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Forum topic by Tom66 posted 03-30-2015 09:15 PM 1198 views 0 times favorited 22 replies Add to Favorites Watch
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Tom66

6 posts in 618 days


03-30-2015 09:15 PM

Topic tags/keywords: lathe application advice question lathe turning

I’m a newbie here hoping to get some advice on tooling for a unique wood-turning application from the many gurus I see posting here.

We’re looking to transition into higher volume production on an oak barrel head product we make from scratch as a carved sign, wall clock, serving tray, lazy susan, etc. We start with an 18 or 21” round plywood blank, then glue on a perimeter of 24 ~2” long oak or alder “side staves” which have been edge beveled so that they fit very tightly around the perimeter. The goal is to turn this assembly to shape the outside into a smooth tapered bevel so that a steel barrel hoop will fit down snugly over it, and also to shape the inside of these side staves with a decorative bevel – known as a “chime” in the cooperage world. See before and after milling photos attached.

We currently use a home-made “router-lathe” I built with a variable speed DC motor driving a slow turning platter which holds the barrel head assembly, while two slide-mounted routers mill the inner and outer bevels. This works ok for low volume production but is pretty mickey mouse, lightweight, and labor intensive.

So here’s my questions:
- Do I even need live cutters ? Can I turn this assembly on a wood or metal lathe fast enough to use non-live tooling ? I guess it depends on how well the side staves are glued on – good I think – now that we’ve dialed in the glueing process. Any thoughts on an optimal rpm ? ...optimal cutting tool ?
- Assuming non-live cutters, how to “semi-automate” ? I envisioned buying a heavy old metal engine lathe, and mounting the cutters on the carriage which would move “automatically” into the turning head to mill the outside and inside bevels in a single pass. Any thoughts on that ?

Finally, if anyone out there – ideally not too far from Medford Oregon, is willing and able to help me prototype this solution I’d be happy to pay for the help, and/or buy their suitable lathe.

-- tom@ewoodart.com


22 replies so far

View OSU55's profile

OSU55

1058 posts in 1454 days


#1 posted 03-30-2015 09:49 PM

Need live cutters – no
Turn fast enough on a lathe – yes, it’s a function of surface speed, 18” rough at ~330rpm, finish ~ 500 rpm

This is called segmented turning – search and you’ll find quite a lot of info. I do this type of turning, and use Titebond III glue without issue. I’m not sure how well the outside ply will hold, I’ve never tried it with plywood. The cutting forces are a function of the cut depth, so there’s adjustment available. Take a look at this Ring Master Tool http://www.ringmasterlathe.com/store/ring-master-tool-a-accessories?page=shop.product_details&flypage=flypage.tpl&product_id=139&category_id=2. It says for 18”, but they may make one for you larger. This may also give you some ideas of how to build a custom machine – look around their site at their lathes. A larger metal lathe with at least 22” swing will have the automation you desire built into it and can easily have some simple HSS cutters adapted, but the lathe will be expensive. Carbide inserts for wood are also available but do not leave as good of a surface finish. With a metal lathe with a tool changer, you could use carbide for roughing and HSS for finishing.

My biggest question is work holding. If a 1/2” hole in the center is allowable, or a 1/2” plug, not a problem. How thick is the ply and can the opposite side have screw holes? Look up faceplate. Otherwise you will need a block attached (called a glue block), usually by glue, to then hold with a chuck, attach a faceplate, or use a screw chuck. This then involves an efficient means of attaching and detaching the glue block and reusing the glue blocks.

View Wildwood's profile

Wildwood

1886 posts in 1599 days


#2 posted 03-30-2015 09:49 PM

Yes, a wood lathe could do that lot faster with turning skills and easy to change profiles if you like. Even faster if round those blanks on a band saw to get them round first. You will have to use traditional spindle or bowl turning tools. Problem will run into is swing of the lathe and mounting those blanks to turn over the ways. Old wood lathes will accommodate out board turning to avoid problem with swing but will need left hand threaded faceplate. New lathes with sliding headstock will also solve that swing problem with right hand threaded faceplates. Both old and new wood lathes would need an auxiliary tool rest!

