Home Built Grinder WIP

KnuckleDownKnives

KnuckleDownKnives

Time to make the doughnuts..
Joined
Feb 12, 2015
Messages
1,715
Decided to make a move and buy some steel to build a 72" grinder. The 30" harbor freight one just doesn't perform very well, but it will make a knife shaped object. Currently opting for using a 2.5 hp treadmill motor since my funds are very limited I got it for free and with what I have built in my mind as far as mounting the motor and keeping it from getting destroyed by dust I think it will work pretty good. A lot better than the harbor freight grinder to say the least.



















 
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You will enjoy the new grinder - looks like you've got real welding skills. Congrats

Ken h>
 
I'm jealous. I am gathering the parts to make a grinder this summer. Keep on posting pictures...I am getting ideas!
 
Ken H> said:
You will enjoy the new grinder - looks like you've got real welding skills. Congrats

Ken h>
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Thanks Ken, I could do a lot better with better equipment, but the $300 RealGear welder from Air Gas gets the job done. That and a new lens for the helmet. Wish I has replaced it before attempting to weld the parts for the pulley modification together, I couldn't see what I was doing a burned a hole in one spot. They came out quite crappy but they'll stick. It's for function not looks...
 
Great project, looking good!

Everytime the little $30 Harbor Freight unit is mentioned in the context of knife making, I can't help but post this picture showing the difference between a real belt grinder and that little toy: :D

IMG_20141206_200149-small-small.jpg
 
Putting the motor away make the design more complicated. I would let the motor drives the drive wheel directly and make a good cover for the motor.
 
mrlocchoc said:
Putting the motor away make the design more complicated. I would let the motor drives the drive wheel directly and make a good cover for the motor.
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YES and NO. Using belts gets more complicated and expensive since you need pillow blocks, step pulleys, axles, etc... however, it lets you adjust (to some extent) the speed. And also, may allow you make your grinder smaller, so you can use off the shelf belts (2x72"). If you go with a direct drive, you better use a 3ph motor with a VDF for speed control. And you may bump into design constrains... that end up with a bigger than desired grinder, which only accepts custom made belts... ask me HOW I KNOW....
 
Thought about going with the direct drive, but the shaft on the motor is very small so I would need custom belt pulleys which i don't want to get into plus if I ever get a different motor I won't have to buy another set of pulleys they'll be a direct 3/4 fit. Also from what I've read dust is a problem so putting the motor farther away from the belt seems a good idea in my head and leaves me room to build some sort of enclosure. Thinking light weight sheet metal with some sort of filter on the side away from the grinding belt.

I'll have some more progress in the next few days, got an unexpected side job replacing a front bearing on my wife's cousins van. Kinda glad it came up as I came up with a much better plan for the belt tensioning for the motor to the drive pulley. When I get it done and post a pic I think you all will like it as I have never seen one done like my plan. Also if my desired max RPM isn't achieved I will very simply be able to add an addition jackshaft and step pulleys to increase the belt speed. Here are some crud drawings.




With adition Jackshaft and step pulleys to increase belt speed.

 
Well I just couldn't wait. Got my wife's cousin's bearing done and decided since I was already hot and dirty to go ahead and make some more parts and mock them up. Decided that I'm going to go ahead and get some more pillow blocks and step pulleys and make a second jackshaft now so if I don't like it I don't have to do it later. This also gets the motor farther away from dust and sparks. I Also came up with an easy belt tensioning system that will be next to easy to adjust. Had a different idea at first, but this popped into my head and don't think it could be done much easier considering the design.

The entire grinder is a little long, but that isn't going to be an issue for me nor do I care.



It will be quite simple to tension the belt. Just loosen the locking bole on the side and turn the bolt on the top. Need more tension, get a longer bolt. Plus kinda keeps everything in the back modular and easy to completely remove if needed, and if in the future I need to change to a different motor it wont be much to adapt it to what's here.









And in case anyone is wondering why I haven't put any legs on it yet, I need to get the hinge material because it will be able to rotate 90 degrees and use horizontally.
 
Looking good... However, you will end up with a bigger than usual footprint for a grinder. If you have plenty of room... it is ok. If not, well, you could think about putting the motor UNDER the pulley... and use gravity as means to help tensioning the belt (at least when vertical).

Beware of step pulleys... I don't know about the states, but here in Spain, you can either get them custom made of find a replacement set for a drill... anyway, expensive!
 
Mikel_24 said:
Looking good... However, you will end up with a bigger than usual footprint for a grinder. If you have plenty of room... it is ok. If not, well, you could think about putting the motor UNDER the pulley... and use gravity as means to help tensioning the belt (at least when vertical).

