EdCaffreyMS
"The Montana Bladesmith"
Often I hear/read of newer knifemaker who are excited about saving some money by building their own grinder. I always try to be as kind as possible, but after thinking on this subject for some time, I have some very pointed advice for anyone who has it in their mind to save a bunch of money by building their own grinder.....that being if you do not possess the skills to make modification, nor understand how a belt grinder operates, you're going to be money ahead, to just purchase one of the top end grinders on the market. I'm partial to the KMG, but any of the top end machines on the market are worth every penny you pay for them.
OK, that being said, this thread is all about those who choose to build their own grinder(s), and how to make it the best it can be. Personally, I chose the EERF plans that are free out there on the net. To have the parts waterjet from 1/2 mild steel runs around $200 per grinder. You'll spend another few hundred for a motor, controller (if you choose variable speed), drive and tracking wheels, and any attachments you choose.
This grinder is very simple, but I feel there are some MUST HAVE modifications that must be made for it to reach it's full potential.
First and foremost is the belt tensioning setup. The plans call for a tension spring, mounted to the rear of the idler arm, and fixed to the rear of the frame.....forgive me, but that is simply a "hob-knob" way of doing it....and it doesn't work worth a darn. The number one mod to make to this grinder is set it up with a compression spring tensioning system.
The way I do this is to located the idler arm center on top of the attachment receiver, and then drill/tap a 3/8-16 hole. I thread a small length of 3/8" all thread, and lock it in place with a jam nut (making sure the threads DO NOT protrude to the interor of the attachment receiver)
The spring seat, I turn out on the lathe, from a 1" piece of mild steel, then bore/tap it with 3/8-16 threads. this allows for up/down adjustment of the spring. The spring itself is something I purchased at the local Ace Hardeware store.
Next, I turned out a "spring keeper" from the same 1" mild steel, and drilled/tapped the bottom of the idler arm...then mounted it with a 10-24 socket head screw.
Another issue that is easily fixed on these machines is the lateral movement in the idler arm if it's mount with just a nut/bolt arrangment. Adding a 1/2" fender washer to each side might look a little goofy, but it will take nearly all of the lateral play out of the idler arm. Always use a "Ny-loc" nut on this bolt...you can ajdust it to achieve just the right combination of free movement and rigididty.
Finally, the last mod that I feel is a requirement on these machines, it to ensure you get the correct spacer on the tracking wheel. This can be tricky because how deep you mount the drive wheel, and the location of the attachment's center come into play....the trick is to measure/find dead center between the drive wheel and attachment(s), and then make this spacer the correct thickness to center the tracking wheel with the drive wheel and the attachment(s). On this machine, it requred that I grind the 1/2-13 nute to 3/8" thick to achieve the correct spacing.
All of this takes some thought, work, and time, but doing it can make a grinder "kit" that can rival one of the top end commercially available machines.
Cost wise, in the end, it ends up being SLIGHTLY less expensive then purchasing one of the top end grinders outright, but if you don't have the skills, or the knowledge to make these mods.....go buy....rather then build!
UPDATE: The VFD arrived this morning, and everything is now operational. Here's a quick video I took with my iphone......with the mods I've outline the grinder tracks like a dream, and run so smoothly that it's a bit difficult to tell it's running in the video (if the sound wasn't on)
[video=youtube;cs7QHbHSzR0]http://www.youtube.com/watch?v=cs7QHbHSzR0[/video]
OK, that being said, this thread is all about those who choose to build their own grinder(s), and how to make it the best it can be. Personally, I chose the EERF plans that are free out there on the net. To have the parts waterjet from 1/2 mild steel runs around $200 per grinder. You'll spend another few hundred for a motor, controller (if you choose variable speed), drive and tracking wheels, and any attachments you choose.
This grinder is very simple, but I feel there are some MUST HAVE modifications that must be made for it to reach it's full potential.
First and foremost is the belt tensioning setup. The plans call for a tension spring, mounted to the rear of the idler arm, and fixed to the rear of the frame.....forgive me, but that is simply a "hob-knob" way of doing it....and it doesn't work worth a darn. The number one mod to make to this grinder is set it up with a compression spring tensioning system.
The way I do this is to located the idler arm center on top of the attachment receiver, and then drill/tap a 3/8-16 hole. I thread a small length of 3/8" all thread, and lock it in place with a jam nut (making sure the threads DO NOT protrude to the interor of the attachment receiver)
The spring seat, I turn out on the lathe, from a 1" piece of mild steel, then bore/tap it with 3/8-16 threads. this allows for up/down adjustment of the spring. The spring itself is something I purchased at the local Ace Hardeware store.
Next, I turned out a "spring keeper" from the same 1" mild steel, and drilled/tapped the bottom of the idler arm...then mounted it with a 10-24 socket head screw.
Another issue that is easily fixed on these machines is the lateral movement in the idler arm if it's mount with just a nut/bolt arrangment. Adding a 1/2" fender washer to each side might look a little goofy, but it will take nearly all of the lateral play out of the idler arm. Always use a "Ny-loc" nut on this bolt...you can ajdust it to achieve just the right combination of free movement and rigididty.
Finally, the last mod that I feel is a requirement on these machines, it to ensure you get the correct spacer on the tracking wheel. This can be tricky because how deep you mount the drive wheel, and the location of the attachment's center come into play....the trick is to measure/find dead center between the drive wheel and attachment(s), and then make this spacer the correct thickness to center the tracking wheel with the drive wheel and the attachment(s). On this machine, it requred that I grind the 1/2-13 nute to 3/8" thick to achieve the correct spacing.
All of this takes some thought, work, and time, but doing it can make a grinder "kit" that can rival one of the top end commercially available machines.
Cost wise, in the end, it ends up being SLIGHTLY less expensive then purchasing one of the top end grinders outright, but if you don't have the skills, or the knowledge to make these mods.....go buy....rather then build!
UPDATE: The VFD arrived this morning, and everything is now operational. Here's a quick video I took with my iphone......with the mods I've outline the grinder tracks like a dream, and run so smoothly that it's a bit difficult to tell it's running in the video (if the sound wasn't on)
[video=youtube;cs7QHbHSzR0]http://www.youtube.com/watch?v=cs7QHbHSzR0[/video]
