# Dressing Assembly For Toolpost Grinder In Lathe



## petertha (Mar 12, 2016)

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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## Phils69 (Mar 21, 2016)

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.


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## TommyD (Mar 21, 2016)

We used a right angle mounted diamond in our tailstock chuck. Out of the way and there when you needed it.


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## petertha (Mar 21, 2016)

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?


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## chips&more (Mar 21, 2016)

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.


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## rgray (Mar 21, 2016)

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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## petertha (Mar 21, 2016)

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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## TommyD (Mar 22, 2016)

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.


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## petertha (Mar 22, 2016)

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.


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## TommyD (Mar 22, 2016)

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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## rgray (Mar 22, 2016)

petertha said:


> 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.



I make them with a carbide hole saw set from harbor freight. The set was cheap and it cuts the wheel easily.
Pic shows the hole saw set, the wheel and a couple of ID mandrels I made for my dumore tpg. One has been trued up and used the other not yet trued and you  an see by it that the saw can cut some what crooked. Just start truing with a carborundum or the carbide file that comes in the set (I haven't tried that yet) then finish with the diamond dresser.
Glued my wheels on with metalset A4. It's alot like jbweld just a little tougher. JB weld would probably work fine.

For some unknown reason those wheels seem to be cheap on ebay they are 1" wide (that may be why) and a 60 K grit. They are recessed so approx 1/2" in the recessed area. It's a 7 x 1 x 1 1/4 wheel.
The hole saw set will put about a 3/8 hole in the cut wheel. I enlarged to 1/2 for my arbors with a drill bit. Changing the supplied drill to 1/4 might come in handy also. That's next on my list for some jig grinder wheels.


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## petertha (Mar 22, 2016)

Hmmm.. I never thought of a diamond hole saw.Do you drill the blanks dry or wet? I see those all over the place like in lapidary or glass suppliers. Maybe I can find some in my diameter size & I'm home free.

Do those spade center bits do a decent job of making a center hole? I don't have to have a counter bore recess in this particular application, but imagine it should be semi decent fit to the shank OD. I have some smaller wheels supplied with grinder in the .5" diameter range which have a hole for 5-40 retention bolt. Its just your ordinary clearance hole. I think the grip comes from the obligatory card stock washers on either side of grinding wheel & the bolt itself is just applying enough force to safely secure the wheel axially to the arbor.


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## rgray (Mar 23, 2016)

petertha said:


> Hmmm.. I never thought of a diamond hole saw.Do you drill the blanks dry or wet? I see those all over the place like in lapidary or glass suppliers. Maybe I can find some in my diameter size & I'm home free.



Those are just carbide. Diamond would probably work even better but these were cheap  http://www.harborfreight.com/1-14-in-3-14-in-carbide-grit-hole-saw-assorted-set-9-pc-68116.html
The spade bit does make a decent center hole. A plain old drill bit works well also.  Seems I always have an old bit that I don't feel to bad about using. I drill them dry.
The center fit would save alot of wheel truing if it fit decent. If loose maybe a wrap of solider or strip of lead like is used in the center of the surface grinder wheels would fill the void and help with centering.
If you have enough arbors a wheel could be left on till used up. 
Yes the card stock "blotters" are necessary. Definitely make some for new wheels.


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## MikeWi (Mar 23, 2016)

Seems like making a dressing fixture to clamp on to one side of the ways like a carriage stop would be a good solution.  Easy to take on and off and doesn't get in the way of the work.


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## dbassing (Apr 1, 2016)

Hi all,
Thought I would show what I did to make a holder for dressing the wheel for my tool post grinder. Mine clamps to the bed ways. I found the base at an estate sale and modified it to work on my lathe. The 1/4" flat piece of steel fits on the flats under the bed. The part I found (the painted piece in the photo) clamps to the front edge of the bed. Since the back part has nothing to rest against I drilled and tapped for the carriage bolt that you see pointing down that rests against the top of the cross piece. This is adjusted so that when tightening the clamping bolt the forces are even and level in the area that squeezes against the front edge of the bed. This carriage bolt is treaded into the end of the vertical rod that is clamped by the body of the dresser. This can be raised or lowered to get the proper height for the diamond point in relation to the wheel. 
I included a diagram copied from the users manual for an Atlas Tool Post grinder showing the suggested angles that the diamond should be set to for dressing the wheel.
It is fast and easy to set up and can be reset at any time to dress the wheel while the part is in the chuck.
Cheers,
David


	

		
			
		

		
	
Dresser on lathe

Bed Clamp detail



Diamond dresser angles


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## petertha (Apr 2, 2016)

Thanks David. Well, that gives me some more confidence to what I drew up. The below center dressing was something I hadn't realized so I'll have to pay attention there. Thanks!


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