D-bit grinder work head swap

[Winegrower]

You know what they say about broken clocks. I'm curious, about the name on your machine. Is it Kao Ming? That would be significant, they are a maker of grinding machinery in Taiwan that plays reduced budget competition to some major toolmakers like KO Lee and Cinci. Was it a new or used purchase?

It's a Kunming, clearly mainland Chinese. Seems well built and is very functional. I need to get the U3 head placed and finish some wheel hubs for inexpensive diamond cup wheels.

 

[Winegrower]

Regarding the U3 5C unit, here's what I found: Collets would not fit in the unit because the locating pin was too long. It was easy to file it down with the Butterfly die filer. The 180 degree rotation is actually about 184 degrees, may be a bit harder to fix since it's a function of placement and diameter of a couple stop pins. Also, not really a problem, but something needed, is that the dovetail is much narrower than my cutter-grinder's. While a gib came with the U3, it's too thin, so I'll have to make another.

The seller sent a polite note asking for feedback so I reported these issues, and he promised a fix. I'm not unhappy even without that.

 

[pontiac428]

The 180 degree rotation does not need to be exact for a d-bit, because the end point of the rotation when grinding the relief is what you index to. So those extra 4 degrees plus 5 to 15 degrees you leave behind for the cutting edge will just hit empty space, because a d-bit is half round.

What do you think about the rotation smoothness, centerline runout, and bearing play on the new head?

 

[petertha]

The dog point set screw in my work head was too long as well. It was jamming in the slot of my collets. PITA. It appeared that getting at it from the outside meant essentially work head disassembly. That meant removing the two thin 4-slotted nuts which adjust bearing preload. No tools were included & I wasn't sure if they were standard hook wrenches which can be pretty cheesy in their own right & you need 2 side by side to back off from one another & reset again upon assembly. Or tappety-tap them off with a pin punch as a certain Youtuber likes to say, which I am not particularly crazy about, especially with 2 nuts face to face.

So I gave myself a bit of 'wandering grind stone protection', masked off adjoining area of the protruding screw. I could reach in with my grinder & get at it that way. Kind of ghetto but it worked. In hindsight now that I have been disassembling other parts of the machine, I have less fear about looking under the hood. These are certainly not Swiss watches & I have either been making fixes or inventory list of fixes/mods along the way.

The cylindrical threaded bar you see fits into a matching hole in the dovetail base. Mine is poor alignment fit & explains why slide adjustment basically didn't work from the get-go. You can see where they beavered away at the hole in the plate to fudge it, which is another ill fitting component. The Shars equivalent was much better made & an improvement on this version.

I'll start gathering some more pictures together when I have time. It would be good to compare notes.

 

[Winegrower]

What do you think about the rotation smoothness, centerline runout, and bearing play on the new head?

The head is basically a sleeve held by a collar secured with a set screw. Adjusted right, which it needed, and slathered in oil, which it had, it rotates adequately smoothly, all seems axially ok, play is acceptable, but I don't have any quantitative data yet. Overall, it's OK, not overwhelming good or bad.