Recommendations for faster grinding on damaged knifes? Tormek diamond vs CBN

[LarK]

Hello friends! My first post here on the forum and just recently started accepting knifes from customers. Have been doing home sharpening for 2 years on a T8 and after many requests from friends/colleges I have decided to start a small side business with sharpening.

My question is as follows: I have the Tormek DF250 wheel and recieved a knife with a few serious dents/chips in the edge. This took me quite a while to sort out with the 600 grit diamond wheel. Can I expect a substantial speed increase with the DC250 or should get a coarser CBN wheel like 80 or 160 grit?
My second question is if it is ok to swap between a CBN and tormek diamond wheel without changing the support height? The tolerances on ex: knifegrinders CBN wheels and the tormek diamond ones seem pretty close?
Does anyone here have experience with this and might be able to make a recommendation?
Thank you for this amazing forum, been learning alot both here and on YouTube 😊.

[John_B]

Since you mentioned that this would be part of a business I would suggest doing a quick cost vs. benefit calculation. For severely damaged knives the 80 or 160 grit would speed up the grinding time. How many of these knives do you see and will the profit from them offset the cost of the wheel? Your time is important as well so you need to assign yourself a $/hr wage to see what you save there.

I have a small concierge business with limited select customers. I do not see many larger chips from them as I think they may have listened to my knife use talk and print out. When I do have a bad knife I start by truing my SG-250 which results in its coarsest grit possible. This speeds up the grinding for me and has worked well on the couple of nicked knives I got.

[LarK]

Thank you for the reply! For clarification this is more like a small side business hobby thing and cost isn't really an issue for me. I do this because I enjoy it  so I would say that my priority is time per knife not really wheel/cost/knife. Point is that the knives I got weren't catastrophic but had a few dents of 0.5-1 mm size and they took me a good 40-60 min to sort out on the 600 grit DF-250. Maybe I'm really slow and to catious but I like being thorough and getting a good result. So just wanted an input if the DC-250 is a significant decrease in time spent on each knife or if it is better to go even coarser and if so; its possible to swap between diamond and cbn wheels without adjusting the support as this is another time consumer. I like sharpening but like I said I also have a day job, family and can't spend all my free time sharpening even if I enjoy it 

[Hannsi1957]

there is a completely different problem to be illuminated here. if you grind knives with clear chips and work on your stone for 20 minutes, then this is only recommended in an emergency. you can compare this figuratively when a carpenter grinds a planed tabletop, he doesn't start with a 600 grit. no he increases from coarse to fine. of course it would also work with 600 but he needs days and the sandpaper will be worn out afterwards. it is exactly the same with the grinding of knives. the right stone for each job saves costs and frustration in the medium term. an example: i use my CBN stones starting with the 80 grit stone. with this i have removed any chips and created my desired angle with just a few strokes. This is exactly what this stone is suited for. after that, and this is the good thing about it, i only pull over the 160 grit 2 more times. then once over 400 and once over 1000 and everything is done. the big advantage is that the coarse stone does the work and the finer stones are not burdened with hard work, which multiplies the service life. Now comes the big disadvantage..... it is cost-intensive to equip yourself in this way. however, once you have it, you will never give it up and ask yourself.....why haven't I done it this way for a long time?
I can usually finish a knife with 1-2 mm deep chips in a maximum of 5 minutes, including changing the stone.
cheers Hanns

[Stickan]

Hi,
Just a reminder of the DC-250, which many knife sharpening services use. Removing material from a knife-edge is normally a fast procedure since the amount of metal is very little on regular chef knives. Even with some chip-out, the 360 grid DC-250 makes it an easy task. The time it takes to exchange several stones/wheels is more time-consuming than using a maximum of two wheels.

I am also surprised why so many seem to try diamond or CBN before they learn to use the SG stone, with its 220-1000 capabilities. You can apply a higher pressure than on a CBN or Diamond wheel and quickly get it coarser with the SP-650, stone grader. This stone is my go-to any day.

My best tip still is to learn about how much pressure to apply. You can easily save minutes when this has become a part of the skill to sharpen.

Best,
Stig

[Ken S]

Lark,

Set up between a  diamond and a CBN wheel should be a very minor procedure taking almost no time. The Projection should remain constant. If the wheel diameters happen to be the same, the Distance would also remain constant.
If you happen to have two wheels with slightly different diameters, any correction needed is easily done with the microadjust. One full revolution of the microadjust equals 1.5 mm. One number change (1/6 of a revolution) equals .25 mm change. This should quickly become almost automatic, requiring almost no time. The EZYlock makes wheel changes very fast.

As to using the SG versus other grinding wheels, I realize that both diamond and CBN wheels cut faster than the SG.
I have also seen many posts from members wanting different wheels, sometimes more coarse and sometimes more fine (SJ). I always wonder if this is based on mastery of the SG. Over the years, I have had the pleasure of getting to know Stig. I hold his sharpening knowledge and technique in high regard. Whether or not you end up adding another wheel, I would be certain to try Stig's advice before deciding.

