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spiral spindle cutter

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john constable18/06/2018 19:15:48
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High everyone! New member, first post and first project!

I want to cut spirals on spindles (aka barley twists) in wood and it looks like its going to need a custom tool.

It's basically as 'simple' as replacing a lathe tool with a router and getting the work to rotate slowly in sync with the tool moving along the bed and not at a cutting speed. Hope that makes sense.

All of this is just for miniature work on spindles up to 1.5" thick and up to 6" long so a full sized lathe is overkill.

A metal work lathe that can cut threads will sync rotation and tool travel but I can't see how you would get the work to rotate slowly enough, the pitches seem to be too small and from what I can see see I couldn't justify such a large cost. A smaller one would be cheaper but would it cut threads and support a dremel?

Having set metalworking lathes to one side, I looked at woodworking lathes. On full sized older and cheaper lathes you can disconnect the belt drive and turn the work by hand but you can't sysnc tool movement to rotation. Smaller lathes have a direct drive motor which wont turn slowly with any kind of torque but there's still no easy way of syncing them.

My current plan is to bolt a milling table onto a drill stand with a dremel in it and fabricate a headstock and tailstock to hold the work. Then I can turn the headstock (large chuck?) by hand and link the rotation of the headstock using a sprocket and chain arrangement to the bed advancing wheel to move the work under the tool.

So, I'm really looking for ideas - alternative ideas that might fit my skills and budget to achieve my desired result or just where to get suitable sprocketage and chainage from.


A couple of other thoughts - the pitch of the spiral is in the order of 1:1 (that's the diameter of the spindle in tool movement versus number of rotations) but of course I really need to vary that slightly to increase and decrease the spiral pitch. And I looked at a stepper motor solution but its an area i'm unfamiliar with and I know its going to involve controllers, iterfaces, pcs and software etc so I dont think it would be an easy or inexpensive path for me .

Any advice offered gratefully received!

JasonB18/06/2018 19:59:35
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Have a search for "legacy ornamental mill" or the old Trend router lathe to see how with some pulleys and cables the spindle is linked to the tool movement

Michael Gilligan18/06/2018 20:09:46
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Predictably enough, Jason beat me to it

I think the Trend RouterLathe uses the operating principle that you need, John

Here, with a ridiculously long URL, is the Instruction Manual: **LINK**

MichaelG.

 

 

Edited By Michael Gilligan on 18/06/2018 20:10:27

john constable18/06/2018 20:30:03
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Believe it or not I had a TRL but it got lost in a house move before I had the chance to use it and I never had the opportunity to replace it.

If dremel made one that would be great but that arrangement of strings and pullys looks harder for me to achieve than using a couple of cogs and a chain - especially on the scale I need to work at.

larry phelan 118/06/2018 20:34:20
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Hi John,

I have an old Trend catalog buried deep [not seen it for years],in which the is a machine,using a router to do just that kind of work. The router is arranged to move along the workpiece while the work revolves. The speed of the advance is dictated by a wheel,turned by hand.

Might be worth checking out Trend

JasonB18/06/2018 20:40:16
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Posted by john constable on 18/06/2018 19:15:48:

Then I can turn the headstock (large chuck?) by hand and link the rotation of the headstock using a sprocket and chain arrangement to the bed advancing wheel to move the work under the tool.

Due to the gearing you will find it easier to move the tool (mill table handwheel) and have that drive the chuck. This is how very coarse threads can be cut with a screwcutting lathe, the leadscrew is turned by hand and that is geared to slowly turn the spindle. So small gearwheel on the mill table and a big one on the spindle to get the pitch you require.

Edited By JasonB on 18/06/2018 20:40:53

john constable18/06/2018 20:46:41
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I think I see what you mean. So it's basically what I was proposing but instead of turning the chuck by hand I'd turn the table advance knob by hand? Either way the tool would still be static in the drill stand.

Would some kind of flexible shaft be a mad idea? Too much play?

john constable18/06/2018 20:51:31
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Posted by larry phelan 1 on 18/06/2018 20:34:20:

Hi John,

I have an old Trend catalog buried deep [not seen it for years],in which the is a machine,using a router to do just that kind of work. The router is arranged to move along the workpiece while the work revolves. The speed of the advance is dictated by a wheel,turned by hand.

Might be worth checking out Trend

That's the trend router lathe that the guys have pointed me towards. Its quite a complex arrangement of runners, pulleys and strings. I think it would be hard to make one from the few pics available but I dont think it would be suitable in a smaller form for the size of work i need.

Michael Gilligan18/06/2018 21:33:03
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John,

I've just been browsing around, and found this page: **LINK**

https://stusshed.com/tag/beall/

The first couple of pictures are another [perhaps the original?] routerlathe-style device ... but then it gets more interesting: Maybe sufficient to get your inventive streak going.

MichaelG.

.

Edit: Here is Beall's website: 

http://www.bealltool.com/products/penwizard/penwiz.php

Where you will find detailed instructions and some excellent photographs angel

Edited By Michael Gilligan on 18/06/2018 21:41:20

john constable18/06/2018 23:05:29
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Posted by Michael Gilligan on 18/06/2018 21:33:03:

John,

I've just been browsing around, and found this page: **LINK**

https://stusshed.com/tag/beall/

The first couple of pictures are another [perhaps the original?] routerlathe-style device ... but then it gets more interesting: Maybe sufficient to get your inventive streak going.

MichaelG.

.

Edit: Here is Beall's website:

**LINK**

Where you will find detailed instructions and some excellent photographs angel

Edited By Michael Gilligan on 18/06/2018 21:41:20

Fantastic! You star! A bit worried it'll only do pen-barrel size stock but maybe I can stretch it. Holding stock will need some though because pen barrel blanks are hollow and held in a mandrel.

