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Counter-sinking screw holes

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Counter-sinking screw holes

OpenSCAD mailing list-2
My initial 3D printing focus is on small boxes for my practical electronics stuff. Most are simply rectangular enclosures with lids. The latter could be sliding, hinged, buckle-latched, snap-fitted, etc. But by far the majority will be simply screwed or bolted in two or four places. I’m currently only at the stage of just modifying the x,y and z dimensions of (mainly) thingiverse downloads. But all of those I’ve found so far have plain holes. I’d prefer to use countersunk screws or bolts.

What would be the easiest way to convert a flat hole to a countersunk one for an M3 screw please? Should I think in terms of using Difference() with a cone, the latter derived from a tapered cylinder? A small example to get me started would be much appreciated please!

Terry



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Re: Counter-sinking screw holes

nophead
See https://hydraraptor.blogspot.com/2020/12/sinkholes.html. It is quite complicated getting accurate countersinks due to the rounded staircase nature of printed slopes.

On Sat, 10 Apr 2021 at 14:02, Terrypin via Discuss <[hidden email]> wrote:
My initial 3D printing focus is on small boxes for my practical electronics stuff. Most are simply rectangular enclosures with lids. The latter could be sliding, hinged, buckle-latched, snap-fitted, etc. But by far the majority will be simply screwed or bolted in two or four places. I’m currently only at the stage of just modifying the x,y and z dimensions of (mainly) thingiverse downloads. But all of those I’ve found so far have plain holes. I’d prefer to use countersunk screws or bolts.

What would be the easiest way to convert a flat hole to a countersunk one for an M3 screw please? Should I think in terms of using Difference() with a cone, the latter derived from a tapered cylinder? A small example to get me started would be much appreciated please!

Terry



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Re: Counter-sinking screw holes

OpenSCAD mailing list-2
Have you considered just using brass inserts with bolts?
These also make it possible to unbolt and close the lids many times without stripping the threads of the hole.
It is also harder to over-torque an screw in a brass insert which is a problem with bolts or screws directly screwed into plastic.

https://www.youtube.com/watch?v=iR6OBlSzp7I is a very good video showing their use and comparing the strength (pull and torque) of inserts and direct plastic.

You may still want to counter-sink the bolts which takes you back to your original question unless you use bolts that do not have a conical shape at the top of the shaft or want to be able to use a wrench to tighten or loosen the bolts.

Not countersinking the bolt into the removable piece makes the piece stronger than lid where material has been removed from the lid for a countersink.



On 2021-04-10 9:08 a.m., nop head wrote:
See https://hydraraptor.blogspot.com/2020/12/sinkholes.html. It is quite complicated getting accurate countersinks due to the rounded staircase nature of printed slopes.

On Sat, 10 Apr 2021 at 14:02, Terrypin via Discuss <[hidden email]> wrote:
My initial 3D printing focus is on small boxes for my practical electronics stuff. Most are simply rectangular enclosures with lids. The latter could be sliding, hinged, buckle-latched, snap-fitted, etc. But by far the majority will be simply screwed or bolted in two or four places. I’m currently only at the stage of just modifying the x,y and z dimensions of (mainly) thingiverse downloads. But all of those I’ve found so far have plain holes. I’d prefer to use countersunk screws or bolts.

What would be the easiest way to convert a flat hole to a countersunk one for an M3 screw please? Should I think in terms of using Difference() with a cone, the latter derived from a tapered cylinder? A small example to get me started would be much appreciated please!

Terry



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Re: Counter-sinking screw holes

Roel Vanhout
In reply to this post by OpenSCAD mailing list-2
I use the BOLTS library, linked from the openscad.org website under 'libraries', for such things. Find the right screw type and size, scale it up a bit for some clearance, then use difference() to cut it out from the part.

Cheers

On Sat, Apr 10, 2021, 15:03 Terrypin via Discuss <[hidden email]> wrote:
My initial 3D printing focus is on small boxes for my practical electronics stuff. Most are simply rectangular enclosures with lids. The latter could be sliding, hinged, buckle-latched, snap-fitted, etc. But by far the majority will be simply screwed or bolted in two or four places. I’m currently only at the stage of just modifying the x,y and z dimensions of (mainly) thingiverse downloads. But all of those I’ve found so far have plain holes. I’d prefer to use countersunk screws or bolts.

What would be the easiest way to convert a flat hole to a countersunk one for an M3 screw please? Should I think in terms of using Difference() with a cone, the latter derived from a tapered cylinder? A small example to get me started would be much appreciated please!

