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deker

The grinder build begins....

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Gentlemen,

 

I built two of these KMG Clones three years ago and have been using them almost daily since then, and they work great!!!

 

If anyone is interested, I have a complete set drawings available along with pictures and material sources. Here is a small sample of the photos (below) and drawings (PDF file attached)

 

Grinder%20Help-3.jpg

 

They aren't that hard to make, I made my first one only having a drill press available, everything else was done by hand, hacksaw, files, elbow grease etc. They are well worth the effort, especially if you can't afford to buy one.

 

-Mike

 

Grinder__Main_Supports_.pdf

 

 

 

 

Hi Mike I am Felipe Torres from Mexico City and I am very interesting in obtain a copy of your plans,

Could you send to me I will apreciate

Thanks a lot.

my mail is torresmondragon@yahoo.com.mx

greetings from Mexico.

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Hi Mike I am Felipe Torres from Mexico City and I am very interesting in obtain a copy of your plans,

Could you send to me I will apreciate

Thanks a lot.

my mail is torresmondragon@yahoo.com.mx

greetings from Mexico.

 

If you look above at Don Fogg's post he has a link to the plans there.

 

Good luck!

 

-d

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Ok...so, here's the math for figuring out your RPM at the drive wheel:

 

For starters, you need to know the circumference of each wheel. Go back to geometry class for this:

 

C = Pi * d

 

Where C is your circumference, and d is the pulley diameter. We'll just use 3.14 for Pi since I'm lazy. So:

 

C = 3.14 * 3 = 9.42" for your 3" pulley

C = 3.14 * 4 = 12.56" for your 4" pulley

C = 3.14 * 5 = 15.7" for your 5" pulley

 

Now, to figure out the RPM with your various pulley pairs, you need the RPM, and the circumferences of the two pulleys being connected by the belt. Then, a little more math gives us some answers. There's a couple ways to do this. One with ratios, and one with some goofy math that I tend to do because my brain is a little sideways from the rest of you :)

 

Using Ratios:

 

You need to figure out the ratio of the drive pulley to the driven pulley (the one attached to the motor is the drive, and the other is the driven). So the pairings you'll have with this setup are:

 

drive -> driven

------------------

3" -> 5"

4" -> 4"

5" -> 3"

 

To calculate the ratio, divide the driven diameter by the drive diameter.

 

5 / 3 = 1.666 = 1.666:1

4 / 4 = 1 = 1:1

3 / 5 = 0.6 = 0.6:1

 

So, for each 1 revolution of your drive pulley (the right side of the ratio) at the 5" drive, you get 1.666 revolutions on the 3" driven pulley.

 

Now, add RPM into the mix to get the grinder driveshaft RPM:

 

d = m * r

 

Where d is driveshaft RPM (what we're solving for), m is motor RPM, and r is the drive ratio from above. So:

 

d = 1760 * 1.666 (for the 5" drive, 3" driven scenario)

d = 2932.16 RPM

 

Now, to calculate how much belt you're moving in SFPM (Surface Feet Per Minute) you need to know this driveshaft RPM, and the circumference of your belt drive pulley. I'll assume a 4" pulley from Rob @ Beaumont for these calculations. So, if we look back up above, we can see that the circumference of a 4" pulley is 12.56". So, we know that for each revolution of the belt drive pulley, we're moving the belt 12.56". Time for more math to figure out the SFPM at a given RPM (we'll stick with the 5"->3" setup for this one).

 

SFPM = (RPM * IPR) / 12

 

Where SFPM is Surface Feet Per Minute, RPM is the figured driveshaft RPM from above, and IPR is Inches Per Revolution of your belt drive pulley. So:

 

SFPM = (2932.16 * 12.56) / 12

SFPM = (36827.93) / 12

SFPM = 3068.9942

 

So just about 3,069 feet of belt pass over your platen every 60 seconds you have the grinder running at your highest speed.

 

Just as a point of reference, a mile is 5280 feet, so it would take a little less than 2 minutes for a mile of belt to pass under your blade as you grind...

 

Hope that helps!

