Official Luthiers Forum!

I'm trying to create these in sketchup but not having a lot of luck yet. I have a friend with a CNC to build them for me but I need a drawing. I know I'll figure it out in time but was hoping someone here has already gone through the process and could help me.

_________________
Hutch

Get the heck off the couch and go build a guitar!!!!

Don't know, but maybe this may help
http://birdwire.net/boaw/wp-content/uploads/2018/05/bowrad5292018.pdf

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Thanks for this. Will be helpful if I want to make them myself but I really want to do it in sketchup. I can make a sphere or dome but I'm just having trouble figuring out how to slice off what I want. Then I imagine it's just an export to dxf to send to my friend.

_________________
Hutch

Get the heck off the couch and go build a guitar!!!!

Fast way is to use a screenshot of the pdf content as an imported image into sketchup, then export as a dxf.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Is that all he needs is a 2D flat drawing? I thought he would need a 3D image. That's great if it's all he needs.

_________________
Hutch

Get the heck off the couch and go build a guitar!!!!

Hmm, not so sure - expert opinion needed....

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

What is he using a CNC Mill or a CNC Lathe? If he can swing the diameter of the dish on a lathe that would be the simplest and most accurate way to make one. If he is going to make it on a mill he will probably need a 4th axis. As far as the drawing you should be able to call it out as a spherical radius. Hopefully he has a some sort of CAM software that he uses.

Try giving him a 2d drawing with dimensions and call the radius out as a spherical radius and see what he says. That will be easy to draw and if he needs more you will still have the basics. Usually there will be an exploded view that is a cross section showing the radius on the cutaway section and from where it was taken. Usually lined and tagged with an
!____! or some identifying letter ( vertical marks s/b arrows ) and the A should be under the arrow.
A A

Make sphere with desired radius, make cylinder 1" tall and diameter 1" larger than you want the dished area. Use the equation here http://www.liutaiomottola.com/formulae/sag.htm to calculate the saggita for the radius and dished area diameter, and set the sphere y position to radius + half inch - saggita. Then boolean the two of them. Not sure if CNC needs a slice of the sphere (intersect sphere and cylinder) or a model of the dish exactly as you want the final product (subtract sphere from cylinder).

The guy has a 4 axis CNC with the lathe. He doesn't really know how to use it yet. He's just learning. He's got the flat stuff down pretty good. I'm going to see if I can get a copy of his software so I can help him and get a better understanding. Thanks Dennis and Tim. That gives me something to mess with over the weekend.

_________________
Hutch

Get the heck off the couch and go build a guitar!!!!

here's code for a generic fanuc type control -haas, fadal, etc... no 4th needed. stick the board down to the table and center it. G54 Z0. is taken from the top of the board.

the program assumes a 25ft radius on a 2ft dia. dish (typical) since none was specified and uses a .75 diameter ball endmill.

edit feeds and speeds as desired. the program has a local subroutine -hence the M98/M99. also, make sure the control has program rotation enabled hence the G68/G69

basically, the arc was drawn in the front plane and the toolpath is rotated about center every one degree from the top plane. G68 begins the rotation about X0., Y0. and the increment is defined as R-1.

the program starts from left 180 and moves CCW a full 360 degrees.

enjoy!

