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Platen adjustment on a KMG belt grinder?

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Alan H

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#1
I believe you should adjust the platen on KMG grinder a bit "proud" of the rollers.

When I first began to use my KMG, I set the platen in line with the infeed and outfeed rollers. That was fine for rough work. However, I have now been using the grinder to grind HSS tool bits and have discovered that this is not the proper setup.

I have started setting the platen slightly proud of the rollers to keep the belt firmly riding platen. I have not set it up with any sort of thickness gauge, just by eye to assure the belt is flat on the platen.

Is this how you do it or do you go to the trouble of measuring the setup? If you measure it what do you shoot for, 15 or 20 thousandths proud?
 

mikey

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#2
I do it like you do it, Alan. Grinding belts are not fussy; they just need to contact the platen without fluttering but you do need a Pyroceram liner to handle the wear and heat. It is really important to round the top and bottom of the platen liner to avoid chafing the belt.
 

Alan H

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#3
Thanks Mike, I am planning on using the belt grinder to radius the liner a bit.

I have some Norton and 3M higher grit belts that should work well.

Is that how you do it?

BTW, if you break a liner, how do you get the old JB Weld off to put a new liner on?
 

firestopper

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#4
Alan,

The Rockwell/Delta manual states the platen should be at 3mm proud of top and bottom rollers. Not sure on KMG but it seems to me if it was inline or behind the rollers it would result in uneven platen wear. Also try to use the entire width of the belt not dwelling in on spot.

EDIT: The correct value is 1/32" (.03125') NOT 3mm.
 
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Alan H

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#5
Thanks Paco - that's way more than I expected - 0.118". Of course that is for a 6" wide belt too.

Only because I am now curious, I am going to check the manual for my Powermatic which is like your Rockwell and see what it says.

EDIT: the PM31 A sander manual says adjust the platen 1/32" (.03125") proud of the rollers. Again, that's for a 6" wide belt. BTW, I do not remember ever even checking it and certainly not adjusting it! I pulled it out of the box, put it together and used it.
 
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ddickey

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#6
I had no idea how "proud" to adjust mine but ended up pulling my platen all the way out. Was probably a little more than a quarter inch past the rollers. It's the only way I can keep the belt on the wheels.
 

Alan H

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#7
I had no idea how "proud" to adjust mine but ended up pulling my platen all the way out. Was probably a little more than a quarter inch past the rollers. It's the only way I can keep the belt on the wheels.
Is yours a Beaumont KMG or another maker? Curious about the tracking adjustment yours has.

Sounds like you may have some misalignment in the drive pulley relative to the others. As I am sure you know, tracking is independent of the platen adjustment.

By the way, that's got to be really hard on the belts and in my mind, makes it a bit dangerous. An acquaintance of mine received a very serious laceration to his arm when a belt came apart and hit his arm.
 

ddickey

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#8
It's a Reeder.
My thought was that it kept the belt tighter so didn't wonder of the wheels when grinding.
I've monkeyed around with the alignment but at this point figured it must just be normal for belt grinders.
I'll back off the platen if it's a safety issue.
 

Alan H

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#9
I took a quick look at their website.

Does their tracking adjustment uses a bit of a different concept than the KMG? It appears that the angle of the tracking/tension roller was far more skewed than on other grinders I have looked at. Could be the angle of the shots in the video.

Regardless, I would suggest you get in touch with Redder and get the tracking/alignment issue squared away.

My fear is that with your platen that far out you are going to fray the belts quickly or worse yet, damage the tape connector on the belt and it will come apart. While my KMG is variable speed, it sometimes is running at 5000 fpm and a belt traveling at 55 mph would be hard to dodge.
 

ddickey

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#10
You can adjust the tilt and also the angle, I guess for running in reverse. Not sure why you would want to do that.
I'll contact them.
 
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Buffalo20

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#11
I do it like you do it, Alan. Grinding belts are not fussy; they just need to contact the platen without fluttering but you do need a Pyroceram liner to handle the wear and heat. It is really important to round the top and bottom of the platen liner to avoid chafing the belt.

Mikey,

please, explain the need for a Pyroceram liner. I have a Jancy 2" x 48" (3600 sfm) at the home shop and a 2" x 72" (vs 2300 to 6000 sfm) Burr-King at work, they have plain steel platens. The Jancy runs sometimes 1-2 hours straight and the Burr-King round 6-8 hours a day. We have no belt issues, great results and great appearances on the ground edge. We use the same style belts, a 50 grit, Carborundum brand, ceramic grit belts.
 

