Tool Post Grinder

[PeterT]

Shop made wheel dresser example

Toolpost grinding wheel dresser

I wanted something rigid & adaptable I could set up quickly on the lathe for wheel dressing in whatever orientation the wheel diameter happened to present. Then knock it down quickly without fuss but preserve the height setting if required again. The parts are just from scrap box metal on hand...

canadianhobbymetalworkers.com

 

[DPittman]

Mac tools stopped by and had some small grinding stones on sale so I bought some.

Still looking for 3 to 4 inch wheels for outside grinding. I can make my own arbour for them.

Spin up the motor for the first time yesterday. Smooth as silk and "feels like" it will do the job!

Need to finish the motor holder and also make a chuck jaw expander so I can use the grinder to true up my 3jaw chuck. I'll be doing before and after comparisons when I do.

I forgot, Little Machine Shop has a nice selection of 80 mm diameter grinding wheels

 

[Susquatch]

One of my many interests in a grinder was to true up the Jaws on my 3-Jaw chuck. It's been a while since I measured the run-out though. Since I am close to finishing the spindle motor based tool post grinder, I figured it was high time that I got a good baseline with a few baseline measurements. So I mounted a precision ground indictator rod this afternoon and checked it out.

As soon as I made the first rotation, I realized that my Asimeto tenths indicator had crapped the bed - hardly any runout at all. I've been waiting for that thing to die anyway so I took it off and mounted my good Mitutoyo Tenths. But wait a second..... Same thing! Maybe 3 tenths at worst. Axial concentricity brought that to 4 tenths at 5 inches out......

So much for grinding my jaws to improve concentricity...

More experimenting is obviously required. It shouldn't have been that good.......

 

[140mower]

Damn, I hate it when that happens, hoping for junk and stuck with quality, and no reason to complete the latest project...... I feel your pain friend.

 

[thestelster]

One of my many interests in a grinder was to true up the Jaws on my 3-Jaw chuck. It's been a while since I measured the run-out though. Since I am close to finishing the spindle motor based tool post grinder, I figured it was high time that I got a good baseline with a few baseline measurements. So I mounted a precision ground indictator rod this afternoon and checked it out.

As soon as I made the first rotation, I realized that my Asimeto tenths indicator had crapped the bed - hardly any runout at all. I've been waiting for that thing to die anyway so I took it off and mounted my good Mitutoyo Tenths. But wait a second..... Same thing! Maybe 3 tenths at worst. Axial concentricity brought that to 4 tenths at 5 inches out......

So much for grinding my jaws to improve concentricity...

More experimenting is obviously required. It shouldn't have been that good.......

Try it with different diameter rods.

 

[Susquatch]

Try it with different diameter rods.

All the ones I have are all basically small ( 0.20000 (+/- 0.00001) to 0.50000). I don't have anything bigger than that. All the ones I have measured virtually the same.

I plan to make a bigger one myself today, but it won't be anywhere near that precise. But it will be good enough for this job. Even so, I expect that it will be worse. My jaws are in relatively good shape except at the very ends closest to the tool post. You can actually see the damage in one of the photos above. It isn't as bad as it looks though. The very end bevel is factory. But I probably made those tiny cuts somehow myself. I do not know how nor do I remember doing anything like that. I often grip threaded parts in my jaws and perhaps something held very short spun.

Which raises another question. Should I try facing off my jaws?

I plan to remove the chuck and re-install it today and check again. Back when I first got it I indexed it so it always goes on in the same place and it is a very tight fit, so I'm not expecting it to change.

But the odd thing is that I do not recall it ever being so good. In fact, I remember it being a fair bit worse. Very odd. Things don't usually get better with time.

The other thing I plan to do today is to make a stepped rod/bar, then reverse it. That might be very telling because it will load the Jaws. I was not about to ruin a very expensive indicator rod by gronking on it. It was tight, but not gronked. But a home made rod will definitely be suffering that fate.

 

[ShawnR]

gronked

learned a new word today

ps...the smiley only worked caused I used : & ) so

 

[140mower]

learned a new word today

ps...the smiley only worked caused I used : & ) so

...... perhaps your emojis are gronked too......

 

[Susquatch]

I suppose I should be laughing at everything.

I just turned my own indicator rod. Well, more like an indicator bar given that it's 1" in diameter.

I just chucked a 6 inch shaft and cut 3" of it down smooth. Then I reversed it and cut the other end smooth. Then I reversed it again and measured the runout. About 3 tenths. So I started clocking it in the Jaws and retested about every 45 degrees to test for any coincidental concentricity. Turns out the worst I measured was 5 tenths and the best was 1 tenth.