%
O1234
N100 G20
N110 G0 G17 G40 G49 G80 G90
N120 T1 M6
N130 G0 G90 G54 X-11.9705 Y0. A0. S1528 M3
N140 G43 H1 Z.4889
N150 Z.4389
N160 G1 Z.2389 F30.56
N170 G18 G2 X0. Z0. I11.9705 K299.7611
N180 X11.9904 Z.2397 I0. K300.
N190 G1 Z.4389
N200 G0 Z.4897
N210 G17
N220 X-11.9687 Y-.2089 Z.4889
N230 M98 P0001
N240 G90 X-11.9632 Y-.4178 Z.4889
N250 G0 G90 G68 X0. Y0. G91 R-1.
N260 M98 P0001
N300 G69
N270 G90 X-11.9541 Y-.6265 Z.4889
N280 G0 G90 G68 X0. Y0. G91 R-1.
N290 M98 P0001
N300 G69
N300 G90 X-11.9413 Y-.835 Z.4889
N310 G0 G90 G68 X0. Y0. G91 R-1.
N320 M98 P0001
N300 G69
N330 G90 X-11.9249 Y-1.0433 Z.4889
N340 G0 G90 G68 X0. Y0. G91 R-1.
N350 M98 P0001
N300 G69
N360 G90 X-11.9049 Y-1.2513 Z.4889
N370 G0 G90 G68 X0. Y0. G91 R-1.
N380 M98 P0001
N300 G69
N390 G90 X-11.8813 Y-1.4588 Z.4889
N400 G0 G90 G68 X0. Y0. G91 R-1.
N410 M98 P0001
N300 G69
N420 G90 X-11.854 Y-1.666 Z.4889
N430 G0 G90 G68 X0. Y0. G91 R-1.
N440 M98 P0001
N300 G69
N450 G90 X-11.8231 Y-1.8726 Z.4889
N460 G0 G90 G68 X0. Y0. G91 R-1.
N470 M98 P0001
N300 G69
N480 G90 X-11.7886 Y-2.0787 Z.4889
N490 G0 G90 G68 X0. Y0. G91 R-1.
N500 M98 P0001
N300 G69
N510 G90 X-11.7506 Y-2.2841 Z.4889
N520 G0 G90 G68 X0. Y0. G91 R-1.
N530 M98 P0001
N300 G69
N540 G90 X-11.7089 Y-2.4888 Z.4889
N550 G0 G90 G68 X0. Y0. G91 R-1.
N560 M98 P0001
N300 G69
N570 G90 X-11.6637 Y-2.6928 Z.4889
N580 G0 G90 G68 X0. Y0. G91 R-1.
N590 M98 P0001
N300 G69
N600 G90 X-11.6149 Y-2.8959 Z.4889
N610 G0 G90 G68 X0. Y0. G91 R-1.
N620 M98 P0001
N300 G69
N630 G90 X-11.5626 Y-3.0982 Z.4889
N640 G0 G90 G68 X0. Y0. G91 R-1.
N650 M98 P0001
N300 G69
N660 G90 X-11.5068 Y-3.2995 Z.4889
N670 G0 G90 G68 X0. Y0. G91 R-1.
N680 M98 P0001
N300 G69
N690 G90 X-11.4474 Y-3.4998 Z.4889
N700 G0 G90 G68 X0. Y0. G91 R-1.
N710 M98 P0001
N300 G69
N720 G90 X-11.3846 Y-3.6991 Z.4889
N730 G0 G90 G68 X0. Y0. G91 R-1.
N740 M98 P0001
N300 G69
N750 G90 X-11.3183 Y-3.8972 Z.4889
N760 G0 G90 G68 X0. Y0. G91 R-1.
N770 M98 P0001
N300 G69
N780 G90 X-11.2486 Y-4.0941 Z.4889
N790 G0 G90 G68 X0. Y0. G91 R-1.
N800 M98 P0001
N300 G69
N810 G90 X-11.1754 Y-4.2898 Z.4889
N820 G0 G90 G68 X0. Y0. G91 R-1.
N830 M98 P0001
N300 G69
N840 G90 X-11.0988 Y-4.4842 Z.4889
N850 G0 G90 G68 X0. Y0. G91 R-1.
N860 M98 P0001
N300 G69
N870 G90 X-11.0189 Y-4.6772 Z.4889
N880 G0 G90 G68 X0. Y0. G91 R-1.
N890 M98 P0001
N300 G69
N900 G90 X-10.9356 Y-4.8688 Z.4889
N910 G0 G90 G68 X0. Y0. G91 R-1.
N920 M98 P0001
N300 G69
N930 G90 X-10.849 Y-5.0589 Z.4889
N940 G0 G90 G68 X0. Y0. G91 R-1.
N950 M98 P0001
N300 G69
N960 G90 X-10.759 Y-5.2475 Z.4889
N970 G0 G90 G68 X0. Y0. G91 R-1.
N980 M98 P0001
N300 G69
N990 G90 X-10.6658 Y-5.4345 Z.4889
N1000 G0 G90 G68 X0. Y0. G91 R-1.
N1010 M98 P0001
N300 G69
N1020 G90 X-10.5693 Y-5.6198 Z.4889
N1030 G0 G90 G68 X0. Y0. G91 R-1.
