alternative use of old grinding wheels

[thats sharp]

As per the Tormek instruction book I always replace my sg-250 wheel when the stone gets to about 200mm. Over the years I have accumulated a lot of stones in this category.
Occasionally, I will fit one on my Tormek to sharpen a large cleaver or double axe. Other than that I have not found any other suitable use for them. Considering the cost of these wheels I was hoping to hear some ideas of how to use them beyond the Tormek recommended wheel life. Thanks for your input.

[Elden]

Ken,
   Is the width of the SG-200 the same as the SG-250 or is it thinner?

[Ken S]

Elden,

The width  of the SG-250 (and all 250 wheels, meaning having a diameter of 250mm or just under ten inches) is 50mm, or just under two inches.

The width of the SG-200 (grinding wheel for the T 3 and T4) is 40mm, or somewhere around an inch and a half.

Ken

[RichColvin]

I put a query a while ago about this to Tormek, hoping that I could buy a T4 and continue using the T2000's stone until the stone was no longer useful.  What I got back was that the stone is about 9mm wider on the T2000 (or T7), and wouldn't fit onto the T4.

It would be great if we could use a worn Sx250 stone on the T4, getting more value for the cost of the stones.

Plus, I would use the T4 for only flat-ground tools.  I am a woodturner, and sharpen mostly gouges.  The stone on the T2000 gets lots of groves where it isn't smooth across.  By having a stone dedicated to flat tools (skews, scissors, knives, etc.), I could also extend the Sx250 stone's life (as I wouldn't have to flatten it as often using the diamond truer).

[SharpenADullWitt]

I brought this up before and was shot down, by the size issue.

So let me go at this from another perspective......
While the duty cycle isn't the same on the T4's motor, does it have the same power as the T7's?  If the same power, where one is not going to easily burn it up, or do this all the time (consider even a lighter duty cycle), then couldn't one replace the T4's shaft, with the T7's shaft and swap the stone over?  (my understanding is they are the same diameter)

[Elden]

Randal (SADW),
   Your thoughts are running close to where mine are. I do not think I would want to use a full sized SG-250 even if it would fit, however. But if it were worn to 200mm, would it work if it had the T-7 shaft? If it would, I think the US bar would have to changed as well.

[Ken S]

Several things to answer here:

I think we need to ask two questions:
1) Is it possible?
2) Is it practical?

Without disassembling either my T7 or T4, I measured the length of the two shafts. The length is about the same. The threads are the same 12mm at either end. I don't know if it would be possible to switch out the shaft in the T4 for the T7 shaft. I imagine Stig can answer this. The other constraint, and I have not checked this, is that getting the water trough to work might require some minor jury rigging.

Both the T7 and T4 have approximately the same flat area on the side of the wheel. Both have approximately 50mm or two inches at full diameter. (Yes, I know the diameter is different.) A 250mm wheel worn down to 200mm will have only half the flat area (25mm or one inch).

For the cost of a T4, one could purchase two replacement SG-250 grinding wheels.

For not much more than the cost of a second T7 shaft, one could purchase a replacement wheel (SG-200)

The minimum size constraint with wheel wear is keeping the wheel wet. Again, this could be jury rigged.

I wish Tormek would forget the 50% motor duty. The operator will tire long before the motor. I suspect the 120 watt T4 motor could drive a larger wheel, if one really needed to do that. The T7 has a 200 watt motor with more than enough power.

Tormek recommends only using the side of the wheel for flattening plane blade and chisel backs. This seems logical. However, the general taboo about using the side of the grinding wheel, even though almost everyone does, pertains to much narrower wheels driven at much higher speeds. I do not see it as an issue with the Tormek.

My wheels are flat. I have not tested flattening the side of the wheel. If we look at the use of the platform tool rest (SVD-110), if a grinding wheel dressing stick is placed where the hand scraper is placed, it should be easy to correct any out of flat condition.

The universal support bar would not need to be repositioned. Tormek has very cleverly placed the sleeves such that even the knife jigs work identically.

To answer the two questions, in my opinion, this is all possible. I think it is more practical and less costly to just replace the wheel when it is worn down.

Ken

[SharpenADullWitt]

Ken,

In answer to part of your questions, I do not think this would be specifically a reason to go out and buy the T4, but I do think if one had already bought it (for portability purchases), then one would already have the other shaft, water tray, etc. to try.
I view this as a way to expand stone use, and for special projects (like the cleavers which has been mentioned).

Also, what do you consider "about the same"?  Is 1cm about the same?

[Ken S]

SADW,

Good points.

I had not considered someone (like me....) who already has both models. I should disassemble both and see if the T7 shaft will fit with the T4. I do not see motor capacity as a real issue for occasional use.

I made a quick measurement of the width of the flat portion of the sides of the two wheels. With full diameter remaining, both wheels have two inches. If the SG-250 is worn to 200 mm or eight inches, the flat plane is only one inch.

Good thinking outside the box, SADW.

Ken

[RichColvin]

A new T-4 is $400 (at Amazon ... Just a quick check).  And the SG-200 stone is $130. 

