Simple lathe

[brian_harnett]

I have a few pics of a simple lathe I made for my shopbot. It is not a indexer the workpiece rotates under the router.
I made this spring when I was asked to make some custom chairs with turned legs.
It worked very well and has come in handy and is very simple to build.
Its posted on the frapper link
http://www.frappr.com/shopbot/photo/434823

[jhicks]

Very cool Brian. Beautiful in its simplicity.
I know I'll be calling when I get a moment to discuss. How is the stability over long lengths?
Do you think it could manage 10' columns?
Thanks

[Allegheny (Unregistered Guest)]

Looking at those pictures reminded me of an article in an old issue of Popular Mechanics (? 1960's or even late 50's) about constructing a router lathe to turn spiral fluted columns (like stair ballusters).

The base of the lathe was essentially as Brian constructed it, with the addition of a large gear (bicycle sprocket IIRC) at one end to which the workpiece was attached. The router was mounted on a movable base held to a set of rails/pipes above and parallel to the workpiece such that the router bit was directly above and parallel to the axis of rotation. These rails/pipes were of a length sufficient to allow the router to cut along the entire workpiece.

Attached to the movable router base was a loop of cord or rope that passed over idler pulleys at each end of the contraption. At the sproket end of the lathe, the rope was turned 90 degrees and looped around a pulley. As the router/base was moved along the workpiece, it would pull the rope, which in turn would rotate the pulley. The pulley was sandwiched to a sproket that in turn would rotate the sprocket/workpiece via a bicycle chain.

By using different combinations of sprockets (i.e., the number of teeth), the "pitch" of the resulting spiral could be altered. Using no gear would allow for a straight fluted column. Turning the column to multiple positions by hand would result in a smooth round column - much easier to do with a drive motor as shown in Brian's setup.

While this was a rather crude contraption, it struck me as rather clever for the time and it could certainly be improved upon greatly by using precision sprockets and chain.

While nothing is likely to be as accurate as a CNC indexer, this thing would probably be accurate enough for stair ballusters and the like. There might also be other drive options available that might even be more accurate. Just think about the original drive system for the ShopBot and the kind of accuracy it gave.

Just a thought.

Brian

[billp]

Sure sounds like a pre cursor of the "Legacy" mill
which a few Shopbotters have in their shops.
www.legacywoodworking.com (http://www.legacywoodworking.com)
I'll bet that some enterprising 'Botter could figure a way to "cross pollinate" the two technologies....

[bkronmueller@centurytel.net]

Bill,
I've been trying to figure out how to do this for the last 6 weeks. I can't see spending 6k or more on a legacy mill to do what my bot can do. The problem that I'm having is the distance between the x-carriage and the table and the travel distance of the z-axis. I don't want rebuild the bot but it appears in order to cut a large diameter, long spindle I may need to do this. Maybe someone at Shopbot has ideas or someone in the forum. I would love to see a section in the forum for lathe and indexer work and ideas.
Bill (Merln)

[billp]

Bill,
I'll attach a picture of Wayne Locke's custom table. I think it's been posted here before, but I wouldn't know under what topic. It is a VERY clever design and gives Wayne his full table size, and also lets him use his "indexer" at full depth.
Seems like it would be a LOT less expensive to change the table rather than buy the Legacy...
8369

[marshawk]

Bill,

ShopBot sells a larger Z rail which gives us the clearance to do our turning. Take a look at our setup at: http://www.marshallsmillwork.com/shop.htm

We can turn about 12" diameter with this setup.

Just another way to do things.

Cheers!

Chip

[jhicks]

The challenge is clear and I too feel there is synergy between the Legacy and the Bot. I have a Legacy and find it OK for one offs but its a labor intensive set up with marginal tolerances compared to CNC. It does seem there should be some way to cross pollinate but I havent focused on it and keep hoping someone smarter than I will figure it out. In the mean time if there is someone out there who would like to collaborate on this, I'm open to participation in what seems like a natural marriage between the Bot and the Legacy. At this point I had resolved to just sell the legacy and move on but somehow its hard to let go of perfectly functional paid for tools.

