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"Sit on" grinder.


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I have been experimenting with different ways to grind.

It is very obvious to me that the way we use our grinders is incredibly inefficient. we are trying to push material horizontally into a belt, very hard work on the arms and no where near enough pressure to grind with speed or to make the most of the high tech belts we use. I have tried using levers with varying levels of success for outline grinding but when it comes to grinding bevels I have not found they work.

 

If you have a look at Josh Burrells Blog

 

http://thenewhearth.blogspot.co.uk/2014/09/portland-works-andy-cole.html

 

You can see how incredible the grinder is that Andrew Cole uses.

 

He is sitting on a suspended "arse board" using his body weight to apply pressure.

 

I am not familiar enough with stones to go that route , but I am with belt grinders , I have built a few and altered loads, I want to build a sit down grinder where I can use my bodyweight to put the force through an arse board into the blade, either against a water cooled platten or 12 inch grinding wheel.

 

My experiences using my cross as a means of transferring body weight through my knees against a board are that It has changed my world of grinding , 2 or 3 times a fast and belts last a lot longer. I will never go back, it has its limits and is more prone to overheat the metal after hardening, due to the increased pressure. so my mind foes to a wet grinder.

 

I have a 5.5 hp motor and VFD and sealed bearing contact and tracking wheels from an old industrial wet grinder. I will start by building the grinder as a Dry grinder , however I want to be able to use it wet. I spend as much time dipping blades as grinding them, there has to be a better way. I have owned a couple of upright wet grinders and they were much too messy.

 

Here is what I have come up with as a very basic idea, I will have to play around with relative heights and angles to get it to work, I want to use the 2" by 11.5 foot belts that are my standard belts . Most of the belts I use are suitable for using wet.

 

I will build the protection around my legs from inch ply and 3mm steel facing , if I get the angles right I am, hoping the water will be thrown away from me into a suitable catch trough. It will very much be a suck it and see build.

 

very basic sketch let me know if you see any obvious problems. I hope to work on this over xmas.

23404318609_5cfb62cad7_k.jpg

Edited by owen bush
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Mr. Bush,


I've had similar thoughts myself. There are a few pics wet belt sander in ' The Art of the Japanese Sword ' by Kapp & Yoshiwara. The Japanese seem to prefer this type of set up for linishers and I've seen a few incarnations along the same theme, Belt appears to move away from the operator like you have described. I have some old drums from an ancient wood belt sander which I began playing around with. I was most concerned with keeping water out of my electrics so postulated a total loss water system with the Drive wheel where you have your idler, belt driven with the motor mounted vertically.

Since I was looking at backing this thing into a wall , I thought I could mount the motor high and keep the thing out of harms way.


On the few Japanese ones I've see pic of, they have two wide box type water guards projecting out each side. I assume these are to catch the run off from long blades. They look like an inverted 'T' in plan view.

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Are you planning on having the water feed onto the belt. Or have the bottom wheel sitting in a bath of coolant picking up water as it goes?

I've used water grinding wheels which used a great of coolant that you used a pedal to do onto the bottom of the wheel which seemed to work well.

I'd look at having the motor high to keep it away from water drips.

Have you don't any research on industrial coolants for grinding?

Keep an eye on your lungs as my asthma gets set off being near cold damp air especially when in airesol form.

Andrew

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Interesting idea. Will the seat/board swivel behind the "Rider" so that it moves along with the part you are grinding?

 

I think my legs would get tired if they were very bent for very long trying to control the weight I applied to the seat. Were I making this for me, I think I would set it up so I could stand on one leg, and use the other knee to kneel on the board to apply pressure.

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the board will either be pivoted or hung and is free to move in an arc.and up and down. I am imagining that it will either be sprung from above or below , but this may not be needed.

A lot of this is going to be suck it and see, I have a couple of 2 wheel grinders and a weight training bench that I can play with to get the positioning of the ass board and platen right as they are complete fixed units so I can just bolt them in place and try out angles etc.

this should give me a much better idea of what works - is needed.

I do not imagine I will be using my whole body weight...hard to know.

Edited by owen bush
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Might be good to have something that catches the seat in case anything were to fail. Like a post that sits just blow the seat when grinding so if the hinge on the back or the piece pushing on the work breaks. The though being that if something goes wrong it will help catch you before you fall into the grinding belt.

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That will be fun to try with that water-cooled radius platen you have. I was thinking of this last week when I delivered a load of axes. The client lives near Smoky Mountain Knife Works (nasty retailer of cheap imported crap-knifelike-objects etc.), and out in front of that business there is an old industrial wet stone wheel grinder from (I think) one of the old pocketknife factories in New York. It has a nearly enclosed wheel about three feet diameter and a saddle with a hinged arm in front much like your arse board arrangement. I do not know the direction of rotation.

 

I am also reminded of an illustration I can't find at the moment of a sword grinder lying face down on a board suspended over a six-foot wheel, usling a push-up type method of body weight application. Seems tiring, but at least gravity is helping.

 

I look forward to seeing what you come up with.

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Might be good to have something that catches the seat in case anything were to fail. Like a post that sits just blow the seat when grinding so if the hinge on the back or the piece pushing on the work breaks. The though being that if something goes wrong it will help catch you before you fall into the grinding belt.

 

Gasp...

 

"No Mr. Bond, I expect you to die!" comes to mind...

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Might be good to have something that catches the seat in case anything were to fail. Like a post that sits just blow the seat when grinding so if the hinge on the back or the piece pushing on the work breaks. The though being that if something goes wrong it will help catch you before you fall into the grinding belt.

 

I will have the whole belt enclosed with 1" ply and 3mm steel. so its all covered apart from the working area.

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One thing to also consider is your position while grinding. Just looking at your posture on there, and nothing else. That's a rough posture to hold for any length of time. Hard on the arms, shoulders and mainly the low back.

I understand you're using your body weight for the pressure against the belt but if your body won't hold that position for too long it may not be optimal. Just bringing your trunk up a few more degree's will have a huge impact on your ability to tolerate that posture for extended periods of time. Of course it's a compromise on the amount of pressure applied to the belt.

Just something to think about before building. I am looking forward to the result!

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I will have the whole belt enclosed with 1" ply and 3mm steel. so its all covered apart from the working area.

Yeah, I was envisioning you falling forward with your face hitting the platen (and still moving belt). Granted, you're no super model, but it would still be a shame. ;)

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I have mocked up my grinder , using an old weight training bench and a horizontal grinder.

this is just a mock up to get all the dimensions right before building the real deal. seems to work very well. and gives a nice even grind with movement to use the wheel or belt.

 

23741197551_49e4919ab9_z.jpg

 

23797556946_829e3550af_z.jpg

Edited by owen bush
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I have a video but have no idea how I would get it on here.

Edited by owen bush
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  • 3 months later...

Yes! I gave up on it, used it for a couple of days and found the position uncomfortable. the rate of material removal was amazing ......but not for me.

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Yes! I gave up on it, used it for a couple of days and found the position uncomfortable. the rate of material removal was amazing ......but not for me.

 

to bad, loved the ingenuity and creative concept......

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  • 8 months later...

Pieter-Pauld just posted a video in this thread that made me think those following along here may be interested in the device shown at the 10:30 mark. It is a stand on version (one foot in a stirrup) in addition to a "seat" that may be a bit more ergonomic for some.

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