Simple Pantograph

[garryh]

Dave, I love looking at your work, You make everything look like a piece of artwork.

Garry

[J.F. Custom]

Allen and Dom, I'd be inclined to have the two halves separate, but I think with care you could do either.

My reasoning/thinking/steps are thus -

I'd have both cutter and stylus adjustable in height. I'd set the stylus to the depth of the specific template perfectly, align it to where I want to start the cut and leave it there. Then I would align the stock to be cut under the cutting head in reference to my stylus starting point. Finally I'd move to the cutter setup and adjust its height - this may take plunge cutting to get perfectly set.

That is straight forward enough. My concern over having them fixed together comes at the plunge point. Say that your desired depth of cut is lower than the depth of your pattern - your cutter will strike the stock before the template engages. Now if the pattern were large and you could guesstimate reasonably accurately the centre or a "safe" area, no problem. However on something intricate or like a signature for example, if the cutter were to engage first, you could accidently cut 'outside' of the template by misjudging where to plunge down. That said, the same applies really even if they were the same depth. If, on the other hand, your stylus is already separately down inside the template guide securely, you could then plunge your cutter without fear of falling outside.

The same goes for multiple start points - lift the cutter out first to disengage any cutting action, then lift the stylus to the new starting position and let it down inside securely first, before plunging the cutter down once more. I'd feel more secure of repeatable accuracy this way. To my thinking with your concern Dom, I'd be using the unit with one hand holding the stylus and the other holding the cutter head for complete control over the job. Care would be needed of course but I don't think the stylus popping out where it shouldn't is something that could not be overcome with a steady hand guiding it. On a fixed unit though, I'm not sure how you might overcome the potential plunge outside template.

This is only theory though - I have not built or used one yet so maybe someone will bring another potential issue to notice. On the building side, I've got a few spindles to choose from. Dom, you've got me thinking on the air powered grinder. I've got a nice US made Foredom 350K (that's 350'000rpm ) that I haven't used yet. Picked it up thinking it would make for a smooth cut but never quite liked the idea of the compressor running constantly in the background. This might be an ideal use for it though and I can't really say a Dremel is "quiet". But I have a spare flexible shaft for a dremel too so maybe it will come down to cutter availability as the 350K uses specific bits.

My thoughts anyway.

Jeremy.

[DarwinStrings]

I have been designing one in my head as well and have been thinking about potential problems. I reckon I will have the cutter and the stylus connected so although they can be hight adjusted separately, once they are height set then they will always move together on the Z axis for these reasons. If the stylus pops up and out of my template for any reason and the cutter does not move up with it then, groan, a bit I don't want pocketed becomes pocket. I figure when I make a plastic template from cut pieces of pearl the template is easily made to the exact same depth of the thickness of the pearl, usually I keep my pearl proud and flush it back so my pocket is shallower than the pearl thickness which means I can set my stylus on the top of the mould (that is on the flat surface outside the pocket) and then height set my cutter just a smidge above the work piece. I will make my template with a sufficient amount of flat area surrounding the pocket so that if the stylus pops up out of the pocket then the cutter will be a smidge above the work piece. Also I might use it for some small 3D carving. I suppose I could make both sides move independently and then use a removable connector just in case as Jeremy mentioned I ever want to make my pocket deeper than my template but I can't, right now, see a need for that.

Jim

My eyes are dim I can not see, I have not brought my specs with me, I have not brought my specs with me....Quote, some old song my dad used to sing.

[Puff]

Jim: "just in case as Jeremy mentioned I ever want to make my pocket deeper than my template"
Simply raise the stylus Jim.

[J.F. Custom]

Jim: "just in case as Jeremy mentioned I ever want to make my pocket deeper than my template"
Simply raise the stylus Jim.

But that wouldn't account for the potential pitfalls I outlined above.

Also, if a deeper pocket is required, wouldn't you need to lower the cutter as opposed to raising the stylus? The depth of the mounting board on its hinges is fixed and will only drop to a certain point. Or am I missing something or misinterpreting you Puff?

Jim, to my thinking, a template is reusable and therefore may be used in future for other thickness of shell; let alone other materials such as plastics/resins and timber. Therefore different depths are something I would factor in from the start.

What is your take on what I mentioned above? For some reason to me, jumping out of the template independently and causing unwanted cavities feels like less of a risk then plunging down inaccurately together on detailed work.

Jeremy.

[DarwinStrings]

Okay I see your point about reusing templates but if any future inlay material was thinner then I could raise the cutter even more and still have no risk of unwanted cutting outside of the intended pocket. If my materials were thicker then I just leave them more proud and flush them back more or maybe thin them a little first.

I reckon if you are careful then popping out of the template is a small risk as you say but if I use the set up I mentioned then there is no risk of "plunging down inaccurately" cause the cutter can not hit the work piece unless the stylus goes into the template pocket.

Jim

[Puff]

Jeremy and Jim -sorry had gotten to bed when I realised something was left unsaid.
My style of these use pipes, tubes or rods, with simple 'linear bearings' drilled out of low friction nylon blocks, for the Y and X axis travel, with the Z axis perfomed by a radial pivot on the X axis that allows cutter and stylus to swing below as well as above the horizontal.
By vee-ing the closing edges of the hinge joint on the model in the video, so that the 'door' shuts at 220 instead of 180 degrees say, it too could do this therefor allowing most adjustment to be made solely on the stylus side. The stylus effectively becomes the plunge setting.

