My Knobs not working.

[BigC]

It must be something I'm doing wrong
Today I wanted to make a slide rule marking gauge as all the shops are shut and I have a spare 12" steel rule kicking about.
First things first let's make the tightening star-shaped knob, seems simple enough. How wrong I was.
I set everything up knob shape and size from a file, Hex pocket for bolt head and hole in the centre.
I cut this 5 or 6 times and the bloody hole is never in the center Drat!
I began to think it was my machine, I walked away in disgust.
I went back and if I replace the knob outline with a centered circle it cuts true.
So even though I centered the Knob vector it's not true centred, because I overlayed a circle vector and the legs of the knob star-shape were at different measurements around the circle perimeter ...does that make sense..
Am I doing something elementary wrong>
Regards
C

[Adrian]

Guessing the knob has an odd number of "arms"? If so what you're seeing is correct. It would only work with an even number.

[BigC]

Guessing the knob has an odd number of "arms"? If so what you're seeing is correct. It would only work with an even number.

DOH!
Never even entered my mind, I'll set up again in the morning, see if that works
Cheers Adrian
C

[mtylerfl]

Hi C,

Remember there are TWO center points for an "odd-number shape" (like a 5-point star or pentagon).

One of the centers is the center of an "invisible bounding box" that encloses the shape. This is the default center and can easily be seen if you draw say, a star, then a small circle and center the two items. The circle will not be centered in the star shape, but rather the center of that invisible bounding box for the entire shape. (Thus, it will be off-center to the shape.)

The second center is the actual center of the shape itself. Make sure your Geometry Snapping is turned on. You can then click-n-drag your circle to the center of the shape, and it will "snap" in place (it can "snap" to the boundary box center also, but you just keep dragging until it snaps to the center of the shape itself).

[BigC]

Thank You, Adrian and Michael, for putting me to the wise on this one. I should have paid more attention to the Vectric Tutorials.
I will be more aware of this information in the future, cheers guys.
Hopefully, the part cuts true this time around and I will have a fully functional working Knob, with no more firewood at my feet.

Regards
C

[sharkcutup]

You finally got your "knobs" working ---- AWESOME!!!

Sharkcutup

[BigC]

You finally got your "knobs" working ---- AWESOME!!!

Sharkcutup

Yup! all working, and correctly positioned.
Part of a project (to follow)
I realized that I needed a measuring gauge ruler, the shops are all shut so I decided I was going to make one, all be it a little crude/ethnic
but it works, I'm currently waiting on the varnish to dry but I've tested it and it works a treat. This will surely be of great assistance in marking out small jobs and across end-grains.
Thank you for all the help and assistance, another small lesson learned.

Regards
C

[BigC]

Well, here it is, more practical to me than pretty.

The knob was essential
Regards
C

[Timvmax]

That's so cool. Can't beat making your own tools

[highpockets]

Well done.

Just a thought, did you put a brass plate between the bolt and ruler? If not over time you'll have swirl marks all up and down the center of your ruler.

[BigC]

That's so cool. Can't beat making your own tools

Thanks!

Well done.

Just a thought, did you put a brass plate between the bolt and ruler? If not over time you'll have swirl marks all up and down the center of your ruler.

Hi, Yes, it's not brass though and I get where your comming from. but yes there's a little shim in there to act as a ruler protector.
Having said all that, and although I expect this to last for a while. I was never really intended to better an existing commercial shop bought tool but something to aid me in these small jobs until things get back to some kind of normality. With its functionality and practicality I guess its an OK job from me
Regards
C

[highpockets]

Some of the best tools I still have in my toolbox are ones I made back when I was a machinist working my way through school. Don't get much use anymore, but I get a smile every time I run across one.
Keep it up... and keep sharing your ideas.

[MichaelCNC]

Thanks. This explains why my star shaped knob is not centered. But it is fun to watch it rotate.

Hi C,

Remember there are TWO center points for an "odd-number shape" (like a 5-point star or pentagon).

One of the centers is the center of an "invisible bounding box" that encloses the shape. This is the default center and can easily be seen if you draw say, a star, then a small circle and center the two items. The circle will not be centered in the star shape, but rather the center of that invisible bounding box for the entire shape. (Thus, it will be off-center to the shape.)

The second center is the actual center of the shape itself. Make sure your Geometry Snapping is turned on. You can then click-n-drag your circle to the center of the shape, and it will "snap" in place (it can "snap" to the boundary box center also, but you just keep dragging until it snaps to the center of the shape itself).