Small pantograph

[arnoldb]

Well, no leave for me on the 31st - I forgot I have to decommission the old systems at one customer  . 

A bit done today - progress of sorts but still not satisfactory.

I took the fly-cutter to the mating surfaces of all the arms - skimming off 0.2mm to smooth things out around all the pivot points:


Then I assembled everything the other way around - to get the knuckle-knocking bit out of the way.  I decided to plunge in with experiments on a bit of brass plate; I simply screwed my tooling plate to the pressed-wood base board  The base board is not all that flat - I had to shim one end of the tooling plate up a bit to get things level.  I made up a very crude engraving bit from an old 3mm drill shank; as the shank is soft I just turned a point on it and filed a bit of a flat on it.  Far from ideal - but I decided to try it out anyway.  A quick print-out from the PC provided the copy material.

The first test didn't go well at all.  I found a lot of wobble between the flex shaft handle and it's mounting.  What was happening was that it was not gripping properly on two sets of knurls to keep things stable - a paper shim in there cured that problem quick and easy.  The spring washers I used were just too stiff; while the joints moved much more freely after flycutting the faces, the spring washers still added too much pressure, and by the time the bolts and nuts were loosened enough, things started to get wobbly; even with the close-fitting bushes in the joints, there is enough play to allow things to twist slightly.  The 5mm flat bar is just too thin to make for reliable bushing in this application.  I removed all the spring washers and just tightened up the lock nuts and then released each a tiny bit to just ease up the joints.  This works much better, and everything works fairly smoothly.
The set-up after the trial and error work:


Even while improved, the results are still far from satisfactory though  .  Free-handing the job, even with the printed guide makes it look surprisingly like my own handwriting  .  While doing the last bit, I did have a couple of major oopses while following the lines; I could feel them while going along.   Gripping on that threaded rod stylus is definitely not comfortable.  While engraving the surrounding box, I used a rule as a guide; that helped a bit, but for some reason the right hand edge has a wavy shape...  I don't know if that's down to me, the cutter, or some free-play somewhere.  Well, if it's the cutter or free play, it's still down to me  .:


For now, I'll shelve this project - as much as I dislike doing that.  I have a bunch of milling cutters on order, and I added a selection of proper engraving cutters to it.  That will take about 4-6 weeks to get here.  In the meantime, I'll scout some shops for goodies I can use as copy lettering - most local shops with anything that might be suitable will only open in a week or two anyway  .

Time for an engine build...  I'll sleep on things and try to decide just what 

Kind regards, Arnold

[zeeprogrammer]

I was just thinking about this thread about an hour ago.
If I do finish Spinster and give it to daughter, it would need a plate.

Still thinking about a little x-y table with steppers.

Well you might shelve this project Arnold...but your projects need a nameplate.
Don't wait too long. 

[Jo]

Commiserations , it looks like your output is suffering from hand wobble due to lack of commercial copy .

Edit: Have you got any old drafting lettering stencils?

Jo

[DaveH]

Arnold,

I think that black stuff you used for the washers is Vesconite.
http://www.vesconite.co.za/  It's good stuff but expensive.

All that 'wobble' seems to me that you have had too much wine over the Christmas period mate.     
Guides for the stylus (pointed bit) is really needed,  freehand is really difficult.
 
DaveH

[mklotz]

Look around for the templates that accompanied a Leroy lettering set, e.g....

http://www.mccoys-kecatalogs.com/KELeroy/3245-15L/3245-15L.htm


When I was young, (a long time ago; I lit the fuse on the Big Bang), we used these to letter titles on hand-drawn graphs and presentation slides.

They're still available on the bay...


http://www.ebay.com/itm/Leroy-Lettering-Set-Keuffel-Esser-CO-Vintage-Wooden-Box-Pens-NICE-/310401244987

but ask around the old-timers where you work.  One of them might have one stashed in his desk next to his slide rule.

[ScroungerLee]

Have you considered making washers from Teflon sheets to reduce friction?

How good is the engraving head bearing?  I would think that having play in it could lead to the wobbly line.

Lee

[arnoldb]

  I won't wait too long Carl - things must just get back to "normal" here from the holidays...  Just about everybody closes shop and go away; I'd guess at least 60% of residents leave town to go to the coast, South Africa, or the North of the country.  It's amazing what it does for the morning "commute" to work though...  My average travel time to my principal customer site goes down from about 20 minutes to 5 minutes  .  If I don't get anything suitable to use as guides and satisfactory results, a CNC router / micro mill is still a viable option.  I'll have fun building it, and I'm pretty sure I won't have problems operating it with available software; even if I have to study up a bit on G-code, it's just a programming language.  Can't be much worse than C or the various assembly languages for different CPUs - though I might have to drop my Z80 or 8052 brain banks to add in the G-code one

Thanks Jo.  I've been digging through my old draughting stuff - I found all the old compasses, refillable ink pens, triangles and a couple of stencils, but the largest one I have has 6mm letters and is designed for 0.5mm ink pens.  It might be usable with a suitable tip on the stylus, but it's NBG for making copy from...  In the meantime, I'll see what I can scare up from art/stationary suppliers for bigger stencils 

Cheers Dave  - It's not quite Vesconite; it's lighter in colour.  The local branch of Huster Machine tools have a nice rack full of Vesconite standing right in their showroom.  My wallet cringes every time I walk past that rack - I once bought some of it to make a shaft bush for a high-speed printer from.  Fortunately they sell it by the cm  .   The wobble might be withdrawal symptoms; I've had a pretty dry holiday season so far 


Thanks Marv - that's some seriously nifty kit!  I've never seen something like it; I wish I had it in school for my draughting classes.  Alas, somehow I'm turning into the "old" guy in the circles I move in; I'd take the kit and slide rule off anyone that has it, but the crowd I mostly come into contact with can't do anything without computers and Google.  Or bl**dy "smart phones"...  I'd better stop before I go into a rant.

Lee, thanks.  I was hoping the washers would do the job as-is.  Teflon sheeting's a bit scarce around here, but I'll keep my eyes peeled for some.  Or I'll go with roller bearings; that should sort things out nicely as well.  I'm not too sure about the flex shaft's bearings; I cant detect any lateral play on it, but it could be a factor.  I'll see what happens once I get the proper engraving bits though - the crude one I made is far from ideal.

Kind regards, Arnold

[Jo]

  Teflon sheeting's a bit scarce around here, but I'll keep my eyes peeled for some. 

Teflon sheeting is sold as non stick baking sheets for use in the kitchen .

Jo

[Pete49]

Nice tip Jo, I'll file that in the top drawer. Arnold the stuff you used loks like delrin to me. I use it for bearings and so forth and while it gets rat nests I found it helps to throw a trand over the splashback of the lathe into a bin and it just goes nice. Nice to work and real good finish. Seeing this build I am thinking of a similar setup using the dremel. I have a larger set up which uses my router for making nnameboards an signs.
Pete

[arnoldb]

  Thanks Jo - I'll add kitchenware suppliers to my list of shops-to-visit.  Those sheets could even come in handy the next time I bake biscuits.

Pete, thanks.  It might very well be Delrin - I'll try it out for bushings at some point and see how it works.  I know the white PTFE I have is great for bushes as well; the engine I built using it runs slick as anything.  This feels slightly harder than that PTFE; it might ream better; I had a bummer of a time reaming the PTFE to size.  I'll play around when the occasion arises.

Kind regards, Arnold