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scissors? - Ken S - 11-27-2017
We have had much discussion about polished vs. toothy edges for knives. What about scissors?
Whereas knives have one edge, usually with two bevels, scissors have two edges. Should each edge be sharpened the same way? Should the edge which supports the material being cut have a toothy edge to help prevent the cut material from slipping? What about the other edge? Should both edges receive the same amount of polish?
I have read that there is an advantage in using two grinding wheels when sharpening scissors. I have also read that often only the coarser wheel or belt is used.
I have seen machines which sharpen scissors with small diameter grinding wheels, large wheels and flat grinds.
Thoughts?
Ken
RE: scissors? - Rupert Lucius - 11-27-2017
My opinion the 8" diameter works better than the compact TAS 5" machine less concave with larger dia.
Here we go again in ref to wheel dia and motor RPM.
Also depends on the sharpener his/her touch.
Rupert
RE: scissors? - Ken S - 11-28-2017
Good thoughts, Rupert.
Although certainly not new, I think larger diameter grinders (eight and ten inches) are only recently entering the mindset of the home workshop. I still have my six inch (now worn to around five inches) grinder from 1972. I believe most of our attitudes about hollow grinding go back to those earlier times.
I do not remember our present 1x42 and larger belt grinders being prevalent back then.
At my request, our own Grepper posted some microscope photos on another forum. Grepper's photos clearly showed the difference made by having the last pass or two be very light. For all of our grit standardization, I agree that there is much to be said for the individual grinder's touch. Our Tormeks, Viels, Kallys, TASs, etc. are marvelous labor saving machines, but for fine work, all depend on the operator's skill. The manufacturers of these fine machines seem more concerned with marketing them than with training operators to become really skilled. Vocational and formal training seems on the decline. Digital technology offers enormous educational potential, however, that potential seems largely untapped. We can and should do better.
Ken
RE: scissors? - EOU - 11-29-2017
Good topic Ken and I hope that some of our scissor guys jump on this one. Had a conversation this morning with one of the best. If you think knife guys can talk the ins and outs of knife sharpening you should get a scissor guy on the phone. Its pretty amazing stuff.
RE: scissors? - Mark Reich - 12-02-2017
Mr Ken, these are very pertinent scissor questions!
"Should each edge be sharpened the same way?"
It certainly is easier. The important thing is to maintain the original performance for which they were designed, or sharpen them to suit your need.
I'm not sure larger Diameter wheels are inherently better. You can get the same edge angle with practically any size wheel, but the edge bevel would be wider with a large wheel at the same edge angle.
Should the edge which supports the material being cut have a toothy edge to help prevent the cut material from slipping?
If you have one smooth blade, hard material can slip away from it regardless of the other blade's status. I have used a coarse wheel on both blades, instead of having one serrated blade, which seems to work for me.
If you need super traction, they make scissor files to cut serrations into blades. I have no experience with a serration file, but I wouldn't mind giving it a shot.
I have read that there is an advantage in using two grinding wheels when sharpening scissors. I have also read that often only the coarser wheel or belt is used.
This sounds like a TAS statement to me, since you have two wheels at your disposal. If you use the grinding wheel alone, your tool will cut difficult material, like thick plastic or "tin" (as in "tin-snips") better. Actually, they don't really "cut" better, they bite better. No free lunches though. Coarse edges usually don't cut fine material like paper very well, but it's very easy to refine an edge on the "polishing" wheel of a TAS.
A big advantage of a Tormek over a TAS is heat buildup. Tormeks have no heat related issues. Ever. You definitely have to be more careful with a TAS. That follows Mr Rupert's thoughts of SFPM on the wheel.
A very good way to combat heat buildup with a TAS is to start near the tip of the scissor, which takes a bit of practice. Then you're pushing the heat toward the larger mass of the blade which can easily absorb a lot of heat. If you go from the pivot to the tip, the heat can easily build up to the point where the tip will turn blue before the wheel gets close to the tip.
