KO-Lee Cutter/Grinder Revamp

[Ray C]

So sorry for the long delay. My day job has been very demanding lately.

I did a course correction and changed the shaft from a taper on the hub end to just straight. I'm "inventing" another mechanism to center the grinder hub. The idea of a steep taper on a thin diameter shaft was not sitting well with me. Quite frankly, it was just bugging me because I'm not all that crazy about friction tapers in the first place and having one on shaft less than 1" diameter was doomed for failure.

Anyhow, another precision shaft was made. When I heat treated the raw stock for the last one, I did 3 others along with it. Without stopping to take pictures and do write-up, it only takes about 45 minutes to re-make that shaft. Tolerances on this one were the same and everything is inside 1-2 tenths.

The shaft was assembled last night and a couple very simple pieces of stock were cut to serve as a precision guide while the bearings were pressed on. There was one fairly big surprise... A fairly large extra spacer was needed to supply spring pressure. My initial calculations were to put 25lbs force on the taper bearing. I calculated that much into the dimensions and also added a good bit of extra on the spring support, with the intention it could be trimmed down if needed. Instead, that extra bushing/spacer (next to the thrust bearing) was needed. Turned-out, 25lbs was nowhere near enough. The calculations and dimensions came-out right as far as I could tell but, I just miscalculated how much force is needed to keep the bearing seated. Now, the force is about 125lbs.


Here's what the assembled setup looks like:





The indicator is showing TIR inside 1.5 tenths which I suspect is mostly surface irregularities. For now, the bearings were lightly greased and a motor was rigged-up to spin it for increasing periods of time from 10, 20, 30 and 60 minute periods. No heat at all -meaning, ABEC 5 bearings are good things and also, 125lbs is not too much force. Should be fine really because that bearing should be able to handle axial load of 5,000 lbs safely.

So... Here's what I'm working on instead of a tapered shaft. The idea is conveyed in the close-up of the hub attachment assembly. I'm going to use 2 very simple tapers and hardened smooth surfaces to self-center the hub. The added complication is that a couple drive pins are needed. I might change the drive pins to a slot-type arrangement but for now, pins will do. The pins free-float in the back of hub plate.



And here are some of the prototype pieces...




So, we're in free-wheeling territory now, thinking on-the-fly -which is how most of my projects are hatched...

So, any thoughts, suggestions? I'm all ears.

Ray

 

[Ray C]

In the light of a new day, things are looking OK. Here's a simple roller/balancer fixture that was rigged-up out of scraps many years ago. Back when it was made, I never imagined it would be one of the more useful pieces of equipment in the shop. One of these days, I should touch it up and improve it.

So... As best I can tell, the shaft is has no perceptible bow. Everywhere the indicator looks, it sees no more than 0.0002 TIR. I'm calling it good and time to move on with making those tapered centering do-dads.



Ray

 

[Ray C]

Moving along...

Here's another piece to the puzzle. Just need to drill holes and put the drive pins in there, heat treat it and finish the surface with emery cloth. Heat treating will be done with open flame and all I'm after is the tapered cone. We're solidly in prototype mode here so if this does not work out, we'll fall back to plan B (and at this time, I have no idea what plan B is -may need to skip over to plan C).



The two tapered do-dads (I'm calling them centering rings for now) fit very snugly on the shaft. The rear one (with the pins) will be affixed to the shaft by some TBD means. The front one will be held in place by a nut by some yet-to-be-cut LH threads.

Anyhow, they fit very snugly now and will "stay-put" once squeezed into place. Testing TIR on the hub shaft showed absolutely no sign of needle movement so, it looks like the centering technique stands a chance of working.




Time to grab some grub and walk the dogs...

Ray

 

[Ray C]

The rear hub centering ring (with the drive pins came-out OK. It's not the prettiest thing in the world and is still a little ugly from the flame hardening. The rear of the hub (which has a 30 degree chamfered edge) centers on the taper of the smaller piece. The pins are TIG welded to the small piece and extend to fit very loosely into the back of hub to transmit power. The little centering assembly is made of 1045 and is intentionally quite hard so it will not bind-up with the softer metal of the spindle. The spindle was also 1045 but only RC 35-ish.



Here it is, positioned on the shaft. It will be pushed a little further back later on.



In case you're interested how this is all coming together, here's a sneak preview. The new spindle is just (precariously) sitting atop that column for now but, a suitable bracket will be dreamed-up sometime between now and probably tomorrow morning. I have a 3 phase motor to drive it and that will sit above the spindle, also attached to the TBD bracket. There will be a flat drive belt and sheaves transmitting power at the rear of the spindle, similar to how a toolpost grinder works. -Matter of fact, this thing is nothing more than a gigantic toolpost grinder.

The KO Lee base will be used for now, as a proof of concept. If I like it, I've had ideas circulating for a while to make an X-Y roller bearing table and some day, I might get around to making my own mini surface grinder.


