Program for drilling ovals

[2y2]

Hello, Russelldean started this topic:

viewtopic.php?f=7&t=6897&hilit=formula+oval

In consequence I made this little program. It is designed to give you the possibility to drill any oval hole along the Y axis only, elliminating the need to use complex tables for each angle and the use of the X axis crank so it is more accurate I think.

Here it is:

http://www.2y2.com.mx/ovalator/Ovalator10-abr.html



1. You lay your ball as usual and find the center of your pilot hole,
2. Trace a line passing through that center with the oval angle you want.
3. Use the program to input your stats and it will give you modified pitches with the rotated ball.
4. Place the ball and align the oval line to the Y axis.
5. Drill your pilot hole and cut in very small increments until you reach the oval hole width.

Note that because I'm still testing the program you use it at your own risk. (Test it on an old useless ball before you make the final drilling)

Any feedback is well received.
I want to thank Labrat for giving me the concept of the rotational matrix to make this little program.

[2y2]

I forgot to say that you need flash player 10.2 plugin on your browser to run the program.

[elgavachon]

Great work 2y2.
I added this to the wiki for quick reference:
http://wiki.bowlingchat.net/wiki/index. ... on#Fitting" onclick="window.open(this.href);return false;

You have the disclaimer on your web page. Great.

[kellytehuna]

I'm not sure the outputs are correct. I just tested it with my thumb pitches of 0 lateral, and 5/16" reverse and oval angle of 20 and it gave me 5 left (I assume that 5/16 left) and 0.03 forward.

[2y2]

You found a bug, output is in decimal inches, and it cannot be 5 by no means. Let me fix it at once.

Your output should be 0.294 left and 0.1065 reverse

[2y2]

Hi Kelly, the bug has been fixed, the program now gives your output right.
Again, results are given in decimal inches.

[Rjf300]

can some one help me out here. 0.065 Left, and 0.272 rev

my stats

Right handed
1/8 lateral right
linear 1/4 rev
50deg

I have a scale that is in 16ths can some one help me convert the numbers above

[JMerrell]

Changing decimals to a fraction:
1) Move the decimal point to the right the number of places required to achieve a whole number. This number will then become the numerator of the fraction.
2) The denominator is calculated by add the corresponding number of zeroes to the right of the number 1 that were required to change the decimal to a whole number.
3) Reduce to lowest terms.

Examples: .2, .25, .125
1) .2 requires moving the decimal point one place to the right to achieve a whole number
2) Moving the decimal point one place to the right changes .2 to 2 (this number is the nominator of the fraction)
3) Add one zero to the right of the number 1. One zero added to the right changes the number 1 to 10.
4) Therefore .2 equals the fraction 2/10. Which can be reduced to 1/5 (.2=1/5)


Using the same method for .25 & .125
.25 = 25/100, which can be reduced to 1/4
.125 = 125/1000, which can be reduced to 1/8

Conversion of .0625 & .272
.065 = 65/100, reduced to 1/15.38 (rounding to 1/16 on your scale) 1/16=.0625
.272 = 272/1000, reduced to 1/3.68 (rounding to 1/4 on your scale) 1/4=.250 (.022 smaller than .272)
5/16= .3125 (.040 larger than .272).

Halfway between the 1/4" and 5/16" marks on your scale would be approximately 9/32=.281. (much closer to .272)


Or you could just use the attached conversion chart.

[2y2]

I will soon update this program to give the results in fractional inches also.

[2y2]

Hello, some people have asked me to post some instructions to clarify what I'm trying to do, so here are two graphics to explain it a little, I hope they're useful.

[kart300]

I see two problems with these instructions to cut an oval;

1) It only works if your thumb pitch is 0 ,0
2) If you only cut in one direction the span measurement will be incorrect.

It is not possible to cut a hole with both pitches and simply rotate the ball in the jig as it needs to be repositioned to take account of the pitches using either the x axis or y axis as a 0 point
Please correct me if I'm wrong.

If I am wrong then there must be a zero point that the ball can be set in the jig, depending on the oval angle. This should be a fixed point and could be calculated from the pitch measurements and degree of oval.

Any help out there from any of the spherical mathematical genii!!

[LabRat]

I see two problems with these instructions to cut an oval;

1) It only works if your thumb pitch is 0 ,0
2) If you only cut in one direction the span measurement will be incorrect.

It is not possible to cut a hole with both pitches and simply rotate the ball in the jig as it needs to be repositioned to take account of the pitches using either the x axis or y axis as a 0 point
Please correct me if I'm wrong.

You are wrong.

If I am wrong then there must be a zero point that the ball can be set in the jig, depending on the oval angle. This should be a fixed point and could be calculated from the pitch measurements and degree of oval.

