rotary index questions

Hi,

I'm very interested in adding a rotary indexer to my arsenal. A few questions for those who already have one with the handibot:

1) It mentions a 3" diameter, - but 3" diagonal on a square blank. I'm most likely to cut square blanks - and if my calculations are correct, I'll fit about a 2"-2 1/8" square on the 3" indexer - meaning about a 2" round blank that I could make myself, correct?

2) Do the jaws actually hold that full 3" diameter? I've seen some pictures/videos where a pocket had to be made on the end of the blank in order to grip it from the inside of that pocket. Can someone tell me the max size I can fit without having to do that?

3) With the accessory base, how long of a piece can I actually index? I look at the accessory base and think to myself that I could make a longer slotted table to run through it. Could I theoretically do about a 3 ft long piece with a custom slotted table?

4) How little can you make 'tabs' on either end of the stock? Example: if I wanted to machine a small 3d model in the blank and leave 1/8" cylinder on top and bottom, then I could cut it from the blank and sand it.

Thanks!

RS Wrote:
-------------------------------------------------------
> Hi,
>
> I'm very interested in adding a rotary indexer to
> my arsenal. A few questions for those who already
> have one with the handibot:
>
> 1) It mentions a 3" diameter, - but 3" diagonal
> on a square blank. I'm most likely to cut square
> blanks - and if my calculations are correct, I'll
> fit about a 2"-2 1/8" square on the 3" indexer -
> meaning about a 2" round blank that I could make
> myself, correct?
The 3" rating is quite arbitrary. You can cut what you can get to rotate without bumping and doesn't run you out of Z movement. I bet you could cut 4" dowel with the right set up. That said, always start simple and start by cutting round dowel.
>
> 2) Do the jaws actually hold that full 3"
> diameter? I've seen some pictures/videos where a
> pocket had to be made on the end of the blank in
> order to grip it from the inside of that pocket.
> Can someone tell me the max size I can fit without
> having to do that?
Just as there is a learning curve to mounting parts for flat cutting there is a learning curve for rotary cutting. The chuck that comes with the indexer is not very versatile but you can buy a nice one with interchangeable jaws from "Penn state" for around $100. You can also make custom mount solutions. I often 3d print mount jigs.
>
> 3) With the accessory base, how long of a piece
> can I actually index? I look at the accessory
> base and think to myself that I could make a
> longer slotted table to run through it. Could I
> theoretically do about a 3 ft long piece with a
> custom slotted table?
I have not tried this but yes the tray locks up very tight and repeatable so you should be able to cut longer pieces if you can figure out how to code for this.
>
> 4) How little can you make 'tabs' on either end of
> the stock? Example: if I wanted to machine a
> small 3d model in the blank and leave 1/8"
> cylinder on top and bottom, then I could cut it
> from the blank and sand it.
This is strictly a software thing. I am using Desktop Proto and it has provisions for tabs. Vcarve Pro or Aspire has provisions for tabs if you are using a cut, turn cut scheme but nothing I know of for true rotary cutting. Fusion 360, sorry, I have no idea as I have not explored the CAM side of it yet.
>
> Thanks!

The 3" thing is a point of debate even within the shopbot office. The old woodworkers point out that a 3" swing means that you should be able to turn a square bar with 3" sides. To me it seems to make more sense to call out the distance between the center of rotation and the bed (plus some allowance). However, to avoid disappointing anyone, I chose to go with the most conservative definition of the 3" sqaure (meaning a 4.25" circle).

With the jaws on the chuck reversed, I measure a 2.5" max diameter. What we usually do here when holding larger wood--is to bolt a little wooden hockey puck onto the end that is being clamped in the chuck.

I've indexed a 10" part through the base--the one thing that I would change if I did it again would be to have a little overlap between the two parts of the cut. My part ended up with a little ridge where the ball nose bit stopped at the end of the first cut and picked up at the start of the next. I was able to sand it away but it still bugged me that it wasn't quite right.

I think the tabs question sort of depends on your material. I Tend to go with bigger tabs because my parts are usually flat on top and bottom (like a chair leg). I wouldn't generally go smaller than 0.5" though--just to be sure that nothing breaks at the last minute.

Ok - Just want to be clear.

On the shop description, it mentions the rotary axis can take up to 3" cylindrical parts; but you are saying it can actually take a 3" square piece of stock - not a 3" diagonal piece (which would be closer to 2" square stock)?

That is correct--3" square stock.



Edited 1 time(s). Last edit at 07/30/2016 12:02AM by Brian Owen, ShopBot.