How much grinder do I need?

[Houndogforever]

I make this one part that needs to be surface ground on a face. The part is 1.30 x 1.500 and is made from hardened D2 steel at Rc60-62.

I have .005/.010 grind stock to remove and I have a fixture that holds 8 parts at a time.

My old grind shop shut down, and the new one I have tried really doesn't seem to want to do these.
I have an old Taiwan hand feed surface grinder which I have used, but it is just too small.

I'm looking to spend $4-7000 on something automatic or at least semi auto.
What direction and what type machines should I consider, and avoid.
Thanks

 

[jccaclimber]

Final tolerances?

 

[eKretz]

What kind of quantity also? These only get ground on one side while mounted in a fixture? Probably why nobody wants to do them. That kind of work (putting into and removing from fixture to grind one side of each part) is labor intensive and nobody wants to pay for that these days. You might consider whether you've really done all you can to optimize your fixturing to make the insertion and removal of your parts as quick and simple as you can - for instance, using something like DeStaCo clamps or similar. That will make vendors more likely to want to do the work and also make the price better for you.

 

[michiganbuck]

To achieve the best production practice you should add your location and describe the part process completely from receiving stock to out the door along with the finish specs, for size, squareness, and surface finish. Along with your type of holding fixture for each operation and the quantity and the current amount of grinding time per part average so it includes set-up loading and dressing. not just the grinding,
And if the grinding is a simple flat topping or a form or other special feature.

 

[Houndogforever]

ok, here is the fixture I made that was entered into the mittee bit top dog contest a few years ago.

Top Dog Entry: Jon C. Baker, Bag Parts International Corp. | Mitee-Bite Products LLC.

www.miteebite.com

The run is usually about 75 to100 per batch. Tolerance is wide open. The over-all thickness is 0.470-0.475 but the only requirement is the face must be ground flat 100%. The parts move a bit during heat treat, but that is why I leave .005-.010 for grinding.
The problem comes when holding 8 parts, and only 1 doesn't clean up at .4730 Then you have to run another pass.

 

[michiganbuck]

Is there a reason why you don't just mag hold them on the chuck?
Are you grinding 2 sides or 6 sides?

 

[Houndogforever]

The part is located on a tapered surface and ground flat on the opposite mating surface.

 

[stephen thomas]

That is a beautiful fixture.
Are the parts non-magnetic?
(edited, never mind, i just registered they are D2)
Or is it the fact that the side that is down on the fixture might, as you say, have moved a bit and is not flat?
IOW, with a long tilt or sine chuck, you could gang a dozen up against the rail and grind them with a block at the far end. Unless one of the items mentioned is a factor? My Hitachi tilt chuck is 18" long, e.g.

To answer the Q you asked, if you do "lots" of these, get something with a 10" wheel and coolant. Which probably means an 8 x 24" machine. Though your fixture would fit on a 6 x 12 with a 7" wheel if you only do a few, occasionally. The bigger wheel is much more productive with less dressing than it might be imagined just based on proportion. But beyond that you can only grind about as fast as the work can be kept cool. That can be another advantage to grinding a long string.

If quantities are not too large, a 2 axis auto machine will work fine. With the allowance and tolerance you mentioned, dress and set the wheel to infeed about .003" to .005" per reversal, and set the height at your finish dimension. If you make 2 fixtures, you could be cleaning and loading one, while the other grinds.

OTOH, D2 is one of the nastiest materials to grind, so some experimentation is in order. Is the previous guy available to discusss his method with you, since he is no longer competing?

smt

 

[Houndogforever]

Thank you for the compliment. I did try to make it simple but effective. During heat treat, since it has a thick end and a thin end, the corners tend to wiggle around. Maybe .002 at most. Add in production tolerance and .005 to .007 will clean up. But my hand fed, 6" manual grinder wears my damn left arm out and I get impatient and cause some burns.
I was thinking something like a 8x18 Chevalier or kent. Probably 15 years old but that I could set it up, let it go, walk over in 15 minutes, drop down and take another pass while doing something else.
All of this needs to be highlighted by the fact I know next to nothing about grinding.
Oh, the first guy retired and sold all his machines.

