Indexer confusion??

[myxpykalix]

OK, I guess i just don't "get it". All I want to do is round a piece of 3"x3" square stock down to 2.5" round. I go to the indexer tool and make the shopbot file (I think ok). Now i have my 3x3 stock mounted in the indexer.

As I understand the zeroing instructions from the way they are printed I center my bit in the Y axis to the center of the board.

But it doesn't say where you center/zero the Z axis. My assumption is that i Zzero it just like i would a flat piece on the table however when i do that and tell it to run the "test round" file i created the Z raises up, the indexer starts spinning and it starts moving in the X axis very slowly but it is at least 1" above the stock cutting nothing.

The way I read the instructions it led me to believe that i center the Z axis with the center of the stock (so if the stock was not in indexer the bit would be at the same Z height at the center of the chuck and tailstock center).
In doing that i initially Z zero to the top of the stock, then lowered it 1.5 inches and rezero'ed the Z there. That meant the tip if the bit would be in the center of the stock in the Z axis.

By doing it either way when i ran the round test file it started at least 1" above the stock and never cut wood.
Can one of you who has an indexer mounted in the X axis make a simple rounding file for me? My stock is 3"x3"x65" long I want to take it down to 2.5" round. I have a "indexer valley" like wayne lockes design so the Z height would be below the table height. Is there any other indexer tutorials or info anyone has that might help me understand this? THANKS!

[myxpykalix]

Also just for grins i Zzero'ed at the bottom of the material -3" and it STILL went to about an inch above top of material to start cutting but never hit wood.

[bill.young]

Hi John,

1) You read the instructions correctly...you need to zero the Z axis at the center of the blank which is also the center of turning. That way you'll get a consistent Z-zero location...if you zeroed from the surface of the blank and had it mounted the least bit offcenter, the z-zero location would be different depending on which side you zeroed on.

The best way to do this is to zero off of some fixed spot on the indexer...maybe the top of the chuck or the tailstock...and then measure the distance between that point and the center of turning. Most ShopBotters with indexers just create a second z-zero routine that adds that difference value to the "plate thickness" and use that Z-zero routine when they use the indexer, but you can manually do it as well by zeroing on your spot on the indexer and then using the VA command to change the Z-axis location.

2) At the moment I don't have an explanation for why the Z axis moved to the same location no matter where the Z-axis is zeroed..if I'm understanding correctly it sounds like the first time you ran it the Z-axis was at 1" or so, the second time the Z-axis was at 2.5" or so, and the third time the Z-axis was at 4". It's a new one on me...once again I think the easiest and quickest way to get going is to call support.

The way it SHOULD work is that there are a couple of settings that work together. The finished radius is actually 2 settings...the starting radius and ending radius so that you can turn tapers..., but we'll consider them just one value since you're turning a cylinder. In your case it should be 1.25"

The second is the rough radius, and you'll want to set that to the largest radius of your blank which in your case is the distance from the center of the 3x3 blank to one of the corners. Something around 2.2" or so should be good for your 3x3 blank.

Next is the safe-z setting which is above the rough blank...so that the tool can move while the blank is spinning without the bit hitting the corners. The default is .25 which should be fine.

These 3 values determine how high the Z-axis will go in the beginning so that the bit will clear the spinning blank.

One more setting that you need to be aware of is the Stepdown setting which is used to calculate if a blank needs to be cut in multiple passes. The program takes the difference between the rough radius and the finished radius (which is really the amount of material that needs to be removed to make it the finished size) and divides it into "stepdown-sized" bites and then cuts each pass at that depth. If the stepdown size is small and the amount to be removed is large it can take a lot of passes.

Sorry for the long-winded explanation but hope this helps clear it up. If you'll send a copy of your indexer file to support with a note to forward it to me, I'll be glad to take a look at it.

Bill

[myxpykalix]

Bill,
Thanks for the "long winded" explaination, I love it...thats more info than i've gleaned from the instructions to begin with so please make all your explainations that way!

Now for a confession...you know how we all do stupid things but never admit them? Well my problem was in my initial setup of the turning round file. It asked me to input the "radius" of the blank, and as Ed Lang stopped by today and reminded me, the radius is the distance to the CENTER of the blank, not the DIAMETER which I input as 3" and should have been 1.5". So it was doing just as it should have done thus it positioning 1.5" above the turning. DOH!

So now I have a round blank....YAAAAA, my first one. However here is where the next questions pop up.
I now have a 2.5" round blank. I have a 2" spiral bit. On the legacy ornamental mill in order to turn a traditional rope spiral (in first pic) it is called a 3 start spiral. As illustrated in the 2nd pic it would cut the red spiral first, move carriage back 1" then it would cut blue spiral next, repeat, then white spiral in a total of 3 passes.

I could not find any information on how to calculate it to figure out how to make a spiral.

Here is what i have. I have a 2.5" diameter round blank on the indexer (1.25" radius)

I have a 2" diamter rope molding bit (1" radius to center of bit)

My length of part is 65"

How do I figure out the "number of times the pattern wraps around the blank" to get a spiral pattern as in the first picture? Keep in mind i just barely got thru high school "readin, 'ritin, and 'rithmatic". Scott tried to help me but when he started talking about pi (3.14) I knew he wasn't talkin, cherry or apple and I just didn't understand.

If anyone can figure out the equation above:
1) I have a 2.5" diameter round blank on the indexer (1.25" radius)
2)I have a 2" diamter rope molding bit (1" radius to center of bit)
3)My length of part is 65"
Or explain it to me in extremely simple terms I would appreciate it much. Also in turning a simple rope pattern as in first pic does it do it in one pass (in the X axis) as opposed to the "3 start" as talked about here?

9156

9157

[myxpykalix]

still confused...but getting it a little.

[ed_lang]

I think I would look at the fill-in box that said number of copies.

[bill.young]

John,

If you want a specific angle of twist...one full twist every 4 inches along the length for instance...then the traditional turning option in the Indexer Virtual Tool will let you easily do that.

If you need a specific spacing between twists, though, to match a particular bit then I've uploaded a program to ShopBot Labs that does the math and creates the files for that sort of turning. If that's what you're looking for then you can get it at...

http://www.shopbottools.com/files/LabFiles/twister.htm

Bill

[myxpykalix]

Bill,
This sounds like exactly what I need. I will try it and report back my results. Thanks very much for your efforts.