 

-d

 

 

I am still working on my KMG belt grinder clone and now I'm wandering "at what speed I want my belt to run?". I have no money to buy a variable speed device so I'll go on 3 or 5 steps pulleys. I'm trying to find step pulleys to obtain more or less 280 m/min (920 ft/min) on the middle pulley. The other speeds will follow. Do you guys agree on this average speed for knife making? Isn't it too slow?

Edited by loneronin

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Loneronin. I do not know if this is what you want but, maybe it'll point you in the right direction. Beaumont Metal Works has this posted on one of their web pages, but it's kinda hard to find:

 

3 Speed KMG set-up:

 

Using a set of 3-groove step pulleys, the std. (KMG-4x2) KMG will yield belts belts speeds of approx:

 

 

3500 ft/min,

1750 ft/min

800 ft/min.

 

 

--------------------------------------------------------------------------------

 

With the optional high speed drive wheel (KMG-6X2), the belt speeds are approx:

 

5250 ft/min,

2600 ft/min

1200 ft/min.

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Loneronin. I do not know if this is what you want but, maybe it'll point you in the right direction. Beaumont Metal Works has this posted on one of their web pages, but it's kinda hard to find:

 

3 Speed KMG set-up:

 

Using a set of 3-groove step pulleys, the std. (KMG-4x2) KMG will yield belts belts speeds of approx:

3500 ft/min,

1750 ft/min

800 ft/min.

--------------------------------------------------------------------------------

 

With the optional high speed drive wheel (KMG-6X2), the belt speeds are approx:

 

5250 ft/min,

2600 ft/min

1200 ft/min.

 

 

OK, I also found the page. I will go for these speeds. Thanks!!!

Edited by loneronin

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Hi to the forum,

I just joined Don's forum and have started on Javelinas PDF plan. Deker, Javelina and all of you guys have done incredible work on your grinders. I hope mine comes out half as nice as yours.

Regards,

Fred

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I figure I’ll bring this back from the dead since a bunch of people that have built these things are probably subscribed…

 

Seems like most of you are sticking to a standard size tooling arm (1.5x1.5” square, from the pictures I’m guessing somewhere between 18 and 22” long), I can only guess with the idea that you might want to interchange with someone else’s arm or with an original KMG arm… if someone had a cool setup or you got lazy or whatever (otherwise I don’t see why everyone would stay with a somewhat odd dimension and not go to 2” and use existing parts that you can buy over the counter rather than building up).

 

If that is the case, I would assume that the center line of tooling arm to centerline of contact wheel distance is standard (the same) on everyone’s machine? What is that distance on your setups?

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If that is the case, I would assume that the center line of tooling arm to centerline of contact wheel distance is standard (the same) on everyone’s machine? What is that distance on your setups?

 

I'd say your assumption is fairly close, also assuming that most people used Mike Clerc's plans to guide their build. I say "guide" their build because material considerations, personal preferences, etc., dictate certain modifications and departures from the plans at will. Mine is built close to, but not exactly in accordance with his drawings since I wanted to do this and that a little differently just to suit my own whims. The distance from the center line of the tool arm to the center line of the contact wheel on my machine is 2.75" + the thickness of a 1/2" grade 8 nut, whatever that is. Someone else's machine might be the same or off that by a 1/2" or more. So, for the sake of estimation call it somewhere close to 3". If I knew what you're planning to do with that measurement I might be able offer a little more in the way of enlightenment.

 

If you are planning to build your own grinder you will find plenty of help in this forum. Check out Pellalito's "Problem with Grinder Build" thread right here in Tools and Toolmaking and you'll get a flavor of this.

 

Ken

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I figure I’ll bring this back from the dead since a bunch of people that have built these things are probably subscribed…

 

Seems like most of you are sticking to a standard size tooling arm (1.5x1.5” square, from the pictures I’m guessing somewhere between 18 and 22” long), I can only guess with the idea that you might want to interchange with someone else’s arm or with an original KMG arm… if someone had a cool setup or you got lazy or whatever (otherwise I don’t see why everyone would stay with a somewhat odd dimension and not go to 2” and use existing parts that you can buy over the counter rather than building up).

 

If that is the case, I would assume that the center line of tooling arm to centerline of contact wheel distance is standard (the same) on everyone’s machine? What is that distance on your setups?