[J.F. Custom]

I reckon if you are careful then popping out of the template is a small risk as you say but if I use the set up I mentioned then there is no risk of "plunging down inaccurately" cause the cutter can not hit the work piece unless the stylus goes into the template pocket.

Jim

Fair call Jim. I think this gets back to what I said originally in that, either will work with care. Both ways you just have to be aware of the potential pitfalls and work around them. So I'll make mine split, you make yours solid and we'll discuss further down the track when we have some practical 'hands on' experience as opposed to theoretical.

Also Jim, on the 3D front incorporating a Z axis. I have no intention of making mine to do this - I am primarily concerned with the basic 2D plus a depth set for my use. However, thinking a little on it, could you not use a joined double parallelogram arm/head? The depth limitation therefore set by the length between the uprights? If this is not clear, I am talking about the style of head seen on the binding jigs that make use of drawer runners and a lazy susan. This would make the whole unit much larger of course, but that would be required for the third dimension anyhow. At least this should allow you to keep your cutter vertical at all times and "float" over a template the same way it does over a curved back.

By vee-ing the closing edges of the hinge joint on the model in the video, so that the 'door' shuts at 220 instead of 180 degrees say, it too could do this therefor allowing most adjustment to made solely on the stylus side. The stylus effectively becomes the plunge setting.

Ok, so really you are talking about a totally different style of unit, for comparison sake. For this model however, I am still confused in that I would have thought if you were to pivot the hinge so that it "shuts" at say 220, not 180, are you not also changing the angle of the cut? To my thinking, your cavity edges will then also be cut on the same angle. Perhaps in use this small amount would not be much but as you are primarily moving in X and Y, if your Z is at a 20˚ angle to the bed, the "top" edge of your resulting cavity will be "undercut" a little, while the bottom edge would be slightly "overcut" (for want of a better term), resulting in a slight gap. That is the way I perceive it. I would think you would need a Z axis that does not affect the cutter alignment such as that which I suggest above.

Jeremy.

[Puff]

Jeremy the guts of it are here http://www.wood-carver.com/construction.html
With the radial arm for the Z axis 12" from pivot to cutter/stylus and the depth of cut half inch, the undercut 'gap' would be about the same thickness as a gnats pubic hair. The idea is that the cutter follows the stylus, which is the same shape as the cutter, exactly.

[J.F. Custom]

...the undercut 'gap' would be about the same thickness as a gnats pubic hair...

I guess that's just a more 'eloquent' way to say what I did -

...Perhaps in use this small amount would not be much...

Jeremy.

[DarwinStrings]

For the way you want to do things then I think the split system is a great idea and it obviously works well for Keith MacKensie. I was thinking that the less elaborate then the better, that is that if I separate the stylus and cutter there is more potential for a bit of slop between the two but if I build it separate then use a rigid removable link I would have the option of using it both ways, so maybe that is the best way for me (no concrete decisions made yet). I think you are correct about the 3D job as well but again I want to keep it as simple as possible and the 3D I was thinking of would be small "standard" carvings that I may repeat on headstocks around a logo maybe and nothing more than 3 or 4mm on the Z axis so I think the hinge system like Keith's will be all I need. One more extra though I have in mind is to add another place for a stylus, not next to the cutter but placing the cutter in the middle and putting the stylus out the back (if you know what I mean) this way I may be able to get to a sound hole for some fancy rosetteish stuff. My design is limited to the size of the linear bearing that I bought a few years back when I had CNC on my mind. Also my limited work space, it needs to be something I can get out of my way on a hook or a shelf.

It is on my next project list after I finish making another de-humidification cabinet, this time to house some of my nicer tools in a attempt to keep the rust at bay.

Jim

"Rust never sleeps"...Quote, Neil Young

[Puff]

Jim this could be what you are looking for. Dead simple locking system. http://www.youtube.com/watch?v=TYCubwav ... re=related
Just Googling "homemade copy carver" throws up heaps of ideas too.

[DarwinStrings]

Thanks Puff but that just locks them down and is not what I meant by locking them together. If you had a inlay with several small separate pockets you would have to unlock it to change pockets, not that that is a big humbug I suppose but it does take the Z axis out and wouldn't do 3D.

Jim

[Puff]

Jim -with the utmost respect, and that is totally sincere so no need for a smiley, the whole idea is for the cutter to follow the stylus exactly. Hence the cutting/burring piece and the stylus must be exactly the same in 3D.
There is some diversion here in just cutting inlay and the cavities in which they go. Ergo 2D plus depth. For mine that is 3D.
Theorising on this is a good mental exercise but the reality happened many moons since.

[DarwinStrings]

Jim

[Dominic]

This debate still going!! We are all obviously going to build this thing exactly as we want despite the arguments to and fro. I think it has been theorised to death so far. So lets get on and build some so we can do some real world tests and then we won't have to argue about it any more.
I'll have a go tomorrow and post my results.
Dom

[Allen]

I'm waiting for all of you to come to the definitive, fool proof build for under $100 and it rivals a $20,000 CNC router. Free plans posted to please.

[DarwinStrings]

Sorry Allen, can't begin to help you there as the linear bearing I am going to use alone cost me more than $100 mind you I did get them cheap as, at the time I just kept throwing in low bids on ebay. I was not in a rush to buy them and eventually got lucky with a low bid, god I love Ebay.

Hey Dom, good on you, it is about time someone got off their date and did something with their life. Will look forward to seeing your work and pinching any new ideas you come up with.

Jim

Life is good when the wood is in your thoughts.