KMG style grinder upgrade help

Grinding bevels at 8,000 SFPM speed is for the true experts, Check with Stacy, and a few of the other experienced knifemakers and see how many grind at 8,000 SFPM.

This is the main point that seems to be somewhat overlooked. I'm all for getting the most out of my more expensive ceramic belts, but if my knife blades evaporate in front of me every time I try to grind one..... ;)

It's fine if your profiling and hogging material, but then all of the finish work will be done at slower speeds anyway. Also, there are plenty of other types of belts that work just fine with lower speeds. Ceramic belts aren't exactly the end all/be all. Just something to think about I suppose...
 
Well I am sitting on 500$ worth of Cubitron II belts, last year I spent almost a grand on ceramics ...i made a little over 30 kitchen knives. Any other belts Ive tried would just dull/burn/smear and heat up my hardened blades. I think its 90% of my problem is the belt slip, which I had thought was due to my loss of power transmission with the pulley/v-belt set up. I am hoping even with 700$ worth of upgrades on my grinder I wont need to buy any more belts for the next year. That would be awesome!
 
This is what I would do. Keep the 1800 rpm motor. Make/buy a 7-8" drive wheel. Double hertz in the vfd. Get a 30 lb gas strut and mount it so the tracking arm sits level.
If you do this you will have a monster of a grinder with enough finesse to file your fingernails at low rpm.
 
. Also, there are plenty of other types of belts that work just fine with lower speeds. Ceramic belts aren't exactly the end all/be all. Just something to think about I suppose...

Very true. I currently only use ceramics in 36, 50 and 100. Much of my grindings with with Gator, AO and cork
 
I went to convert to direct drive this past friday. Foiled again! I forgot that even though my motor shaft was 5/8" my step pulley/ arbor/ drive wheel was 3/4" ...grrr. So I ordered a 6" drive wheel to use for the direct drive. I had to get some grinding done this weekend so I put this grinder back together with the step pulley. Now that I understand a bit better about the belt slip being the main culprit I worked on mounting the motor to have more tension on the belt. I also replaced the belt. I did not realize how beat up the old one was. I did get better results. I ground 6 pettys and 4 full size chef knives with only two 40 grit 3m 967s.
Of course these were soft steel, Its the hardened steel where I really seem to have the problem.

Interesting to note though that I do believe I can stall my 1.5HP 1 PH motor. If I really bear down on it the surge protector the grinder is connected to trips. Which got me thinking...Am I somehow limiting myself being plugged in to a surge protector?
 
OK, since this is the thread where I was sorta poo-pooing the use of ceramic belts as being only in the ream of experts when grinding bevels. Please allow me to provide an update on my use of ceramic belts today grinding a couple of blade bevels.

Running grinder at 4,086 sfpm (call it 4,000 sfpm) with a new ceramic belt - boy did it remove some metal on the bevel! I think I'm going to like it as I learn a bit more. Today it removed so much metal I actually cut into the edge a bit and had to narrow the blade a bit to fix where I'd over ground doing the bevel. I've got a couple 50 grit VSM ceramic belts and plan to use those grinding bevels. Just got to be careful.

I can imagine what a good ceramic belt would do at 6,000 SFPM - WOW!!! That's for the experts.... hmmm, wasn't that what I said about grinding at 4,000 sfpm? {g}

Ken H>
 
Interesting to note though that I do believe I can stall my 1.5HP 1 PH motor. If I really bear down on it the surge protector the grinder is connected to trips. Which got me thinking...Am I somehow limiting myself being plugged in to a surge protector?

What the max current rating of the power strip? If running a 1.5hp motor at 110VAC, the current should peak around 15A or so. If you're running a 15A circuit breaking power strip (and especially if there's other things plugged into it) I can see how it might trip when you were really hogging. If it's a lighter gauge cord, or a relatively long cord, this could contribute a little to the current draw as well. If it always trips the strip, but never the breaker that the strip is connected to, you might be better off just plugging straight into the wall.

Not sure if you have a surge protecting power strip, or just a circuit breaking power strip, but either way, for the purposes of a grinder motor, there's really no advantage that I can think of for plugging into a power strip. Surge protection really shouldn't be a huge concern (surge protectors are for massive voltage spikes), and power strips really aren't meant as a substitute for overload protection (as a breaker would be), but they simply include the breakers because it's easy to overload them when filling up all the slots with high wattage devices.
 
Running grinder at 4,086 sfpm (call it 4,000 sfpm) with a new ceramic belt - boy did it remove some metal on the bevel! I think I'm going to like it as I learn a bit more. Today it removed so much metal I actually cut into the edge a bit and had to narrow the blade a bit to fix where I'd over ground doing the bevel. I've got a couple 50 grit VSM ceramic belts and plan to use those grinding bevels. Just got to be careful.

I can imagine what a good ceramic belt would do at 6,000 SFPM - WOW!!! That's for the experts.... hmmm, wasn't that what I said about grinding at 4,000 sfpm? {g}

Ken H>
Well , I'm glad that you find out that the speed is good , Ken :thumbsup: I promise that I will make video about grinding on 8000 SFPM and I will do that this days . It will be very short video if I use fresh/new belt :D 6000 SFPM ....... no way :) friend of mine work on little bigger drive wheel for my grinder , 10 000 SFPM is right speed to grind bevels ..with help of jig of course ;)
 
Welll, for me even though knifemaking isnt my full time job, its my part time job/ second job/ wife can stay home with the kids kinda job so time is money! with the way it is now I can grind a full size chef knife about 75% pre heat treat, then about another 24% post heat treat in an hours time. Also its important to note that these type of knife is so much more thin and so much more distal taper , most knives would be finished when this knife is only 75% ground. this is what it takes to julienne an onion, the customers say it "ghosts" right through because you cant even feel the knife when its in the cut! yah seriously thin tips...anyway ...I can grind this knife in an hours time but it cost me about 60$ in ceramic belts. So if I can improve this, I must! tomorrow is my day to set up the new motor/vfd and get a start on the new grinder...Do you guys know , what is the tool to measure SFPM?
 
kuraki kuraki Beaumont metal works. I was also looking on the bay, theres a nice looking wheel for about 80 bucks
 
Yeah vwjackstraw. I've bought parts from him in the past. Probably will buy his wheel since my new grinder tracks off the drive wheel.
 
Hi All, I want to say thanks again for all of your guys help. Ive got the VFD wired and new motor mounted along with a 6" crowned drive wheel.
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I know I mounted my VFD funny, I will probably change it eventually but for now it works fine.
It does seem like my abrasive belts are working more efficiently when I have the 1.5 HP 1750RPM motor cranking full speed with the 2x jumper set on the VFD. The 6" drive wheel helps too.
The damn thing is still very loud, after 5+ years its probably time to change some bearings. My tracking wheel also needs to be resurfaced. Thanks again all.
 
Ok, I replaced my 6 year odl 20 lb gas spring with a 60lb gas spring, It makes a huge difference in the life and efficiency of my ceramic belts. I notice it is putting a TON of pressure on my motor shaft/drivewheel. I need to bolt the motor down with bigger bolts at the very least as it is actually pulling up a bit. Even then I am afraid of my almost $400 motor having a premature death. Is this something I should worry about?
 
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