 

Hey Mark :)

 

I can tell you that on the "real" KMG that the measurement from the edge of the tooling arm (rather than centerline) to the edge of a 2" wheel (again, rather than centerline) is .980". I had Rob measure that for me when I was building mine.

 

So, to translate for you, it should be 2.73" center to center. Not certain why it's that .02" off, but that's what I know.

 

Oh, and yeah, the tooling arms are 1.5" square by 20" long. I'd buy cold-rolled for the arms, I've found that the variance in hot rolled bar can be JUST enough to cause some cursing.

 

-d

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If that is the case, I would assume that the center line of tooling arm to centerline of contact wheel distance is standard (the same) on everyone’s machine? What is that distance on your setups?

 

...

If I knew what you're planning to do with that measurement I might be able offer a little more in the way of enlightenment.

 

I thought that I said it in my post but I guess I didn’t…

 

What I’m planning (or at least considering) is if I’m going to bother make something KMG like I might as well make it so KMG accessories work in it, and besides using the same size tooling arm, the biggest other issue I could see is getting the centerline of the tooling/contact wheel… whatever to match that on the KMG so that the drive and tension/tracking wheel end up properly inline. I might as well take advantage of the existing standard so I don't need to "reinvent the wheel" if one already exists.

 

FWIW, Deker, it’s not like I finally found time to actually do this, but you’ve almost convinced me that I’d be wasting my time building something smaller so I thought about it last night and I think that I might have a more “efficient” approach to the thing. Instead of these heavy ($$$) blocks of steel that you’re all using I’m considering bending a complete chassis out of probably 1 or 2 pieces of some 3/16” or ¼” steel plate (sheet? When does sheet become plate?) and then welding it together. If I have enough scrap sitting around I might just slap it together…. It would be nice if I can find 12-18” of something hefty like some 6 or 8” channel or rectangular stock to attach it to. Sheet metal bent or welded into a proper 3 dimensional shape, maybe with a welded gusset or 2 should be every bit as strong as some of these setups, and if the finished assembly proves a little too light to dampen vibrations it’s easy enough to make a base for it full of sand or concrete….

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I can tell you that on the "real" KMG that the measurement from the edge of the tooling arm (rather than centerline) to the edge of a 2" wheel (again, rather than centerline) is .980". I had Rob measure that for me when I was building mine

 

Huh… are you sure it was a 2” wheel? The site lists the wheels and idlers as 2-1/5 and 2-1/4 when it gives width dimensions, and since those don’t seem to be consistent that was the reason that I was looking for CL to CL distances.

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Hey Mark :)

 

I can tell you that on the "real" KMG that the measurement from the edge of the tooling arm (rather than centerline) to the edge of a 2" wheel (again, rather than centerline) is .980". I had Rob measure that for me when I was building mine.

 

So, to translate for you, it should be 2.73" center to center. Not certain why it's that .02" off, but that's what I know.

 

Oh, and yeah, the tooling arms are 1.5" square by 20" long. I'd buy cold-rolled for the arms, I've found that the variance in hot rolled bar can be JUST enough to cause some cursing.

 

-d

Hi Deker,

Maybe the 20 thousands difference is because of the slight radius on the end of the arm. Or it might have happened if some material was taken off the end of the arm to clean and deburr the end. I am trying to come up with a logical reason.:>)

Regards,

Fred

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Huh… are you sure it was a 2” wheel? The site lists the wheels and idlers as 2-1/5 and 2-1/4 when it gives width dimensions, and since those don’t seem to be consistent that was the reason that I was looking for CL to CL distances.

 

2" wheels on the platen, 2 1/5" for drive and idler. ;)

 

-d

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Hey - Hoping to revive this old thread for a second.

 

The link to the PDF of Mike's plans is no longer active - I tried it linkning to bladesmithforum.com...

 

Anyone have a copy they can post? or ...?

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Hey - Hoping to revive this old thread for a second.

 

The link to the PDF of Mike's plans is no longer active - I tried it linkning to bladesmithforum.com...

 

Anyone have a copy they can post? or ...?

 

I don't know, but I've been playing with the idea of building another grinder for a while and will probably make up a set of plans. If I get around to it I'll be sure to post them.

 

Of course, I also need to go back through my posts here and fix all of the broken images....

 

-d

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