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Bar grinding

bigbert74

Plastic
Joined
Aug 5, 2016
Hey. It’s been a while. Got a job about a month ago centerless grinding steel bars not sure what kind of steel. 1 1/2 to 4” bars 12-24 ft. Having lots of problems. No one to really discuss them with right now. One guy quit, one hurt his shoulder. 24” x 20” wheels. Having a problem with a section in the bars Same spot. Where as I told a coworker. It feels like I’m making Allen keys. Center height ok at least according to the formula I was given. Bronze work rest. 45 degree angle. Usually occurs as the part leaves the support heading into the grinder. Vibrates terribly. Not sure why. Bar and work rest seem parallel. Has happened on more than one job. Like the job and hope I can figure this out so I can keep it. Any suggestions? More info needed? Reg wheel 32 rpm. .012 taken off per pass. Crazy. Only about a 6-10 in section bad. Bar grinding much different than bolts. Lol
 
Caveat: I do not have direct experience with centerless grinding. But your problem sounds to me that the support needs adjusting. Depending how close or how far from the wheel/other supports is, you need to compensate for the natural flection of the bar due to gravity, so that the bar doesn't drop when leaving the support.

Paolo
 
Bars must be very straight. Sounds like maybe bearings gone on reg wheel. edit: check the drive system on reg wheel, belt was bad about 8 years ago and had us scratching our heads.
 
If the bars are bent or not supported correctly and a section of the bar travels up in relationship to the GW and RW the bar will bounce between the wheels.
Based on the information you provided it sounds like something is increasing the work piece height. What tangent angle are you set up at?
Tangent angle is the angle from the RW to the centerline of the work piece added to the angle from the GW to the centerline of the work piece.
You should be adjusting the tangent angle for different diameter work pieces.
 
If the bars are bent or not supported correctly and a section of the bar travels up in relationship to the GW and RW the bar will bounce between the wheels.
Based on the information you provided it sounds like something is increasing the work piece height. What tangent angle are you set up at?
Tangent angle is the angle from the RW to the centerline of the work piece added to the angle from the GW to the centerline of the work piece.
You should be adjusting the tangent angle for different diameter work pieces.

Seems like the blade may be going downhill but not 100% sure. Really helped grabbing end of bar and pulling slightly away from grinding wheel. Not the best or safest solution but seems to work.
 
Bert, can give us a pic or drawing of the set up? Are you using a long bar attachment? 4" bars seems like slant bed territory.
 
Trying to figure out how to add a picture but it seems no matter what I’m doing I have to be slanted down hill entering the grinder in order to be even against the work blade. Blade not sitting on any thing. Cleaned pocket out real good.
 
No, but with a 4 " bar you likely don't have room to. Are you depending on the wheel to pull the bar in or does it get some help until the wheel has a grip?
When you say "blade not sitting on anything", what does that mean? You say that you have to have the bar "slanted down hill to be even against the work blade". Does this mean your bar feed is not at the right height to enter the wheels at the proper height?
 
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I put the bars in the fixture and roll them until they start to grind. It seems as if when I am even(level) on the entry rolls. And flat on the blade(first 6 inches) entering the wheels, if I push the bar through, on the exit side I am .050 to .085 off the blade. And to get it even on the blade or work rest. Not sure what is the correct term, I have to lift the front of the bar enough so that it looks like it’s slanted down hill.

I remember when I first got on here my old company wouldn’t let me dress the wheels, here I cannot I honestly do not know what I’m dressing the wheel with. I asked if they rotate their diamond. They said nah. Well look at it next time we change the wheels. Which could be months!! Tried to take a picture of it but due to dirt and the odd shape of the thing I couldn’t tell what the heck I was looking at!!
 
It sounds as though the bar attachment is too low. The bar should feed smoothly onto the guides and into the wheels. This means adjust every stand on the bar attachment or feeder as some call it , to get the correct height. It sounds as though your wheels are having to pull the bar down on to the guides. Until that pull down of the wheels get it flat on the rest it has no choice but to chatter. I think the height of the bar attachment is your problem.
 








 
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