N1040 M98 P0001
N300 G69
N1050 G90 X-10.4696 Y-5.8034 Z.4889
N1060 G0 G90 G68 X0. Y0. G91 R-1.
N1070 M98 P0001
N300 G69
N1080 G90 X-10.3668 Y-5.9852 Z.4889
N1090 G0 G90 G68 X0. Y0. G91 R-1.
N1100 M98 P0001
N300 G69
N1110 G90 X-10.2607 Y-6.1653 Z.4889
N1120 G0 G90 G68 X0. Y0. G91 R-1.
N1130 M98 P0001
N300 G69
N1140 G90 X-10.1516 Y-6.3434 Z.4889
N1150 G0 G90 G68 X0. Y0. G91 R-1.
N1160 M98 P0001
N300 G69
N1170 G90 X-10.0393 Y-6.5196 Z.4889
N1180 G0 G90 G68 X0. Y0. G91 R-1.
N1190 M98 P0001
N300 G69
N1200 G90 X-9.924 Y-6.6938 Z.4889
N1210 G0 G90 G68 X0. Y0. G91 R-1.
N1220 M98 P0001
N300 G69
N1230 G90 X-9.8057 Y-6.866 Z.4889
N1240 G0 G90 G68 X0. Y0. G91 R-1.
N1250 M98 P0001
N300 G69
N1260 G90 X-9.6843 Y-7.0361 Z.4889
N1270 G0 G90 G68 X0. Y0. G91 R-1.
N1280 M98 P0001
N300 G69
N1290 G90 X-9.5601 Y-7.204 Z.4889
N1300 G0 G90 G68 X0. Y0. G91 R-1.
N1310 M98 P0001
N300 G69
N1320 G90 X-9.4329 Y-7.3698 Z.4889
N1330 G0 G90 G68 X0. Y0. G91 R-1.
N1340 M98 P0001
N300 G69
N1350 G90 X-9.3028 Y-7.5333 Z.4889
N1360 G0 G90 G68 X0. Y0. G91 R-1.
N1370 M98 P0001
N300 G69
N1380 G90 X-9.1699 Y-7.6945 Z.4889
N1390 G0 G90 G68 X0. Y0. G91 R-1.
N1400 M98 P0001
N300 G69
N1410 G90 X-9.0342 Y-7.8533 Z.4889
N1420 G0 G90 G68 X0. Y0. G91 R-1.
N1430 M98 P0001
N300 G69
N1440 G90 X-8.8958 Y-8.0098 Z.4889
N1450 G0 G90 G68 X0. Y0. G91 R-1.
N1460 M98 P0001
N300 G69
N1470 G90 X-8.7547 Y-8.1639 Z.4889
N1480 G0 G90 G68 X0. Y0. G91 R-1.
N1490 M98 P0001
N300 G69
N1500 G90 X-8.6109 Y-8.3154 Z.4889
N1510 G0 G90 G68 X0. Y0. G91 R-1.
N1520 M98 P0001
N300 G69
N1530 G90 X-8.4644 Y-8.4644 Z.4889
N1540 G0 G90 G68 X0. Y0. G91 R-1.
N1550 M98 P0001
N300 G69
N1560 G90 X-8.3154 Y-8.6109 Z.4889
N1570 G0 G90 G68 X0. Y0. G91 R-1.
N1580 M98 P0001
N300 G69
N1590 G90 X-8.1639 Y-8.7547 Z.4889
N1600 G0 G90 G68 X0. Y0. G91 R-1.
N1610 M98 P0001
N300 G69
N1620 G90 X-8.0098 Y-8.8958 Z.4889
N1630 G0 G90 G68 X0. Y0. G91 R-1.
N1640 M98 P0001
N300 G69
N1650 G90 X-7.8533 Y-9.0342 Z.4889
N1660 G0 G90 G68 X0. Y0. G91 R-1.
N1670 M98 P0001
N300 G69
N1680 G90 X-7.6945 Y-9.1699 Z.4889
N1690 G0 G90 G68 X0. Y0. G91 R-1.
N1700 M98 P0001
N300 G69
N1710 G90 X-7.5333 Y-9.3028 Z.4889
N1720 G0 G90 G68 X0. Y0. G91 R-1.
N1730 M98 P0001
N300 G69
N1740 G90 X-7.3698 Y-9.4329 Z.4889
N1750 G0 G90 G68 X0. Y0. G91 R-1.
N1760 M98 P0001
N300 G69
N1770 G90 X-7.204 Y-9.5601 Z.4889
N1780 G0 G90 G68 X0. Y0. G91 R-1.
N1790 M98 P0001
N300 G69
N1800 G90 X-7.0361 Y-9.6843 Z.4889
N1810 G0 G90 G68 X0. Y0. G91 R-1.
N1820 M98 P0001
N300 G69
N1830 G90 X-6.866 Y-9.8057 Z.4889
N1840 G0 G90 G68 X0. Y0. G91 R-1.
N1850 M98 P0001
N300 G69
N1860 G90 X-6.6938 Y-9.924 Z.4889
N1870 G0 G90 G68 X0. Y0. G91 R-1.
N1880 M98 P0001
N300 G69
N1890 G90 X-6.5196 Y-10.0393 Z.4889
N1900 G0 G90 G68 X0. Y0. G91 R-1.
N1910 M98 P0001
N300 G69
