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bradcfisher

3/4" rod end holders

by bradcfisher May 6, 2018
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Hi. Do you know it fits a 19,5 mm (3/4 " = 19,05 mm) rod? Is there enought clearance?

It should accommodate a rod that is a maximum of about 24mm diameter. The 3/4" designation is essentially the inside diameter of EMT, and the outside dimension is larger (0.922 inch +/- 0.005 or around 23.42mm). There may be some extra wiggle room with a 19.5mm rod, though you could scale it down a bit in your slicer to get a tighter fit.

Thank you. I never used the feature to scale a model. If I did the maths correct I have to scale it to 84% (= 19,67 mm)? How much clearance would you consider? 0,1 mm is enough?

The Maths:
23,42 mm = 100,00% | /100
00,2342 mm = 1,00% | (19,5 / 0,2342)
19,50 mm = 83,26 %

I would consider leaving at least 1 mm of clearance. In the original model, there is 24.5mm for the rod to fit in, so it seems I left about 1.08mm of clearance, which has worked well for my purposes.

How much to leave is really dependent on how tight a fit you want, and the tolerance that your printer can achieve. My printer tends to bleed over about 0.1mm or so over the tolerance of the model, so I would add at least 0.2mm to try for an exact (very tight) fit.

When computing your scaling factor, I'd use the dimensions which include the tolerance, so 24.5mm for the original instead of 23.42mm, and 20mm instead of 19.5mm. So, you'd get a scaling factor of 20mm / 24.5mm = 81.63%

One other thing to take into account when scaling the model is that all of the features of the model will scale proportionately. That includes the holes for the M3 bolts and the cutouts for the M3 nuts to nest into. Unfortunately, those will be too small after scaling to function as intended. The holes could be drilled out larger easily enough, but the nut cutouts would require a bit more work to address.

These printed beautifully, work great, and are super nice and sturdy! Thanks for the upload!