Messages

For fear of repeating what Ken has already said let me add to this discussion by briefly telling you my technique.

I have bought myself an 80G CBN for this this purpose., to establish a new bevel or repair severe damage.

Second, high hardness steels are problematic with the SG wheel so I have bought diamond to sharpen those. An SB would also be good for high hardness steels.

As for out of square, as Ken says, I also use a small double square in my case to check for square as I go finely adjusting the screws to get it perfect. TBH slightly out of square is not really a big deal for most chisels and irons, but it is nice to get it just right.

In both cases, BESS tests showed significant improvement after PA-70 honing on the leather wheel.

Yes. Makes sense. If it were me I would hone lightly strop on a bench leather strop with a good quality green compound. That should improve the final sharpness significantly.

Midnight my time.

Seems that Tormek have heard the cries of despair and are introducing a new product that helps with water management. 8:30 pm Swedish time. Looks like it is time to open up the wallet again.

3/16" bradpoint bit,

Brad point bits are specifically for wood and are not for drilling steel. You will need a HSS twist drill. I have used them on aluminium but would never use them on steel.

After a discussion on the latest video from Tormek (yet to see) I have been rethinking my answer. In it they state that no honing is required after the SJ since it leaves little to no burr. If your last few strokes on the SJ are very light then that will pretty much eliminate the burr. Also, in theory if you lightly redress the wheel before the final light passes, with, say a diamond plate, then the grit will be sharper and thus be fresher this will also reduce the burr.

Also (again I think too much sometimes) Bazz from Findon Sharpening does strop from the SJ but he hand strops on a leather strop with a quality green compound and that does give him a slightly better edge than straight off the SJ.

Even though the Tormek honing compound is only marginally coarser than the SJ it does seem like you are going backwards. I would have thought that very light strokes on the SJ would give you a better result.

the burr might not be visible after the SJ grinding/polishing, but there is one.

If the grit is still sharp and you use very light strokes on your final passes then there should be pretty much no burr. Doing that would be very similar to honing. Sharp grit reduces the deformation which is what produces the burr and light strokes wll result in less deformation as well thus reducing the burr to almost nothing.

how long will this last before it gets clogged with steel particles and will need to be regraded

How long is a piece of string? Depends on how much sharpening you are doing, and even more so how soft the knives are that you ar4e sharpening. Cheapo knives will clog your wheel faster than higher hardness knives but very hard knives will glaze the wheel.

Once you get used to the feel of an effective wheel you can tell when it has stopped cutting. Also if the sound changes indicating that the wheel is too coarse then you can re-grade.

How would we know what (Rockwell C) hardness a knife may be? 

Rockwell hardness is not what we are interested in. Mohs hardness is what determines which griding material we should be using. Rockwell hardness is testing the deformation (ductility) of the material. Mohs hardness is testing its resistance to scratching. If you can scratch the knife with aluminium oxide then you are good to go. But if aluminium oxide does not scratch it you need something harder, say silicon carbide (SB) or diamond or CBN.

reason

The key is in the chemical used in the respective wheels. The SG us aluminium oxide which is suitable for carbon steels which is most knives and hand tools. The SB wheel is silicon carbide which is harder than aluminium oxide and so is better at sharpening alloy steels which are too hard for aluminium oxide. I am talking abut scratch hardness are used in mineralogy. What you are using to sharpen has to be able to scratch the tool or knife being sharpened.

If you have hard alloy steel knives such as Japanese knives that are glazing your SG wheel then you will need to use something harder to sharpen those knives. Either buy the SB, ur hand sharpen using a silicon carbide stone or diamond hone.

Not really. However, there are many different grit standards and it depends on the actual grain size. I think you would be better off with a 2 micron or finer honing compound. One solution is to use a metal polishing paste which is usually super fine.

You should be able to check a couple of things. Remove the grinding wheel and see if there is any play in either end of the shaft. It should be rock solid. If there is any lateral play then the bearings or shaft are worn. Set up something, such as blocks or such under the grinding stone end of the shaft that comes up to the almost touch the underside of the shaft without touching. Say with one or two mm lower. Then watching the gap rotate the shaft. If it is bent you should see a change in the gap whilst rotating the shaft. This is also another way of checking to see if the bearings are worn. Joggle the honing wheel and see if there is any variation in the gap.

To check for wear on the shaft remove it completely and check the area where it contacts the nylon bushings. You can see any wear since it will form a ridge where it contacts the nylon bushings.

Depends. Remove the honing wheel and drive wheel and see if it makes the same "variation". If it goes away it is in the drive, if not in the motor. It may be bearings or some change in the drive wheel. But without hearing it it would be difficult to say. If it runs well and the sound is not too harsh, as in a worn bearing, then I would not worry.

is the gap from 600 to 4000 too big

Yes. It would take you a long time to remove the scratches from the 600 on the 5000. You need to go to 1000 first. Even 600 is too fine for badly damaged knives. The aim of "going through the grits" is to remove the scratches from the previous grit. If you jump too many grits then it becomes extremely difficult to remove those scratches.

A small tube of white lithium grease works very well for the shaft.

You should be able to source one at your local automotive store.