Beware of step pulleys... I don't know about the states, but here in Spain, you can either get them custom made of find a replacement set for a drill... anyway, expensive!
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Thanks for the reply Mikel. Where I plan on setting this up, the extra length compared to other grinders isn't going to be an issue for me, plus I kinda like the motor being farther from the grinding belt considering it's a treadmill motor and what I've read about them having problems with dust. It will be easier to keep it out of the motor farther away. As of now the overall length is right about 38" it looks a lot longer in the images than it really is. It looks like it around 4' or better, but it's not. As far as the step pulleys I found some for $21.29ea + $6.99 shipping so that fits in my budget. When I ordered the 3/4" keyed shaft I got a 3' section for $22 dollars and a second set of pillow blocks were only $10 each. So a total of somewhere around $50 is ok with me. If I don't need it, I can loosen a couple bolts and take them out, but would rather have them now than need to order them, plus if I don't use them now I'll have a few extra pillow blocks and some pulleys I may make a buffer out of.

Last night I got some more parts cut and welded up. Got the tensioners welded on. The locking bolt for the arm the motor and shafts drilled and tapped. The legs and hinges cut and welded up. Still need to do some final welding and some bracing to cut and weld but it's getting close to being complete and ready for clean up and paint.






My daughters kitty Rapunzel sneaking in the shot..












 
I just noticed that you haven't fabbed the belt tensioning system.... instead of going with a spring actuated system... I used the shortest gas strut I could find... and I couldn't be happier! With this system you don't have to worry about a spring bending sideways instead of compressing shorter. I will try to get a couple pictures for you.

So far it looks great!

Mikel
 
Mikel_24 said:
I just noticed that you haven't fabbed the belt tensioning system.... instead of going with a spring actuated system... I used the shortest gas strut I could find... and I couldn't be happier! With this system you don't have to worry about a spring bending sideways instead of compressing shorter. I will try to get a couple pictures for you.

So far it looks great!

Mikel
Click to expand...

I am leaning towards the gas strut, I have one I bought the other day. It's a little long but I think I can make it work. I want to get the step pulleys in and the belt pulleys in belt so I only have to fab it once. I kinda guesstimated on how tall to make the tensioning arm.


Made some more progress over the weekend. Go the second jack shaft fabed and mounted, motor, wired up, a support arm for the controller set up that swings up and down to move out of the way. I made the arm out of more re purposed metal from the treadmill. Welded on a steel rod for ease of rotating to the horizontal position, and mounted the transformer and circuit board for the motor in a small air tight cooler I had laying around to keep dust out of it.

The middle shaft is still really long and needs to be cut and the remainder will be used to replace the front shaft in the image. I just don't want to cut it until I get the step pulleys in and can mock them up.

I also need to make a permanent mount for the magnetic pickup that goes to the pulley for the motor to the controller, currently I just taped it to a small piece of metal I bent and is being held to the grinder with a magnet. Thinking of making the permanent mount hinge-able that can lock in place so I can rotate it out of the way when dealing with the lock down bolt for the jack shaft but locks in place so when the grinder is rotated to the horizontal position it stays in place.











My little one Mallory decided she was going to play with the old aluminum pot I'm going to use as a bucket to col what ever i'm working on.

 
Got a makeshift tool rest built. It's a far shot from what I want, but out of cash for a week or two and the materials I'd like to build it out of. Just made it out of whatever I had laying around. Hopefully pulleys will be arrive in the mail tomorrow so I can get them mounted and the shafts cut to length.







 
Lieblad said:
Nice work.
Sort of an irony.
A guy receives kudos as he builds a neat & effective junkyard machine. Yet many of the same congratulators will berate a guy for using junkyard steel to make a knife.
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Not quite the same. A better example would be if the O.P was going to make his drive wheel out of plywood, us bladetards would tell him that aluminum would be a much better choice.
 
Lieblad said:
Nice work.
Its fun to see machines cobbled up of junkyard materials.

Sort of an irony.
A guy receives kudos as he builds a neat & effective junkyard machine. Yet many of the same congratulators will berate a guy for using junkyard steel to make a knife.
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With the exception of the motor, hinge for the tracking wheel, the metal the main body the platen is cut from, and a few items on the tool rest nothing here is junkyard material. This may not be a KMG, Hardcore, Bur King, Travis Wuertz, or some other multi thousand dollar machine, but I'll guarantee you at the end of the day it'll work just as good. So I cut the steel with a $100 saw and not a $100K waterjet and welded it together with a $300 welder with flux core wire and a $50 drill press and not a $20K milling machine. Yeah I could have spent more time making the welds look better, spent more money on steel and designed it a little different. I haven't even started the cleanup process of grinding and sanding before paint, but this is no cobbled up JUNKYARD machine...

The first two knives I made, those were junk yard knives. Made from files I found in the woods next to my house that had been laying in the dirt probably 10 years or better.. But they still came out decent. I know the owners are very pleased.. It was more for learning than it was for trying to create perfection, and see if this was really something I wanted to get into. Now I'm hooked trying to make a dream a reality.

Sort of an irony the only person I received offense from it the one knocking other for something they haven't done to me. Just sayin.... :cool:



 
pleasanthill said:
Sort of an irony the only person I received offense from it the one knocking other for something they haven't done to me. Just sayin.... :cool:
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I would like to think that the comment made by Lieblad was not meant to offend you... and that actually the junkyard mention was sort of a compliment! As in recognizing the effort behind putting a working machine together using less than ideal equipment.

And old files are perfectly good knife making material, don't let anyone tell you otherwise!

Mikel
 
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