 

[jccaclimber]

Thank you for the compliment. I did try to make it simple but effective. During heat treat, since it has a thick end and a thin end, the corners tend to wiggle around. Maybe .002 at most. Add in production tolerance and .005 to .007 will clean up. But my hand fed, 6" manual grinder wears my damn left arm out and I get impatient and cause some burns.
I was thinking something like a 8x18 Chevalier or kent. Probably 15 years old but that I could set it up, let it go, walk over in 15 minutes, drop down and take another pass while doing something else.
All of this needs to be highlighted by the fact I know next to nothing about grinding.
Oh, the first guy retired and sold all his machines.

Going from a completely manual machine to one where you can walk away and let it work is an amazing thing. I’m not sure where machine pricing is at the moment, but I will say that for something like your described tolerances, the e lack of major grinding experience shouldn’t be an issue. If you can find it, some coolant and an auto down feed really do reduce “just clean it up” parts to button pusher difficulty.

 

[eKretz]

Yep, that is a pretty good fixture. I'm not sure why you couldn't find anyone to grind those. Was it that they didn't want to do them, or that they didn't want to do them for a price you liked? And I agree that a sine chuck seems like an even better way to go unless we're missing something.

Anyway, an automatic grinder will fit the bill perfectly, but you will probably pay a hefty price for one unless you luck out. And if buying used, make sure you check that the machine grinds flat and isn't worn out.

 

[michiganbuck]

I would likely dress the angle on a 1 1/2 wide wheel and grind a full chuck row of parts on the bump rail and flat on the chuck with down grinding to a spotter for +.005. Filip the parts and grind the other side to a zero-size spotter. Likely do the whole run on the first side, then the whole run on the other side. On a 618 likely grind 10 parts. On a larger machine more parts. I might even do two rows of parts in one grind. likely hold .0005 easily.
Yes, I would first experiment with a dress and grind one or a few parts with your current grinder to assure getting the spec surface finish. The load would be very fast so not much need to walk away. Likely try a Radiac 46- L White AO semi-open wheel.

This is a top machine sales and repair shop so this machine is likely to be very good.
I have a manual slide dresser that I think goes over 1 1/2, a over-head dresser is common for dressing an angle to a wheel. On the chuck is often the fastest and most accurate way to grind. *Good to have a 1.5 or 3 HP spindle to pull a 1.5 wide wheel.
But you can experiment with your grinder to test this method on a few parts.

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* This machine has an overhead dresser, but it is a flat dresser not an angle dresser and it still is only a 18" machine. It does have incremental dow feed but that would be best with having a programable stop,-> take .005(or what).
It was/is not uncommon to set a row of parts on angle parallels or wires to make angular parts. This kind of grinding is even done on Blanchard rotary grinder. it is old school, but dressing the angle to a wheel is is likely the easiest metod.

 

[michiganbuck]

Finding a good condition machine with programable down feed might be good.
Yes, programable to take an amount of stoc. not sure if this one does that.

Chevalier FSG-3A1020 10" x 20" Hydraulic Surface Grinder Auto Down Feed | eBay

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[eKretz]

Buck, can a little grinder handle a near full width plunge grind on a 1.5" wide wheel like that okay? I have never tried it but wouldn't have thought it possible. If that's the case, they are a heck of a lot stiffer than I would have expected.

 

[michiganbuck]

Buying a long-travel machine it is good to inspect with a shimmed-up straightedge to assure that it will grind a long row of parts to your spec...Yes, you can just set it (SE) on a ground chuck close to the operator position and get a .001 or so check.

Having perhaps 6 exact same height parts and finding the down dial registers the same on each is also a good/Ok check that a machine can grind flat, but that is counting on the chuck being ground flat.

 

[michiganbuck]

Buck, can a little grinder handle a near full width plunge grind on a 1.5" wide wheel like that okay? I have never tried it but wouldn't have thought it possible. If that's the case, they are a heck of a lot stiffer than I would have expected.

