A couple of newbie problems

Hi all,

I’m brand new to Sketchup, but loving the feel of it so far. I’ve recently gotten in to home 3D printing and have reviewed the various 3D design software options, and decided to learn Sketchup.

I’m doing my first own-design print at the moment - a very simple one, it’s a key for our sash window locks, since we don’t have nearly enough in the house. Very simple, the business end is a narrow cylinder with a square hole inset into the end.

I’ve got a working version built now that my printer software says should be printable, so I’ll give it a go at the weekend, but that wasn’t without some major confusion/headaches about a couple of things in the design that I thought would be very straightforward in Sketchup but weren’t - I’m assuming I’m missing something. They were…

  • for the basic key, I drew a circle to the correct size centred at the origin, then extruded it 1cm, then drew a square to the correct size on the top which I was then going to extrude backwards for the inset hole part. However, try as I might, I couldn’t find an easy way to center the square face on the centre of the circle face. I would have assumed that both centres would be available as easy snap points to make that centering easy, but it seems not, and I couldn’t find anything in the help files, tools or right-click menus to help me - surely I’m missing something, this must be easy ?

I eventually got round it by drawing the square first, with one corner on the origin, then moving the square to be centred on the xy origin by doing two moves, snapping each of the midpoint sides to the axes - then I moved that square out of the way along the z axis while I drew the cylinder, then moved the square back on top of the cylinder and extruded it.

  • the second problem came when I was working on the shaft of the key, I want a broader stem, 1cm diameter, which tapers down to the narrow tip (6.125mm diameter), so for the tapering part, i drew another circle, extruded that, selected one of the circle faces and using the scale tool on one of the corners while holding the ctrl key down I can get the shape I want, like a 3d slice out of a cone. However the problem here is trying to get the measurements exact. I can type the measurements in the little field in the bottom right of the screen, but without the ctrl key pressed that just moves one of the scale anchors and you get a skewed shape. However if I’m holding the ctrl key down, then I can’t type in the text field. I can of course hold the ctrl key and drag with the mouse and get close to the right size, ‘~1.6’, but for printing that’s not good enough, I want it exact, and couldn’t find an easy way to do it, which again I’m sure there must be.

I eventually got round this by drawing a guideline from each axis where I wanted to grow the circle to, giving me a guide point that I would want the corner scale anchor to snap to, but even that didn’t work, it wouldn’t snap to it. Eventually I had to draw a random rectangle starting at that scale point, and then I could get the scale anchor to snap to that corner, scaling the circle correctly, and then deleted the rectangle afterwards. There must be an easier way than this ??

Sorry for the long post, it’s hard to express in words, but I’d like to be using Sketchup properly and efficiently, so any pointers on how I should do these things are much appreciated !



Use the Polygon tool instead of the Rectangle tool. Set the number of sides to 4 before starting to draw and set the center on the center of the circular face.

Scale as you did, release the mouse button and then the Ctrl key in that order. Type the dimension.

Alternatively, use the Move tool on a cardinal point on the circle. Move the point (scaling the circle) by the difference in radius between existing and desired values. You can find the cardinal point by hovering the Move tool over the edge of the circle and finding a point where the circle is not highlighted. Click and start the move.

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Dave typed word for word my reply as I read your post.

ahh thanks very much, makes perfect sense, I knew there’d be an easier way to do it