If look long enough might find a metal lathe with enough swing to handle those blanks over the ways and let use cutters vice turning tools. An old metal lathe will cost a small fortune.

Ring-master thingy to light to handle the weight of your blanks.

You might find a CNC router that will get the job done lot easier. Blank lays flat and cuts very repeatable once dialed in.

-- Bill

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Tom66

6 posts in 618 days


#3 posted 03-31-2015 12:22 AM

Thanks for the fast and great replies:

RE beveling with a “bowl turner” style wood lathe: Certainly lower cost approach than metal engine lathe that size. Any pointers to jigs, tools, holders to facilitate repeatable cuts ? Is there a turret lathe like solution for wood lathes ?

RE work holding: Plywood may be as thin as 1/2”. On current home-made router-lathe we use 18” custom faceplate with 4 holes drilled around perimeter so that self-tapping screws go thru the holes, thru the plywood, and into the side staves. These holes are later hidden by rubber feet installed on back.

RE beveling with CNC router: We have a shopbot 3 axis cnc machine and considered this. Would work well for the inside bevel but could only do the outside bevel with a stout 6-7 degree tapered bit – which does not seem to exist. Any help on that ?

-- tom@ewoodart.com

View REO's profile

REO

889 posts in 1539 days


#4 posted 03-31-2015 12:56 AM

first thought would be to vac chuck the part with a disk made to just fit the inside rad of the head. routers would be the fastest if the machine were made properly. often with router lathe setups the router is being used in the wrong plane to get good results on a particular piece. what is your current production? how fast do you need to produce them. I realize that “the faster the better” but realistically what is a solid number for the future. can you supply a cross section of the “head” and the cuts you want to perform? I use converted or custom lathes in my shop. the lathe in my avatar was a 14×96 metal lathe but we turned 2 feet x 16 feet on it.

View Rick M's profile

Rick M

7922 posts in 1845 days


#5 posted 03-31-2015 03:41 AM

I’m not sure a buying lathe is the best starting point if you are looking at high production. The reason is that most workshop machinery is designed for flexibility and to work with a variety of projects. If you are going to have one product then a purpose built machine would certainly be faster and more efficient. I would contact a mechanical engineering firm that designs for manufacturing and let them tell you.

-- http://thewoodknack.blogspot.com/

View Bluepine38's profile

Bluepine38

3341 posts in 2550 days


#6 posted 03-31-2015 04:01 AM

JoeinGA posted this link in answer to another lathe question. I gives you one idea for building a big bowl
lathe.

http://www.winburn.com/BowlLathe.asp

You might be able to adapt this idea or add to it to make something that will work.

-- As ever, Gus-the 77 yr young apprentice carpenter

View Wildwood's profile

Wildwood

1886 posts in 1599 days


#7 posted 03-31-2015 10:12 AM

For type turning you want to do length of the lathe not important. So a homemade lathe with enough swing will work as well or better than what is available commercially. You can check out Google or Bing images for examples.

Both Powermatic & Oneway make a lathe claiming 24” swing over the ways inboard. Powermatic has a sliding headstock, Oneway has a fixed headstock. Woodturners prefer turning inboard because those optional commercial auxiliary tool rest available expensive and not safe without modifying. Many turners prefer to make their own!

Here is a picture of outboard turning with, no idea of the swing with this set up. Remember outboard turning requires left hand threads & inboard turning requires right hand threads.

Powermatic lathe 24” swing over inboard and less over tool rest base. See links for specs and manual for optional out board tools rest that would allow you to turn 88” items at back of manual.

http://www.equipmentsalesandsurplus.com/v/vspfiles/photos/1791-254-2T.jpg
http://www.powermatic.com/us/en/p/4224b-lathe-with-lamp-kit/1794224K
http://content.powermatic.com/assets/manuals/1794224B_man_EN.pdf

Oneway makes 24×36 wood lathe that might also work. See site for details! http://www.oneway.ca/lathes/2436lathe.htm

For mounting blanks on the lathe have to decide between 4-jaw scroll chuck, faceplates, or vacuum chucking. Faceplates cheaper than 4-jaw chuck, so could buy 3 or 4, 8” faceplates for lot less money. Each method requires Blank Prep before mounting!

