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2x72 belt grinder for knife making

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Simko
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2x72 belt grinder for knife making

Postby Simko » Wed Feb 14, 2018 10:25 am

A friend and I both started making knives and quickly found that a regular belt sander and a pedestal grinder can only do so much. After doing a little research we found that the Cadillac belt grinder for knife making was the Beaumont KMG. The only problem is that is also came with a price tag to match. With all of the different attachments, the price was approaching $3,000.

We found that many people have made their own KMG clone and decided to take on the challenge. At first, we were going to design a grinder from scratch using pictures, but a little Googling started to uncover prints that were already posted online. I finally stumbled onto a website http://sayberosg.com/ in which the owner built a KMG clone grinder, but mounted the frame onto a pivoting base so that the whole grinder could be tilted 90*. The whole premise of the Sayber OSG website is for people to download his prints, use them to make the grinder and then to share any improvements with the group.

I downloaded the prints and converted the DXFs into a 3D model in AutoCAD so a friend and I could make any modifications. After going back and forth a few times we settled on the final model below. At first glance it looks pretty much like the Sayber OSG but there are some minor differences.

Image
3D_rotated.JPG


1) The Sayber OSG was originally designed so that a person could download the prints, take them to a local waterjet or laser cutter, and them bring the parts home and assemble with basic tools (drill press, angle grinder, drill/taps). I really didn't want to drill and tap dozens of holes when I could easily weld the grinder together so I converted the prints for welding. Besides for deleting a bunch of holes, I modified the front and rear pivot plate to allow for welding and shortened all of the tabs in the base by 1/8" so that I would have some space to weld. I may have been expecting a little too much of my plasma cutter to have these pieces fit together nicely like a puzzle, but actually it wasn't too bad. A little bit of hand filing to remove the radii in the corners of the tabs/slots and the assembly went together nicely.

Front hinge.JPG

Back hinge.JPG


2) Most people who build these grinders use a 1 or 2 hp motor. A little bit of research showed that most wished that they had gone with 3HP. We made a few changes to the motor pass-through and raised the pivot point up 2" to account for the extended length of a 3HP motor. You can never have too much power!

3) The original Sayber OSG design uses springs to keep the belt under tension. I converted the tracking arm to use a gas shock for tension. I moved the pivot point up and back to make some extra room for the shock and placed a row of holes on the arm and on the frame. This allows the shock to move forward and backward so that different tensions could be applied for different types of sanding belts. In the picture below, I show the bottom mount being separate pieces like the Sayber, but I changed it in the final design so that the spacer is machined from aluminum rather than being stacked cut pieces. The shock, shock ends and ball studs are inexpensive and available from McMaster Carr.

shock.JPG


4) There are also a lot of small changes such as widening the front and rear supports due to the extra height for the 3HP motor, changing angles / fillets to make parts match better, etc.

A friend and I cut three sets of parts last weekend and went to town on the slots/tabs with hand files to get everything pieced together nicely. Is there anything that I could do to make this puzzle piecing process easier in the future or is it just the nature of the beast when cutting small 3/8" wide slots in 3/8" thick plate. I calculated what the taper should be with a 2* bevel and increased the openings by that amount (x2) plus a little extra for good measure. I made a few test cuts and the test tab fit into the test slot, but that was with a brand new electrode and nozzle. When it got to the point of cutting the actual slots I think there must have been some change in how the electrode was cutting because it required filing to fit. I think next time I do something like this, I will put the critical cuts on a separate layer and cut them first with fresh consumables.

Image

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TimP
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Re: 2x72 belt grinder for knife making

Postby TimP » Wed Feb 14, 2018 11:31 am

I am very interested in your project. My son is figuring up a bunch of stuff to build his own grinder.
If you'd like to share your dxf files, he'd be forever in your debt.

Thanks,
Tim

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Re: 2x72 belt grinder for knife making

Postby steel 35 » Wed Feb 14, 2018 12:12 pm

I have the intention to build one this summer, thanks for sharing another that lays down :mrgreen:
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Re: 2x72 belt grinder for knife making

Postby Simko » Wed Feb 14, 2018 1:00 pm

Here are the DXFs... I was going to wait until I started putting it together before posting up, but I can always update later if I find any issues.

I included the plasma cut frame spacers that I had designed before changing my mind to have the spacers machined out of aluminum.

I included the nested file, but it's probably not going to do people much good as it is for three grinders and was done to use up some partial sheets that I had.

Also.. you will need to plasma peck the hole locations and drill them out in a drill press as plasma cutting 1/4" holes in 3/8" plate doesn't work so well.

