Tormek T7 SG 250 wobble/accelerated wear

[gregg]

Hello,
I bought the T7 a few months ago, and use it primarily to "rough out" stainless cutlery for my sharpening business. This has helped cut down the time, (and effort!) spent on that part of sharpening so I can finish on benchstones, my "selling point". The problem is that I can barely do between 7 and 10 knives before having to re-dress the stone, as it gets out of round extremely quickly, it seems to me. When I pass the dressing tool, the amount of out of round I can see sighting along the surface always seems enormous, and it causes a lot of vibration as i near the outside of the stone. I've checked the axle, and it seems true, but the stone wobbles about 2 mm at the outside edge, (already down to 215 mm diameter!)on the shaft when not screwed on. A tech from Tormek indicated that this was normal due to grinding stainless steel, but at this rate I'll need a new stone for each 2 or 3 hundred knives. Does anybody have any ideas about a solution? (I've considered the black stone, but this has got me a bit worried.

[Ken S]

Stig, I think we could use some factory expertise on this question.

Ken

[Rob]

I upgraded to the SB Blackstone for grinding HSS turning tools for much the same reason ie harder metal, more suitable stone being the theory.  I must say, I've not really noticed a huge difference in its "stamina" compared to the original grey wheel.  I would be interested to hear any factory response to the actual scientific differences in the two wheels

[gregg]

Yes, pleeeaaase!
By the way, I'm looking at less than 200 knives so far; figure about 7" average=@230 total feet of stainless steel; times 14 passes, give or take, to make @3220 feet! I just would like to know if the amount of play shaft to stone is normal. Thanks for your interest.

[gregg]

I upgraded to the SB Blackstone for grinding HSS turning tools for much the same reason ie harder metal, more suitable stone being the theory.  I must say, I've not really noticed a huge difference in its "stamina" compared to the original grey wheel.  I would be interested to hear any factory response to the actual scientific differences in the two wheels

That's also why I asked about the Blackstone; not because stainless is harder, but it is abrasion, ie. grind resistant. (Easier to benchstone Aogami super @63 HRC than X50CrMo14 hardened to 55HRC!, for example!)

[Rob]

That's my understanding behind the theory of the blackstone.  Apparently it doesn't cut any faster than the grey stone (which I found acutely disappointing if I'm honest) but it is meant to resist wear better for the modern exotics like HSS.  It doesn't do carbide though.

[Stickan]

Gregg,
Dismantle the stone and check if the bushings are correct on both side, look for cracks or uneven wear.
Also, make a mark on the lowest point of the stone and true it again. If it appears at the same time over and over again there might be something with the stone.

You did not write if you sharpen knifes with or against the stones rotation, that would also be helpful.
Shapening with the stones direction does need more training. It´s normal that the stone wear´s more when you are new using the system. After a while the right technique gets better and the wear of the stone gets better.
Sharpening against the rotation makes it easier to hold the blade flat on the stone, using the water as a guide. Even makes it faster and less burr to hone.
I will again point out that using support@tormek.com will make any answer faster to get an reply on.

Best,
Stig

[gregg]

Hi,

Thanks for the reply. When you refer to the bushings, do you mean on the stone itself; (there seems to be one on the inside that looks to be about 4 mm, with some "minor" chipping, scallop-style, and an outside bushing which seems to be about 2 mm thick, from what I can discern). The recesses seem to be pretty much the same. I do very little free hand on the Tormek; a few butchers' cleavers a month, plus a few of mine "for fun", but save the free handing for finish work on the benchstones. The knife jig/angle plus angle master are good for keeping track of clients' knives from one sharpening to another; quicker dial in for the angles.

I'll try the pencil marking trick; moving the stone around on the shaft doesn't seem to ameliorate the speed at which it gets out of true. Also, what about the side to side wobble with the stone not locked down? At the moment on the inside of the stone difference between high and low are easily 2 mm.

One more thing; when I'm using the TT-50, when it starts to vibrate, starting about 2/3 of the way across from inside to the outside, I have sometimes left the tool in place a bit to see if it would "calm down""; the result has been the stationary grind getting louder and louder, contrary to my expectations. I haven't dared to leave it in one place  because of that, and even going extra slow still leaves major waves on the surface.

Basically, I know that getting out of round a bit is normal; I've worked with several different powered wet grindstone systems over the years, and I know how to let the machine "do the work", as they say, it's just that it seems to be a lot, (as opposed to just wearing down in general), which entails a lot of dressing, and often, (four times on the last series of 15 knives to make the "egg"  go back to round), which, in turn means more stone diameter reduction. The difference between high and low on the circumference gets up to almost 1 mm in 10 knives or so, which makes the work disagreable until I re-dress.

Enough ranting on my part; I appreciate your help, and will try the pencil low point trick tomorrow and let you know the results. (I presume you mean "at the same place over and over again", not the "same time").

Thanks again, gregg

[gregg]

Hi,
So today I did a bit of truing with the TT50, stating at the high point, doing a slow pass each time, (I dropped it after two full passes 1/2 of the distance between numbers on the micro-adjustment nut each time), until I had "full contact" across the stone. I also tried letting the diamond housing "free ride", (there is some vertical play there) and with it wedged in lowest postion. The result in both cases was as pictured.

Still waiting to re-do to see if high/low spots remain constant; had to take time off from work for some photoshooting for the business.




http://i1361.photobucket.com/albums/r669/gregg31/SG250_zps2bc8f52a.jpg

[Rhino]

my diamond truing tool does not vibrate at all going across the stone when I did a minimal trimming of the stone.  Minimal trimming for me still means taking something off 360 degrees around.  Have you tried taking a lighter cut or a deeper cut to cut down on vibration or maybe your system is not aligned.  Just a thought.