What to sharpen with ?

[robin wood]

A fellow by the name of Joseph Whitworth popularized this technique in the 1800s.

http://en.wikipedia.org/wiki/Joseph_Whitworth

Sorry to take the thread off topic but I am interested in flattening stones so had to follow this interesting thread up. In fact Whitworth changed the method from grinding two planes together to a method of scraping the surface to achieve increased flatness.
This is the first paragraph of his paper on the subject

"The method hitherto adopted[1] in getting up plane surfaces has been (after filing to the straight edge) to grind them together, with emery. In some cases it has been customary to try them previously on a surface plate, and to go over them with the scraping instrument; but they have always been ground afterwards. The surface plate itself has been invariably treated in the same manner.[2] The process of grinding is, in fact, regarded as indispensable wherever truth is required, yet that of scraping is calculated to produce a higher degree of truth than has ever been attained by grinding. In reference to both processes a great degree of misconception prevails, the effect of which is materially to retard the progress of improvement, and which it is of great importance to remove. While grinding is universally regarded as indispensable to a finished surface, it is, in fact, positively detrimental. On the other hand, the operation of scraping, hitherto so much neglected, constitutes the only certain means we possess for the attainment of accuracy. " source

 

[ged]

Sorry to take the thread off topic

Well if it is off topic, it's not far off.

... In fact Whitworth changed the method from grinding two planes together to a method of scraping ...

I think one major contribution was the use of a dye to highlight the areas that needed attention. Nearer the topic, similar methods are used to check the edges on knife blades.

 

[ged]

I think im getting closer.

I think my strop was too thin and I only stropped it 20 times. I think this was my failing point.

Mmmm. You can easily strop too much. The last little bit needs to be very gentle. You're aiming hardly to do more than clean the blade.

 

[sxmolloy]

Hi,

Both are same steel. Mora is a scandi grind F1 is a convex.

Hi Ski.

The Mora won't have the same blade material as the F1. The F1 is a laminated VG10 steel, not sure what the material is for the Mora, either carbon steel or stainless depending on the model. I've had a Mora and still have my F1 as my first user knife, from memory both were sharp enough to shave hair.

 

[MSkiba]

Thanks chaps, all part of the learning process

 

[PeterHW]

On the query of the Mora not taking a shaving edge easily I have encountered issues of a similar nature when sharpening using the scandi grind flat on a stone .... if the angle is too acute .... meaning it has such a thin pinnacle that the steel is either tearing or will roll far too easily .... then you lose the performance you are trying to achieve by going for such a thinned out edge ....

When taken this thin I find to get true cutting performance and a lasting edge you need to apply a micro bevel or remove sufficient steel that the angle becomes less acute ....

Taking RM sharpening tutorial on his DVD's and which is now available for free on his web site ... if you look at his stropping the edge using his belt and the technique used .... plus his figure of 50 times for doing this which is a lot by any standards .... you will see that as he comes to the end of each stroke he is raising the knife considerably just before going the opposite way .... this effectively will give the thinned down edge a micro convex bevel which will enable the edge to be thick enough to last .... combine that with the raised running of the edge on the car window and a definate micro bevel is being created .... and one that is "toothy" from the window work too .... which means it will be much more effective ....

Your moving to a thicker stropping leather is probably helping by way of the curve and "give" in the thicker leather enabling a less acute and more obtuse angle to be created for the micro bevel .... enabling in essence the micro bevel to be a convex curve albeit a very small one .... and this will give the best results ....

Micro bevels for all my Scandi's give a longer lasting edge and a better one by far than I get just from the stones using the scandi grind .... and that goes for any number of different heights for the grind .... even the lowest height of grind on my scandi's is still sufficiently high to cause edge tearing and deformation issues .... the micro bevel does however cure this instantly and gives one of the best long lasting edges there are ....

If confirmation of this is sought look to how Competition Cutting blades are ground and sharpened .... they are ground very very thin at the edge and given a micro convex bevelled edge .... the same applies with scandi/woodlore style blades if you follow RM's tutorial .... but miss out a step and the edge is not as good as it will otherwise be.

However from years of use I can say that after using the blade the easiest way to bring back the micro bevel is to do a little stropping with a compound loaded strop .... this ought to work at least on a ratio of 4 to 1 before going back to sharpening the scandi grind flat again and starting all over from there ... it also prolongs the life of the blade considerably ....

 

[MSkiba]

Thank you for your write up and words of wisdom. Your point of view, along with my experiments makes a lot of sense, and I managed to get hair shaving sharpness onto my mora by doing exactly what you mentioned, by stropping at a higher angle (lightly 5 times on each side).

I knew it was the "finishing" touch that i was doing wrong but didnt know what. It all makes sense now, and can only get better from now on.


Next step, convex *runs and hides under his desk*

 

[robin wood]

It's going back a while but this thread set out pros and cons of sharpening a mora with or without a secondary bevel with close up pictures.

http://www.bushcraftuk.com/forum/showthread.php?t=29512&page=1

I don't own a mora 2000 but thought it was scandi grind near the handle probably with a secondary? and convex toward the tip.

Secondary bevels are great fast ways of sharpening if you are cutting (as all cutting in cutting comps is done) with the blade at right angles to what you are cutting. This is what we do when cutting a piece of string, food prep cutting leather etc. When you are carving wood you normally run the bevel down the wood effectively using it as a jig to control the cut, in this case then a zero scandi is best.