I'm looking to build a 2 x 72 grinder. I just have a question about the motor. Is a 1/3 hp to under powered for it? I have seen most builds between 1-3 hp but I did watch a video a guy used I believe was a 1/3 hp. He said it so quick lol. Found this one on kijiji for $30 this HTML class. Value is http://m.kijiji.ca/p
I have a 1/3 hp on my 2 X 48" and it's VERY underpowered. It's better than nothing, but not by much. I'm getting it changed to a 1hp motor soon. I can't wait.
I ran my 2x72 on a 1hp table saw motor for a couple years and could stall it when really hogging. It all depends how you grind, but I felt 1hp wasn't enough and stepped up to 2 hp and am happy now.
I guess that depends on how you define heavy grinding. I wound up going with a 1 1/2 HP for mine, as I've only got a single 120V/15A circuit to work off of, and short of just crushing my steel into the belt, haven't had many issues with stalling. I guess my point is, more power is generally better, just keep an eye on what the current draw is going to be and what the limits of your circuit are. 1/3 HP would be a nightmare to work on. I figure 1 is the minimum, unless you're prepared to spend your life feathering the steel onto the belt.
I'll be working with a 1/3hp. Maybe even less than that. But that's the price I pay for not having a space to set up a workshop.
My 1x30 has a 1/3hp motor and I can stall it out quite easily. I would think for a 2x72 1.5 is about as small as you'd want to go.
What I call heavy grinding is when I'm grinding big trail knives from 1/4 cpm3v 12" blade and useing a push stick . But everyone grinds different so what every works for you go with it. I see use people use 1x30 and get the done and do some nice work. I'm glad for them but I just could go back to that today .
So true. The 1 x 30 worked for me at the beginning. I made about 5 knives with it but once you try a 2 x 72 you can't go back very easily. I found I made a lot of dumb mistakes with the 1 x 30 because I was trying to do things with it that it just wasn't capable of. With my 2 x 72 I have the confidence and rigidity to get the grind done and move on to the next grind. It may just be me but knowing the power is there helps.
Feeling a bit like Confucius today. I think it's Nerd Week. I came up with this on my way to work: When starting out...what seemed obvious was that you needed more power. Once you have more power...what seems obvious is that you needed more patience. I have a 2 horsepower motor and find that's plenty of power. If you are stalling a 1 or 2 horsepower motor, maybe you are going about it the wrong way. It's great to see the sparks flying, but it's not all about brute force. There is much finesse to grinding. Sometimes it takes me 200 passes to get it right; and the majority of those passes do not require much horsepower at all. Take every opportunity to learn and master the techniques. The patience that you learn is transferable. Dan
Is 4 HP over kill? Found a guy who is selling his treadmill for $50 because it needs a new motherboard but the motor works. Thinking if I can talk him down it would be good.
Treadmill motors are usually DC but I have seen a few 3 phase AC motors. DC motors will require the SCR/power & possibly the controller. DC motors often require some protection from dust. With my treadmill motor, I was able to toss the controller as the SCR board has a 0-12V speed control signal. If you use the original controller, you need to keep the speed feedback sensor in the system or the controller doesn't know how fast the motor is going. Now, if the motor is a 3 phase AC inductor motor that is a steal. You'll need a VFD and 240V at about 20A power.
@dancom since you seem to know a lot about motors and electrical aspects of them. Would it be practical to convert a 3 phase 240v or 440v table saw motor? I know that I can get 100% free because its about to be tossed in the trash even though it works.
That is a beautiful motor! Again, you'll need a VFD and some 240V mains, but after that you're cooking on gas. You can never go wrong with a Baldor. I can guess a single phase 3 horsepower VFD will be around $250 plus an enclosure, but you'd end up with something you'd find on a $3000 grinder. Dan