Ray

 

[Ray C]

Just so you know, I have not lost interested in this project. The motor spindle and motor brackets are the next big items to work on however, two things are slowing down progress. I ordered a 1 HP, 3 phase motor and the wrong one was delivered. Until the motor is here, I'm holding off on drawing-up the design that's floating around in my head. Also, I'm basically working 2 full time jobs these days and have been doing 12 hour days at the office for a couple months now. In all honesty, I'm tired. I check in and BS on this forum to relax but, have not been able to muster-up the extra energy it takes to finish this off. Soon, I'll get my second wind.

Here's a tiny little piece today related to the motor bracket that is OK make w/o the finalized design.

I had a piece of 316 stainless laying around in the shop for several years now. It's been put to use for a bunch of things and now, it gets a permanent purpose. It's about the size of a hockey puck.

Here's something I use all the time. It's a ram bar that fits in the ram of the tailstock. Make one sometime. They're very handy for this purpose. The SS block is lightly held in the jaws and a couple of parallels between the jaws to prop-up the part. The ram bar does a great job of applying even pressure to hold the piece nice and flat. Of course, it can be pushed by hand but, it's very easy to apply uneven pressure. REMINDER: Remember to remove the parallels before spinning-up the lathe.

When you press on the part by hand, when tightened, the jaws overpower you and the part shifts. This is less likely to happen with the ram bar. I used the ram bar when facing-off both sides of the piece and the width varied within 0.0003" measuring all the way around. You could tap on it with a dead blow hammer but, instincts tell me that the spindle bearings would prefer not to be pounded on.




Speeds and feeds are critical with stainless steel. This part was spun at 250 RPM and increased to around 400 (controlled with the VFD) as it reached the center. The finish is beautiful. Too bad stainless scratches just by looking at it too hard.




The part needed some holes and recesses to clear a bolt head. Once again, cutter RPM was critical here. FWIW, I drilled the thru-holes first then, cut the counter-sinks. This way, the center of the endmill does not take such a pounding even though it is a center-cut endmill.




It came out looking nice. I went way over-board with the detail on this part but, the time spent in on this was pure relaxation time.




And this is the purpose it serves... It sits atop the grinder column and will be held to it by 2 bolts. The recess in the center will accommodate a matching feature on the bottom of a plate that sits atop the stainless puck. The plate will later hold the spindle and motor assembly. A bolt in the middle can be tightened/loosened to let the spindle/motor assembly have a full range of motion. The OD of that puck fits the ID of the column perfectly. The diameter of that recess is 1.2505". It's important that the matching feature on the bottom of the plate fit perfectly and I'll be shooting for 1.2500".



All that work on that pretty piece of stainless will be covered-up completely when the matching part covers it up. Say goodbye...

So, that's it for today.

Ray

 

[mattthemuppet2]

that came out beautiful. I hear you on the limited time, it sucks. During the semester I rarely have time to work on anything and when I do bike maintenance takes priority. Still little jobs keep the flame alive - made a hamster powered LED light with my daughter this weekend (and a gerbil habitat with the other daughter), so I got my fix that way!

 

[Ray C]

Hampster powered LED and a gerbil habitat? Did you post pictures here? That would put a smile on my face.

Ray

 

[FOMOGO]

Great project Ray, I'm enjoying watching your progress. Wondering how you are liking the 6-jaw, and if it's doing everything you hoped? Cheers, Mike

 

[mattthemuppet2]

Hampster powered LED and a gerbil habitat? Did you post pictures here? That would put a smile on my face.

Ray

I have to get the pics from my daughter as I forgot my camera at work. She presented it at her science fair last night and people seemed interested. Unfortunately the LED stopped working - I think the reverse voltage when the wheel was spinning the other way killed it, should have put a diode in series with it.

 

[Ray C]

Great project Ray, I'm enjoying watching your progress. Wondering how you are liking the 6-jaw, and if it's doing everything you hoped? Cheers, Mike

Hi Mike,

The chucks are beyond my expectations and they get a lot of use. Those two new chucks are my primaries now -along with the 5C collet chuck. I'm using the collet chuck less these days because the others are doing so well. I'll probably keep the existing 8", 4 jaw but may sell off the other two 3 jaw chucks I have.

The new chucks hold zero within about a thou over the full range of usable diameter and they hold parts in a pretty nice straight line; usually within 3 thou over 20 inches.

I had to develop a little technique to tighten them -not complicated. First snug the part up followed by backing-off about 1/4 turn then, wiggling the piece so it settles the jaws into position. A firm tightening after that and the part is usually right on. Since the shoulder was cut back on the backplate, I can do precise centering in matter of moments if needed.

Really good buy for the money...

https://www.hobby-machinist.com/threads/ordered-a-6-jaw-lathe-chuck.65884/

Ray