Lap line on pinkers

[grepper]

On the top (cutting edge) of pinking shears, there is a dark layer metal called a lap line.  It is written that if this does not exist, has been sharpened away, don't bother to sharpen them because they will never get sharp and cut well.

I thought surely, with careful sharpening, that even with a missing lap line they should cut!  Even minus the lap line, the whole thing is steel right?  Of course it would get sharp and cut.

My wife had an old pair of Wiss pinkers that were dull and didn't cut well at all anymore.  Only portions of the lap line were left as they apparently had been sharpened many times before.  So, I had at them.  When I had established  an even edge with each tooth evenly ground, the lap line was completely gone, just leaving shiny steel with nice sharp edges.

Looking at the results I thought, how could that not work?  It looks very sharp!  I've sharpened other pinkers with great success. 

Guess what.  They cut like crap.  Material just tore and folded between the blades.

More honing.   More sharpening.  More honing and sharpening...  No luck.  No happiness.

I can attest:  If the lap line is missing, don't bother trying to sharpen them.  It won't work.  If the shears are not yours you might get blamed for wrecking them even though you were just trying to get one last sharpening out of them.

[Stickan]

That puzzles me a bit, why would it not work?
I don´t think I have sharpened scissors like that though.
One tip is not to hone scissors,  the little burr from the sharpening should be removed by drawing the scissors through the end grain of a piece of wood.

Stig

[grepper]

Puzzles me too.  It's a real head scratcher.  Hopefully someone with more scissors experience will chime in.  I don't know why it didn't work.  But you see stuff like this where they say don't sharpen if no lap line:
http://www.wolffind.com/7DD3D054ED7E446B85FC1E341B3FCFD4.asp?ccb_key=826FF0DD86754A799B8DF9A21065500D

Same here:
http://jimsharp.blogspot.com/2008/02/left-handed-pinking-shears.html

I tried not honing, just closing to remove burr.  I tried honing too.  For whatever reason they just would not cut.  Must have something to do with the lap line.

Can't really drag pinkers through wood.

[Elden]

   Pinking shears have multiple cutting surfaces. They all must mate properly for them to cut cleanly. This is not achieved in the casting and the machining process. Machining gets it close to being correct. Lapping finishes off the job. It is similar to the valves on an engine. The valves can be ground but without lapping, proper seating or sealing between the valve and the valve seat will never occur. If you try MANY pinking shears with the lap line gone, you might eventually find a pair you could get to cut properly. However, I doubt it.

   We are told that lapping can not be as accomplished by an individual. Mark, that would be something for you to try since they are quote say ruined.

[Elden]

   After doing some reading about pinking shears, I see that lapping is definitely a highly specialized process using specialized equipment. I don't believe that an individual would accomplish hand lapping them. I originally thought maybe honing compound of some sort between the blades might work (thinking of the engine valve thought).

   The following link about patents issued to J. Wiss and Sons is interesting.

http://jwissandsons.com/patents/pinking-shears.htm



   The article about "Device for lapping the cutting edges of pinking shears" is informative. The second paragraph of the text, tells why pinking shears will not function properly without lapping. Its link is:

http://jwissandsons.com/patents/US3130521.pdf

That paragraph in part reads as follows.

   "It is of paramount importance for the functioning of pinking shears that all cutting edges and contours of the cutting blades mesh with one another with equal precision and under equal pressure. Shears in which this high degree of precision does not prevail do not cut, but rather rip or pinch the material to be cut. In manufacturing these shears, several steps have to be taken, for which several machines and devices have been invented and developed, such as being covered by my co-pending applications for a special drilling apparatus and for a blade milling machine."

[grepper]

Yup.  They rip and pinch rather than cut.

I read some article where some guy said he tried lapping them by opening/closing with honing compound.  It didn't work.

Maybe, like Elden said, if you had a whole bunch of them you might get really lucky, but generally if the lap line is gone (or really messed up) their useful life as scissors is history.

Maybe they could be repurposed?
https://s-media-cache-ak0.pinimg.com/236x/95/f5/f4/95f5f49b92c1097b6e7236c25c72bcfa.jpg

[Stickan]

Hi,
I learn something new every day. This time I thought pink shears was a regular scissor with a pink handle 
I'll do my reseach better next time!

Stig

[grepper]

You might not be wrong, Stig.  Here you go!
http://www.amazon.co.uk/Professional-Dressmaking-Stainless-Pinking-Scissors/dp/B0087OVP9G

Don't feel bad.  I always thought pinking shears were for cutting a decorative edge for making doilies or something.  But my wife, who did seamstress work many years ago, informed me that the zig-zag edge is to ameliorate fraying.

[Elden]

Stig if we aren't learning, we become stagnant. I hope that I am able to retain a fair portion of what I learn here and else where.  They say that with the fabrics that are used in today's world, the need of pinking shears is greatly reduced as the fabric doesn't ravel as much.