That's all with gronking on the chuck key.

Totally amazing and very hard to believe. So ya, I'm not gunna be messing with the Jaws on my 3 jaw chuck. They are good enough just the way they are!

 

[thestelster]

I suppose I should be laughing at everything.

I just turned my own indicator rod. Well, more like an indicator bar given that it's 1" in diameter.

I just chucked a 6 inch shaft and cut 3" of it down smooth. Then I reversed it and cut the other end smooth. Then I reversed it again and measured the runout. About 3 tenths. So I started clocking it in the Jaws and retested about every 45 degrees to test for any coincidental concentricity. Turns out the worst I measured was 5 tenths and the best was 1 tenth.

That's all with gronking on the chuck key.

Totally amazing and very hard to believe. So ya, I'm not gunna be messing with the Jaws on my 3 jaw chuck. They are good enough just the way they are!

I suggest you never remove that chuck. In fact I suggest paying homage, give offerings, or a sacrifice to the lathe gods. Don't even cast a look at it in an ambivalent way!

 

[Susquatch]

I suggest you never remove that chuck. In fact I suggest paying homage, give offerings, or a sacrifice to the lathe gods. Don't even cast a look at it in an ambivalent way!

Ya, I'm thinking the same thing.

I'm torn. A big part of me wants to take the chuck off and try it again just for poops and giggles. The other part says: "ARE YOU CRAZY!"

But it has to come off. UNLESS I buy another lathe...... Hmmmm......

Honey, I need another lathe.....

Big noise far in excess of 90db, grass looks root white for some reason, and I suddenly have a dozen brand new sparkly clean lathes and a dozen matching mills, and I could swear I hear angels singing.......

 

[PeterT]

I've noticed some +/- runout repeatability variations on my 3-jaw chuck too. Its a Bison 6", jaws & scroll in good shape, never abused or crashed or overtightened etc. Always mounted on same marked (lowest runout) D1-4 orientation. Same dowel which is hardened, known circular tolerance. The resultant indicator deviation range is typically 0.001 to 0.0015" runout which is pretty good for 3-jaw. So when I get a rogue reading like 0.003" it stands out for further investigation. Assuming all the obvious things like debris, I find I can usually make it revert to the mean by re-inserting & gradually tightening all the jaws in progressive succession and to the same (hand estimated) torque. Over-gronking or worse yet gronking on one jaw only is not good practice IMO. I know there is some kind of primary or dominant jaw, but I've found equal tightening to be better. Shorter length dowels that don't fully contact the jaws fully might be another discrepancy source. Measuring close or further from jaws is another variable. The dowel could be circular, but is it perfectly straight?

I think there a few subtleties to testing runout that people may not think of as important but may actually may be in the range. IE blaming the chuck, but it could be external factors. I've heard countless times something to effect: I chucked a shiny ground piece of O1 tool steel and.... Hope this isn't stating the obvious but Tool steel in its typical annealed ready-to-machine form is no harder than most other common alloys, so may as well say I chucked a piece of stainless or 4140. The hardness only comes after heat treating. Also, every tool steel bar I've had varies by 0.0005"-0.001" across the axis (non circular) which is actually stated by specs if they can be found. So right off the bat there will be at least this runout to contend with in otherwise perfect jaws. But this eccentric shape will present itself differently to the 3 jaws as a function of shape & orientation. If you rotate it slightly & re-grip, runout will be different again. Insertion: if the jaws are wide open and you 'drop' the bar kind of in between 2 supporting jaws & start scroll tightening, the jaws could be squeezing up the bar OD differently until fully tangent contacted. VS. getting the jaws close to OD & lightly turning the dowel as you tighten. I do this spin thing routinely on drills as I tighten chuck. Its how I discovered the crazy raised stamped marks on the shank affecting grip It probably pays to have some known (hardened) dowel standard for testing, ideally of a few different diameter ranges. Maybe the jaws faces are OK but scroll is worn or distorted in different areas? Not sure what can be done about that but at least you aren't chasing your tail fixing the wrong perceived problem source.

I haven't actually purchased a set of jaws for a chuck yet, but I've heard of people who did & majority of headaches went away assuming that's all it was. May not be the answer but something to compare as baseline cost to alternatives assuming the chuck body, scroll & slide ways are good. I'm a fan of Set-True type chucks where you can tweak the chuck axis relative to spindle axis. Unfortunately the backplate adapters & chucks themselves can add considerable cost. This discussion is related to repeatability issues of typical 3-jaw. Many will advocate getting a collet chuck for precision work. That may be helpful, but maybe not, depends on quality of chuck, collets & same axis orientation issues. And a 5C or ER collet chuck wont do us much good if we need repeatability on parts outside the typical range of collets.

