OT Rotab indexing

[tom_d]

Not sure if it was this site or an other, some one had posted a site where if you put in the number of spaces it would give you the coordinates in degrees , minutes and seconds cumulative . I think the site was from Canada could really use it. I only have a rotary table at home.

Are you looking for the degrees when positioning an even number of spaces, like you would find on a bolt circle? If so, then give this site a try: http://theoreticalmachinist.com/BoltCircleCalc It's a simple web site, so no need to download a program, and will give you the angle in degrees to a decimal, which can be converted to minutes and seconds.

[Jaakko Fagerlund]

But how do you make that "one good plate"? Easy if you have something like CNC, but then, you probably can sell the RT.

I described a method that guarantees accuracy.

You mentioned a rotary table, so I presume it has a handle with degrees marked on it.

[Paul Alciatore]

But how do you make that "one good plate"? Easy if you have something like CNC, but then, you probably can sell the RT.

I described a method that guarantees accuracy.

Or just make one good plate and be done with it, no need to make it again and again.

[Jaakko Fagerlund]

Most rotary tables can be fitted with indexing plates, just like the ones used on indexing heads. I plan to do this for mine when I get the chance.

If you are worried about making accurate hole circles, it can be easily done in any shop using only the rotary table itself. The worm gear in the table acts like an accuracy amplifier when making hole circles so you can start out with a very, VERY inaccurate one and two generations later have one that is as accurate as your rotary table itself is. You can do it like this:

For each number of holes you need in a circle:

1. Mark out a circle and divide it by HAND. Do it as accurately as you can without taking too much time but don't worry about accuracy at this point. If each hole is +/- as much as one degree, you will be just fine. They do not even have to be evenly spaced. Drill those holes.

2. Use that rough, 1st generation plate to make a second generation plate. Now each hole on that plate will be 40 or 90 times more accurate due to the division by the worm gear. So, +/- 1/40 or 1/90 of a degree. Take a moderate amount of care in making this plate.

3. Finally use the second generation plate to make a final, third generation. At this point you want to be very careful. Watch backlash at all times. This third generation plate will again be 40 or 90 times more accurate than the second generation one. So it will be +/- 1/1600 or 1/8100 of a degree. That translates to 2.25 arc seconds or 0.44 arc seconds. Unless you have a really expensive rotary table, it will not be that accurate. Mine is specified as +/- 30 arc seconds and reads to the nearest 10 arc seconds.

Since they will only be used once, for making the third and final plate and each hole will only be used once; the first and second generation plates can be made with aluminum or plastic. You could even use plywood for the first generation plate. I would use a good steel alloy for the third generation plate.

Or just make one good plate and be done with it, no need to make it again and again.

[SGW]

OpenOffice, which is free, will run the spreadsheet just fine: http://www.openoffice.org/

You don't need Microsoft Office...for anything.

[Paul Alciatore]

Most rotary tables can be fitted with indexing plates, just like the ones used on indexing heads. I plan to do this for mine when I get the chance.

If you are worried about making accurate hole circles, it can be easily done in any shop using only the rotary table itself. The worm gear in the table acts like an accuracy amplifier when making hole circles so you can start out with a very, VERY inaccurate one and two generations later have one that is as accurate as your rotary table itself is. You can do it like this:

For each number of holes you need in a circle:

1. Mark out a circle and divide it by HAND. Do it as accurately as you can without taking too much time but don't worry about accuracy at this point. If each hole is +/- as much as one degree, you will be just fine. They do not even have to be evenly spaced. Drill those holes.

2. Use that rough, 1st generation plate to make a second generation plate. Now each hole on that plate will be 40 or 90 times more accurate due to the division by the worm gear. So, +/- 1/40 or 1/90 of a degree. Take a moderate amount of care in making this plate.

3. Finally use the second generation plate to make a final, third generation. At this point you want to be very careful. Watch backlash at all times. This third generation plate will again be 40 or 90 times more accurate than the second generation one. So it will be +/- 1/1600 or 1/8100 of a degree. That translates to 2.25 arc seconds or 0.44 arc seconds. Unless you have a really expensive rotary table, it will not be that accurate. Mine is specified as +/- 30 arc seconds and reads to the nearest 10 arc seconds.

Since they will only be used once, for making the third and final plate and each hole will only be used once; the first and second generation plates can be made with aluminum or plastic. You could even use plywood for the first generation plate. I would use a good steel alloy for the third generation plate.

[danlb]

Duckman, it works for me using firefox in Linux.

Go to https://sites.google.com/site/bluewa...xing-converter. Enable javascript for google.com. Click on the link at the bottom. For me that was https://drive.google.com/file/d/0B4R...ew?usp=sharing but that may be dynamically created.

Once you click on that it will bring up an example with 25 steps of 14 degrees. At the top is a box to "Open with gooogle sheets" Click on that and you get on online spreadsheet program with the XLS spreadsheet loaded. THAT is where you can change the number of steps. No need for MS Office.

[loose nut]

Most spreadsheet programs should open it. See above, post 9.

[duckman]

OK I found it was the blue water site and then found the reason it wouldn't work I don't have Office and you need office to open it, so looks like ISOOL.

[bjmh46]

FWIW, anyone running linux can use Marv's utilities under dos emulator, or "dosemu". It's in most repositories. Simple to run--I just keep the utils in a folder in the home directory. Open the folder, find the appropriate exe, right-click, open with dos emulator. Thanks Marv!

[H380]

This is the fork that is still being developed. 100% free.

https://www.libreoffice.org/download/download/

[loose nut]

Duckman, if you have a tablet or phone (Ipad or Iphone for sure. Android or any MS device should work) you can download the MS Office Excel App for free and run the spreadsheets on them. You can also run it on the Google office apps for free or if you use Bing you can sign up to use Excel on line for free. It should work OK on Open Office or one of the other open source spreadsheet programs that are compatible with Excel. It might format a bit differently.

[duckman]

Thanks guys went to all the sites none have the program that I'd seen bluewater needs office to open I don't have it, engineersedge doesn't use degrees and minutes. Guess I need to keep looking.

[H380]

http://www.engineersedge.com/calculators.htm

[mars-red]

I have a simple web page that gives exactly this, for any number of divisions given, and shortly after I put that together I turned it into a quick and dirty native android app so I could use it on my smartphone during manual dividing operations. I never bothered putting it in the store because I figured most people probably already used other machining phone apps that gave the same functionality, so without knowing if there was any interest I wasn't going to spend the money to open up an account to be able to publish to the store.

If anyone wants the app to install through "untrusted sources", I'll happily provide it (PM through the forums is probably the best way to let me know). If there's enough interest I'd consider paying the $20 or whatever it is to be able to publish it to the app store.

-Max