Indexer questions

[dauntless]

Hi,

I am considering purchasing or building a 4th axis rotary indexer for my 2007 PRSstandard 96x48x24. The ShopBot website advertises three sizes: 3", 6", and 12" (PRSalpha only).

Question 1: Is that size software limited or mechanically limited? IOW, could one expand the max turning diameter by elevating the headstock and tailstock above the mount, as long as the workpiece isn't hitting anything as it rotates?

Question 2: The indexer page illustrations suggest the indexer can be oriented along either the X- or Y-axis. Is that correct?

Thanks, Stan

[waynelocke]

1. Mechanically limited. Some users have made much larger diameter ones for special projects.
2. Yes - oriented either axis.

[JimmyD]

You should at least consider the other options that are able to be done. I modified an acutal wood lathe and attached it to the shopbot.
The answer to your first question, is yes, you theoretically can elevate the head and tail stocks and increase the max turning diameter. That's not practical in the real world. You've got to be able to hold the workpiece while it is being machined. Those little indexers from shopbot will be limited real fast.

Here is a link to what I did. Good luck.

http://www.talkshopbot.com/forum/sho...-indexer-lathe

[dauntless]

Thank you both for the helpful replies! One question I have for Jimmy is why you consider it not practical to elevate the headstock and tailstock? Thanks, Stan

[JimmyD]

You can certainly elevate them. At some point, the motors cannot hold the mass in position. Presumably, you want to elevate to put bigger pieces of stock in. It depends on how much you want to elevate, the diameter and length of the stock will drive the mass.

I cut off the center line on mine, so I needed more holding power. The other benefit of using an actual lathe is then you have an actual lathe. Both drive systems are in place on my indexer/lathe.

[dauntless]

Yes, excellent thread Jim! I mainly machine 6 pcf tooling board, which is very light weight, and I figure I can make a frame stiff enough to hold the work piece. A while back I machined a 3-sided project that would have been far easier with an indexer instead of having to turn it 90 degrees and realign it, which turned out to be quite a challenge.

[coryatjohn]

A while back I machined a 3-sided project that would have been far easier with an indexer instead of having to turn it 90 degrees and realign it, which turned out to be quite a challenge.

An underused and perhaps underappreciated capability of an indexer. It's not just for indexer toolpaths.

I've used my indexer as a hold down clamp that can rotate. Since an indexer is nothing more than a clamp that can turn to any point on a circle, if you need to machine one side of an object, then turn it 30 degrees to machine another, it's a matter of MB 30 in the console and you're ready to zero. I have a 12" model and it's quite strong with very little backlash.

[dauntless]

An underused and perhaps underappreciated capability of an indexer. It's not just for indexer toolpaths.

I've used my indexer as a hold down clamp that can rotate. Since an indexer is nothing more than a clamp that can turn to any point on a circle, if you need to machine one side of an object, then turn it 30 degrees to machine another, it's a matter of MB 30 in the console and you're ready to zero. I have a 12" model and it's quite strong with very little backlash.

I know this is primarily a wood working forum, so it stands to reason people might think first of an indexer for its turning abilities, but I exclusively use my ShopBot to make 3d patterns in tooling board from which to pull molds. In that sense I am much more like a traditional VMC machinist than a woodworker. I've attached several photos showing the finished engine cover for a Swift-Honda Formula Atlantic (the project I mention above). It is full of compound curves, with negative draft on the lower sides, necessitating machining from three sides. That project used all but about an inch of my ShopBot's 24" Z to do without slicing, but for future work a 12" indexer would work fine. ShopBot sells the 12" only configured for the PRSalpha, but I imagine they could be talked into substituting a stepper for the servo. They've always been more than willing to help me customize my machine.

[waynelocke]

Jimmy's indexer looks great and Gary has developed a wealth of knowledge and has really pushed the envelope but the indexer does not need to be all that complicated. This is my setup on a 2001 0r 2 PRT which uses a Harbor Freight lathe which can be run as an indexer or a lath and has a fabricated extension which allows for an 8' piece. The stepper is whatever SB was selling at the time for indexing. I don't know the specs or anything else. It can be pulled out of the lathe to spin the lathe. I have never pushed it beyond its capacity so don't know where that line is. I use it only a few times a year but it has made me a fair amount of money over the years. Here are a couple of pics of my setup and some candlestands and a college mace.

It has really extended the boundaries for me.

[waynelocke]