Another advantage for the Tormek is the wide wheel, which makes it much easier to keep an edge straight and true.
The profile of the edge, be it flat, hollow or convex means little compared to it's Angle.
Just my 2¢
RE: scissors? - MaxtheKnife - 01-11-2018
well let me tell you this story......3 of us use variable speed veil's. we all use the veil arm, we all use the wolf clamp.
as far as i know, we all use a160 trizacts (120grit) or 120/150 grit by others and the scissors are outstanding.....THESE ARE: kitchen, fabric, upholstery scissors.......they need teeth to grab and hold the material being cut.
our buddy doug r in texas always used a65 trizacts (320 grit or so depending on who's chart you look at)....i tried them and i considered them fine.
if you ever watched the veil video on sharpening scissors, he uses a a16 trizact at 1200 grit.
i think the TAS white wheel is 150 grit, that should tell you something........and like 3400 rpms.
now, my other two scissor buddies both have bought TAS's and no longer use their veil's AND THEY BOTH told me the TAS does a much nicer job and seem much sharper than the belt ever did. both said it took a bit to get use to the speed, but once mastered, the end result on any scissor was outstanding.
my 2 cents.
looking comments to follow ........
RE: scissors? - Ken S - 01-12-2018
Mark and Max,
Thanks for the excellent informative replies. The TAS seems an ideal candidate for CBN wheels. No wear or need to dress. Also cooler running. The cost increases with the diameter of the wheels. I would think the cost of TAS small wheels would be reasonable.
For my limited need, I'm sure either my Viel or my Tormek will be more than adequate.
Ken
RE: scissors? - Mark Reich - 01-13-2018
I mis-spoke earlier. The large diameter Tormek wheel leaves a Smaller (narrower) edge bevel than the TAS, but if you are Very Exact setting the edge angle, it's negligible.
Mr. Ken, do you know of CBN wheels for the TAS?? I haven't even needed to dress my plain-jane wheel in years, but I've been planning to get a diamond wheel when the need arose. I would rather use a more forgiving CBN wheel (with very slightly radiused corners).
If you can maintain the factory, convex, primary zero grind of hair scissors with a belt machine, you have No problems. I do it edge up (edge leading), freehand on a slack belt, so I can see. It's easy to maintain the factory "twist" that some people spend thousands of dollars to do with a jig. This only comes into play with hair scissors, and only when the hollow ground primary bevel of the TAS or Tormek becomes obvious.
I'm not surprised the TAS is most popular in Mr. Max's circle. Used properly, it does work amazingly well. Yes, it's trickier using a high speed, 1/2" wide wheel than a low speed, 1.5" wide, water cooled wheel, but there's a LOT of give and take involved.
It's worth saying that there is one thing that makes a big difference for me. I always get the arms of the TAS positioned, then make a false pass. Every time. This assures the arms are positioned perfectly for a straight grind, and you know exactly what it's going to feel like. This way I never make a wobble, so I never make more than one, light, true grind.
RE: scissors? - Rupert Lucius - 01-13-2018
(01-12-2018, 05:59 PM)Ken S Wrote: Mark and Max,
Thanks for the excellent informative replies. The TAS seems an ideal candidate for CBN wheels. No wear or need to dress. Also cooler running. The cost increases with the diameter of the wheels. I would think the cost of TAS small wheels would be reasonable.
For my limited need, I'm sure either my Viel or my Tormek will be more than adequate.
Ken
This machine utilizing a Variable speed Penn motor can accomodate wheels 8 to 10 inches in dia. http://www.acesharpening.com/Eight_inch_DC_Scissor_machine.html
Rupert
RE: scissors? - EOU - 01-13-2018
Hello Mr. Rupert Lucius! How about getting hold of our mutual friend Mark G. and tell him to bale in on this thread and the Exchange in general. We've tried but with no success. We know that no one can refuse the "Godfather". Mark G. was the first guy to stop by our offices and prove that the KN100 was as effective on scissors as on knives. Make him an offer that he can't refuse. That's what Godfathers do.