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Dimensioning Hole Depth

Question asked by Wing Hoe Tan on Feb 25, 2018
Latest reply on Feb 26, 2018 by Wing Hoe Tan

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Hi all, a general question to all engineers out there regarding dimensioning of hole depth in drawings. In hole wizard, the hole depth is defined as the distance from the surface to the cylindrical edge (5 mm in the example) below. If you measure from the tapered point, the depth is slightly more at 5.75 mm.

In the hole callout, do you specify 5 mm or 5.75 mm? Is there a universal convention for this? How do machinists interpret the callout?
Is it customary to provide a detailed cross-section to prevent confusion?

Tony Tieuli Feb 26, 2018 6:59 AM

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Wing Hoe Tan wrote:

Hi all, a general question to all engineers out there regarding dimensioning of hole depth in drawings. In hole wizard, the hole depth is defined as the distance from the surface to the cylindrical edge (5 mm in the example) below. If you measure from the tapered point, the depth is slightly more at 5.75 mm.
In the hole callout, do you specify 5 mm or 5.75 mm? Is there a universal convention for this? How do machinists interpret the callout?
Is it customary to provide a detailed cross-section to prevent confusion?

As a rule I would dimension that drilled hole depth to 5mm.

As a machinist I would interpret the depth of the drilled hole to 5mm unless I saw the words "To drill tip" in which case I would interpret the depth to be 5.75mm..If the depth was dimensioned to the drill tip I would also expect the angle of the drill tip to be specified.

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Solid Air Feb 25, 2018 11:44 PM

Where I work, dimension goes to bottom of hole not drill point

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Kevin Pymm Feb 26, 2018 3:21 AM

Generally the dimension goes to the bottom of the full diameter of the hole, not the point as Solid Air says. In some cases it might be important to dimension the end of the point to prevent break through of a part but I would still dimension the depth of the hole & maybe specify the angle of the drill point.

In this link you will find very few, if any, examples that dimension to the point.

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Tony Tieuli Feb 26, 2018 6:59 AM

Wing Hoe Tan wrote:

Hi all, a general question to all engineers out there regarding dimensioning of hole depth in drawings. In hole wizard, the hole depth is defined as the distance from the surface to the cylindrical edge (5 mm in the example) below. If you measure from the tapered point, the depth is slightly more at 5.75 mm.
In the hole callout, do you specify 5 mm or 5.75 mm? Is there a universal convention for this? How do machinists interpret the callout?
Is it customary to provide a detailed cross-section to prevent confusion?

As a rule I would dimension that drilled hole depth to 5mm.

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Husein Delic Feb 26, 2018 7:14 AM

1. You should always set the drill depth to the full diameter end not the end point like in your case 5.75mm (only special case where the drill angle needs to be different or it close to a wall to add a note). So 5mm is the right one.

2. On such simple hole callouts I never set a section drawing. A callout like on second image is enough for machinist to get it right done. But on some advanced hole cutouts I would suggest to add section and show important dimension to get away from any confusions that could come up!

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Wing Hoe Tan Feb 26, 2018 7:51 AM

Hi all, thank you for the feedback. In the course of my design work, I am often faced with drill hole depths that are close to the panel thickness. I always have a fear of machinists interpreting the depths wrongly and drilling all the way through. For these cases, it looks like it will be better to provide a dimensioned cross-section. For typical cases, I will dimension to the cylindrical depth. Thanks again.

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Solid Air Feb 25, 2018 11:44 PM
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Where I work, dimension goes to bottom of hole not drill point
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Kevin Pymm Feb 26, 2018 3:21 AM
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Generally the dimension goes to the bottom of the full diameter of the hole, not the point as Solid Air says. In some cases it might be important to dimension the end of the point to prevent break through of a part but I would still dimension the depth of the hole & maybe specify the angle of the drill point.

In this link you will find very few, if any, examples that dimension to the point.
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Tony Tieuli Feb 26, 2018 6:59 AM
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Wing Hoe Tan wrote:

Hi all, a general question to all engineers out there regarding dimensioning of hole depth in drawings. In hole wizard, the hole depth is defined as the distance from the surface to the cylindrical edge (5 mm in the example) below. If you measure from the tapered point, the depth is slightly more at 5.75 mm.
In the hole callout, do you specify 5 mm or 5.75 mm? Is there a universal convention for this? How do machinists interpret the callout?
Is it customary to provide a detailed cross-section to prevent confusion?
As a rule I would dimension that drilled hole depth to 5mm.
As a machinist I would interpret the depth of the drilled hole to 5mm unless I saw the words "To drill tip" in which case I would interpret the depth to be 5.75mm..If the depth was dimensioned to the drill tip I would also expect the angle of the drill tip to be specified.
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Husein Delic Feb 26, 2018 7:14 AM
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1. You should always set the drill depth to the full diameter end not the end point like in your case 5.75mm (only special case where the drill angle needs to be different or it close to a wall to add a note). So 5mm is the right one.
2. On such simple hole callouts I never set a section drawing. A callout like on second image is enough for machinist to get it right done. But on some advanced hole cutouts I would suggest to add section and show important dimension to get away from any confusions that could come up!
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Wing Hoe Tan Feb 26, 2018 7:51 AM
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Hi all, thank you for the feedback. In the course of my design work, I am often faced with drill hole depths that are close to the panel thickness. I always have a fear of machinists interpreting the depths wrongly and drilling all the way through. For these cases, it looks like it will be better to provide a dimensioned cross-section. For typical cases, I will dimension to the cylindrical depth. Thanks again.
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Dimensioning Hole Depth

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