Find easily the center of any circle or round object.
Also is suitable for finding the center at regular hexagon, or dodecagon shapes
and can divide the 90° angle of a square or rectagle shape into 30° / 60°
or into 30° / 30° / 30°.
But it isn't suitable to finding the center at square or rectangular shapes.
Not interest me at all, I can use my vernier my caliper or my rule.
And yes, I know that using a square V-block or a carpenter’s square can do the job.
But I wanted a tool at my own design,
and its own different capabilities.
Step 1: Tools and Materials
- Pen Scriber
- Welding Machine
- Angle grinder 115mm 4 ½” or 125mm 5”
- Cutting disc ø115 x 1mm/ ø4 ½” x 0.04” or ø125 x 1mm/ ø 5” x 0.04”
- Grinding Sanding Flap Disc
- Flat file
- Small file
- Vise Grips 2pcs
The needed materials are only two
- Stainless Steel Flat Bar 25x2mm about 400mm at any quality (AISI 430, 304, 308, 316, 316L)
- Stainless Steel Stick Electrodes (at any quality)
- A piece Scotch Brite for finishing/polishing of welds (optional)
Step 2: Plans and Assembly Guide Helper
Step 3: Marking and Cuts
Remember Safety First.
Welding Cutting and Grinding Tools are Dangerous!
Do it at your own Risk!
Use Always the Suitable Protective Equipment.
These pieces that I have used are from a stainless steel (AISI 430) sheet metal that they have had cut with a punching mold and had left over.
So ignore the holes at the photos, not needed.
The dimensioning of material can be varying from 18~25mm width, and 2~4mm thickness, with no problems.
If you decide to use aluminum, then the combination 25mm/4mm is the best choice.
Cut from flat bar (25x4mm) two pieces at 95mm length and another one at 190mm.
Be sure, that your cuts are absolutely on the square.
Using a protractor mark a 30° bevel at the one of edges (If you have a protractor).
I haven't such tool and will need to be calculated.
Don't worries, not need to go back to school.
We can use a free program like Google Sketch Up or any other we like, that will do this job for us.
You can view a how to here.
Use your grinder perpendicular, and gently,
without any haste,
and moving parallel to line, as close as be possible,
do the cuts.
Step 4: Assembly the Tool
Place the assembly guide over a flat metal surface.
Place the two pieces over the guide.
The bisector of the angle DEF and the bisector of the angle A of Equilateral Triangle ABC must be common.
The sides AB & AC must be on the square to ED & EF respectively.
If your cuts are correct and all the above are true, then you are ready to proceed.
Clamp the two pieces using vice grips and do two tack welds.
Release the vise grips (remove and keep the assembly guide, will needing again)
turn it upside down.
Once again turn it upside down.
Grind the tacks, and do a groove 4~5mm wide and depth till the root of the down side weld.
Weld and let it cool.
Grind the welds at both sides and refine them using a file, so to be flat and very smooth.
Don't forget to do the gap at the inner corner of the angle using a smmal file.
Now we are redy to attach the third piece.
Place again the assembly guide over the flat metal surface.
Place the pieces over the guide.
Use a piece of the same material to keep all, at correct level.
Adjust the flat bar so to be parallel and on the square over bisector AE.
A small offset 0.02~0.03mm to the right is required for correct marking.
Use again the vise grips to keep in place,
Check, do tack welds
For Right Handed Users, mount at the right of common bisector AE
For Left Handed Users, mount at the left of common bisector AE
Grind the welds and finishing/polishing using a piece of Scotch Brite.
Ready for test.
As you can see at photos the results are pretty good.
All lines pass through exactly from the center of circle.
Thanks for your reading.
Good Luck if you try it.
Never say I can't do it.
Necessity is the mother of invention.