Terry



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Re: Counter-sinking screw holes

caggius
In reply to this post by OpenSCAD mailing list-2
This is what I use - but there is probably a library some where that I don’t know about!

difference(){
    cube([10,10,10],true);
    translate([0,0,-5]) screwHole (2,10,4,2);
}

module screwHole(r1,h1,r2,h2){
       // r1 rad bottom of cone and the bolt hole
       // r2 rad top of cone
       // h1 full height of screw + cone
       // h2 height of cone
    
       // shaft first
      cylinder(r=r1,h=h1);
       // cone second
      translate([0,0,h1-h2]) cylinder(r1=r1, r2=r2, h=h2);
}

On 10 Apr 2021, at 14:02, Terrypin via Discuss <[hidden email]> wrote:

My initial 3D printing focus is on small boxes for my practical electronics stuff. Most are simply rectangular enclosures with lids. The latter could be sliding, hinged, buckle-latched, snap-fitted, etc. But by far the majority will be simply screwed or bolted in two or four places. I’m currently only at the stage of just modifying the x,y and z dimensions of (mainly) thingiverse downloads. But all of those I’ve found so far have plain holes. I’d prefer to use countersunk screws or bolts.

What would be the easiest way to convert a flat hole to a countersunk one for an M3 screw please? Should I think in terms of using Difference() with a cone, the latter derived from a tapered cylinder? A small example to get me started would be much appreciated please!

Terry



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Re: Counter-sinking screw holes

rew
In reply to this post by nophead
On Sat, Apr 10, 2021 at 02:08:04PM +0100, nop head wrote:
> See https://hydraraptor.blogspot.com/2020/12/sinkholes.html. It is quite
> complicated getting accurate countersinks due to the rounded staircase
> nature of printed slopes.

Just aim for the head to sink into the top surface for say 0.5mm. That
gives you plenty of margin, and if the head ends up 0.2 mm higher than
expected, it's still sunk below the surface.

If you really want the top surface of the screw to be precisely flat,
trial and error would be my way-to-go. Make one box with 4 holes,
like above, then measure how deep the screws end up. And adjust the
deepness of the holes accordingly.

Also note that the top surface of your box will be "rounded" to your
layer height. So if you first make a box of 15mm height, and then
decide to make one 1.5 times larger, 22.5mm, then the "3mm below the
top surface will be off-by-0.1mm for sure! Even after "finding the
right offset".

        Roger.


>
> On Sat, 10 Apr 2021 at 14:02, Terrypin via Discuss <
> [hidden email]> wrote:
>
> > My initial 3D printing focus is on small boxes for my practical
> > electronics stuff. Most are simply rectangular enclosures with lids. The
> > latter could be sliding, hinged, buckle-latched, snap-fitted, etc. But by
> > far the majority will be simply screwed or bolted in two or four places.
> > I’m currently only at the stage of just modifying the x,y and z dimensions
> > of (mainly) thingiverse downloads. But all of those I’ve found so far have
> > plain holes. I’d prefer to use countersunk screws or bolts.
> >
> > What would be the easiest way to convert a flat hole to a countersunk one
> > for an M3 screw please? Should I think in terms of using Difference() with
> > a cone, the latter derived from a tapered cylinder? A small example to get
> > me started would be much appreciated please!
> >
> > Terry
> >
> >
> > ------------------------------
> > Sent from the OpenSCAD mailing list archive <http://forum.openscad.org/>
> > at Nabble.com.
> > _______________________________________________
> > OpenSCAD mailing list
> > To unsubscribe send an email to [hidden email]
> >

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Re: Counter-sinking screw holes

OpenSCAD mailing list-2
In reply to this post by OpenSCAD mailing list-2
Many thanks for this great set of very helpful replies. Pursuing the many suggestions will keep me busy for a good while!

I’m determined to resist the temptation to reach for my Dremel :-)

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Re: Counter-sinking screw holes

mondo

Most small plastic cases I come across use small round headed pozidrive selftappers, holes are counterbored. some have countersunk screws to hold the pcb , but those holes are not countersunk (most likely to stop pcb moving sideways).

On 10/04/2021 16:50, Terrypin via Discuss wrote:
Many thanks for this great set of very helpful replies. Pursuing the many suggestions will keep me busy for a good while!

I’m determined to resist the temptation to reach for my Dremel :-)

Sent from the OpenSCAD mailing list archive at Nabble.com.

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Re: Counter-sinking screw holes

nophead
I have started using countersink screws where I want repeatable positioning. E.g. to mount an extruder.

On Sat, 10 Apr 2021 at 18:18, Ray West <[hidden email]> wrote:

Most small plastic cases I come across use small round headed pozidrive selftappers, holes are counterbored. some have countersunk screws to hold the pcb , but those holes are not countersunk (most likely to stop pcb moving sideways).

On 10/04/2021 16:50, Terrypin via Discuss wrote:
Many thanks for this great set of very helpful replies. Pursuing the many suggestions will keep me busy for a good while!

I’m determined to resist the temptation to reach for my Dremel :-)

Sent from the OpenSCAD mailing list archive at Nabble.com.

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