Not cheap but it looks worth the money and probably cheaper than building my own from scratch.

Thanks, Michael.

john constable18/06/2018 23:13:28
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thought I'd post these for your interest.

Ive listed them in reverse so you can see the results first then how he built it.

I wonder if you can get tiny bikes complete with gears?

https://www.youtube.com/watch?v=v1kpXPzYhoM

https://www.youtube.com/watch?annotation_id=annotation_2902547835&feature=iv&src_vid=v1kpXPzYhoM&v=2eDaGgi1lpQ

JasonB19/06/2018 07:33:18
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This is how it can be done on a mill which is what your drill and milling table will effectively be.

The large handwheel has gears just inside it which are driving the feed screw on the mill table and then the work is being rotated via a dividing head.

You would just need a simple setup between the handle and spindle, say you wanted a 3" pitch to your spiral and one turn of the table handwheel moved it 0.100" then a 30:1 ratio would give you 30 turns of the handwheel (30x0.1=3 ) to 1 turn of the spindle. As the leadscrew and spindle axis will be parallel it should not be so hard to set up.

Martin Kyte19/06/2018 08:46:30
1428 forum posts
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If you are going to do it on the lathe you need to drive the lead screw. If you have a hand wheel on the lead screw just wind that and let it drive the chuck.

regards Martin

Andrew Johnston19/06/2018 08:52:48
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Posted by JasonB on 19/06/2018 07:33:18:

This is how it can be done on a mill which is what your drill and milling table will effectively be.

Seems a slightly odd way to do it as he seems to be driving the dividing head through the worm reduction. It would be simpler to drive the table leadscrew directly and have a reduction gear direct to the dividing head spindle.

Andrew

JasonB19/06/2018 10:10:23
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He does seem to be doing some sort of dividing as well as he can be seen turning the div head handle a number of turns while the mill table is not being moved. Have a look about 2mins into the video. Possibly getting the correct tooth profile by using co-ordinates consisting of Z-height and an angle either side of his starting point.

A rotary table may have been easier for just a helix as the end of the R/T spindle is accessable and could easily be extended to take a gear/pulley that lines up with the mill table handwheel. 

Edited By JasonB on 19/06/2018 10:31:08

Edited By JasonB on 19/06/2018 10:31:37

Andrew Johnston19/06/2018 10:52:50
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Posted by JasonB on 19/06/2018 10:10:23:

He does seem to be doing some sort of dividing as well as he can be seen turning the div head handle a number of turns while the mill table is not being moved. Have a look about 2mins into the video. Possibly getting the correct tooth profile by using co-ordinates consisting of Z-height and an angle either side of his starting point.

Indeed, not sure why, although you may well be right? It doesn't look like a multistart worm. Got to be easier using CNC. smile

worm setup.jpg

Andrew

john constable19/06/2018 13:01:21
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Wow... I wish I understood what you are all saying!

What I do pick up from it is that what I need is model/hobby sized helical milling machine?

I suspect they dont make them.... so how do I create one? Can a mini metalworking lathe be modified? In my original post I outlined how I thought I might go about making one from scratch. I just need a way to link the hand-turned chuck with the milling table wheel in such a way I can control the spiral pitch. A simple gearbox I suppose or an arrangement of cogs and chain like you'd have on an old lathe to control speed. That much eludes me.

So frustrating a metalworking lathe just can't quite do it!

JasonB19/06/2018 13:32:20
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It can be done on the mini lathe.

 

-Make a bracket to hold Dremel or router on the cross slide where the cutting tool would normally go.

- Make something to hold a large gear/pulley etc on the far end of the main spindle

- Make or possibly use the existing gear position on the end of the lead screw to hold the smaller pinion that will drive the large spindle gear. The leadscrew is the long screw that runs along the front of the lathe.

- Make a handle to turn the leadscrew with, this could just be a ply or MDF arm with a knob to get hold of.

- Set the Dremel running, use the cross slide to move it into the work and then turn your leadscrew handle which will make the Dremel move along the work as it slowly rotates.

EDIT this guy did a 1 turn per inch spiral using the supplied gears by setting them in teh right order, may be possible to get a steeper spiral that way.

Edited By JasonB on 19/06/2018 13:37:16

Keith Long19/06/2018 13:42:50
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As Jason says above, it can be done on a lathe - easier than messing around with a mill and dividing head etc.

Assuming that you haven't got a lathe or milling table etc yet, keep a look out for an old simple lathe that has screw cutting abilities, ie one where you can gear the lead screw to the main spindle. For your usage you probably won't be too worried about the state of the bearings on the main spindle - so long as the spindle isn't flopping around everywhere, you won't need the sort of rigidity and precision that metal turning would. The issue to solve then is getting the gear train to connect the lead screw to the main spindle and here you needn't stick to the "correct" gears so long as you can construct a working gear train. Gears can be bought from EBay as well as dealers, but for your usage gears from the like of Technobots would also be suitable.

If you haven't got access to metal working machinery (a lathe) for making the odd bits that you'll need, give us a clue to whereabouts in the country you are, the chances are that there wi8ll be someone near to you who would the able and willing to help you.

john constable19/06/2018 13:53:47
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I'm doing my best to picture that. I'm ok with mounting the dremel to the crossslide somehow.

The lead screw is the long threaded rod that is motor-driven to move the carriage along the length of the lathe. Presumably it can be disconnected from the drive and you are proposing I turn it by adding a knob on the end? If its what I think it is, dont most lathes have a wheel for manually turning the lead screw already?

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