Knife vibrating on belt grinder

[Amber_2477]

Hi everyone,

Im experiencing a weird vibration at around the midway point while doing the bevels on my most recent kitchen knives on the belt grinder. I have a 48inch shopmate variable speed belt grinder. Lately Ive been making kitchen knives, so long and thin-ish blades, doing the bevels using a creative man bevel jig. Ive had to extend the bench by clamping a large bathroom tile to the existing bench. When i hit the midpoint along the bevel the blade starts doing these mini-vibrations, which seems to screw with the cleanness of the bevel.
Im not sure if this is caused by the combination of a mild bend in the forged blade (im not at the level where i can get them dead straight yet) and using a jig, or if the tile bench extention is contributing. Or something else? Anyone else had this problem?
The grinder itself is not vibrating at all.
Thanks!!
Amber

 

[Del Raso Knives]

Hi Amber, your shop mate and creative man bevel grinder will not be well known products here. My guess is the vibration is coming from grinding a long thin blade on a much shorter jig.

 

[john april]

if i feel any type of vibration or skipping, its usually either because the belt is dull and grabbing, or i am pushing with too much pressure, or the belt is going too fast.

 

[SBuzek]

Usually a dull belt running too slow and trying to grab.

 

[Drew Riley]

I'll second a dull belt. Change to a fresh one and see if that helps.

 

[Amber_2477]

Awesome, thanks for the advice. Yep, the belts are probably at the end of their use. Ill buy up some new ones and try clamping on an extension plate on the jig and see how i go! Thanks for the feedback guys!!

 

[fitzo]

If you are not doing it already, don't leave belts on the machine under tension when not in use. They can stretch and pucker, making for bumps, vibrations, etc.

 

[Mecha]

I can get a resonant vibration in the billet while grinding, if it's being pushed too flat and evenly against the belt/platen. The trick is to push ever so slightly harder on one side of the platen. This is for high-pressure, low belt speed grinding.

 

[Stacy E. Apelt - Bladesmith]

There are two ways to deal with this
(1) You have to measure the exact size of the grits left on the belt in microns. Then, you need to know the exact speed of the belt in meters per second. Using that and the length and surface contact area of the blade ( in meters) you can calculate the resonant frequency.

OR:

(2) Change your belt and speed up the grinder.