Turning tools come in traditional HSS gouges, skew, parting tools that require resharpening. Or could go with carbide tools that require replacement cutters.

-- Bill

View OSU55's profile

OSU55

1058 posts in 1454 days


#8 posted 03-31-2015 11:54 AM

Yea a vacuum chuck might well be the best work holding, and can be pieced together by you. I am not aware of any commercially available wood lathes with auto feed and a tool changer. I think you need to look at metal lathes. I think there are a few large mfr’s up in your region making wood products. Find some that do automated turning and try to get a tour and/or talk to their tooling/engineering/maintenance guys about the equipment. Any large scal wood bowl/platter mfr’s up there? The actual cutters are easy, and the tool holders not hard at all. The automation is your challenge and expense.

Please post where you end up. I do large scale metal machining (millions pcs/yr) for a day job and woodworking as a hobby. I’m always interested in large scale wood processing.

View Tom66's profile

Tom66

6 posts in 618 days


#9 posted 03-31-2015 07:22 PM

Thanks for all the suggestions. They are a bit all-over-the-map, but much appreciated. I am following up on 2 or 3 of them.

Seems like most straightforward approach is to use our cnc router. Again, inner bevel is easy but outer bevel would require 6 or 7 degree tapered bit. No such cnc bits but can I use Tapered end mill made for milling machine ?

In answer to REO: Current home-made router lathe can produce one piece in about 15 minutes – due to labor intensive part hold down and manual crank operation of two routers one after the other. Would like to get semi-automated process down to under 5 minutes per unit. Here is sketch showing cross section of “barrel head” and the two bevel cuts: 1) outside bevel 6.5 degrees, 2) inside bevel 45 degrees.

-- tom@ewoodart.com

View REO's profile

REO

889 posts in 1539 days


#10 posted 03-31-2015 10:54 PM

hollow shaft gearbox so you can incorporate the vac chuck. two routers set in a jig to cut both bevels at the same time and a pivot that ends the swing at the proper location. five minutes absolutely possible!

what routers do you have?

View Nubsnstubs's profile

Nubsnstubs

826 posts in 1195 days


#11 posted 04-01-2015 12:03 AM

Use a rim chuck attached to a face plate to help hold the piece up against the head stock. Use a live center with a flat disc instead of a point or cup ring. That will provide the support to keep the piece between centers from taking flight. Make a duplicator that incorporates a quick change tool holder. Set it up once, and you’re spinning out these trays faster than you can assemble them. . ............. Jerry (in Tucson)

-- Jerry (in Tucson)

View Tom66's profile

Tom66

6 posts in 618 days


#12 posted 04-01-2015 07:31 PM

Thanks again for all the great suggestions. Since we have a cnc router, and since I’ve found no reason we can’t use a 7 degree tapered end mill built for milling machines for the outer bevel, I’ve ordered some bits and plan to test this solution. Tool change on every unit will be a pain…

-- tom@ewoodart.com

View Rick M's profile

Rick M

7922 posts in 1845 days


#13 posted 04-02-2015 03:24 AM

I picture something like this, where you load each lid, press the drive wheel against the edge to spin it while the routers trim it. Obviously lots of specifics missing like how to mount the routers but this would be fast, under a minute per lid.

-- http://thewoodknack.blogspot.com/

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REO

889 posts in 1539 days


#14 posted 04-02-2015 10:19 AM

hey rick your good with the drafting!

View Rick M's profile

Rick M

7922 posts in 1845 days


#15 posted 04-02-2015 05:13 PM

Thanks, though that drawing is just a quicky sketch. Once upon a time in a galaxy far away I was trained as a draftsman.

I picture the drive wheel running continuously and being on a lever. You drop the lid into place which registers against the right side wheels, press the drive wheel against the edge and spin the lid. The routers could maybe be on a foot activated lever and raise into position, running continuously. Probably a more elegant way of doing it, I’m no mechanical engineer. It just seems easier to build from scratch than trying to retrofit a lathe.

-- http://thewoodknack.blogspot.com/

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