N1920 G90 X-6.3434 Y-10.1516 Z.4889
N1930 G0 G90 G68 X0. Y0. G91 R-1.
N1940 M98 P0001
N300 G69
N1950 G90 X-6.1653 Y-10.2607 Z.4889
N1960 G0 G90 G68 X0. Y0. G91 R-1.
N1970 M98 P0001
N300 G69
N1980 G90 X-5.9852 Y-10.3668 Z.4889
N1990 G0 G90 G68 X0. Y0. G91 R-1.
N2000 M98 P0001
N300 G69
N2010 G90 X-5.8034 Y-10.4696 Z.4889
N2020 G0 G90 G68 X0. Y0. G91 R-1.
N2030 M98 P0001
N300 G69
N2040 G90 X-5.6198 Y-10.5693 Z.4889
N2050 G0 G90 G68 X0. Y0. G91 R-1.
N2060 M98 P0001
N300 G69
N2070 G90 X-5.4345 Y-10.6658 Z.4889
N2080 G0 G90 G68 X0. Y0. G91 R-1.
N2090 M98 P0001
N300 G69
N2100 G90 X-5.2475 Y-10.759 Z.4889
N2110 G0 G90 G68 X0. Y0. G91 R-1.
N2120 M98 P0001
N300 G69
N2130 G90 X-5.0589 Y-10.849 Z.4889
N2140 G0 G90 G68 X0. Y0. G91 R-1.
N2150 M98 P0001
N300 G69
N2160 G90 X-4.8688 Y-10.9356 Z.4889
N2170 G0 G90 G68 X0. Y0. G91 R-1.
N2180 M98 P0001
N300 G69
N2190 G90 X-4.6772 Y-11.0189 Z.4889
N2200 G0 G90 G68 X0. Y0. G91 R-1.
N2210 M98 P0001
N300 G69
N2220 G90 X-4.4842 Y-11.0988 Z.4889
N2230 G0 G90 G68 X0. Y0. G91 R-1.
N2240 M98 P0001
N300 G69
N2250 G90 X-4.2898 Y-11.1754 Z.4889
N2260 G0 G90 G68 X0. Y0. G91 R-1.
N2270 M98 P0001
N300 G69
N2280 G90 X-4.0941 Y-11.2486 Z.4889
N2290 G0 G90 G68 X0. Y0. G91 R-1.
N2300 M98 P0001
N300 G69
N2310 G90 X-3.8972 Y-11.3183 Z.4889
N2320 G0 G90 G68 X0. Y0. G91 R-1.
N2330 M98 P0001
N300 G69
N2340 G90 X-3.6991 Y-11.3846 Z.4889
N2350 G0 G90 G68 X0. Y0. G91 R-1.
N2360 M98 P0001
N300 G69
N2370 G90 X-3.4998 Y-11.4474 Z.4889
N2380 G0 G90 G68 X0. Y0. G91 R-1.
N2390 M98 P0001
N300 G69
N2400 G90 X-3.2995 Y-11.5068 Z.4889
N2410 G0 G90 G68 X0. Y0. G91 R-1.
N2420 M98 P0001
N300 G69
N2430 G90 X-3.0982 Y-11.5626 Z.4889
N2440 G0 G90 G68 X0. Y0. G91 R-1.
N2450 M98 P0001
N300 G69
N2460 G90 X-2.8959 Y-11.6149 Z.4889
N2470 G0 G90 G68 X0. Y0. G91 R-1.
N2480 M98 P0001
N300 G69
N2490 G90 X-2.6928 Y-11.6637 Z.4889
N2500 G0 G90 G68 X0. Y0. G91 R-1.
N2510 M98 P0001
N300 G69
N2520 G90 X-2.4888 Y-11.7089 Z.4889
N2530 G0 G90 G68 X0. Y0. G91 R-1.
N2540 M98 P0001
N300 G69
N2550 G90 X-2.2841 Y-11.7506 Z.4889
N2560 G0 G90 G68 X0. Y0. G91 R-1.
N2570 M98 P0001
N300 G69
N2580 G90 X-2.0787 Y-11.7886 Z.4889
N2590 G0 G90 G68 X0. Y0. G91 R-1.
N2600 M98 P0001
N300 G69
N2610 G90 X-1.8726 Y-11.8231 Z.4889
N2620 G0 G90 G68 X0. Y0. G91 R-1.
N2630 M98 P0001
N300 G69
N2640 G90 X-1.666 Y-11.854 Z.4889
N2650 G0 G90 G68 X0. Y0. G91 R-1.
N2660 M98 P0001
N300 G69
N2670 G90 X-1.4588 Y-11.8813 Z.4889
N2680 G0 G90 G68 X0. Y0. G91 R-1.
N2690 M98 P0001
N300 G69
N2700 G90 X-1.2513 Y-11.9049 Z.4889
N2710 G0 G90 G68 X0. Y0. G91 R-1.
N2720 M98 P0001
N300 G69
N2730 G90 X-1.0433 Y-11.9249 Z.4889
N2740 G0 G90 G68 X0. Y0. G91 R-1.
N2750 M98 P0001
N300 G69
N2760 G90 X-.835 Y-11.9413 Z.4889
N2770 G0 G90 G68 X0. Y0. G91 R-1.
N2780 M98 P0001
N300 G69
