First belt grinder build help

D

Doomhand

Joined
Jun 6, 2020
Messages
7
Hello Community,

I'm in the process of building my first 2x72 belt grinder to get into knife making. I'm looking to build the machine based on a video found on youtube from a guy by the name of "Old hickory forge", but I don't have much details on the extension spring he used.

He says the spring is 3.5” x ¾”, but when I go online to shop for springs I see extra details like "Rate (lb/in)", "Initial Tension (lb)" and "Suggested Max Load (lb)". I've seen and read in different forums that people use some 30 lb compression spring, but does it matter if I use an extension spring for the pivot arm instead?

Aside from the Length and spring diameter, what other details should I look for when buying an extension spring?

Here's an image for reference of the spring im talking about:

https://imgur.com/a/e1XPigg
 
Last edited:
Doomhand said:
Hello Community,

I'm in the process of building my first 2x72 belt grinder to get into knife making. I'm looking to build the machine based on a video found on youtube from a guy by the name of "Old hickory forge", but I don't have much details on the extension spring he used.

He says the spring is 3.5” x ¾”, but when I go online to shop for springs I see extra details like "Rate (lb/in)", "Initial Tension (lb)" and "Suggested Max Load (lb)". I've seen and read in different forums that people use some 30 lb compression spring, but does it matter if I use an extension spring for the pivot arm instead?

Aside from the Length and spring diameter, what other details should I look for when buying an extension spring?

Here's an image for reference of the spring im talking about:

https://imgur.com/a/e1XPigg
Click to expand...
Power of spring is max. when you push/pull with force direct on spring .You use it in different way ...depend on how long is lever from pivot point .I hope you understand my broken English ...try it as it is now and if it is to weak/ to strong work with point of attachment
VVerPBw.jpg
 
Thanks for the quick reply. Basically you are telling me to drill different holes on the pivot arm to adjust spring tension?

What about "Rate (lb/in)", "Initial Tension (lb)" and "Suggested Max Load (lb)" of the spring itself?
 
rate of spring...............Meaning that if you have a spring which measures 0.250” and you want it to travel 0.050” with a spring rate of 15 lb/in, you must multiply the rate by the travel to get a total of 0.75 lbs. This means that with a rate of 15 lb/in, you will get 0.75 pounds of force for 0.05” of travel.

30 lb compression spring mean that you need 30lb force to compress it full, I think ....
"Suggested Max Load (lb)" meaning is clear , right ?
About inital tension .........
It is the tension that has already accumulated between coils of extension springs. This tension helps keep the coils together.
 
Yes.. thats the tracking wheel arm

Here's the youtube video.. Its just a different kind of build.

 
If you're not too far along with purchasing parts I'd use Brad Jensen's design. Much better design and won't cost much more either. By ALL MEANS get a 3 ph motor and VFD for variable speed. If purchasing new that will run around $168 for motor shipped and $70 or so for a NEMA 1 VFD. You will always be so happy you did.

Here's a couple of threads detailing the build of the grinder. This first thread is from 2018 and next thread is an updated version he did in 2020.
https://www.bladeforums.com/threads/2x72-grinder-build-2018.1577263/

https://www.bladeforums.com/threads/free-2-x-72-belt-grinder-plans-2020-version.1705344/

Brad will send you plans, or I can email a set to you and point direction to purchase the aluminum parts. You'll have around $100 to $200 in the frame, then wheels, motor, and VFD. Seems like I figured a total cost around $500 to $600 if purchasing everything for a top of line grinder.

you might look at the Reeder chassis for around $600. That does not include wheel set. You'll have closer to $1K in total package cost there, but it's a REALLY NICE grinder. "IF" I were purchasing a grinder I think that's what I'd get, but I build my grinders.

Good luck and have fun.
 
That motor will work just fine. It will be a while before you'll be wanting more than 1.5 hp. If you've got a 220vac source you can use the cheap Chinese VFD for $70 or so, but if only 120vac source you'll need the expensive KBAC drive.

You made a VERY wise decision going with a 3 ph motor.
 
Thanks a lot Ken.. Yes.. I will have an electrician wire a 220v source.. Labor in my country is pretty cheap, so I don't think ill pay more than $40USD for that.
 
"in your country"? Where are you located? Your profile isn't filled out. Having your general location helps with offering suggestions.
 
For those reading this thread, Panama has the same electric current type and plugs at the USA - 110VAC 60 cycle.
 
Yes, but the standard house current is 110VAC/60cycle. 220 is just how tey tap the transformer, which is the same as in the USA. Most homes have two opposed phase 110V lines coming in with the reference to ground ( center tapped 220V transformer winding). This allows normal 110V appliances as well as heavier current appliances that need 220VAC.
 
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