Any help out there from any of the spherical mathematical genii!!

http://en.wikipedia.org/wiki/Rotation_matrix" onclick="window.open(this.href);return false;

y2y's program simply calculates what the pitches change to when the ball is rotated so the oval is vertical in the press. Works very well (my version outputs in 64ths though lol).
Quick tip when using it - drill the pilot in the normal orientation and unadjusted pitches, then rotate onto the oval line and dial the adjusted pitches in. The bit should then still line up with the hole - if it doesn't, something is wrong (usually input wrong oval angle fwiw). You can then crank backwwards as normal. It's MUCH easier to cut ovals this way, especially if (like me) you have a crappy press.
Nice work 2y2, btw, like the graphical interface!

[elgavachon]

Changing decimals to a fraction:
1) Move the decimal point to the right the number of places required to achieve a whole number. This number will then become the numerator of the fraction.
2) The denominator is calculated by add the corresponding number of zeroes to the right of the number 1 that were required to change the decimal to a whole number.
3) Reduce to lowest terms.

Examples: .2, .25, .125
1) .2 requires moving the decimal point one place to the right to achieve a whole number
2) Moving the decimal point one place to the right changes .2 to 2 (this number is the nominator of the fraction)
3) Add one zero to the right of the number 1. One zero added to the right changes the number 1 to 10.
4) Therefore .2 equals the fraction 2/10. Which can be reduced to 1/5 (.2=1/5)


Using the same method for .25 & .125
.25 = 25/100, which can be reduced to 1/4
.125 = 125/1000, which can be reduced to 1/8

Conversion of .0625 & .272
.065 = 65/100, reduced to 1/15.38 (rounding to 1/16 on your scale) 1/16=.0625
.272 = 272/1000, reduced to 1/3.68 (rounding to 1/4 on your scale) 1/4=.250 (.022 smaller than .272)
5/16= .3125 (.040 larger than .272).

Halfway between the 1/4" and 5/16" marks on your scale would be approximately 9/32=.281. (much closer to .272)


Or you could just use the attached conversion chart.

Very good (cheat sheet) chart for us poor people using old machines trying to oval with 2y2's work. I added it to the wiki in case anyone wants to edit or change where it is or just learn it's whereabouts for a quick reference.
Thanks Jim

[2y2]

kart300 if the pitches were 0,0 you only need to rotate the ball and that's it, there would be no need to make any calculations at all, the program is designed to work for all other cases. Try it.

Labrat I think it's more accurate to drill the pilot hole with the ball rotated beforehand, otherwise you're adding more human factors to the drilling process. Thankyou for your comments.

[LabRat]

Labrat I think it's more accurate to drill the pilot hole with the ball rotated beforehand, otherwise you're adding more human factors to the drilling process.

I agree, but it does reinforce the first few times that the pitches are the same, and it can be a bit disconcerting hitting cut lines at odd angles until you get used to it.

[2y2]

I see two problems with these instructions to cut an oval;

1) It only works if your thumb pitch is 0 ,0
2) If you only cut in one direction the span measurement will be incorrect.

It is not possible to cut a hole with both pitches and simply rotate the ball in the jig as it needs to be repositioned to take account of the pitches using either the x axis or y axis as a 0 point
Please correct me if I'm wrong.

If I am wrong then there must be a zero point that the ball can be set in the jig, depending on the oval angle. This should be a fixed point and could be calculated from the pitch measurements and degree of oval.

Any help out there from any of the spherical mathematical genii!!

kart300 all pitches are relative to the line you start measuring from. Do this, trace line through your thumb hole, at a different angle from the center line, measure pitches relative to that line, they won't be the same, and you made no change at all to your thumb hole. The program is made so that you don't need any special and expensive equipment to make an accurate oval and you can make it without having to move both crancks, it considers the fact that while in the press and with the bit in, the pilot hole is always a vertical cylinder no matter how you orient the ball. So using this program you get the input to make it all at once, less movements means more accuracy. If you need a more technical or detailed explanation please let me know.

[elgavachon]

I agree, but it does reinforce the first few times that the pitches are the same, and it can be a bit disconcerting hitting cut lines at odd angles until you get used to it.

This is a good point.
You could also just drill the hole until the diameters are marked & then rotate the ball (when full circumference of the bit has entered the shell). Otherwise you could leave a few wrinkles on machines not calibrated perfectly & old machines using 1/8" increments & eyeballing the 32ths & 64ths.

[2y2]

This is a good point.
Just drill the hole until the diameters are marked & then rotate the ball (when full circumference of the bit has entered the shell). Otherwise you could leave a few wrinkles on machines not calibrated perfectly & old machines using 1/8" increments & eyeballing the 32ths & 64ths.

I think if you do so, then you have to drill the hole, then move the base to the output given by the program and only then you rotate the ball, trying to align it with the bit. Makes any sense?

[2y2]

Just to let you know that the program now gives the output in fractional inches also (up to 1/64")

[elgavachon]

I just made myself another thumb IT. Quickest, Easiest, I ever did it.
Not even a wrinkle to sand off!
Well done.
This deserves a thumbs up.
It is stuff like this that makes this site invaluable. I hope everyone considers helping Eric out with donations to keep it open & to keep the information coming.

Thanks 2y2.