N2790 G90 X-.6265 Y-11.9541 Z.4889
N2800 G0 G90 G68 X0. Y0. G91 R-1.
N2810 M98 P0001
N300 G69
N2820 G90 X-.4178 Y-11.9632 Z.4889
N2830 G0 G90 G68 X0. Y0. G91 R-1.
N2840 M98 P0001
N300 G69
N2850 G90 X-.2089 Y-11.9687 Z.4889
N2860 G0 G90 G68 X0. Y0. G91 R-1.
N2870 M98 P0001
N300 G69
N2880 G90 X0. Y-11.9705 Z.4889
N2890 G0 G90 G68 X0. Y0. G91 R-1.
N2900 M98 P0001
N170 G69
N2910 G17
N2920 G90 X.2089 Y-11.9687 Z.4889
N2930 G0 G90 G68 X0. Y0. G91 R-1.
N2940 M98 P0001
N300 G69
N2950 G90 X.4178 Y-11.9632 Z.4889
N2960 G0 G90 G68 X0. Y0. G91 R-1.
N2970 M98 P0001
N300 G69
N2980 G90 X.6265 Y-11.9541 Z.4889
N2990 G0 G90 G68 X0. Y0. G91 R-1.
N3000 M98 P0001
N300 G69
N3010 G90 X.835 Y-11.9413 Z.4889
N3020 G0 G90 G68 X0. Y0. G91 R-1.
N3030 M98 P0001
N300 G69
N3040 G90 X1.0433 Y-11.9249 Z.4889
N3050 G0 G90 G68 X0. Y0. G91 R-1.
N3060 M98 P0001
N300 G69
N3070 G90 X1.2513 Y-11.9049 Z.4889
N3080 G0 G90 G68 X0. Y0. G91 R-1.
N3090 M98 P0001
N300 G69
N3100 G90 X1.4588 Y-11.8813 Z.4889
N3110 G0 G90 G68 X0. Y0. G91 R-1.
N3120 M98 P0001
N300 G69
N3130 G90 X1.666 Y-11.854 Z.4889
N3140 G0 G90 G68 X0. Y0. G91 R-1.
N3150 M98 P0001
N300 G69
N3160 G90 X1.8726 Y-11.8231 Z.4889
N3170 G0 G90 G68 X0. Y0. G91 R-1.
N3180 M98 P0001
N300 G69
N3190 G90 X2.0787 Y-11.7886 Z.4889
N3200 G0 G90 G68 X0. Y0. G91 R-1.
N3210 M98 P0001
N300 G69
N3220 G90 X2.2841 Y-11.7506 Z.4889
N3230 G0 G90 G68 X0. Y0. G91 R-1.
N3240 M98 P0001
N300 G69
N3250 G90 X2.4888 Y-11.7089 Z.4889
N3260 G0 G90 G68 X0. Y0. G91 R-1.
N3270 M98 P0001
N300 G69
N3280 G90 X2.6928 Y-11.6637 Z.4889
N3290 G0 G90 G68 X0. Y0. G91 R-1.
N3300 M98 P0001
N300 G69
N3310 G90 X2.8959 Y-11.6149 Z.4889
N3320 G0 G90 G68 X0. Y0. G91 R-1.
N3330 M98 P0001
N300 G69
N3340 G90 X3.0982 Y-11.5626 Z.4889
N3350 G0 G90 G68 X0. Y0. G91 R-1.
N3360 M98 P0001
N300 G69
N3370 G90 X3.2995 Y-11.5068 Z.4889
N3380 G0 G90 G68 X0. Y0. G91 R-1.
N3390 M98 P0001
N300 G69
N3400 G90 X3.4998 Y-11.4474 Z.4889
N3410 G0 G90 G68 X0. Y0. G91 R-1.
N3420 M98 P0001
N300 G69
N3430 G90 X3.6991 Y-11.3846 Z.4889
N3440 G0 G90 G68 X0. Y0. G91 R-1.
N3450 M98 P0001
N300 G69
N3460 G90 X3.8972 Y-11.3183 Z.4889
N3470 G0 G90 G68 X0. Y0. G91 R-1.
N3480 M98 P0001
N300 G69
N3490 G90 X4.0941 Y-11.2486 Z.4889
N3500 G0 G90 G68 X0. Y0. G91 R-1.
N3510 M98 P0001
N300 G69
N3520 G90 X4.2898 Y-11.1754 Z.4889
N3530 G0 G90 G68 X0. Y0. G91 R-1.
N3540 M98 P0001
N300 G69
N3550 G90 X4.4842 Y-11.0988 Z.4889
N3560 G0 G90 G68 X0. Y0. G91 R-1.
N3570 M98 P0001
N300 G69
N3580 G90 X4.6772 Y-11.0189 Z.4889
N3590 G0 G90 G68 X0. Y0. G91 R-1.
N3600 M98 P0001
N300 G69
N3610 G90 X4.8688 Y-10.9356 Z.4889
N3620 G0 G90 G68 X0. Y0. G91 R-1.
N3630 M98 P0001
N300 G69
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N3650 G0 G90 G68 X0. Y0. G91 R-1.
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%

