FELT wheel not burning the edge

[wootz]

We have been using this modified felt wheel for a while for deburring and honing, with excellent feedback from butchers.



This is a rock-hard felt wheel where I cut cross-slots using this Dremel cutting wheel


I run this wheel on a half-speed grinder at 1400 RPM, and thanks to the slots it works like a good fan, cooling the edge as it hones.

I had to think of a powered quick honing method when one butcher commented on the edge we get after the grinding and paper wheels that the "shoulders" as seen in the 2nd edge below somewhat hinder the cut; while he prefers a smoothed V-profile


Felt smooths away the bevel line so well that the edge continues into the blade face seamlessly. My butchers are happy ever since.

[WolfY]

This is great Wootz,

I just got a high speed grinder with 2 speeds (1450/2850) exactly for this reason. Haven't assembly it yet.
I have 2 pcs of 25mm MDF not ready for use yet. Do you think it is as good as felt for this purpose?

[wootz]

We considered the felt wheel because we wanted a honing "base" more pliant than paper wheels to better polish the bevels for a smoother cut. MDF is even less pliant than the paper wheel and wouldn't suit the purpose. Paper wheels are our choice to deburr the edge apex not rounding it, but for the edge bevel felt has proved the best.

I had been cautious about felt since we saw in one meat plant where they use a felt wheel at high RPM, that honing/deburring on the felt wheel compromises edge retention - details are in this thread on the BESS forum http://www.bessex.com/forum/showthread.php?tid=237 ; a Meat News article about our meat plant research is also on the BESS forum.

Felt wheel manufacturers do not make 10" split laps at all, while the 8" felt split laps they make are all too narrow to use for knife honing.
But when it dawned upon me that I can cut the slots in the felt similar to the slotted paper wheel, we re-discovered the felt for honing.
Felt has some attributes that make it unique compared to paper or leather wheels.

[Ken S]

Interesting post, Wootz.

One of my too many projects in progress is using an eight inch hard felt wheel placed in the grinding wheel side of the T4. I debate between hard and rock hard felt. Before the testing is over I may end up with both. I also may end up using a ten inch diameter wheel. This fits easily on the T4, as no water trough is needed with dry felt wheels.

The formerly wet side is an easier place to use, as the felt mounts on the shaft. No working around the drive wheel is required. In my case, I could set up the grinding on the T7/8 and switch to the T4 with a ten inch felt wheel with essentially no changeover time.

Too many projects.

Ken

[WolfY]

We considered the felt wheel because we wanted a honing "base" more pliant than paper wheels to better polish the bevels for a smoother cut.

I had been cautious about felt since we saw in one meat plant where they use a felt wheel at high RPM, that honing/deburring on the felt wheel compromises edge retention - details are in this thread on the BESS forum http://www.bessex.com/forum/showthread.php?tid=237 ; a Meat News article about our meat plant research is also on the BESS forum.

Felt wheel manufacturers do not make 10" split laps at all, while the 8" felt split laps they make are all too narrow to use for knife honing.
But when it dawned upon me that I can cut the slots in the felt similar to the slotted paper wheel, we re-discovered the felt for honing.
Felt has some attributes that make it unique compared to paper or leather wheels.

Most Interesting thread at "bessex" forum. I signed up and will follow.

Can you tell what kind of felt is used to make the wheel? Or where can I get it? Is there many different felt materials that differ? , widt, Prefered RPM, etc...

Did you check their honing method. E.g, angle, pressure, and other characteristics?

[wootz]

Rock-hard felt for honing, we get ours from http://durofelt.com

I know many knife sharpeners use felt wheels at high RPM, thinking that loading them with a buffing compound saves the edge from burning - unfortunately, it does not save the very edge apex, your fingers on the blade don't feel any heat but the 0.1 micron apex gets partially annealed.

That meat plant sharpener hones knives freehand on a rock-hard felt wheel with a buffing compound similar to White Rouge, at 2850 RPM, 2-3 passes each side alternating till he sees the burr is gone.
They try to avoid Chromium containing compounds due to food safety, the 5% Chromium Oxide content in the green rouge and similar compounds makes it controllable - the regulated threshold is 1%.

My approach is that felt is great for polishing bevels, but not for deburring the edge apex. At that high RPM the deburring wheel must be slotted not to cause overheating.
Even on the slotted felt wheel I hone at 0.5 degree less to spare the apex, e.g. the edge sharpened at 15 dps I will do on the felt wheel at 14.5 dps; I then deburr the very apex on the paper wheel.
But this may be an overkill, with the slotted felt wheel we should be able to complete deburring, just I haven't finished testing it in this mode.

[Ken S]

Interesting and informative post, Wootz.

The more I learn about sharpening, the more I become aware of what I do not know, and must know. I have often stated my belief that a well trained sharpener should be fluent with different sharpening methods and techniques. I am becoming increasingly aware that the well trained sharpener should also be knowledgeable in food regulations, both in restaurants and in processing plants.

When I purchased my felt wheel (also from Duro Felt), I debated between hard and rock hard. In hindsight I should have chosen rock hard. I will work with my hard wheel. Even if I eventually end up with a rock hard wheel, it will be a good point of comparison. Whenever I start one of these experiments, I do not expect success on the first attempt or in every case. Incidentally, the present kenjig is a couple generations away from the initial prototype and being redesigned for diamond wheels.

I am fascinated with the factors which go into our desision making process. In this case, why do we use paper wheels at high RPM, 2850 for you in Australia and 3450 in the US?Is it because the paper wheels cut better at high speeds? Or, is it because higher speed motors are less expensive to manufacture and easy to market?

The wax which holds the grit needs the higher temperature of high RPM to melt properly. This makes a good argument (not definitive, but good) for using high RPM with the first paper wheel for performing the finer grid grinding. Does the higher RPM (and higher temperature) benefit the polishing wheel? Or, is it a marketing and cost expedient just to use the same high speed motor and mount the polishing wheel on the other end of the same shaft?

If we always run the risk of overheating the steel with high speed, is the expedient worth the risk? I understand modern developments in sharpening have considerably lowered the heat risk. The slots in the felt and paper wheels seem a practical solution. CBN and diamond wheels transmit much of the heat away from the ground edge, another practical improvement.

Wootz and I are exploring the same problem from different points of focus. As an innovative professional sharpener, Wootz must balance sharpness with sharpening efficiency. If he has fifty knives to sharpen for a plant, he must work efficiently. If part of that efficiency requires a second or third motorized unit, that is a cost of doing business.

As a home sharpener, I have the luxury of less time pressure. I want the same sharpness that Wootz achieves, however, time is not a pressure with my half a dozen home kitchen knives. If it requires a bit more time to achieve the same results using my felt wheel with my Tormek, that is not a problem for me. Naturally I am interested in the work that professionals like Wootz and others do. We all benefit from it, just like my small SUV has benefitted from the innovations of racing cars, even if I do not drive 200mph down my street.

I wonder if Torgny Jansson imagined today's Tormek forty years ago?

Ken

[WolfY]

I'm little puzzled with the use of Felt for deburring compared to the slow turning leather wheel.
Could you summarize the pro's and con's in comparison?
Does it save time?
Are you sure it does not affect the apex at all?
If you compare it to sharpening the knife at about 10 dgrs first and then raising to the required apex (let say 16~18dgrs) giving a thin shoulder above the apex.
For me being out to the clients place it is not very practical to bring a bench grinder too.