Author Topic: scissor edges  (Read 737 times)

Offline Ken S

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scissor edges
« on: November 28, 2017, 12:46:52 am »
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

Offline RichColvin

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Re: scissor edges
« Reply #1 on: November 28, 2017, 03:09:23 am »
Steve Bottorff has a great discussion on this at http://sharpeningmadeeasy.com/Scissorangles.htm.
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Rich Colvin
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You are born weak & frail, and you die weak & frail.  What you do between those is up to you.

Offline Ken S

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Re: scissor edges
« Reply #2 on: November 28, 2017, 11:44:09 am »
Good comment, Rich. Steve has been my sharpening mentor. His very well done Sharpening School DVD essentially provides individual instruction with the ability to watch the lessons many times. I have found that I learn more every time I review Steve's DVD. Combined with email and personal conversation with Steve, it is a powerful combination!

Ken

Offline kwakster

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Re: scissor edges
« Reply #3 on: November 28, 2017, 02:00:29 pm »
One of my customers for scissor sharpening is a small company that specializes in making custom made ballroom dancing clothing as well as custom made swimwear, and they use quite a few different fabrics (many of which can be very finicky to cut well with scissors, a.o. Lycra-based fabrics)
The female owner knows exactly how she wants her scissors to cut, and she tests each pair herself on a few different fabrics every time after i sharpened them (and i've been sharpening their scissors for over 10 years now)

I sharpen all their scissors on the SB-250 stone at it's natural coarseness (no extra grading beforehand), both edges the same, and remove the tiny burr by laying each blade flat on a clean Spyderco fine white stone and doing a few light edge leading passes.
The resulting edge lasts them about a year (give or take, also dependent on steel quality) before they return it for a new sharpening, unless they manage to cut a needle with it (which happens sometimes)
What is extremely important to the edge life is the adjusting of the scissors, and the range i aim for is when the scissors open & close effortlessly while at the same time the fabric won't fold or slide.
Too tight and you will lessen the edge life, while too loose will make the fabric fold and/or slide.

The edge angles on most of their larger scissors (they have many different sizes) i keep in the 60-65 inclusive range, and so far i have found that for artificial fibers a toothy edge works better & longer (especially on harder to cut fibers like kevlar & dyneema), while for human hair a (much) more polished edge works better & easier for the user.
These i do freehand on Paper Wheels with diamond compounds.
« Last Edit: November 28, 2017, 02:02:06 pm by kwakster »

Offline stevebot

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Re: scissor edges
« Reply #4 on: November 28, 2017, 02:16:48 pm »
Thanks for the question and the compliment, Ken.
I let the angle be my guide to roughness. 90% of scissors are 30 degrees or less and a rough rind is fine, ie Tormek SG or SB. As they approach knife edge, >40 degrees. I polish the edge. That i usually only the finger blade on dressmaker shears.
Some mysteries.  KAI makes an excellent shear, 7000 series, that have two knife edges. When I resharpen them they cut like new but the edge does not last like new. Problem never solved.
I also worked on a pair of high leverage shears (long handles) that I could not get to stop pushing fabric. Owner had then sharpened by her sewing machine repairman and they were perfect. I never did find out why.
Steve Bottorff; author, teacher and consultant on knife and scissor sharpening.

Offline RichColvin

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Re: scissor edges
« Reply #5 on: November 29, 2017, 12:06:48 am »
What is extremely important to the edge life is the adjusting of the scissors, and the range i aim for is when the scissors open & close effortlessly while at the same time the fabric won't fold or slide.
Too tight and you will lessen the edge life, while too loose will make the fabric fold and/or slide..

Kwakster,

Would you be able to specify a range of pressure (e.g., pounds required) ?

Kind regards,
Rich
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Rich Colvin
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You are born weak & frail, and you die weak & frail.  What you do between those is up to you.

Offline kwakster

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Re: scissor edges
« Reply #6 on: November 29, 2017, 06:44:01 am »
I can't specify a range of pressure, but that company always provides me with several pieces of their most finicky fabrics for test cutting, and that is what i use for the adjusting of the scissors after sharpening.

Offline Fernando

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Re: scissor edges
« Reply #7 on: April 10, 2018, 10:01:42 pm »
This topic is very interesting, I sharpen scissors for stylists, and I can tell you that each one has different tests, that if all the tests before using them, some close them to the ear and listen to the noise they make when they open and close and they can swear to decipher if the scissors cut well or badly, others have told me, "the short scissors moving only one of the parts", move only one finger to close and open the other part remains fixed, and the tests grabbing the scissors by one of the handles and release the other and hope that the scissors does not slow down in the path, it should close completely without the fall being free only gradual, and the vast majority only use dry and wet hair, although many say if you cut hair Dry will not have problems with wet hair.
Between the scissors of tailor and the stylist, I think they are more demanding in terms of edge, that of the stylists.
almost all of his scissors are at 60°