KMG Belt To Direct Drive

DanF

Well-Known Member
While I am rearranging the shop, I want to (I think), switch my belt pulley system to VS direct drive. I have a 2hp wired for 220v, that I can stall out very easily. Will the DD alleviate this problem, and will I get more sfps? Just don't want to go through the changes for only the ease of variable speed alone
Thanks,

Also, I have read that you can turn stuff on a mini mill just as if it were a lathe?
Thanks x2 :)
 
I agree with Dave..... if you're "easily" stalling out a 2hp, something is amiss somewhere. Lots of possibilities. If you can, take a pic of the motor plate (the metal plate on the motor housing) it will list the info we'd need to give you some direction on why the motor is stalling.

That being said, I converted my KMG to direct drive about 2 years ago, using the same motor as when it was belt driven...... for me it was a world of difference. The machine runs smoother than it ever did with the belt drive (I suspect that because of eliminating all those belt drive parts), and in every aspect the grinder is "stronger" then it was with the belt.
 
Sorry, bad terminology on my part, belt slipping without what I would consider a lot of pressure on my part, even after applying more pressure on tension spring by extending the arm a bit.
 
@OA, looks like the bit is held in a vice? No live end needed underneath the turned piece (is that what it's called?)? I primarily want to turn wood and g10 into guards and spacers.
Thanks,
 
Dan, do I understand your current setup is a 1 ph motor? If so, you'll need a 3 ph along with a VFD drive to go variable speed.

Will it make it faster? Well, that depends (don't you love those type answers?). What is diameter of your drive wheel? With a 4" drive wheel and the motor spinning at 3800 rpm you'll have around a 4,000 SFPM belt speed. The 3800 rpm is the same if you're using a 1800 rpm motor with a double RPM jumper, or a 3600 rpm motor and only overspeeding to 3800 RPM. Both about the same, and in use you'll never know the difference if the motor is 1800 rpm or 3600 rpm, except the 3600 rpm motor is less weight and less expensive. Yes, at 1800 rpm there is more torque and power, but at 1800 rpm you're not using anywhere neat all the motor HP anyway, so it's a mute point.

Nope, going to a VFD isn't going to help any with belt slippage. You might try wrapping a layer of rubber tape around the drive wheel - that does help.

Changing to VFD/direct drive is worth the money just for the extra smoothness and speed control. I preached for a couple of year my 3 speed gave me all the speeds I needed..... until I finally built another grinder with VFD. I'm sold! I've got 4 VFD drives running in the shop now, one on a lathe, one on disk grinder, a horizontal grinder, and standard old 2X72 grinder. They're all the cheap Chinese drives - well, the lathe is a Telco, but it's still "made in China", just had to pay extra for the Telco name. It was my first.

Ken H>
 
Ken, I believe we have the same lathe. When you went variable speed, did you leave the lathe set for high speed or low? Does it still have good torque at low speeds?

I want to change mine to get lower speeds and to get rid of change gears
 
Thanks Ken, for some silly reason I thought it was 3 ph variable-- it's not.
 
John, I've got a G0602 Grizzly lathe that came with a 1 hp motor. I changed to a 1 hp 3ph motor with a 1 hp rated Telco drive. I removed the idler for the belt drive and it's used as a single speed. The low speed is around 60 rpm, with max motor speed around 800 rpm at 60 hz. I've not ran into any torque issues, except on a 10" diameter disk I was turning down. There I had to take very light cuts because it didn't have the power needed for heavier cuts. I have considered changing the belt for more speed, but that would raise my minimum speed and I really like a slow rpm (60 to 90 rpm) for threading. I never use the thread dial for threading, just engage the half nut, make a light pass, stop, back out tool bit a few thou, reverse, set tool depth, forward again. That way the tool is always at the right spot to track in threads nicely.
 
I want to change mine to get lower speeds and to get rid of change gears

Ooops, I forgot to comment on the "change gears" comment. Not sure if you meant "changing belts" to get different speeds, OR - if you did mean "changing gears" for different feed speeds for threading. The VFD does NOT affect the need to change gears for threading speeds, you'll still have to change gears for threading.

I have wished I'd purchased the G4003G gunsmith lathe, but that was a LOTS more money and I didn't know enough at the time so the cheaper $1300 G0602 was a good start.

Ken H>
 
Do you have a VFD/variable speed set up, or single phase with a step pulley?
Sounds like you may just have some belt slippage, rather than stalling a 2hp motor. Either your abrasive belt is slipping on your drive wheel, or your drive belt is slipping on your pulleys. put a piece of painter's tape on your drive wheel, or make a bright mark of some kind, and then stall your belt. If the drive wheel keeps spinning, your abrasive belt isn't tight enough. If it stops or slows down, than your drive belt isn't tight enough.
Another possibility, IF you have the KBAC vfd setup: The torque setting may be set to VT (variable torque) instead of CT (constant torque). VT will cause the torque to be almost non-existent at lower speeds. Put the jumper to CT and this should fix the problem.

Speed will not be affected by direct drive conversion UNLESS your pulleys (motor pulley and drive shaft pulley) are different sizes. If your motor pulley is currently smaller than your drive shaft pulley, changing to direct drive will speed things up. If the motor pulley is larger, than direct drive will slow things down, all other things being equal.
 
Thanks for all the replies everyone, grinding belt is slipping at the drive wheel, drive belt holds it's speed. I would imagine I could have the same issue with a DD system?
Will try to find something with grip to cover the wheel, or buy a drive wheel with an agressive holding surface on it.
I think I found enough space in my tiny shop to place mini lathe. I suspect I'll be happier with that as I'm more familiar with a lathe vs the mini mill.
Thanks again all,
 
There are a few combo lathe/mill setups, depending on what you are looking to spend. I went Mill first, and glad I did! I didn't have much money, so an X2 is all I could afford. But getting it for $540 shipped is hard to beat dollar for dollar!

Where are you finding that price for it? I've been looking at them and All the x2s I'm seeing are quite a bit more than that.
 
There are a few combo lathe/mill setups, depending on what you are looking to spend. I went Mill first, and glad I did! I didn't have much money, so an X2 is all I could afford. But getting it for $540 shipped is hard to beat dollar for dollar!
I went mill first last year, hind sight being 20/20, I should have gone combo for my tight space needs. HF has gone nuts on pricing and coupons so I'll either go grizzly or little machine shop for the lathe.
Hauled 2 pickup truck loads of junk out of the shop today, heck I got plenty of room in there, enough for two more 6' work benches along the walls.
 
I was told HF no longer accepts coupons for a LOT of the more popular items, and the lathe falls in that category. The fine print on the coupons gets longer and longer.
 
Two store managers, and HF customer service number when I did not take them at their word. Matter of fact, one of the managers said customers would be seeing restrictions on more HF product.
 
Just searched for item #93212 coupons, search came back as, "no valid coupons found".
Maybe it's different in other areas (shrug)?
 
Checked my email for HF, figured I'd have the same flyer, and I did. There was a 25% off coupon there that may have allowed the lathe, but was expired, hence the "no valid coupons found", I had received.
Just wanted to say you may have been correct, OA.
Just as well it had expired since it is not a good performer.;)
 
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