Hole dialog discussion

[uwestoehr]

There is a discussion on what the Hole dialog should allow as cut type in Github: https://github.com/FreeCAD/FreeCAD/pull/3990
I would like to bring to the forum.

Hole dialog as it is does this for the cut type:

- if there is no profile: you can change all hole cut parameters as you want
- if you use a UTS profile:
* you can change the diameter and depth for counterbore
* you can change the diameter and angle for countersink, but not its depth
- if you use an ISO profile:
* you can change the depth for counterbore and cheesehead, but not its diameter
* you can change the diameter for countersink, but not its depth and angle

We meanwhile agreed that for all profiles, also the depth should be changeable.

So there are the following things to debate:

1. should the hole dialog allow to change the countersink angle for ISO profiles?
Pro: same flexibility as with the UTS profiles
Contra: the ISO norms only use 90° angles. If you use another angle, it is no longer an ISO-normed hole and for these cases we already have the hole profile "None". (my opinion)

2. should the hole dialog allow tho change the counterbore and cheesehead diameter for ISO profiles?
Pro: same flexibility as with the UTS profiles
Contra: if the the ISO norms don't define different diameters for countersinks and cheeseheads, different diameters would make the holes not norm-conform. (my opinion) Norm-conformity is an issue for professional application. (my experience)

What y´do you mean? what do the ISO norms define? (I cannot access them because they are behind paywalls.)

[rynn]

I think the cut-types in Hole-Feature should offer:

· None
· Counterbore: fully customizabel by user (diameter and depth), so he can create whatever counterbore he needs.
· Countersink: fully customizabel by user (diameter and angle), so he can create whatever countersink he needs.

These three generic cut-types should work with all thread-types and with no thread.

Then there should be settings for specific screwtypes, that create countersinks and -bores for standard screws. I would not hardcode these but read them from json-files (see https://forum.freecadweb.org/viewtopic. ... 3&p=442239).

I don’t think the “Cheesehead”, “Countersink socket screw” and “Cap Screw” types for ISO threads that are hardcoded into the hole feature and set the diameter and depth to some multiples of the hole-diameter are usefull at all. Personally, I would like to remove them, but are afraid this would cause backwards-compatibility problems.

BTW: The fasteners Workbench has a nice set of different Screwtypes to look at. The ones in the screenshot are all ISO Metric M6.

Screenshot_20201024_172115.png (59.01 KiB) Viewed 1162 times

Of course you can add washers to them, changing depth and diameter of the countersink.

[JulianStirling]

I totally agree with @rynn that the counterbore and countersink should be fully customisable.

Standardised defaults exist for a reason, and the work Rynn is doing to define them in JSON files based of ISO standards is perfect. This way people like me that are not familiar enough with the inner workings of FreeCAD can add to the screw definitions both locally or as pull requests to change the standard definitions. As I said in the other page, I think we need to add other information like Nominal diameter, loose/normal/tight clearance diameters into the JSON file. This way we can add holes for new threads that do not exist yet.

I would not freeze any options in the dialogue. If you select an ISO and then modify the angle then the profile should probably change to have "(modified)" or "(non-standard)" appended on the end. Otherwise it will get annoying.

I am also unsure why depth, diameter, and angle are discussed by @uwestoehr for a countersink? If you define two you have the 3rd.

As for the backwards compatibility of the old, hard coded, weirdly defined profiles. Can we leave them but under the name "Cheesehead (legacy)" and throw a depreciation warning that they will be removed in the future?

[uwestoehr]

BTW: The fasteners Workbench has a nice set of different Screwtypes to look at. The ones in the screenshot are all ISO Metric M6.

Nice catch You convinced me that also the diameter must be changeable.

So the only point is the countersink angle. Should this be changeable or be fixed to 90° for an ISO profile as it is currently?

I am also unsure why depth, diameter, and angle are discussed by @uwestoehr for a countersink? If you define two you have the 3rd.

I know,but in practice one wants to save time. Foe example when I need a slightly deeper sink It is quicker to change only the depth and the diameter is changed automatically as the angle is kept constant. Currently one must change the diameter and therefore need to perform a calculation in advance to know what larger diameter leads to the desired depth.

As for the backwards compatibility of the old, hard coded, weirdly defined profiles. Can we leave them but under the name "Cheesehead (legacy)" and throw a depreciation warning that they will be removed in the future?

Good idea.

[chrisb]

I think it's a good idea that any norm hole allows in some way to change the parameters but it should then no longer be called ISO or UTS.
There are two ways to achieve this:

1) Having selected a norm would make some fields non editable. Changing from ISO or UTS (or any other norm to come) to "No profile" doesn't change any other value. That would allow a user e.g. to select ISO M6 which presets all values according to ISO and then you change to "No profile" and you can change just the angle of the countersink.
I prefer this option, which requires one additional GUI interaction)

2) All fields are changeable. Changing one of the values would change the type automatically to "no profile".
(I'm no friend of such tricks which could get through unattanded or even unwanted.)

[JulianStirling]

Foe example when I need a slightly deeper sink It is quicker to change only the depth and the diameter is changed automatically as the angle is kept constant.

Got you. I suppose it is making it clear in the dialogue that angle is fixed and then depth and diameter you set one and the other is auto adjusted. One way would be to toggle between "define by" options that are "Angle and depth" or "Angle and diameter" or even "diameter and depth". The last one doesn't seem to useful to me, but my experience is that there is always a use case you haven't considered.

How would you define depth for a counter sink? D1 or D2?

contersink.png (22.3 KiB) Viewed 1056 times

[uwestoehr]

Got you. I suppose it is making it clear in the dialogue that angle is fixed and then depth and diameter you set one and the other is auto adjusted.
...
How would you define depth for a counter sink? D1 or D2?

When the user changes the depth the angle will will be used that is currently set. It is neither D1 or D2 in your drawing because the norm defines it so that the screw head is even with the part surface. So in case you say depth = 1 mm, it means you get a 1 mm deeper cut. As result the distance between the part surface and your screw head is then 1 mm instead of zero.

[rynn]

Some words to threads:

ISO threads are defined in ISO 1502 and DIN 13. p.e.

DIN 13-1 ISO general purpose metric screw threads - Part 1: Nominal sizes for coarse pitch threads; nominal diameter from 1 mm to 68 mm

Metric coarse threads are divided into 3 series/rows. One should use a thread from series 1 if possible.
PartDesign Hole feature has hardcoded series 1 threads¹ (except of M1 and M1.2 which are missing and M3.5, M22, M27 and M68 which are in series 2).

This thread-definitions are totally independend of screw-definitions. You could craft your own ISO metric screws with weird head dimensions if you like. So I think that generic counterbores and countersinks should be freely definable on ISO thread holes, because the thread-profile has nothing to do with screws.

There are a lot of screwtypes defined in DIN/EN/ISO using this threads and there is even a DIN for counterbores²
__________
¹ Erster Google-Treffer: https://www.bornemann-gewindetechnik.de ... nmasse.pdf
² DIN 974-1 Diameters of counterbores - Manufacturing dimensions - Part 1: Hexagon socket head cap screws and screws with cheese head or pan head
DIN 974-2 Diameters of counterbores for hexagon bolts, screws and nuts; manufacturing dimensions

[uwestoehr]

We already agreed on diameter and depth. The only open question is of there is another angle than 90° for countersinks in ISO norms or not. With this info, we have all info.
Unfortunately I cannot get the ISO norms directly, only excerpts at some webpages.

[UR_]

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