 

[RobinHood]

As far a buying replacement parts for chucks: it depends on the quality/value of the chuck, IMHO. If a set of jaws are $700 for a 10” Röhm then one has to compare that to the new price of $2000+. It may be a good purchase. Not so much for a $400 import. Oh, btw, for Röhm chucks, any replacement jaws need to be ground in situ once they are installed to achieve the very tight tolerance that Röhm work holding tooling is known for.

Agree with “twisting in” a part as you tighten the jaws. I also use all available key holes to get it tight, with the final torque on the “master” key (as per Röhm [and other high quality] operating instructions).

 

[Janger]

Pete alluded to this but I'll spell it out specifically. The dowel can be round and straight - but is it in the chuck straight? Measure the run out at 1" out from the chuck and then again at say 3" out from the chuck. If it's different it's not in straight (assuming it is a straight bar). The texan guy has a video on this. Joe Pieczynski but I can't seem to find it.

 

[Susquatch]

Pete alluded to this but I'll spell it out specifically. The dowel can be round and straight - but is it in the chuck straight? Measure the run out at 1" out from the chuck and then again at say 3" out from the chuck. If it's different it's not in straight (assuming it is a straight bar). The texan guy has a video on this. Joe Pieczynski but I can't seem to find it.

That's the concentricity measurement I spoke of earlier. I measured it at the chuck and out 3 inches for my homemade indicator bar and at 5 inches with my precision ground rod.

But I'm more inclined to believe that the majority of any of this error is due to non-concentric or belled jaws that need grinding than it is to not putting the part in straight.

 

[Tom O]

This guy shows his grinding setup and mentions other setups on his channel

 

[Dabbler]

Max has a completer video series on OD grinding, ID grinding and taper grinding using a TPG. The series begins here:

 

[PeterT]

Max has a completer video series on OD grinding, ID grinding and taper grinding using a TPG. The series begins here:

Good score @Dabbler I've come across his channel but missed these. Kind of hard to see from this angle perspective but demonstrates the potential tailstock vs spindle competing real estate issue I was mentioning. The only way to work around TS support is if the spindle housing is smallish OD and the grinding wheel biggish OD & part is not too smallish ID. His setup is similar to typical Dumore/Themac/Maximat TPG layout where the spindle is compact OD & larger diameter motor is back up out of the way (and belt driven). Versus if its a direct drive motor, the HP dictates rotor diameter, so you need a proportionately larger wheel to clear. Some lathes can accommodate this if wheel extends outboard of cross slide, but kind of depends.

Grinding angles (with TS support) can also be a bit tricky as the compound can only swing out of the way, not into the lathe axis path. Some parts like the R8 arbors can be flipped end to end to accommodate, but not all parts lend themselves to this.

 

[Susquatch]

Well, big day today. I fired up the new spindle motor based tool post grinder.

Excuse the fancy drop cloth. Didn't want grit on my ways.

The video is huge so I uploaded it to dropbox. I'm no youtube creator.

Dropbox

www.dropbox.com

The lathe isn't as Noisy in person as it is in the video, and the spindle motor is the opposite and much quieter in person. The grinding noise is much quieter in person too. It's probably the way my phone normalizes sound.

It didn't take long at all to grind down that last 1/4 inch to get the bar round. It doesn't bounce unless you push it which isn't in any of my planned uses.

Wish I had a bigger wheel, but not yet. Need to make or buy a wheel dresser too.

In any event, it works. So I'm happy for now. Best of all, I learned a lot along the way with lots of learning yet to come.

Next phase is an enclosure for the control box, a stone dressing system, a proper height adjuster for the holder, some proper stones, and prolly a few stone arbors too. Then I'll try to use it to make something since grinding my jaws as originally planned would be stupid.

 

[Susquatch]

Here is the "almost finished" tool holder. Still needs the height adjuster but the relief for it is cut.

I decided to go with two halves. Didn't have a sharp slitting saw and figured a 2 part clamp would be better anyway. So I just cut it in half on the band saw and then cleaned up the surfaces on the mill.

Drilling, countersinking, and even tapping was a piece of cake with the DRO. No idea how I lived my life so long without one. Like it enough that I might even splurge and put one on the lathe too.