KO-Lee Cutter/Grinder Revamp

After the usual 15 minutes of messing with the VFD parameters just to make the motor spin, the first trial run was a success. There's good news and bad news.

The bad news: I have my doubts about this motor. Just free-running the motor, it vibrates more than I would expect also, the shaft gets hot -almost too hot to touch and finally, when it's shut off, it has no significant period of free running. Within the blink of an eye, it goes from 3600 RPM to 0 RPM and I do not have electronic braking enabled.

The good news: The spindle was running fine. The bearings inside are just greased for now. Long term this will be filled with light oil. During the 10 minute test run at 3000 RPM, nothing on the spindle got warm. Both of the sheaves are running very true.

Before making a permanent mounting assembly, I'll look into the motor issue. We'll see how things go...


IMG_20180304_170230.jpg

Ray
 
Work has slowed down on this because other matters have been keeping me occupied. This picture is not too much different than the last one however, the adjustable motor bracket is finished now. Four threaded rod studs were welded to the frame and the push/pull nuts adjust belt tension.

There's just a bunch of miscellaneous work now before the tests can begin. Right now, all the bearings are just greased but long term (and before the testing starts in-earnest) the seals and breather vent need to be installed and it will be filled with transmission fluid. All the spindle parts are done but only after it's mounted, will I be able to measure and trim the shaft and put a left-hand thread on the end.

Almost there...
IMG_20180311_182035.jpg

I sure hope this thing works. If it does, I'll make belt guards, clean it up and put some finishing touches on it. It's still pretty crude but it's getting closer to the finish line.

Ray
 
Some progress... Hopefully the video is small enough to distribute. Here's a test run while mounted on the grinder and with the spindle filled with oil. It's fairly quiet and certainly no louder than my old B&S #2.

First things first... Yes, I'm well aware there is no belt guard installed yet. These are the first runs and some level of risk is being accepted. Belt guards are indeed a part of the final plan.

When I carefully place a fingertip on either end of the shaft or on the sides of the sheaves (those are sheaves, not pulleys), it feels very smooth. For this, I am both pleased and relieved. There is one issue that will be resolved with a new belt. There's a slight vibration in the overall unit. It's not excessive but is noticeable. The sheaves are running with around 1 thou TIR and I can see the belt grooves are running dead straight and flat. The shafts are dead-on. When looking at the top of the rubber drive belt, I can see it's bouncing; I would guess about 50-75 thou. Side to side, it's running perfectly. The belt must have a thick spot in it causing it to bounce. The sheaves are perfectly aligned.
IMG_20180316_202426.jpg

It's been running at 60% for about 30 minutes now and it's barely warm to the touch. Most of the heat is from the belt. The front bearing cap is cool. We'll let it go for another 30 minutes at 100% and then I'll pull it apart and insect.

There's still a bunch of finishing work on this but, this very near the end.

Ray
 

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Well, it ran at 100% speed for an additional 45 minutes. Bearing caps, shafts etc were warm to the touch but not hot; maybe, in the 110 degree range. Oh, it was the belt causing the problem. I had another one that was 1/2" longer and it ran much smoother despite the extra distance.

I'll disassemble and inspect it tomorrow. Hopefully there will be no metal shavings in the oil. If all goes well, this weekend, I'll mount the hub on the spindle, make a wheel guard and see if it grinds metal.

Ray
 
Through all the machining the six jaws have done great ,, right. God I love mine and Ive had it thirty years . Enjoying the build isn't it great to rebuild upgrading all the time.
 
Silverbullet said:
Through all the machining the six jaws have done great ,, right. God I love mine and Ive had it thirty years . Enjoying the build isn't it great to rebuild upgrading all the time.
Click to expand...

Hi Ho, Silver... You bet, the chucks are doing great. I never used 6 jaw chucks before and I'm a believer now. They are still holding things very straight and true and they have been used quite a bit on several other projects in the shop. I have not used any of the old 3 jaw chucks since getting these and only used the 4 jaw once to hold a square piece.