Simko Sayber 2x72grinder nest.dxf

Simko Sayber 2x72grinder.dxf

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Re: 2x72 belt grinder for knife making

Postby ggeh » Wed Feb 14, 2018 5:41 pm

Thank you for sharing, looks to be a great project.
Thanks, Gary

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Re: 2x72 belt grinder for knife making

Postby acourtjester » Thu Feb 15, 2018 9:49 am

great drawings thanks for sharing opens fine
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Re: 2x72 belt grinder for knife making

Postby Nacs Fab » Fri Feb 16, 2018 4:04 pm

Nice design. Thank you for the share!
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Re: 2x72 belt grinder for knife making

Postby AIRFLOWKID » Sat Feb 17, 2018 5:41 pm

You put a lot of work into this file. thanks so much!

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Re: 2x72 belt grinder for knife making

Postby tylerd » Sun Feb 18, 2018 4:33 pm

Yes this Rocks!!!!!!!!!!!!!!!!!!!!!!!
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Re: 2x72 belt grinder for knife making

Postby nalin400m » Sun Feb 18, 2018 6:53 pm

Which motor are you going with?
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Re: 2x72 belt grinder for knife making

Postby Simko » Sun Feb 18, 2018 8:40 pm

nalin400m wrote:Which motor are you going with?


I bought a WEG 3hp 3-phase 3500 rpm TEFC motor with 56c frame for $288. If you get the 3500 rpm motor, you should use a 4" dia drive pulley, if you get a 1750 rpm motor, you need to get a 6" drive pulley or use the 2x speed function of the drive.

https://www.grainger.com/product/WEG-3-HP-General-Purpose-Motor-52XR40?breadcrumbCatId=3156&functionCode=P2IDP2PCP

and a KB Electronic variable frequency drive KBDA-29 #10003 for $388.50. This will allow me to run variable speed and still connect it to my 30A 240v single phase twist lock plugs in my shop.

https://www.kbelectronics.com/Variable_Speed_AC_Drives_Inverters/AC_Drives_NEMA_4X.html

Most people use a 1 or 2hp motor, but if you do a little searching, you will see that most wished that they went with 3hp.
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Re: 2x72 belt grinder for knife making

Postby abmetal » Sun Feb 18, 2018 10:45 pm

I'd think a 2 1/2hp treadmill motor would work wouldn't it? They're used on drill presses, lathes, and numerous other pieces of equipment. They're cheap. I found one treadmill for $5 and another one sitting on the curb for free. One was a 2hp and the other one was a 2 1/2hp. And they have all the electronics needed. I've been told that the bigger, fancier treadmills even have a larger motor yet.

Allen

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Re: 2x72 belt grinder for knife making

Postby Simko » Mon Feb 19, 2018 11:29 am

abmetal wrote:I'd think a 2 1/2hp treadmill motor would work wouldn't it? They're used on drill presses, lathes, and numerous other pieces of equipment. They're cheap.


You definitely could, but because the treadmill motor does not have a c-face mounting flange (56C), you would need to do the following:

- Build a pillow block assembly to hold the grinder drive wheel, shaft and pulley
- Mount treadmill motor to the baseplate and select a pulley for the motor
- Connect motor pulley to pillow block assembly pulley with a belt
- Verify motor RPM, select pulleys and drive wheel that gives you your desired belt speed (surface feet per minute)

Or you can buy a motor with a 56C frame and bolt it to the side plate and not have to worry about alignment of shafts and pulleys.
Steve

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Re: 2x72 belt grinder for knife making

Postby i_r_machinist » Mon Feb 19, 2018 2:07 pm

Thank you very much! I'm going to drop these little jewels into solidworks.
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Re: 2x72 belt grinder for knife making

Postby i_r_machinist » Mon Feb 19, 2018 2:11 pm

What shock did you go with?
thanks
i_r_

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Re: 2x72 belt grinder for knife making

Postby Simko » Mon Feb 19, 2018 3:49 pm

i_r_machinist wrote:What shock did you go with?
thanks
i_r_


(1) Shock - McMaster-Carr 9416K11 - $11.47 ea
(6) Ball-stud - McMaster-Carr 9512K73 - $1.26 ea
(2) Quick-release rod end - McMaster-Carr 9416K47 - $4.44 ea

I left 3/4" of compression and about 1.25" of extension when the tracking arm is parallel.

