I have ordered a replacement for a cracked plastic dial on a vintage sewing machine. I think drawing it is a bit beyond my skill level, but I’m trying to draw it anyway. top hat and wings.skp (103.2 KB)
Here are pictures of the cracked dial.
I’ve started by drawing the top hat portion consisting of the brim and the crown. I suspect the brim tapers in thickness where I wanted a consistent thickness. I also think I should have made the crown portion solid for later mods to fit on the round shaft..
The wings are tapered in two directions but I’ve only been able to get one taper.
My union of the two parts looks pretty messy from underneath.
Before I go much further, I want to ask if I’m way off base or am I stumbling towards a good drawing?
I think you’re on the right track Terry but the upper part of the hat doesn’t have any thickness and there are missing bits. You also have exposed back faces.
If I were modeling that I would make sure the top hat part is a solid object on its own and then I would model the wings as a separate solid object. I would then use the top hat to first trim the wing component so any unwanted geometry in the middle could be removed. Then I would join the wings to the top hat with the Union tool.
If you’re going to model the internal web structure and intend to make the wings hollow, I would model those spaces as solid volumes and use them to trim the know after adding the wings. Some of that probably isn’t needed for a 3D print and might not be wanted for a 3D printed version.
Dave, you’ve been a big help as usual. I was happy to hear that you think I’m on the right track.
But, I’m embarrassed that I didn’t think to draw the profile of the top hat and then use the follow-me tool to rotate it 360 degrees. You have told me that before and demonstrated it, and yet I forgot about it and came up with a more difficult and flawed drawing..
At least I drew the wings as a separate component with the intention of using the Union tool.
As far as hollows go, the only ones I need are the round core with the flattened side, the side bore to accept the set screw to lock the dial on to the shaft, and the recess at the top for the Singer logo. The wings don’t need to be hollow and the underneath webbing is also unnecessary as I would just print as a solid.
I’ll go back to my drawing with some more confidence now.
Hi Dave. I’m back looking for more hints. top hat and wings.skp (371.9 KB)
I have the top hat and I have the wings, but I’m not sure how to use the trim tool to end up with wings just stuck on the outside of the top hat and not have all the geometry inside the top hat. I’ve been looking for a tutorial or something to review but I haven’t found anything.
I suggested trimming the wings with the top hat thinnking you’d have a space inside the top hat. Trimming the wings would allow you to edit the wing component and remove any unneeded bits. Then you would use Union to joint the wings with the top hat.
In your latest model you’ve trimmed the top hat with the wing component although I suspect you want to extrude the bottom of the wing downward to avoid the gap out near the edge edge of the brim.
Since your version of the top hat has no voids inside, the trim step would really be unneeded and you could just use Union to combine the two components into one.
FWIW, here’s a simple example showing where the trim step would be important. Ignore the fact there’d be nothing to attach the knob to the shaft in this case.
If you just use Union to join the two objects, the center section of the wing component would remain on the inside of the top hat. Trimming the wing component with the top hat
If you trim the wing with the hat you can then select the geometry on the inside of the hat to delete it.
I’m getting there. I think I’m ready to start with making holes for the set screw and for the mounting shaft. I thinking of trying to tap the hole for the set screw, I don’t think there’s a lot of room for any kind of inset. top hat and wings.skp (373.0 KB)
That’ll work fine for printing and has the benefit of making it easy to modify if, for example, you want to make a knob with three wings instead of two or make a knob with no wings.
That will probably work fine. When I’ve done that I model the hole at the standard tap drill size for the screw and add an extra wall line in the slicer just for good measure.
You can draw a “drill” and a shaft of the correct size and shape and then use Trim or Subtract to cut the holes. Currently you have the top hat and wings components gathered together in a nested component that really isn’t needed. Either explode that top level component or you’ll have to out your drill and shaft hole components inside that parent component before you can use Trim or Subtract.
I’ll continue working on it.
But I have another question. In your first (and very prompt) reply to my original question, I noticed that you had drawn the dial yourself just from my posting. I spent hours with calipers and the original part to come up with my profile. I swear you did the same in minutes without the benefit of having the original piece. Do you have a secret for doing that?
Singer 638 buttonhole dial v2.skp (267.5 KB)
I went back to the drawing board and have come up with something that I think will print.
But, I had a small issue trying to slide the set screw shaft into the top hat. It would only go in so far. I’m trying to remember if I used Trim or Difference to get the hole in the top hat. Once the set screw bore was visible I was able push/pull the end of that bore through to the central bore where the set screw will lock onto the shaft.
Can you tell from my skp why I had this problem?
The knob looks great. I can’t tell what happened when you were trying to push it in. When I drew the “drill” for that hole I started with the circle at the outboard end and use Push/Pull to push it through to the D-shaped drill. Since they were outside of the knob component there was no issue pushing them through.
Singer 638 buttonhole dial v6.skp (398.9 KB)
Thank to Dave’s tutoring, I ended up with a functioning dial (even if it took me six versions to get there). And I’m still waiting for my replacement dial to come in the mail.
