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Complete Your Profile- ziqfriq. commented on tonyfoale's instructable Radius Measuring for Reverse Engineering.11 days ago
- ziqfriq. commented on mattaw's instructable Fixing a Monitor With a Breadmaker: AKA Don't Throw It Out!10 months agoView Instructable »
Sounds like in this instance you got lucky on several counts. However, if something is destined for the landfill you have nothing to lose. Even if you break something beyond repair in the process, you're no worse off. The only thing you have to decide is how much of your time it's worth for the possibility of having something working again for free. I've been there many times, with some successes. Yes, the hidden screws can be nasty. Sometimes you have to peel off labels, I don't think you mentioned that, otherwise very thorough.

- ziqfriq. commented on bekathwia's instructable Knife Sharpening Angle Coach With Bluetooth & Arduino1 year agoView Instructable »
Probably one of the most useful to me personally Instructables. Definitely one of my top dozen or so to do projects. In other words, it's probably not going to get built tomorrow, otherwise I'd wait until then before making any suggestions.I think the most useful sort of feedback would be audible. That way, you could concentrate your vision on proper contact between the knife blade and stone. Maybe a pitch you could "zero beat" at the target angle. Or you could set it to one side of the target for instantaneous correction without having to guess which way to correct.If you go too shallow to the stone you're simply doing nothing to improve the edge, whereas if you go too deep you're potentially destroying what edge you've achieved. Therefore it might be appropriate to mak...

see more » - ziqfriq. commented on Jason von Techshop's instructable Drilling Metal With a Drill Press1 year agoView Instructable »
I think for this application pi ~=3 will work just fine :-)

- ziqfriq. commented on Bill WW's instructable Vacuum Cannon Drives Ping Pong Ball at Supersonic Speed1 year ago

These are elegantly simple pieces to take the place of a few hundred dollar or more instrument. All the more impressive being built from scraps. I'm all for doing the math myself and saving the money.Your math is correct, but way too complicated! Using analytic geometry to find the slope of a line is way overkill, let alone solving 3 simultaneous equations.In the spirit of KISS, referring to your second diagram (no need to solve the more general problem): I call your length of AC--the probe length--d, your BX--the measured depth-h, to save tedium in algebraic manipulations. As noted, OB is a perpendicular bisector of AC so AX=Cx=d/2. Applying the Pythagorean theorem givesR^2 = (R-h)^2 + (d/2)^2.which we may easily solve for the unknown R:R=[h^2 + (d/2)^2]/2*hBy taking the sine of t...

see more »These are elegantly simple pieces to take the place of a few hundred dollar or more instrument. All the more impressive being built from scraps. I'm all for doing the math myself and saving the money.Your math is correct, but way too complicated! Using analytic geometry to find the slope of a line is way overkill, let alone solving 3 simultaneous equations.In the spirit of KISS, referring to your second diagram (no need to solve the more general problem): I call your length of AC--the probe length--d, your BX--the measured depth-h, to save tedium in algebraic manipulations. As noted, OB is a perpendicular bisector of AC so AX=Cx=d/2. Applying the Pythagorean theorem givesR^2 = (R-h)^2 + (d/2)^2.which we may easily solve for the unknown R:R=[h^2 + (d/2)^2]/2*hBy taking the sine of the arctan of Ax/XB you are in effect using the Pythagorean theorem anyway. Are you actually doing that, numerically, in your software? If so you may be losing some accuracy compared to a more direct method. Angle ABX is not something you measure directly, or need, so calculating it is superfluous.An even simpler way to get this formula is to use a nifty theorem from geometry that says when two chords intersect inside a circle the products of the segments are equal. To use this we have to extend BO so that it becomes a full diameter. Then the two products that must be equal are (2R-h)*h and (d/2)^2. I believe that theorem comes from, if not Pythagorean itself, the same similar triangle magic that gives us Pythagorean.I admit to having overthought the ball tip case for a while. You're absolutely correct, all one need do is add or subtract the ball radius depending on which side of the surface you're measuring from.I'm sure you enjoyed writing your software but wouldn't it be almost as easy to put the formula in a spreadsheet? Almost everyone has access to either Microsoft Excel or Libre Office Calc (which is free). You're going to have a PC in your shop anyway, apparently.Nitpicks aside, this is an interesting project that I'm sure will find many uses besides reverse engineering for writing G code.