[waynelocke]

Bill, thanks for strokes.

I used to have a legacy and it was a great tool, however. it could do nothing the indexer can't do. The Legacies seem to hold their value pretty well. You can probably sell it and pay for an indexer.

If you are talking about physically blending a Bot with a Legacy. I don't see the benefit over the indexer.

Wayne

[gene_marshall]

The only benefit I could see in a legacy is the speed at which it turns the product out.
The bot indexer is much slower.

However...the bot will do MANY things the legacy can't.
http://marshallsmillwork.com/DSCF0224.JPG
http://marshallsmillwork.com/3dartwork.htm

we also find thet the indexer runs more that any other of our bots.

Cheers
gene

[billp]

Now if you want to do some turnings from your local woodlot, (and aren't worried about dust collection) there's another option;
http://www.woodmizer.com/en/sawmills/options/lathemizer.aspx

[gene]

I have a legacy wood mill and the production is not very fast. It is a very versitile tool and i have gotten myself out of a jam a few times with it . I have turned post for fireplaces and post for in bathroom decor around the hot tub bath . it seems to me if you program your bot to do the up and down cuts along the center line of the piece being turned you could turn stair parts faster on a bot than a legacy.
Magnate sells the tooling for the legacy and have a 1 1/2 " bottob cleaning bit i use to surface my table . on the legacy i use the same bit for rounding the materials . also they have good bits for lettering . Gene

[gene_marshall]

Thanks Gene,
thats a good tip.

I was refering to a raster cut vs the legacy.
I think that the legacy is a great tool, but have never used one, so my opinion of the thing could be off target.
We generally cut raster, 200 passes/inch, at a speed of 1.75/sec(with new motor 2.25/sec).
so our turnings take quite a while.

I assumed that on the legacy, once the blank was rounded, the flutes were cut in a linear fashion.

My point was that the bot can carve columns where the legacy cannot.
I also am not sure of how complicated the legacy is to set up or repeat.
AND, since the legacy is not automated The comparison is slim.
I am sure everyone here would attest to LOVING starting the bot and letting it run.
If you would rather spend the man hours... I assume a copy attachment for a lathe wouldspin the blanks... and then you could transfer the blank to the bot(or legacy) for fluting.

But with the way we cut...
the file is simple,the peices are repeatable, and the machine runs without manpower being dedicated to it.

seriously, the indexer is a good little mony maker. If you have a woodshop, and don't have the indexer...GET ONE!
That part of the market is not something to ignore.
Gene, can you post some pix of the legacy?

Thanks
Gene Marshall
Ps, Gene, does the legacy burn the flutes at the end? The bot does not.

[jhicks]

The more I hear the more inclined I am to sell the legacy. Looks like all of you who are happy are East coast or South East. Anyone in the Midwest with an indexer I could possible get together with?
The Legacy constraints on repeatability, set up, and manual operation definately are NOT the way to go in my opinion.

[gene]

Gene ,
The legacy will burn the end so what i do is to start about 1/2" forward and reverse then go forward. the largest collum i turned on the legacy was 8" x 5.5' then set it on a square base at the corners of a tub .You can index with a legacy but if i could only have 1 machine it would definately be the bot.the legacy is a good MANUAL machine where once you have a file written for the bot then there's no room for errors. Also the legacy is gear to gear driven , if it jumps a tooth then its not going to turn out right, especally on spiral work.
Gene

[Merln Kronmueller (Unregistered Guest)]

Thanks to all of you for your help. I've decided to raise the x-axis, weld up the y-axis (different post) and replace the z-axis and do some bot work and forget the legacy. Looks like we now have our post for lathe/indexer work. Chip, your stuff looks great. Love that lighthouse.
Bill (Merln)

[marshawk]

Thanks Bill,
I appreciate the kudos.

Talk to Gordon about getting a motor with a planetary gearhead for the indexer too. We just bought one and it has made a world of difference. It is a little more pricey than the stock motor, but well worth the cost.

Cheers!

Chip