1 Topic by Tomek (edited by Tomek 2014-07-06 22:54:53)

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Topic: what size are the three countersunk bed screws?

Ello everyone. I was lazy and stupidly used the ball end of an Allen wrench and stripped one of my z bed screws. I run a solidoodle 2.

I measured the screw to be about 40mm long and quite close to 3.82mm/0.150inches.

however 0.15inches is not a common diameter I know of. Could it be #7 size or something?  I also don't have the calipers on me but it seems roughly 32pitch/inch

does anyone know what kind of screws they use?

thanks!
-Tomek

2 Reply by grob

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Re: what size are the three countersunk bed screws?

Hi Tomek,
While I don't know what they are off the top of my head, with those numbers, I'd try either 8-32 UNC or M4x0.7 metric. Haven't measured myself, but I know there's already a mix of metric and imperial fasteners in these things.

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3 Reply by Tomek

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Re: what size are the three countersunk bed screws?

Thanks grub! 8-32 I think will be too big though, and 6-32 too small. I'll try them both tomorrow, though.  I have m4 so I can try those, but that's too big as well.

it's an odd size. I might just cut a slot and use a flat head screwdriver.

4 Reply by Serin

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Re: what size are the three countersunk bed screws?

I've got the bed screws in front of me along with a bunch of M4 nuts.
Fits perfectly.

This is a crowd funding thing that I'm running: http://www.gofundme.com/bvi140 It's for pretty selfish reasons tongue

5 Reply by Tomek

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Re: what size are the three countersunk bed screws?

Serin wrote:

I've got the bed screws in front of me along with a bunch of M4 nuts.
Fits perfectly.

hah. Ok. I should have tried those first!! 3.82mm though, I thought m4 would be m4. Maybe my calipers were offset but I thought I checked.

6 Reply by grob

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Re: what size are the three countersunk bed screws?

Usually they come out a little smaller in OD than the nominal, 3.82 sounds quite reasonable actually.

SD3. Mk2b + glass, heated enclosure, GT2 belts, direct drive y shaft, linear bearings, bowden-feed E3D v5 w/ 0.9° stepper
Smoothieboard via Octoprint on RPi

7 Reply by Tomek

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Re: what size are the three countersunk bed screws?

3.82 is what seems to me a substantial 5% off mark, and that was measured at the shank and not the threads. Still haven't had a chance to go home and try out the screws with my M4 nuts, but I think you're completely correct.

Realizing now (by googling) that an M3 is typically 2.9mm. I guess 3.82mm seems quite far off to me, but isn't crazy.

8 Reply by elmoret

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Re: what size are the three countersunk bed screws?

3.83mm is the minimum diameter allowable.

http://www.engineersedge.com/hardware/m … sizes1.htm

Smaller bolts means less material, means cheaper to manufacture.

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9 Reply by Tomek (edited by Tomek 2014-07-07 17:56:47)

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Re: what size are the three countersunk bed screws?

Elmoret /Tim delivers big_smile. I was looking for a chart just like that earlier. Thank you.

Figures solidoodle parts would be slightly below spec tongue. Or, perhaps, I simply was off and it was 3.83mm. In cases like this however I don't think there is any problem using a thinner screw, it obviously has minimal structural use.

10 Reply by Tomek

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Re: what size are the three countersunk bed screws?

For the record, as previously many times established, I am a fool.

When I got home to check that a 4mm nut fits, I realized that I had exactly 3 4mm nuts on the old z-tabs adjustment nuts that I had long ago added to the bottom of my printer.

...So obviously it was 4mm.
40mm for the record, if anyone else questions that.