Dimensioning to bored hole that has a fillet at the bottom.

[tmech77]

When calling out the depth of a hole, or counterbore that has a flat bottom and a small fillet radius at the bottom of the hole, does the depth refer to the full diameter or to the very flat bottom of the hole? ASME Y14.5-2009 seems to picture it on page 17, Fig. 1-38, but it is not clear as to what the dimension leader line is going to.

 

[btrueblood]

Well, my assumption would always be to the flat bottom...but you know what ASSumptions create. Adding explanatory notes to the hole callout, or dimensioning a side view are better ideas if the hole depth is critical.

 

[KENAT]

What does the text say? I don't have -2009 version, and 1994 doesn't appear to have an equivalent illustration.

In the text in -1994 version, section 1.8.9, it's pretty explicit about the depth dimension of a blind hole being the depth of the full diameter form the outer surface of the part.

Of course, if the dept is unclear it also says to directly dimension it.

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[SnTMan]

I would dimension what I wanted to control

 

[drawoh]

tmech77,

The ASME Y14.5 standard assumes you are drilling the hole, and that there will a 118[°][ ]cone at the bottom. Since you are not doing this, the ASME standard does not help you.

Do a section view, and explicitly show the depth and radii.

This question belongs in forum1103.

JHG

 

[KENAT]

Drawoh, while 14.5 - at least 1994 version - shows holes with the 'cone' at the bottom, it doesn't explicitly say it's assuming this in the text that I see.

You could try and extrapolate, both from what it says about round holes and the analogy to what it says about counter drilled holes, and conclude that the dimension would apply to the full diameter portion.

However, as there's room for misunderstanding I'd look to directly dimension in a section as you say.

Do you have the -2009 standard drawoh? Do you see the figure the OP mentions showing small fillet rad at the bottom of a hole?

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[drawoh]

KENAT,

ASME Y14.5-2009 Figure 1-36 shows a set of holes with depths specified. All the blind ones show a cone. I don't any changes from Figure 1-34 in ASME Y14.5M-1994. This makes sense. If I specify a blind hole with a depth, it is a safe bet that the hole will be drilled.

Note how the drawings do not impose control over the bottom of the holes. The 118[°][ ]cone is shown because the drafter anticipated drilling. If the holes were cast in place, the bottoms could just as easily be round, or flat with a fillet, as noted above. The depth specification indicates full diameter from the top surface down to the specified depth.

JHG

 

[MadMango]

I have 2009, but the figure is too small to see clearly. I vote the dim is to the flat of a c'bore since you can specify the radii in a c'bore call out.

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[geesamand]

If you don't have a section view, how else would you call out the radius?

I would most certainly make a section view and show both the radius and depth on it. We have these powerful CAD tools that make view creation easy - save everyone the time of researching an obscure interpretation of a standard and show what you want.

 

[mfgenggear]

if it's a flat bottom hole is require ~ It is easier to manufacture & inspect with the dimension from the flat bottom.
make sure the radii is tolerance to allow for clearance.

Mfgenggear

 

[Cockroach]

Yes, depth is mesh red from full shoulder of the drill to the bottom of the hole. The reason is that when machinist redress their drills, the angle of the cone is subject to variation, but not the diameter. So we're the cone disappears into that diameter, or shoulder is the proper point from which depths are measured.

Regards,
Cockroach