Ken

[Hannsi1957]

Hi,
Just a reminder of the DC-250, which many knife sharpening services use. Removing material from a knife-edge is normally a fast procedure since the amount of metal is very little on regular chef knives. Even with some chip-out, the 360 grid DC-250 makes it an easy task. The time it takes to exchange several stones/wheels is more time-consuming than using a maximum of two wheels.

I am also surprised why so many seem to try diamond or CBN before they learn to use the SG stone, with its 220-1000 capabilities. You can apply a higher pressure than on a CBN or Diamond wheel and quickly get it coarser with the SP-650, stone grader. This stone is my go-to any day.

My best tip still is to learn about how much pressure to apply. You can easily save minutes when this has become a part of the skill to sharpen.

Best,
Stig

Hi Stig,
From what you've said, I'm guessing that you've never grinded on a CBN stone. I can only say that everyone who switches from "normal" stone and grinds on CBN for the first time is thrilled and can not understand why it is suddenly so easy and fast. And all without any pressure. The removal of a 160 grit CBN compared to the 220 grit of the original stone`s is 5-6 times higher and that "without" exerting any pressure. Here, the grinding wheel does the work, not the pressure. I'm not saying that you can not grind well with a "normal" stone, on the contrary, I also initially always grinded on the normal stone until I finally landed on the CBN Wheels.
Believe me this is grinding on a completely different level than with a normal stone.

Best
Hanns

[Ken S]

Lark,

I would factor in your sharpening volume and business environment. If, as an example, you charge $5 for a typical knife which can be efficiently sharpened with the basic SG, will your customers pay $20 to have you sharpen a knife with damage or harder steel requiring either four time the grinding time or investing $300 in a super abrasive (diamond or CBN) wheel? If so, how many knives do you expect in this condition?
If you expect only a few, I would probably just figure that you are being paid for your grinding time and have at it.
If, on the other hand you are expecting a lot of knives in this condition, and your fees justify the investment, I would invest in a coarser wheel. (or find more careful customers.....

Ken

[LarK]

Thank you guys for all the great inputs. I do have the SG stone and use it alot but really like the feel of the diamond on harder steels. I have to confess that I am also a gearjunkie and can't help myself to trying more stuff. The Tormek system is just to much fun  .
My main question was if the DC250 removes material fast enough in your opinions and will be adequate for the task or if I should just go for an even coarser CBN (trying not to buy every accessory). You have given me really good advise and things to ponder. I realise this is a highly subjective question but I really do appreciate all the input you have provided, many thanks!
As I've already explained, this is still mainly an expensive hobby 
With all this said I must say that the SG is my favorite stone when it comes down to feeling and sound. It gives me a little bit more enjoyment and the sound is not as harsh and hollow as the diamond wheels. Can't say anything about the SB stone as I have not tried it but I can imagine that it has a similar "dense/muted" sound and feeling.

Kristian

[WimSpi]

I am surprised how many knives I have to sharpen do very damaged. Then it's a new customer. So far with me, restoring a damaged cut goes on a belt sander (stationary). The last part of the restoration process then goes on the Tormek.

[capt rich]

 I just did a 12" spoke shave with a 1/4" chip [yard sale]. Used a 2'' baldor sander, ground out the chip and reprofiled. Used orbital sander to take out the grind makes. Rainy day will attempt to finish it. What angle should it be sharpened too???

[RickKrung]

I just did a 12" spoke shave with a 1/4" chip [yard sale]. Used a 2'' baldor sander, ground out the chip and reprofiled. Used orbital sander to take out the grind makes. Rainy day will attempt to finish it. What angle should it be sharpened too???

Seems this is a question for the "Hand Tool Woodworking" forum, rather than knife sharpening.  I did a web search for spoke shave bevel angle and got a variety of hits, all of which were the type with removable blades.  One site said bevel angle should be no greater than 30º.  From your post, it seems you are referring to a solid tool, without a removable blade.  I'd think it would be the same or similar to the removable blade type, but if you do a similar search, you'll find the bevel angles are all over the place, depending on the type of tool and its use.

Are you sure you aren't working with a drawknife?  If so, maybe it does belong in this forum.


Rick

[RichColvin]

Rick,


Either way, it is better in hand tool woodworking.


Rich

[Ken S]

I just did a 12" spoke shave with a 1/4" chip [yard sale]. Used a 2'' baldor sander, ground out the chip and reprofiled. Used orbital sander to take out the grind makes. Rainy day will attempt to finish it. What angle should it be sharpened too???

Capt. Rich,

You ask a good question. As much as I like order, I am more interested with the question and answer than with placement.

As noted in earlier replies, I believe the tool you are discussing is commonly called a drawknife. If sharp and in skilled hands, these traditional tools are quite useful. thirty degrees sounds right for the bevel angle.

Regarding the chip: Unlike a chisel or a plane, only a small part of the sharpened edge does the actual cutting. For future reference, for a tool for your personal use, I would leave the chip and just sharpen around it. That quarter inch, if left on the tool, can provide years of useful work. If you actually arrive at the point where you have sharpened the rest of the blade to match the chip, you will have become quite skilled with your tool.

I realize my answer may not sit well aesthetically. I tend to think of my tools as tools, rather than museum pieces. 

Ken