Always wondered why no one created a table of dimensions using the sagitta formula. Like the highest point of an arc from the center of a chord that is, say, 24" long for a series of diameters.

Then all you need to do is use that sagitta, or offset, and this method to construct an arc in a hurry

https://www.flickr.com/photos/ruby1638/9566635434/in/album-72157635172644427/

Ed

Now I remember why CNC is not for me.

_________________
Joe Beaver
Maker of Sawdust

I like Ed's use of the old carpenter trick (long curve) to layout the curve. Ed , there are tables of "sagitta" know as the "external" for a simple curve in back of every surveyor's field book I ever bought. Didn't think I would run into that building guitars. Also, having been around and owning a lathe, I wouldn't recommend spinning a 24", 1" thick plate on a vertical plane fast enough to cut out a radius. I made my own dishes with a simple sled and a router. It was kind of messy cause I used MDF, but was fun. It only took about 45min/per dish.

This thread perked my interest. I personally don't use the radius dish. But just out of interest or perhaps challenge, I thought I would try to model one and create the tool path. I use rhino cad.

It took me about 30 minutes including the tool path. I think it would be a five minute operation The next time.

Basically what I did was create a 25 foot sphere and attach a point to the edge. Next I measured down from that about a half an inch and created a line. I extruded the line 24 x 24". And created a surface. I then extruded this surface 0.75 inches.
So now I have a square that is 0.75 inches thick and 24 x 24". This represents my stock.
In rhino you can subtract one object from the other. This operation is called a Boolean.
I subtracted the sphere from the rectangle.

This left me with The blank with a 25 foot surface.

I then selected this and created a tool path. Are used a planner surfacing and a half inch ball mill with a close step over. The tool path took a little under one hour of cutting time.



Sent from my iPhone using Tapatalk

_________________
Ken

Boolean subtract -perfect!

I used Mastercam 2018 and made a 2d sketch in wireframe. Basically created a 24" x 1" front plane rectangle. Then I made a 3 point curve picking the two topmost corners of the curve and dragging the center point to a 300" (25') radius.

Toolpath again was wireframe/2d contour. Made the toolpath and chose transform/rotate using the sub-routine option. Posted the code and done.

Old habit using wireframe toolpaths picked up in the mid 80's when machine control memory was like 4MB and DNC'ing tons of code was horrible. Makes simple programming (without model creation btw,) so much faster ime.

This should be easy if sketchup has a revolve feature. Imagine slicing the radius dish in half. Now model half of the section and do a revolve around the center. Shouldn't take more than a minute (assuming sketchup has a revolve)

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

like this....

(it's not centered on the origin because of some silliness in F360 - I'm not 100% up to speed with this software yet but it was the quickest way to illustrate)

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com