Alan H

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#12
You can adjust the tilt and also the angle, I guess for running in reverse. Not sure why you would want to do that.
I'll contact them.
If you ask KMG they will tell you that you cannot run theirs backwards. I think they tell folks that because in order to run it in reverse, the alignment has to be spot on. If it is not, when you reverse it the tracking will cause issues. However, if you align the drive pulley really well with the platen pulleys it reverses quite well. You need some long straight edges and a little time. I tuned my in from the get go and it will reverse with no issue.

However, I do not run it fast in reverse since I am using a power twist drive belt. Those belts are not made for running in reverse. So if I do run it in reverse, I never exceed 1/3 of its top speed.

On a KMG, if the tracking is different in forward and reverse I think you have an alignment issue.

So I am betting your issue is about alignment. But again, I am not familiar with your grinder.
 

mikey

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#13
Thanks Mike, I am planning on using the belt grinder to radius the liner a bit.

I have some Norton and 3M higher grit belts that should work well.

Is that how you do it?

BTW, if you break a liner, how do you get the old JB Weld off to put a new liner on?
Yeah, I just grind the liner on the belt sander with an 80 grit belt.

You can remove JB Weld with a propane torch - heat it until it gives and the scrape it off. I did it only once and decided it is easier to just epoxy on a new liner onto a new platen. They tend to last for 10+ years so not that big a deal. I would recommend putting two socket head cap screws under the lower edge of the liner to keep it from dropping if the epoxy lets go.
 

mikey

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#14
Mikey,

please, explain the need for a Pyroceram liner. I have a Jancy 2" x 48" (3600 sfm) at the home shop and a 2" x 72" (vs 2300 to 6000 sfm) Burr-King at work, they have plain steel platens. The Jancy runs sometimes 1-2 hours straight and the Burr-King round 6-8 hours a day. We have no belt issues, great results and great appearances on the ground edge. We use the same style belts, a 50 grit, Carborundum brand, ceramic grit belts.
The last platen I had with a liner on it stayed dead flat for well over 11 years and it ground hundreds of HSS tool bits, along with most everything else that needed to be ground in a home shop. Good enough reason for me to use one.
 

firestopper

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#15
Thanks Paco - that's way more than I expected - 0.118". Of course that is for a 6" wide belt too.

Only because I am now curious, I am going to check the manual for my Powermatic which is like your Rockwell and see what it says.

EDIT: the PM31 A sander manual says adjust the platen 1/32" (.03125") proud of the rollers. Again, that's for a 6" wide belt. BTW, I do not remember ever even checking it and certainly not adjusting it! I pulled it out of the box, put it together and used it.
Went to the manual and the platen for the Rockwell is 1/32" (.03125') proud of the rollers. Sorry for the misinformation, getting too damn old to remember as new numbers keep coming in. I'm running out of RAM! It would be nice if we could upgrade RAM like we do on computers. My sincerest apologies.
 

ddickey

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#17
Ordered a ceramic platen liner yesterday. My current metal one is nine inch and the new liner is eight. I plan to mill the metal one flat and clean it up some. I'll leave a small ledge on the bottom that the glass platen can rest on. Should probably still use some screws though.
 

Alan H

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#18
Yeah, I just grind the liner on the belt sander with an 80 grit belt.

You can remove JB Weld with a propane torch - heat it until it gives and the scrape it off. I did it only once and decided it is easier to just epoxy on a new liner onto a new platen. They tend to last for 10+ years so not that big a deal. I would recommend putting two socket head cap screws under the lower edge of the liner to keep it from dropping if the epoxy lets go.
Thanks Mike
After thinking about it, another approach is to chunk the old platen and make a new one.
 

mikey

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#19
thanks, Mikey, for the response
I should have mentioned that my cheapy Sears belt sander came with a stamped mild steel platen that I wear down after grinding a few tool bits. I wound up changing them too often to make sense. I happened to visit a knifemaker friend and asked his advice. He showed me his big Burr King grinder with a 1/2" thick steel platen and a liner glued onto it and told me, "Yeah, I got tired of changing platens, too." I've been using a liner ever since.
 

mikey

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#20
Thanks Mike
After thinking about it, another approach is to chunk the old platen and make a new one.
I use a piece of O-1 flat ground stock for a platen and stick the liner on that. Two flat surfaces stick together pretty good with JB Weld.
 

mikey

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#21
Ordered a ceramic platen liner yesterday. My current metal one is nine inch and the new liner is eight. I plan to mill the metal one flat and clean it up some. I'll leave a small ledge on the bottom that the glass platen can rest on. Should probably still use some screws though.
A ledge will perform the same function as screws - its just a ledge to prevent the liner from dropping down and getting caught between the belt and lower wheel if the epoxy lets go. Having had my liner pop loose after a belt snapped, I can only surmise the belt impacted the liner and knocked it loose. It was after over 10 years of use before that thing let go - not too bad.
 
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