Here is a list of all the postings john constable has made in our forums. Click on a thread name to jump to the thread.
|Thread: spiral spindle cutter|
I was thinking I could maintain the same centre-centre distance by having more than 2 gears in the cartridge.They could be as complex as needed as they wouldn't need to be fiddled with once set up.
By two screwed rods, you mean that a chain will engage a cog on each whereas fixed cogs will only allow one?
I'd also considered some kind of cartridge arrangement with 2 or more gears inside for a given pitch and then the cartridges can be changed for each change in pitch required and no need to fiddle with gearwheels and chains.
I couldn't quite work out how to put the cartridges on though.I'm not explaining myself very well...I can feel some sketches coming on.
Thanks, Brian. That looks like the best type of hardware to use. I never came across Delrin before. I wanted to use meccano but as you say the choices are limited although someone mentioned a robotics supply site.
How would you arrange the gears for different ratios? Would you use a pair for each different pitch you wanted and then just connect your chain to whichever you needed for each job? How would a moveable tensioner work? Would it need to move in a slot to take up the slack and then be held there with a nut or something?
Yes - essentially you're all correct. I had a trend router lathe but it was lost in a house move before I could use it and I had to stop woodworking for a while so I didn't replace it.
More recently I've ended up in a wheelchair with mobility problems and a full sized set-up is beyond me to use so I decided to put together a miniature workshop and concentrate on small decorative things like boxes and clocks - hence my desire to make barley twists from maximum 2" x 8" stock but usually smaller.
The trend router lathe will be too large for me and also I think not accurate for the scale I want to work at.
There are two routes that seem to have opened up to me. Firstly getting a mini lathe which has change wheels and a disconnectable motor. That's not cheap but on the other hand offers me the joy of other things a lathe can do.
Or home-made,like Brian's sketch. That's similar to the pen wizard but I don't want to use cords because I think they'll be inaccurate. The part I'm finding difficult at the moment is an arrangement to sync the travel of the tool along the work and the rotation of the work and do it in such a way that it can be changed easily for different pitches (in effect it's some kind of simple gear box needed).
|Thread: Chinese mini-lathe change wheels|
That looks really good.Read other posts on it vs the SC2. Sadly a bit outside my budget.
I'm wanting to barley twists and spirals in wood stock up to about 2" x 8" max. Someone has explained to me I need a small metalworking lathe with change gears so I can radically speed up the saddle to spindle speed and turn the spindle slowly by hand.
I noticed you guys discussing small lathes and change wheels. Could you suggest any new or used mini lathes with change wheels that might fit the bill please?
|Thread: spiral spindle cutter|
Thanks, Keith. The unimats certainly are pricey. You're explanations are bringing my 35 year old engineering lessons flooding back to me....
So, the good news is I might even be able to save some money by finding something without a motor...
Keith - this is brilliant stuff, thanks. I've been browsing ebay and google looking for helical milling machines over the last couple of hours because that seemed the most descriptive term for what I was looking for. I ran across some old lathes with interesting looking gear arrangements, including the unimats, and I was going to come back with some more questions which you have preempted.
Do I need too use the motor or can I turn the spindle by hand? I'd prefer the extra control and overrunning the cut would not be good!
Can I ask the difference between the wheel on the tailstock end of the leadscrew and the large wheel on the slide? Dont they both turn the leadscrew and move the slide?
I thought the unimat might be suitable as there seems to be a lot of options for it which may well include these gears but they look a bit pricey. Could anyone suggest some suitable models to me please? Not too large if possible as I still only need to turn things less than a foot by 2".
I understand I'd need to change the gear ratio but I'm not sure how to do it without reconstructing it every time. I could add more gear pairs with different ratios and move the chain each time but its still only one pitch per ratio and i'm not sure how I would change the chain each time if there's no slack in the system.
Thanks for that video. I think I see whats going on now. The problem this guy has ended up with is one I'm grappling with. How do you vary the gear ratio for different pitches? At least he's managed a low enough pitch to get one working. I didn't think that was possible on a small hobby lathe.
Thanks, Keith... I feel I’m getting closer all the time.
I think which ever method I’ve looked at it’s the issue of driving the lead screw from the spindle that is the trickiest part. At it’s simplest I imagine a cog on the spindle and a cog on the lead screw in line with it and a chain joining the two?
Assuming I can choose cogs that give me the right speed ratio for a barley twist pitch, how do I vary it to vary the spiral pitches or would I just be stuck with one?
If thread cutting lathes had a bigger range of ratios we might be in business!
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?
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!
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?
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.
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.
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?
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.
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.
Any advice offered gratefully received!
|Thread: Hi from Bagshot|
I used to enjoy woodworking decades ago but life got in the way and I couldnt keep it up. More recently I became ill and ended up in a wheelchair with more time on my hands so I decided to set up my workshop again only this time in miniature, using dremel-type tools and making small ornamental items like clocks.
So, I realise this isn't a woodworking forum but there's one thing I want to achieve - decorative spiral cutting - that's going to need a home-made tool and that's why I joined this forum. But I expect to pick up a lot more really interesting things along the way!
Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!
You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.
Click THIS LINK for full contact details.
For subscription issues please see THIS LINK.