So, if I could buy a T-4 with no stone, but with a T-7 shaft, I could have a machine for about $270 that would be able to continue using the stones that no longer fit on my T-2000/T-7. 

I would end up with two machines for $85 more than a single machine with two stones (the SG-250 is $185). 

And that difference goes down if we talk about "handing down" an SB-250 ($270-$190=$60) and I save money with an SJ-250 ($270-$385=$115).

To me, this is a good deal !

[Ken S]

Rich,

Please go very slowly. I think you are about to make an expensive mistake.

Before believing Amazon's many prices, check with a couple regular Tormek dealers. I don't care who gets your business. Affinity Tool is the US importer. Their prices are the legitimate Tormek prices. Sharptoolsusa is a very reliable business, also.

The list price for an SG-200 is $109. You should be able to get a new T4 from many dealers for $399, including shipping.

I do not think you would actually be able to implement your math plan.

Your most cost effective choice is to order a new SG-250 for $184 and not worry about your present wheel.

If your wheel, whether a new or  old wheel, has grooves worn in it, you need to dress it with a TT-50 truing tool. It costs about $89. If, by chance, you have the older model, you can get a TT-50U for around $56. It is the jig minus the diamond cluster. You reuse your present diamond cluster with it.

For future reference, you should true the stone long before grooves develop.

With a new SG-250 and a proper truing tool, you should be in business for a long time. The same grinding wheel will easily sharpen your tools, including flat sharpening on the side.

Do continue posting.

Ken

[Elden]

Rich,

   Ken raised some valid concerns.

   One of them was, will T-7 shaft work on the T-4?  I was alluding to that in my use of "would it work if it had the T-7 shaft?". I don't know if it would fit the T-4. I am guessing that the length of the two shafts are not the same length, but I don't know that as a fact. One would need to know these things before pursuing the idea.

   If perchance the shaft would work, then the cost issue presents itself. There is the shaft and the Universal Support bar. Will the T-4 trough work? If not, can the T-7 trough be adapted?

   Ken mentioned that the T-7 wheel can be used down smaller than 200mm. That is true. My wheel is under 200mm. I do remove the honing wheel to allow more clearance. The trough can be raised higher by using boards, etc. under it.

   Am I back pedaling? Maybe... Ken said go slowly. I agree caution is in order. I had a high school teacher who told us, "Think about it for 5 or 10 years." I guess that is a little bit too long for this situation, but you get the idea!

[jeffs55]

I think there is something being overlooked here. Tormek recommends not using the stone when it gets to 200 mm or less in diameter. Maybe something was lost in the translation here. After all, in the great T4 vs T7 debate I brought this size difference up. The T4 wheel begins life at 200mm. I asked Jeff Farris when he quit using wheels and his response is lost to me now but it seems that it was even less than 200mm. It does not matter what machine it is mounted on, it is still 200 mm in diameter. So, the real reason you have to dump the wheel is the greater concavity of the grind. The smaller the wheel, the greater the curve on the edge, the weaker that edge becomes. You go from razor sharp to broken edge in a hurry. I do not know how handy you are but F Dick knife sharpeners and some others use two stones grinding towards each other to sharpen them. The knife edge is placed into the "valley" between the two wheels. If you could rig this sort of contraption up you would have a superlative knife sharpener.

[Jan]

I think there is something being overlooked here. Tormek recommends not using the stone when it gets to 200 mm or less in diameter. Maybe something was lost in the translation here. After all, in the great T4 vs T7 debate I brought this size difference up. The T4 wheel begins life at 200mm. I asked Jeff Farris when he quit using wheels and his response is lost to me now but it seems that it was even less than 200mm. It does not matter what machine it is mounted on, it is still 200 mm in diameter. So, the real reason you have to dump the wheel is the greater concavity of the grind. The smaller the wheel, the greater the curve on the edge, the weaker that edge becomes. You go from razor sharp to broken edge in a hurry. I do not know how handy you are but F Dick knife sharpeners and some others use two stones grinding towards each other to sharpen them. The knife edge is placed into the "valley" between the two wheels. If you could rig this sort of contraption up you would have a superlative knife sharpener.

Jeff, last year there was a pretty passionate discussion "Hollow vs flat grinding thoughts"  http://forum.tormek.com/index.php?topic=2413.45 concerning the common misconception that "a hollow ground bevel has a weaker edge than a straight ground one". The results were nicely summarised by Rob in the answer #52.

Jan

[RichColvin]

Eldon,

I'm not seeking to make a T4 with a T7 shaft, let's call it a T47.  I am asking Tormek why they don't sell such a device.

As stated, I'm a woodturner so I sharpen gouges a lot on days I can spend turning.   This makes groves in the stone.  And when I have to sharpen tools that are occasionally used (skews, parting tools, etc.) the stone isn't flat enough.  So, do I flatten the stone & sharpen, or work another way.  Usually, the latter. 

This seems like a better way than swapping out stones.

If I could buy a reasonably priced T47, and use stones that are otherwise useless (I.e., <200mm), this seems like a good idea.   

Noted, many are advising caution.  I'm not running out just yet to buy something, but I respect Tormek's leadership in the sharpening world & am interested in their experts' opinions of