Could not be happier! Thanks for asking.


Ray
 
The proof is in the pudding! It grinds really well -better than I could hope for actually...

Here's the self-centering spindle setup. Recall that the hub "floats" on two tapered cones. The drive cone is at the rear of the hub and front cone gets pushed into the front of the hub via the left hand nut. Sorry to say but, I didn't take pictures when making the locking collar. That was a piece of hardened metal made at the onset of the project. A 26 tpi left thread was put on the spindle and locking collar.

When it was snugged up and turned by hand, the hub shaft was within 0.0005 TIR. Actually, it looked to be about 0.0004".

Rear view showing the drive pins.
IMG_20180317_173736.jpg

Front view showing the front collar which centers the whole assembly when the left hand nut is tightened. I need to put a couple spanner holes on the locking collar.
IMG_20180317_173721.jpg


And of course, we had to give it a quick test run. Yes, I was wearing a full-face shield.
IMG_20180317_173310.jpg


So... I grabbed a nearby chunk of cast iron and this was the result after 3 passes. Step-over was about 50 thou on all passes. First was about 0.001" to make full contact. Second was 0.0005 down and third, was a phantom pass.

IMG_20180317_173418.jpgIMG_20180317_173502.jpgIMG_20180317_173942.jpg


Until I get all the safety equipment made, I won't know how flat I can make something. As far as surface finish, this is as good or better than I was able to get out of my old B&S #2.

We're pretty close to declaring success here. I just need tidy things up and get it to hold 0.0005 over a 4" x 4" piece. I'll probably need to make some level adjusting mechanism for the bracket that holds the spindle. It was built into the design but not implemented for this test phase.

Happy St. Pats Day. Time for some green beer.

Ray
 
I'm late to the party but just read the thread and enjoyed it.

I have two questions.

First, in reply #19 (Feb 3) a photo caption is "The initial scrape test showed a little low spot. " Can you describe what you mean by "initial scrape test".
Did you use Prussian blue and mate with a female taper or rub a known straight reference against it while turning or ???

Second, in reply #62 (Mar 4) you mentioned that the motor shaft got hot in a test run and that the spin-down time was very short. How were those issues addressed & resolved?

Thanks for posting.
 
extropic said:
I'm late to the party but just read the thread and enjoyed it.

I have two questions.

First, in reply #19 (Feb 3) a photo caption is "The initial scrape test showed a little low spot. " Can you describe what you mean by "initial scrape test".
Did you use Prussian blue and mate with a female taper or rub a known straight reference against it while turning or ???

Second, in reply #62 (Mar 4) you mentioned that the motor shaft got hot in a test run and that the spin-down time was very short. How were those issues addressed & resolved?

Thanks for posting.
Click to expand...

Thanks 'extropic', I appreciate all the Likes you gave. FWIW, many years ago, I had more Likes than posts but back in 2012 or 2013, we got hit with destructive virus and my post count and Likes got erased.

Answer #1: To check the shaft, I coated it with bluing and used the long edge of a HSS tool blank to scrape the high spots. I checked the tool blank on a grade A table and verified it to be flat. The taper technique is also shown in this build thread: https://www.hobby-machinist.com/threads/bull-nose-live-center.64859/

Answer #2: The motor... I called the distributor and they recommended a test to let it run for a while. They were willing to accept a return if it was not satisfactory after break-in. I decided to let it run in 30 minute intervals for 4 or 5 hours. The heat problem resolved itself and is due to the fresh rubber oil seals breaking in. The vibration also smoothed out to an acceptable level but, I'm still planning to take it apart to see if I can balance the rotor a little better.

Gratuitous BS: FYI: The project is still on hold until while my shop is being reorganized. I need to build a table for that grinder and I'm not inclined to do welding until the weather improves where I can do it outside. Also, the metal frame/box needs to be sandblasted and painted -which I don't do until the garage is opened up.

Ray
 
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