no smaller than 3mm diameter but can be as large as 3.014mm but then the box at the right... 

Is that the tolerance on the perpendicularity of the hole?
...and I guess it's to a datum face "A" if this is correct...http://www.draftingzone.com/shoppingzone/6-1.pdf

Jon


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## RogerP (16 Feb 2016)

Thanks very much gents for the info and very useful links. Now I understand 

Rog


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## alphatec (17 Feb 2016)

Hi
It's been a while since I've seen these symbols but my understanding is it would be a 3.00 mm reamed hole using a flat bottom reamer to obtain depth.
A slow speed with cutting compound to give you the required finish, if you wish to ensure you finish above the 3.00mm but below the tolerance run the reamer at a slightly higher speed.


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## RobCee (18 Feb 2016)

The triangular element you asked about refers to the surface finish of the hole, the closed triangle indicates that it refers to a machined surface (i.e. the internal face of the hole) and the number shows the allowable roughness of the finish in micrometers.


Information about Surface Finish symbols.
Information about Geometric Dimensions and Tolerances (GD&T).


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## woodpig (18 Feb 2016)

Looking at the dates of some those specs many of them are relatively new, at least to me. Years ago it would just say ream 3mm + or - the tolerance.


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