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Gerhard Gerber

Plattens - Q's on new and existing

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My grinders are kit builds, the platten that came with the first one was setup to be mounted on the other side of the tool arm (different grinder I suspect), it worked perfectly but was obviously the wrong way around.  Fixing that entailed moving the platten and wheel to the other side of the backing plate.

While assembling I put the wheels down on a flat surface and adjusted the platten so everything was nice & flush

I'm getting the impression the platten needs to stand bit proud of the wheels to prevent them from contacting the work piece?  How much is safe/recommended?

 

Secondly, I need to build a much bigger platten.  I was hoping to back it with glass.  Recently got schooled by somebody making a living from glass and found out the armoured glass I planned on using would be impossible.....

Questions.....

Would normal glass work and is this feasible at all?

If not, does the platten need to be hardened or would mild steel work?

 

Any further recommendations welcome and appreciated. 

Cheers

Gerhard

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The platen should stand about 3 to 5mm proud of the wheels to get a good flat belt path.  The "glass" most of us use in the US is called "pyroceram" and is usually used for fireplace doors and such.  I have heard of people using ceramic tile and granite tile.  I have also known people to make a new platen out of 0-1 or A-2 and harden it.  Whatever it takes to get a wear-resistant backing.

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2 hours ago, Alan Longmire said:

The platen should stand about 3 to 5mm proud of the wheels to get a good flat belt path. 

I did this for a while, but eventually the top and bottom corners of the platen started to wear, the belts started tracking weirdly, and eventually developed a bubble in the center of the path again. So, I glued a ceramic/glass platen over it. IMPORTANT: you must weld a shelf/stop at the bottom of the steel platen to keep the glass surface from delaminating and exploding as it gets caught between the belt and the lower guide wheel. (Ed Caffrey can get you the details of picking shrapnel out of his face).

I have to say that I do not love the ceramic/glass platen. Although it does not wear as fast as a steel platen, the sides and edges are not as sharp and crisp as the steel one. So I end up switching out platens for doing the plunge cuts on my knives when needed, or doing very sharp grinding like on fittings or folding knives. It also cracked just below the work rest table shortly after installation, but that might be my fault due to a bad install. I recently made a new steel platen from 1/4" x 2" mild bar stock. I have a surface grinder, so I could make the face and edges nice and flat, and square with sharp corners. I don't leave it proud of the roller guides anymore, I just set it with a straight edge. The small amount of play behind the belt takes a fraction of a second to eliminate when grinding and I can see no visible defect from it. YMMV. I can buy a 20 ft long piece of 2" x 1/4" for about $30 so it's fairly cheap to use the mild rather than a piece of tool steel that I have to HT and pay 10x as much for, with very little gained.

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13 hours ago, Joshua States said:

I don't leave it proud of the roller guides anymore, I just set it with a straight edge. The small amount of play behind the belt takes a fraction of a second to eliminate when grinding and I can see no visible defect from it. YMMV. I can buy a 20 ft long piece of 2" x 1/4" for about $30 so it's fairly cheap to use the mild rather than a piece of tool steel that I have to HT and pay 10x as much for, with very little gained.

I had no issues after setting up that way except my platten is not very long so when I try to flatten out forged pieces the wheels leave hollows that have cause me huge issues....

16 hours ago, Alan Longmire said:

 I have also known people to make a new platen out of 0-1 or A-2 and harden it. 

 I have some factory fresh 6mm 5160 but very little else suitable......?

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On 2/4/2019 at 3:41 PM, Alan Longmire said:

The platen should stand about 3 to 5mm proud of the wheels to get a good flat belt path.  

I loosened the platten, put a steel ruler under each wheel and fastened......about 1mm I would say.

I could immediately hear the motor was working harder at start-up, everything sounds different and the platten got very hot very quickly.

I was however able to flatten a blade without the wheels getting in the way.

Not sure what to do TBH........

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Experiment with different platen placement until you get what you like?  That's about all I can offer.

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I just got in a couple of the fire glass panels that are about an inch shorter than my present 3/8 mild steel platen so I will take it to the engineer and get it put into the mill and a section milled out of it to allow the glass to sit into it with the shelf left at the bottom and within a thou or two of the original level so when it all goes back together there will be no disruption to my settings. have the platen  just proud of the wheels.

