Fastest 2x72 grinder ever?

C

chemistguy

Joined
May 28, 2013
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308
[video=youtube;UKZI-Bm_Eyw]http://www.youtube.com/watch?v=UKZI-Bm_Eyw&t=8m52s[/video]

Fun starts at 8:55

EEEEPPIC
 
that guy sure loves his stainless

just imagine how fast you could get a blade roughed out!!! (but also how fast you could screw up or hurt yourself!)
 
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That is surely a pretty show piece - wouldn't want to use it much. Most of my grinding is in the 1,000 to 3,000 FPM range. Top speed is 4,000 on my grinder and I don't even use that much for profiling. With that grinder max'd out at 9,000 FPM, it would not have much power at all down at 2,000 FPM, and where I'm doing critical work, I'll be working a lot at 1,000 FPM - and that grinder wouldn't have any power at 1,000 FPM!!

Could you imagine a small slip while hogging with that grinder? No more knuckle!!

Sure is pretty.

Ken H>
 
Ken H> said:
That is surely a pretty show piece - wouldn't want to use it much. Most of my grinding is in the 1,000 to 3,000 FPM range. Top speed is 4,000 on my grinder and I don't even use that much for profiling. With that grinder max'd out at 9,000 FPM, it would not have much power at all down at 2,000 FPM, and where I'm doing critical work, I'll be working a lot at 1,000 FPM - and that grinder wouldn't have any power at 1,000 FPM!!

Could you imagine a small slip while hogging with that grinder? No more knuckle!!

Sure is pretty.

Ken H>
Click to expand...

I think you are making an incorrect assumption about how torque varies with speed when using a vfd.
 
JT was a member here for a while, but he tended to drift/bounce/ricochet from thing to thing. Bubba Doll is gone as well as his knifemaking, now. He was making 75 caliber guns a while back. No telling what he is doing now. I don't think he has been on BF in about 4-5 years. Hope he is well and happy.

Here is the build thread on the Stainless Grinder.
http://www.bladeforums.com/forums/showthread.php/650362-Stainless-steel-KMG-Build
 
BTW, I agree with ernestrome. Torque rarely matters with belt grinders in the first place, and has almost nothing to do with VFDs. If you were using pulleys and a belt, a grinder that ran at lower than 1:1 speeds ( slower) would actually have more torque. With a properly programmed VFD, torque is about the same over most of the speed range.
 
You beat me to it Stacy.

When JT first started posting here I thought he was quite an idiot. His posts usually looked like something you'd expect a 16 year old kid to be TEXTING.

However, once he got rolling... Turned out he is a mechanically smart guy. He got hired at that machine shop (I think under the premise of sweeping the floors) and was soon making stuff on the shop owner's high dollar CNC equipment. Including stuff like that grinder. In fact, I think that video was shot in the back corner of that machine shop.

JT's problem was the same as mine (and MANY knife makers) he was VERY EASILY distracted... which means great at starting projects and really bad at finishing them. He was a good guy though... I hope he's doing well with whatever has his attention this month. ;) :)
 
Of course you shouldn't be grinding carbon steel with that - stainless only !!
 
And I thought my Bader was smokin' at 6000 SFPM. I agree with Ken about grinding speed though. I do most of my grinding in the 600-1200 SFPM range. I occasionally go up to 2000-2200 but have never found a reason to run it wide open. As a matter of fact I sometimes run it so slow on detail work that I can read the writing on the back of the belt as it goes by. I have to get below 400 SFPM before I find it starting to lose torque.
I'd hate to be in front of a 36X belt if it broke @ 9000 SFPM. YIKES!
 
darrin sanders said:
I'd hate to be in front of a 36X belt if it broke @ 9000 SFPM. YIKES!
Click to expand...

1 mph = 5280 feet / 60 minutes = 88 feet / minute

9000 fpm / 88 fpm = 102.3 mph.... holy crap

So that belt breaking and hitting you in the face at full throttle would be similar to falling off a motorcycle on your face at 102.3 mph... except a grinder belt is a bit more forgiving than hard pavement.
 
He shopped at a surplus place and showed his finds = watch all his videos


Working at a machine shop, the stainless may have been scrap drops


The washdown motor as an ebay close out / suplpus deal too.

There was a skid of them on ebay cheap until they caught on

The retail on that stainless metal alone would be out of sight, let alone a new retail $ washdown motor
 
12345678910 said:
He shopped at a surplus place and showed his finds = watch all his videos


Working at a machine shop, the stainless may have been scrap drops


The washdown motor as an ebay close out / suplpus deal too.

There was a skid of them on ebay cheap until they caught on

The retail on that stainless metal alone would be out of sight, let alone a new retail $ washdown motor
Click to expand...

After looking at retail wash down motors, I knew there was a back story. Thanks. I will probably end up with a TW90. Just interested in a comparative cost.
 
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chemistguy said:
1 mph = 5280 feet / 60 minutes = 88 feet / minute

9000 fpm / 88 fpm = 102.3 mph.... holy crap

So that belt breaking and hitting you in the face at full throttle would be similar to falling off a motorcycle on your face at 102.3 mph... except a grinder belt is a bit more forgiving than hard pavement.
Click to expand...

No, the belt has the momentum from a few ounces as it hit your face. My body would have the momentum from 180 pounds. If the belt weighed .1 pound, that would make the momentum 1800 times ( .05%) less than me falling off a motorcycle at 102MPH. (p=mv) .

That is roughly like comparing the carbon content of 1005 steel with 1095.

You really should stay awake in your physics class :)
 
Probably shouldn't worry to much about what the belt will do, I read a couple years ago that ed caffrey had a belt break on one of his high speed grinders and it ripped the knife out of his hands and jammed it into his thigh, which cost him a trip to the emergency room

Lots of guys sit while grinding exposing the femoral artery, cut that artery and you will pass out from the drop in blood pressure and bleed out in just a few minutes
 
Darrin - you say you have to turn your grind down to less than 400 SFPM to lose any torque? Have you tried to "bog" the grinder down at theses lower speeds? Just a fact of physics, the motor is producing less HP at those lower speeds (lower frequency), than at 100% speed. At 150% speed (90hz) the motor is still only producing name plate HP.

As I mentioned, with my 1 hp lathe with the speed turned low for threading it requires shallow cuts to prevent motor from bogging down, while at higher speeds the same depth cuts wouldn't even load the motor.

Ken H>
 
JT was up and coming when I was just starting to get into knifemaking. He had a handful of videos that were quite helpful to me at the time.

Seems like he definitely has a knack for success in whatever he's interested in at the time, and it shows with that grinder. He did a great job on it.
 
The jewelling is a really nice touch, no need to paint.

I looked into the materials costs for the SS to do that and that idea died petty quickly
 
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