# Measuring Distance on Circle Circumfrence

 Forum topic by Jim Crockett (USN Retired) posted 04-11-2012 02:37 AM 1404 views 0 times favorited 10 replies
 Jim Crockett (USN Retired)852 posts in 2389 days 04-11-2012 02:37 AM I am planning a holder/organizer to hold all of my forstner bits. I want to make it circular with hole spacing so that each bit will have 1/4” clearance from both sides. Have all of the measurements completed but began wondering how I am going to measure point-to-point distances (to 1/32”) on a circle’s circumfrence. Sure, I can use a rule and measure straight-line distance and that will probably be close enough, but there must be a good way to measure along the circle’s edge. Any thoughts, suggestions, or sarcastic remarks? -- A veteran is someone who, at one point in his/her life, wrote a blank check made payable to "The United States of America," for an amount of "up to and including his/her life".

## 10 replies so far

 crank493434 posts in 1627 days #1 posted 04-11-2012 02:40 AM Use a compass.Swing an Arc at the required length from hole to hole. -- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H kizerpea746 posts in 1024 days #2 posted 04-11-2012 04:59 AM yes there is a…. cloth tape used for sewing an making clothes..1st u need to know the dia of the circle u want to make…example 20”dia circle…20×3.14 =62.8 in around the circle…that may b right i have been up to long to think clear. -- IF YOUR NOT MAKING DUST...YOU ARE COLLECTING IT! SOUTH CAROLINA. Doss779 posts in 921 days #3 posted 04-11-2012 05:17 AM Is there any way you can post up a sketch of the holder and the measurement you’re trying to figure out? I can’t seem to visualize what you are talking about… but’s it’s going to be simple math when I see how you envision it. -- "Well, at least we can still use it as firewood... maybe." - Doss a1Jim112104 posts in 2233 days #4 posted 04-11-2012 05:42 AM Since a circle has 360 degrees I would use the compass to walk it around the circumference and divide it up into equal measurements until you get what you want. I guess I would start by dividing it in half. -- http://artisticwoodstudio.com Custom furniture dustbunny1149 posts in 1951 days #5 posted 04-11-2012 09:05 AM Google Sketchup.Fast, easy, and accurate.Free download.Do the layout and print a template 1:1 scale. Lisa -- Imagination rules the world. ~ Napoleon Bonaparte ~ http://quiltedwood.com Jeremy Greiner568 posts in 1428 days #6 posted 04-11-2012 10:21 AM Woo hoo math time!Measuring from center point of the bit, to the center point of the next bit will be just as accurate, realistically this is how circles are produced on computers, just with a ton more points. The key is making sure that it’s always equal distant from a primary center point, the center of the circle. You need to calculate out the radius of the circle, to do that .. measure the size of all your forstner bits together, and add 1/4’’ for each forstner bit. For example:2’’ + 1 1/2’’ + 1’’ + 3/4’’ + 1/2’’ + 1/4’’ = 6’’ + (1/4’’ per bit) = 7 1/2’‘ This is the circumference of your circle, from that you can calculate the radius by taking the circumference dividing it by PI, then dividing it by 2 7.5 / 3.14 = 2.388535031847134 / 2 = 1.194267515923567 (you can round to the nearest 32nd, 16th or 8th if you want, just always round UP, if you round down your could find your circle too small) Rounding to the nearest 16th would be 1 and 4/16ths or 1 1/4’‘ Our radius will be 1 1/4’’ .. now that we know this, draw out a circle with a 1 1/4’’ radius either using a string, or a compass. With the circle drawn out pick an arbitrary point on the circle, this will be your start point. (A on the picture)From your start point, take your ruler and measure out the distance to your next point. The distance from 1 point to the other, is half of the width of bit 1 + half the width of bit 2 + 1/4’‘ Here is a list of distances, based on the bits above.1’’ + 3/4’’ + 1/4’’ = 2’’ 3/4’’ + 1/2’’ + 1/4’’ = 1 1/2’‘1/2’’ + 3/8’’ + 1/4’’ = 1 1/8’‘3/8’’ + 1/4’’ + 1/4’’ = 7/8’‘1/4’’ + 1/8’’ + 1/4’’ = 5/8’‘ So after I just pick out point A, I measure 2’’ from A on the circle, this is point B, then measure 1 1/2’’ from point B along the circle etc.. repeat until all dots are are drawn. Here is a final picture of all the dots. Once you have the dots, those are the center points for your drill bits you just have to drill them. Hope this helps, if you have any questions feel free to let me know :) -jeremy -- Easy to use end grain cutting board designer: http://www.1024studios.com/cuttingboard.html Tootles704 posts in 1158 days #7 posted 04-11-2012 10:36 AM I agree with Lisa – Sketchup. But when working with circles for applicatiions like this, it is worth increasing the number of segments in the circumference of the circle. The standard is 24 so the endpoints of the segment lines are 15° apart. All you do is select the circle tool and immediately type in a bigger number – 60 will give you 6° between segment end points, 180 will give you 2° between segment endpoints etc. -- I may have lost my marbles, but I still have my love of woodworking Tootles704 posts in 1158 days #8 posted 04-11-2012 11:20 AM Careful Jeremy – the straight line distance betwee A & B is 2” in your photo above, but if the circle radius is 1 1/4”, then the segment length is 2 5/16”. What this means is that the radius calculated by Jeremy may be a liitle small. It would take a bit of trial and error to work it all out. -- I may have lost my marbles, but I still have my love of woodworking Jeremy Greiner568 posts in 1428 days #9 posted 04-11-2012 11:46 AM It’s not a little small, it’s actually a little big due to rounding. Here is a picture of the ring with the forstner bits on them. If you drill the holes with the forstner bit you intend to put in that hole, centered on the dot you made, the spacing is pretty close to perfect. -- Easy to use end grain cutting board designer: http://www.1024studios.com/cuttingboard.html Tootles704 posts in 1158 days #10 posted 04-11-2012 11:58 AM Okay, you’re right. I’ve done it mathematically using angles they way I calculated the segment length. It does work out a little bigger, not smaller. Best of all, the emphasis does also turn out to be on “little”. Good Job Jeremy -- I may have lost my marbles, but I still have my love of woodworking

## Have your say...

 You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

 Garage Rooftop Deck 09-12-2014 05:38 PM Window and siding 09-08-2014 12:56 PM Guest Bath - Contemporary Look 07-13-2014 06:51 PM French Doors 06-10-2014 09:02 AM Rotten Door Jamb Repair 05-20-2014 12:47 AM Window replacement 05-05-2014 03:50 PM Upper level deck 04-27-2014 04:23 AM My kitchen 04-22-2014 02:39 PM Daughter's bathroom 04-22-2014 01:04 PM Daughter's ramp 04-22-2014 12:12 PM Bee - Cottage.... 09-07-2014 04:14 AM Stone Staircase 08-31-2014 04:45 PM pond house 08-21-2014 08:55 PM enclosed, raised bed, herb garden 08-05-2014 03:04 PM Garden Chime 07-29-2014 02:53 PM Tomato Plant Support (in a raised bed) 06-10-2014 02:01 AM back yard 06-07-2014 09:22 PM patio privacy arbor, trellis 05-29-2014 08:13 PM garden bridge,new pond, & sacred place 05-28-2014 01:34 AM Outdoor Garden Shed Shower. 05-22-2014 02:27 AM