Merlin Posted June 8, 2018 Share Posted June 8, 2018 Hi, Forget all the olfa and similar types plastic based sliding system circle cutters where user loosens a brass knob and slides to a different diameter, one second its too small by 0.5mm then its too big, back and forth one goes, nudging the darn thing, even when locked there is movement and it will produce something different than thought. I even find the olfa doesnt get back to where it started sometimes, any pressure and the radius changes ! One can see the radius move too much even as the brass knob is loosened. We precision modellers deserve a better tool. I need a precision instrument, turn the wheel between the arms a few degrees, to micro adjust the radius, and it stays put, if well made and a perfect fit between screw thread and socket, it wont move, or so I hope. Better still a locking system. Any one found a source of such, as googling compass cutter precise metal throws up red and yellow plastic things. Modelling at times needs precision and the manufacturers out there are aiming these plastic things at the lower end of the hobby. I need to cut a circle and fit it into a tube end for example. Its for plastic card and precision scratch building and modification and not decal cutting. Making a decal where 0.2 of a mm here or there might not matter so much. Cheers Merlin Link to comment Share on other sites More sharing options...
LotusArenco Posted June 9, 2018 Share Posted June 9, 2018 A google image search for ‘compass cutter’ shows many variations on the classic Olfa design. Alternately, there’s the ‘bearing’ type cutters as seen here:http://www.themodellingnews.com/2018/04/andy-examines-three-new-tools-from.html I’ve only rarely had problems with the Olfa changing size on me, usually down to ‘pilot error’ where I’ve used too much pressure, wrong cut angle, or I’m struggling to cut plasticard with an old blunt blade. Numerous light passes with a sharp blade does the trick, flipping the card over to cut on both sides also seems to help. For super accurate circles on plasticard, I use an old pair of sharpened up spring dividers. Use in the same way as the Olfa one, but will leave more of a ridge that’ll need a light sanding. Mart Link to comment Share on other sites More sharing options...
Merlin Posted June 9, 2018 Author Share Posted June 9, 2018 (edited) Hi Lotus. Anything based on the Olfa design I will reject, I will run screaming off to the horizon, unless its metal, well built with the ability to turn a knob or dial and make precise adjustment to the radius and there is zero play in it when being worked. Also that it can do very small diameters like 3mm. Thank you for the link to the DSPIAE stepless circle cutter, totally different concept, its metal, its got a rail, non slip back, looks well made, a precision instrument, just the thought of this....oh bliss. respect for our skills by someone ! Someone has given the task great thought and realised it needs a different approach to the compass method. Not sure how pressure is obtained on the blade, unless its spring loaded . Thats a start., in fact it well could be the end of my quest. update...watched the only video of this on youtube, wobbly adjustment of radius, chap ham fisted maybe, such a precise device needs a geared edge here as maybe we are back to slight change and cant get the radius value required when requiring 0.1mm or 0.2mm accuracy. and he only cuts masking tape. Another review of one by thinnerline makes a complete hash of cutting plastic card, the blade pressure adjustment looks wobbly and so on, youtube usage of these is a bit worrying. DSPIAE appears maybe the better build, three blades not two, but the radius setting and blade holding and pressure controls are same it seems as the other poorer one, seems lacking in the critical controls. Need to find a metal compass option with radius adjustment wheel as an 'opponent' to this for the decision process, though the DSPIAE can do down to 1mm and its design will allow easy making of such, try doing that with a standard compass. Maybe thats it for me right there 🙂 Cheers Merlin Edited June 9, 2018 by Merlin Link to comment Share on other sites More sharing options...
Gorby Posted June 9, 2018 Share Posted June 9, 2018 I had the same problem, so I made this: It cuts accurately down to 3mm diameter. 2 Link to comment Share on other sites More sharing options...
Merlin Posted June 9, 2018 Author Share Posted June 9, 2018 Hi Gorby, simple, I like the nylon tie ! PRECISE radius adjustment. Ability to replace the blade. Does the blade want to creep upwards with pressure ? moving the scalpel a mm or so upwards would see the end of the slot abutt the rod there and stop that chance. maybe a threaded hole in the arm and a bolt to replace the cable tie might be a refinement, as long as arms can shut down to achieve 3mm. That wins over the two above in the precise adjustment department and if it does 3mm that also wins though its tricky doing small circles with a hand compass. Merlin Link to comment Share on other sites More sharing options...
LotusArenco Posted June 9, 2018 Share Posted June 9, 2018 Pretty much the same as Gorby’s. I sharpened up one of the prongs to act as a cutter, although I haven’t cut plasticard thicker than 20thou with it. Mart 1 Link to comment Share on other sites More sharing options...
Gorby Posted June 9, 2018 Share Posted June 9, 2018 4 hours ago, Merlin said: Hi Gorby, simple, I like the nylon tie ! PRECISE radius adjustment. Ability to replace the blade. Does the blade want to creep upwards with pressure ? moving the scalpel a mm or so upwards would see the end of the slot abutt the rod there and stop that chance. maybe a threaded hole in the arm and a bolt to replace the cable tie might be a refinement, as long as arms can shut down to achieve 3mm. That wins over the two above in the precise adjustment department and if it does 3mm that also wins though its tricky doing small circles with a hand compass. Merlin I'm waiting for a call from the London Design Museum. It'll be any day now I'm sure it will. The blade is solid as a rock, I've been using it for over two years and the blade hasn't needed adjusting, replacing, or even sharpening in that time. Rushing the cut can result in the circle not being accurate or if too much pressure is applied, the smaller the circle, the more care is required. It will also cut thin plastic – but you need many light cuts. Link to comment Share on other sites More sharing options...
Merlin Posted June 9, 2018 Author Share Posted June 9, 2018 (edited) I am wanting it for plastic card primarily, 99% of times I am cutting discs of plastic card. In my other thread in scratchbuilding on how does one remove the discs from the plastic card,,there is posted now a link to a cutter plotter, that is some bit of kit !!! Lotus, thanks, another idea, if I can get the point as sharp as a blade. Honing stone etc. Merlin Edited June 9, 2018 by Merlin Link to comment Share on other sites More sharing options...
Bozothenutter Posted June 27, 2018 Share Posted June 27, 2018 modify an old set of calipers? would give you 0.05mm accuracy...😉 Link to comment Share on other sites More sharing options...
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