How about a full BOM. It might be missing one of two things, but it is fairly complete based on the changes that I have made. The quantities are for three grinders so you will have to divide by 3 for each line item. 8-)

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Re: 2x72 belt grinder for knife making

Postby i_r_machinist » Wed Feb 21, 2018 8:39 am

Thank you for sharing! You wouldn't happen to have a Manufacturing Engineering degree in your background ? Best documented build I've seen on here in a while. Great job!
i_r_

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Re: 2x72 belt grinder for knife making

Postby i_r_machinist » Wed Feb 21, 2018 9:08 am

One more question please. That shock comes in diferent force ratings. Which did you get?
thanks
i_r_

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Re: 2x72 belt grinder for knife making

Postby Simko » Wed Feb 21, 2018 12:57 pm

i_r_machinist wrote:Thank you for sharing! You wouldn't happen to have a Manufacturing Engineering degree in your background ? Best documented build I've seen on here in a while. Great job!
i_r_


My current job title is Senior Manufacturing Engineer. EE degree though. LOL

i_r_machinist wrote:One more question please. That shock comes in diferent force ratings. Which did you get?
thanks
i_r_


I am planning on using a 30# shock. This is based on what I have researched and found from some other builds out there. I was not able to locate any builds where people actually calculated the torque on the tracking arm based on the distance installed from the pivot, so I am kind of winging it right now until I actually get it put together, but I feel 90% confident that the 30# shock will be fine. Most people used a 30 or 40# shock and mounted it in the general vicinity of where this one is mounted. I went with the lower of the two because some reported that the 40# shock worked fine on fabric belts, but stretched the scotch-brite belts.

When mounted on the holes closest to the pivot, it will exert 147 in-lbs or 12.25 ft-lbs.

When mounted on the holes furthest from the pivot, it will exert 278 in-lbs or 23 ft-lbs.
Steve

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Re: 2x72 belt grinder for knife making

Postby steel 35 » Thu Feb 22, 2018 2:44 pm

Dan's list of suggested changes put me to work.

This article got me changing a few things, overlapping all the best grinder's I could find, Drawing changing and digging for more suggestions, Hardest hurdle yet is explaining why the on / off switch costs so much! to She who know's it all. :lol:

Thanks again this is still a fun one
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Re: 2x72 belt grinder for knife making

Postby Simko » Thu Feb 22, 2018 8:59 pm

steel 35 wrote:Dan's list of suggested changes put me to work.

This article got me changing a few things, overlapping all the best grinder's I could find, Drawing changing and digging for more suggestions, Hardest hurdle yet is explaining why the on / off switch costs so much! to She who know's it all. :lol:

Thanks again this is still a fun one


Are you talking about the $35 toggle switches on the KB drives :shock: :lol: I can't bring myself to pay that much for a toggle switch.

Got any 'must have' ideas? We haven't put them together yet, so it's not too late. The only thing on the suggested changes list that has me thinking is the tracking hinge but I decided to leave it as is and hope for the best.

My father in law finished up all of the aluminum parts today, the wheel kits came in and the shocks are in the mail 8-)

IMG_0996.JPG

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steel 35
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Re: 2x72 belt grinder for knife making

Postby steel 35 » Fri Feb 23, 2018 10:22 am

Simko wrote:
steel 35 wrote:Dan's list of suggested changes put me to work.


Are you talking about the $35 toggle switches on the KB drives :shock: :lol: I can't bring myself to pay that much for a toggle switch.

Got any 'must have' ideas?
My father in law finished up all of the aluminum parts today, the wheel kits came in and the shocks are in the mail 8-)


Yes the KB electronics something about the box it comes in!
I have so many changes at this point it's no where close to anything. I have a 12" contact wheel fit for the belt now in theory, may draw or find a 12" platten today and check that. Then the the C face top view, Wheel's, Tracking.

Your aluminum parts are going to dress them up much nicer then original design, and your good at that :mrgreen:
If you haven't seen Northridge grinders rat arm attachment you may take a look, looks simple and effective.

Here is where I was a few days ago,
Biggest change.JPG

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Re: 2x72 belt grinder for knife making

Postby Coppercreek19 » Wed Feb 28, 2018 5:21 pm

Thank you

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Re: 2x72 belt grinder for knife making

Postby Prototypetom » Tue Apr 03, 2018 9:52 am

Any updates

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Re: 2x72 belt grinder for knife making

Postby Simko » Tue Apr 03, 2018 12:52 pm

Prototypetom wrote:Any updates


The plates are all cut. I have a LOT to learn on making 'puzzle piece' designs. I tried to oversize the slot features to account for the plasma taper, but it still required quite a bit of filing to get everything to fit together nicely. I saw a design for a wood burning stove on here where they put little circles on the inside corners of the tabs to help with the radius issue of the tab fitting into the slot. This would have made the pieces fit together nicer.

We have all of the motors, drives, hardware, shocks, spacers, tool bars, etc made/purchased. We are waiting for an opening in 'production that actually pays the bills' to get these set up on the CNC mill for drilling/tapping.

We are hoping to have the plates completed in the next week or two. After that, it should be a pretty straightforward assembly. (Yeah right, it never goes according to plan... LOL)
Steve

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