Best with a 1.5 or 3 Hp spindle. I like a 1.5 HP or better on a 618/7"
For 8" wheel and bigger definitely a bigger motor, and direct drive.
I very often Hog with A SG

 

[eKretz]

Best with a 1.5 or 3 Hp spindle. I like a 1.5 HP or better on a 618/7"
For 8" wheel and bigger definitely a bigger motor, and direct drive.
I very often Hog with A SG

Yeah, I figured it would need to be a higher HP spindle - I was more wondering about whether that itty bitty spindle diameter on the small machines would be rigid/stiff enough for grinding that wide all at once. If there's an issue I suppose it might do better with something like a 3" or 4" diameter wheel I'd think, to get that force applied a little closer to spindle centerline. That'd help ease up the HP requirement too. Not sure how easy that wheel might be to find though... I've never actually tried to grind full width that wide on such a small machine.

 

[gbent]

The problem comes when holding 8 parts, and only 1 doesn't clean up at .4730 Then you have to run another pass.

I would suggest when some number of your parts clean up you change all the parts and set the parts with a bald spot off to the side. When you get a fixtures worth of parts then remount them and grind to clean up. The total amount of material removed by grinding will be reduced this way. This is assuming the parts don't need to be in matched sets of 8.

 

[stephen thomas]

I hate to argue with so much good experience from Buck.
He has helped me a lot.
But not sure i would start grinding with full width wheels, and all the experience and increased accuracy of the set up that implies or requires.

It will be slower, but if you grind with the edge of the wheel rather than the face, it will do quite a few parts before necessary to re-dress. Besides that, since you require less than .010 stock off, you can dress, set height, and walk away even on a 2 axis machine. It will grind to size and shut off. It will be difficult (after a little practice and benchmarking) to get a more accurate flat surface without a lot more experience. If it worries you starting out, make it a 2 pass op, one roughing and one finish @.0005 down, but should not be necessary at that increment and your specified part tolerance.

I am seriously leery of used machines*, especially ones scheduled for painting, but maybe that is just me. That said, I like my DoALL D1030. If you get a DoALL, get one with the cool-grind set up. This manual explains my method of grinding, page 2. Almost deep as you want. I sometimes even go .040 down, but i won't take .010 sideways, usually right around .005" per table reversal.

It's not as fast as Buck's method, but it is low stress for small machines & cost effective unless you are doing 100's of parts at a set up. Also the cool grind feature that is an option on DoALL machines, pages 12 - 14

https://www.kempler.com/sites/default/files/manufacturer/docs/catalog/DoAll%20Model%20D6-1%2C%20D6-3%2C%20D8-0%2C%20D8-1%2C%20D8-3%2C%20D10-1%2C%20D10-3%20Precision%20Surface%20Grinders%20Catalog.pdf

* Used machines - need to clarify that - all my machines arrived used and sometimes abused.
My point is never trust a dealer unless you really know him personally, without doing your own inspections. Many dealers are honest, but many never actually inspected the machines they are selling. Or did not inspect them in a manner that matters to a critical user.

Which brings the old " grind 4 (or 5) blocks scheme in 4 corners & center of the chuck, to "prove" the machine ways are good. It does nothing of the sort. Buck's method of shimming a straight edge and checking both directions (or a small surface plate) is the only way.

However, since the chuck is ground with the machine itself, the chuck face will mirror the ways. If they are humped, so will the chuck face - BUT- it will be dead paralell (if ways are not so bad it's hopping). This means that it might well pass the 4 or 5 block test with flying colors.

The implication of that is, that a machine with poor ways and your fixture, might not grind all the parts flat or the same size. Putting them on a perfectly ground chuck, which mirrors the ways, will force them all to be the same size, and in a small area, you might not be able to measure or indicate on a surface plate, whether they are flat or not.

So, your fixture is really an elegant piece of toolmaking and workholding. If you put it on a less than perfect machine, you might or might not find some error in the parts. With your specified tolerance, it probably does not matter, but just one more way to think about geometry.

smt

 

[Hobby Shop]

What about a small Blanchard grinder? Your budget is more than enough. My No.11 would grind those parts perfect all day everyday. If you’ve never used one before, you’d be shocked at how fast material can be removed and the grind quality. The versatility from large/small die-sections, flywheels and everything in between.

Here’s a flywheel I did for my nephew after I got it dialed in.