Dressing Assembly For Toolpost Grinder In Lathe

petertha

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I have one of these clamp-on affairs for dressing tool post grinder wheels. You clamp the C on the stock held in the chuck. A diamond point tool is secured into one of the clamp holes & you dress the grinding wheel by skimming across the point. At least I really hope that's how its intended to function.

But I find it kind of awkward. For sure I can set it up this way initially & dress. But if I want to re-dress the wheel on the fly with part already in the chuck, it usually not as convenient. The part itself may well have low stick out, particularly grinding ID bores & the point rarely ends up in the right or orientation. The clamp does not really secure properly to a chuck jaw & a collet chuck is even worse.

I was wondering if I made something where the grinding point was secured to a vertical post & based with a magnetic stand attached to lathe bed - would that be rigid enough? The point has to be on lathe center of course, so on my 14" swing lathe the post itself might be say 4" tall. Any ideas or commercial solutions welcome.

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As long as you have a good quality / strong magnetic base it will be fine. Just keep it on the center line of the chuck and do real light dressing passes.
 
We used a right angle mounted diamond in our tailstock chuck. Out of the way and there when you needed it.
 
On my particular setup, the toolpost grinder motor/spindle setup is pre-aligned & clamped down with part sitting in the lathe chuck/collet. The grinding arbor/wheel is pointing towards the headstock. So I need the wheel to be dressed in-situ between chuck & compound to a) expose fresh wheel grit b) ensure its dressed surface is parallel to lathe X-axis ready for in feed traversing. Then its ready for grinding action. So sorry, I'm not quite sure I follow the tail post mounted diamond suggestion. can you elaborate or show me a picture?
 
That clamp is only for the applications that are straight forward and should not be assumed to work for every set-up. For the OTHER set-ups use your imagination. This is where you get to have fun and design/invent your own personal idea for the desired need. Then you can maybe share your diamond dresser holder on the HM…Good Luck, Dave.
 
I built this when I got a tool post grinder. Only works if turning between centers. Usually that's what I was doing. If it needed ground it needed to be accurate so between centers it was.
It's a 5/8 shaft with a 3/8 diamond dresser and a set screw .
It now resides with the cylindrical grinder and I don't grind on the lathe if I can help it.
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Thanks guys. Here is the basic setup. (And no I'm not grinding with that rag on the bed, just protecting things while getting things orientated). Pic shows first attempt, sizing model engine liner. So what I'm envisioning is a sturdy vertical post with the 3/8" dia shank diamond dresser protruding at right angle. It (somehow) gets connected to lathe bed on a base, zing across the diamond point with the wheel, remove dressing assembly & grind the job. You can see on the small diameter wheels, this dressing has to occur somewhat close to the chuck axis +/- my Y-axis my traverse travel. I also want a better indicator setup, but right now I'm just easing into this rather unknown aspect of machining.

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To use a diamond in the tailstock, take a holder like rgray shows but the length he shows between centers will be chucked in your tailstock drill chuck. Loosen set screw to elongate the diamond holder to reach your wheel. Crank your cross slide to contact the wheel then turn the tailstock wheel in and out to dress the wheel.

Are you relieving MOST of the wheel so only a small portion of the wheel dia is left to do the grinding? Kinda like side wheeling on a surface grinder, it's so only a small portion of the wheel is in contact with what is being ground. Heat build up better controlled, and so is dia, with a small portion of the wheel doing the work. We had somewhere in the neighborhood of a .100 land on the wheel to do the grinding with.
 
TommyD you've raised a good point I as wondering about myself. It seems like a lot of the ID wheels come in sizes where Diameter approximately equals Thickness (like 0.5" dia x 0.5" thickness x whatever axle hole). Some wheels are thinner but that gets to my other issue - availability in ideal size & grit & composition. I'm told a rule of thumb is the wheel diameter should be about 3/4 of bore ID. so my 0.945" bore could use a 3/4" diameter wheel or maybe 5/8" or 7/8" if it was available. But the corresponding wheel thickness presents a lot of surface area to be in contact with part. So yes, I was already contemplating some plan to reduce the trailing half of the wheel with dressing tool which is I think what you are getting at? Any guidance on what the contact thickness should be as a function or diameter? (And what makes me wonder why the wheels are offered so thick to begin with. I can see a die grinder, but why for dedicated ID wheels?)

A lot of these issues would go bye-bye if I had 20 wheels to pick from, but I'm finding that's not reality. I have some 1/4" steel shanked wheels coming in that are more appropriate size in this regard. Not quite sure on the grit/composition aspect yet. Colleting them is not my preference, but think it might be do-able with the this particular part length.

I had a bright idea to buy say a 10" diameter surface grinding wheel in exactly the desired thickness, grit & composition I wanted. And then have a water jet cutter make a whole bunch of custom size wheels for me. But I can also envision some danger signs. Not sure how accurate they could cut the axle hole & maybe stressing the wheel with jetting cutting action? The wheels I see look like some sort of molded process. Best I not try this & poke my eye out.
 
I think some of the length vs dia issues stem from having a hole thru the dia, more length to make up for reduced cross section. Safety by increasing length. I always wondered about that too.

We used a diamond or norbide stick to reduce contact area, reduce the wheel dia first then true it up, you need to dress your contact area every time you take the wheel off the arbor. I made bearing seals, therefore we did a LOT of round work and toolpost grinding was a huge part of it all, dead sharp brazed carbide lathe bits too. Finer wheels, useally white wheels, give you a better finish but break down quickly if they are pushed. The coarser wheels do the bull work but you have to make work what you can get. Look for glazed contact surface during grinding and retrue as necessary.

Please make sure you stand off to the back when firing up a new wheel, I've seen them let go when they were cracked OR the pulleys were switched, motor vs spindle. Jog it on and off a few times until it gets to speed.

You can 'sound' some of the bigger wheels. Hold it by something through the center hole then lightly tap it with a small piece of metal. A clear ring means the wheel is sound, if it 'clunks' it probably has a crack and unsafe to use

edit: Wheels are sintered, fired in an oven. I seriously doubt it being a good idea to try to cut one in a water jet or otherwise. Not worth the risk.
 
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