Edited by Garry Keown
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My mentor was in town yesterday and dropped by, first time he's seen my grinders and I came away suspecting that I've been too accepting....

....poet and I didn't know it........ :P

We were discussing building small contact wheels and he said he's been unable to build then without getting the tak-tak-tak-tak-tak and the resulting marred finish.

My blood ran cold because he was describing my platten, and my bloody life the last few days.....

Been working on very wide cleavers and struggling to get rid of horizontal 40 grit scratches, I get a nice finish on the slack belt, as soon as I touch a flat to the platten I'm left with ugliness that requires a lot of hand sanding to get rid of......

I suspect something is wrong.....?

 

BTW, I contacted the manufacturer and was informed the bigger wheel needs to be at the top, and the wheel flush with the platten.

The wheel swop helped even if it's less practical, I have the platten belt thickness proud of the wheels.

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5 hours ago, Gerhard Gerber said:

My mentor was in town yesterday and dropped by, first time he's seen my grinders and I came away suspecting that I've been too accepting....

....poet and I didn't know it........ :P

We were discussing building small contact wheels and he said he's been unable to build then without getting the tak-tak-tak-tak-tak and the resulting marred finish.

My blood ran cold because he was describing my platten, and my bloody life the last few days.....

Been working on very wide cleavers and struggling to get rid of horizontal 40 grit scratches, I get a nice finish on the slack belt, as soon as I touch a flat to the platten I'm left with ugliness that requires a lot of hand sanding to get rid of......

I suspect something is wrong.....?

 

BTW, I contacted the manufacturer and was informed the bigger wheel needs to be at the top, and the wheel flush with the platten.

The wheel swop helped even if it's less practical, I have the platten belt thickness proud of the wheels.

that tak tak tak, i believe i know your culprit, as its mine too. im in the middle of a 2x72 build from scratch, which i will put up a little later when its working. as for that sound, is it coming from mainly aluminium oxide belts? bought locally here in Southern Africa? because what i have been finding is that the joins in the belts are not fully flush, so as that join runs over a hard backing, ie, your platten, it lifts, hence that tak tak tak and those divots in your steel. 

this has been happening on my 1x30 since day one. what i did to minimise it was put a strip of masking tape on the platten when i was finishing up. reduced the issue a lot

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It's called "belt bump" and is due to the joint being thicker than the belt.  The smoother and more frictionless your platen surface is, the less trouble the belt bump will be.  I recently learned to wax the back side of the belt.  It makes a big difference!  I used an industrial belt lube stick, but I imagine any solid lubricating wax would work.  Beeswax or parrafin wax, even.  Just hold it to the back of the belt with the machine running.

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2 hours ago, Alan Longmire said:

It's called "belt bump" and is due to the joint being thicker than the belt.  The smoother and more frictionless your platen surface is, the less trouble the belt bump will be.  I recently learned to wax the back side of the belt.  It makes a big difference!  I used an industrial belt lube stick, but I imagine any solid lubricating wax would work.  Beeswax or parrafin wax, even.  Just hold it to the back of the belt with the machine running.

similar trick to stop v-belts from squealing in your car motor, use a candle! i bet it will probably work with this too

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So it's just the bloody belts....?

Most of mine are Klingspor, but I can order Pferd, maybe they're worth a try.

I've had email battles and very heated telephone conversations thanks to my efforts to source 3M belts locally.

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All of my non-trizact belts are Klingspor, from 36 to 400.  They all have a bit of bump.  My Trizacts, from A300 to A45, have zero bump.

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I tried a less stiff tensioner spring on this grinder and it seem to make the belt bump even worse......

Does that compute? :blink:

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Yes.  Lower tension lets the belt gather up a bit.  Higher tension straightens it out.

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Thanks Alan....so my ridiculously tight spring has actually saving me hassle, I was worried it might cause problems....

 

Probably no the right place to ask, but since we're here.....

Saw a positive review of the Pferd "mud belts", I can perhaps order them, anybody using them?

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I've been toying with the idea of making a new platten and sticking a piece of conveyor belt on the front, might that soak up the belt bump a bit?

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