Razor Sharp system

[dikman]

I have all sorts of gear for sharpening blades - oilstones, Arkansas stones, wet-wheel grinder, belt grinder etc, but while at the annual Adelaide Knife Show a chap was demonstrating the Razor Sharp system. I was quite impressed so bought it. Basically it's two paper wheels with one being coated on the outside with 180 grit and the other (slotted) wheel given a coating of fine rouge.Using them he brought an ordinary kitchen knife to a hair-shaving edge in very little time. I bought the set for a 6" grinder, but because both of my 8" grinders are in use I had to buy a 6" grinder too! I decided to buy the cheapest I could find as I didn't need something with a lot of power for this job - the Ozito is only 150w but has a 3-year warranty so it seemed like the most practical option for $35. It came with two grinding wheels but I reckon it would have been underpowered  for anything other than sharpening drill bits! I stripped the wheels and guards off and raised the base to clear the 8" Razor Sharp wheels. It takes a few seconds to come up to speed but is plenty powerful enough for this job as sharpening knives doesn't load down the motor.

A quick try and it works well, although like everything there will be a bit of a learning curve. Should be good for my leatherworking tools (and woodworking stuff too).

[JKHelms]

I’ve got some of these paper wheels on a grinder and they work good. 

Give you some advice I learned the hard way. Turn your grinder around so wheels rotate away from you. If the knife catches it will throw it away from you. 

[dikman]

Thanks for the reminder JKH, the chap selling them mentioned this but I forgot. I removed the base and rotated it 180* so the switch is still at the front. Now I just have to rig up a guide system to get consistent angles.

[dikman]

So I made a jig to (theoretically) get consistent sharpening angles. My first idea was to just fit a bar across the wheels but I soon realised that wouldn't work because of the knife handle, dragging the knife across the inside of the wheels would raise the blade and change the angles. So, version 2 with blocks the width of the wheels, version 3 with added spacers under the blocks for more clearance. Looked good, but unfortunately there is a slight problem with such a design, because the wheel is rotating away from me it tends to grab the blade and try and drag it forward along with the wheel. This results in an uneven bevel. Pressing down harder on the blade didn't work as that also put more pressure on the wheel and yes, it's quite easy to burn a blade doing this!!

The only way this can work would require a fairly elaborate means of clamping the blade to the guide, such that it can slide but not lift, or perhaps some sort of arm coming from the rear of the guide, over the top and finishing just above the front of the guide by the wheel to stop the blade lifting. This may be the easiest to do but would need to be adjustable for different thickness blades. Could be getting a bit complicated.

 

 

[dikman]

Version 4! The guide wheels are some plastic things that I had and I used the lathe to cut a V groove in them. Not the prettiest of things, but as long as it works (which it appears to do) it doesn't matter. The wheels took a bit of fiddling to get them adjusted right but now the blade doesn't lift as I pull it across. If the wheels prove too soft I'll make some new ones from nylon.

 

[Joachim]

On 11/7/2018 at 10:57 PM, dikman said:

 

 

On 11/7/2018 at 10:57 PM, dikman said:

Version 4! The guide wheels are some plastic things that I had and I used the lathe to cut a V groove in them. Not the prettiest of things, but as long as it works (which it appears to do) it doesn't matter. The wheels took a bit of fiddling to get them adjusted right but now the blade doesn't lift as I pull it across. If the wheels prove too soft I'll make some new ones from nylon.

 

Could you please post a picture of how it is used? I may just be daft but I can't visualize how one would use it. Thanks!

[Squid61]

At a "No Load Speed: 2,950/min" coupled with the surface velocity of an 8" wheel  this seems like a good way to overheat a blade edge.

[dikman]

Joachim, I've dismantled it because I fitted the wheels to a larger grinder, I found the wheels were too close together on the small grinder and sharpening a longer blade was awkward. I now just use it freehand, works fine. I was overthinking it before!

Squid, it's not a problem because you don't apply heavy pressure for extended periods (unlike using grinding wheels or belt grinders). It isn't meant for hogging out steel, only for fine honing, sort of like a mechanical strop.

[Squid61]

I understand dikman.   I never use a power wheel or belt on any of my knives, not even pocket knives; I have plenty of time for hand sharpening and honing.  Manufacturers use belts and wheels for efficiency so many of us resharpen new knives just to get past the factory edge damage.  Edge damage can occur in an instant, particularly on the ultra fine edges used in leather craft and wood carving.  I also do not like the slight hollowing immediately behind the cutting edge produced by a wheel; even with a light touch, repeated honing removes metal.  Most of my carving blades and even a couple I use for leather are a flat grind and any degree of additional metal removal behind the cutting edge would weaken an already delicate edge.

[Joachim]

Tis all good. I'll probably just use my grinder freehand as well. A guide will have to come later. Thanks anyways

 

[dikman]

Squid, I've got all sorts of sharpening gear, collected over many years () and I find the paper wheel to be excellent for a final honing BUT you are quite right in that heavy pressure would still likely cause damage to a very thin blade/edge. The other wheel, which is paper embedded with grit, definitely would if used carelessly. I still keep a leather strop next to my leatherwork tools.