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gr8life
10-11-2008, 12:58 AM
I have found that as time goes by I prefer working with hand ground tools on the lathe. I have a Sears 8" bench grinder with the original gray wheels. The cut ok but slooooooooooooooow. I would like to replace them. Any advice on replacements to grind 5% cobalt lathe tools? What do you use?
Thanks
ed

macona
10-11-2008, 01:03 AM
46 grit is good for roughing

Mike Burdick
10-11-2008, 01:18 AM
ed,

How often do you dress the wheel? One needs to do this in order to dislodge the worn particles and to expose fresh abrasive from the wheel's surface. This will allow the wheel to cut better, faster, and cooler.

.

SGW
10-11-2008, 08:33 AM
I've got a couple of silicon carbide "green grit" wheels on my grinder. They're not intended for grinding HSS, and they wear relatively quickly, but I like them for HSS. They seem to run cooler than other grinding wheels and they stay clean -- probably because they wear more rapidly. Given the amount of grinding I do, the rate of wear isn't a big issue.

I think I've got a #60 and a #120, but at this point I wouldn't be sure.

J Tiers
10-11-2008, 09:15 AM
The original wheels are a hard relatively fine grain, probably......

Hard material, soft wheel, soft material hard wheel. That is what I have been taught, because the grains should tear out during use when they are dull, to keep the wheel cutting. Hard material dulls grins, while softer does not so much

Hard gray wheels seem never to wear, they get loaded up and glazed (the grit is dulled) and must be "dressed" to get rid of the dull grains.

GadgetBuilder
10-11-2008, 11:09 AM
There is considerable info on choosing and using wheels for HSS in the following file: http://www.savefile.com/files/915454 This is the Chaski/Harold tutorials collected and slightly condensed.

Norton alox wheels are often found on eBay for reasonable prices.

I have only a little experience with CBN wheels so far but given a choice I would use CBN for grinding HSS. Champagne taste and a beer pocketbook, unfortunately.

John

Edit: Note source for material in the referenced file.

Alistair Hosie
10-11-2008, 11:26 AM
white or pink wheels cut cooler last longer buy these for hss I am pleased with mine good luck.Alistair

FatWheels
10-11-2008, 12:15 PM
I have a question on dressing wheels. I have the star wheel type and I just got the dresser stick from enco this week (thanks to whoever posted the shipping code). Is the solid stick better than the single point diamond, and how is it used on the wheel? Can it be used for shaping the wheels for form grinding? I just have the simple gray wheels that came on the grinder, 46 and 60 if i recall.

Thanks,

Jim

dan s
10-11-2008, 01:38 PM
these links should be of great help to you.

http://www.chaski.org/homemachinist/viewtopic.php?t=75985&highlight=grind

http://www.chaski.org/homemachinist/viewtopic.php?t=76065&highlight=grind


I'm personally running these on my 6" grinder and the do a great job.

http://www.use-enco.com/CGI/INSRIT?PMAKA=422-0279



I have found that as time goes by I prefer working with hand ground tools on the lathe. I have a Sears 8" bench grinder with the original gray wheels. The cut ok but slooooooooooooooow. I would like to replace them. Any advice on replacements to grind 5% cobalt lathe tools? What do you use?
Thanks
ed

dan s
10-11-2008, 01:55 PM
Jim,

By solid stick, do you mean a solid silicon carbide stick?

one of these:
http://www.use-enco.com/CGI/INSRIT?PMAKA=287-6255



Is the solid stick better than the single point diamond, and how is it used on the wheel? Can it be used for shaping the wheels for form grinding? I just have the simple gray wheels that came on the grinder, 46 and 60 if i recall.

BobWarfield
10-11-2008, 02:46 PM
Here's another wheel that 60 grit if you prefer the "ring shaped" wheels:

http://www.use-enco.com/CGI/INSRIT?PMAKA=317-1449

Can't recommend the Chaski links given too highly (in other words, they're excellent and you can get a lot out of them!).

Best,

BW

Alistair Hosie
10-11-2008, 03:46 PM
Nice to see you up and around Bob how are you doing?Alistair

gr8life
10-11-2008, 05:50 PM
Dan thanks for the link to the posts by Harold_V. I keep looking at the large selection of wheels for surface grinders and thinking I could adapt them to my grinder. That little tidbit about making an adaptor answered my question. Thanks again for a lead to the answer,I only wish the search feature worked better then I could find the answer without having to look lazy.
ed

Boucher
10-11-2008, 09:35 PM
You can do it with a grinder but a belt sander works better and doesn't seem to generate as much heat. I have a 2" X 72" belt sander. They are quick to change from corse to finer abrasives. You set the relief angle like 7 on the tool pedestal and establish the other angle by the angle to the belt. I keep a bucket of coolant nearby and just dunk the bit in it as needed. The belt sander does not burn the edge the way a grinder does. Try it you will like it.

wierdscience
10-11-2008, 09:46 PM
I use a 60 grit for roughing and a 120 grit for finishing HSS tools.

Norton white aluminum oxide(AOX) offers the best combination of grind time per dressing.

http://www.ind.nortonabrasives.com/Data/Element/Node/ProductLine/product_line_edit.asp?ele_ch_id=L00000000000000037 86

I also use the AOX/Sc combination wheels for general purpose grinding.Our grinders at work are fitted with those since they may be knocking off burrs one minute then sharpening drills the next.

http://www.ind.nortonabrasives.com/Media/Documents/S0000000000000001035/Norton%20Full%20Line%202007%20Bench%20&%20Pedestal%20Wheels.pdf

J. Randall
10-11-2008, 10:05 PM
Plus 1 for the belt sander.
James

FatWheels
10-12-2008, 12:05 AM
Sorry Dan, I was away from the keyboard all day. Yes, the silicon carbide dressing stick you linked is the very one I got from enco. I didn't know just what to expect as I've never used that type. I wanted to find a single point diamond dresser but when I saw the SiC stick it was too good a pass up. Any pointers on how they're generally used would be appreciated.

Thanks again,

Jim

dan s
10-12-2008, 02:57 AM
That stick will probably last you the rest of your life..

to use it, just firmly hold it, and touch the end to the wheel, and move it side to side. Just remember this thing is hard as hell and will remove material fast.

It's better if you have a good rest to lay the stick on. I made rests similar to this design.

http://homepage3.nifty.com/amigos/grinder_guide/grinding_rest-e.htm



Sorry Dan, I was away from the keyboard all day. Yes, the silicon carbide dressing stick you linked is the very one I got from enco. I didn't know just what to expect as I've never used that type. I wanted to find a single point diamond dresser but when I saw the SiC stick it was too good a pass up. Any pointers on how they're generally used would be appreciated.

Thanks again,

Jim

Forrest Addy
10-12-2008, 03:42 AM
Chances are there's nothing worng with the wheels you have. They're just dull from use. Look at the wheel surface in grazing light. See a lot of shiney little sparkles? Those are dull abrasive grains. The dressing stick will help you true the wheel and shape it if you need to but it does practically zero for exposing fresh sharp abrasive. The difference betwen a dressing stick and diamond dresser on a shank is like night and day.

Spend about $30 to $50 and buy a good diamond dresser on a shank from MSC and competitors. Keep the wheels sharp and trued and your tool sharpening hassels will fade considerably. You'll use up more wheel but grinding wheels are considered "consumables" in a machine shop.

You may have to dress the wheel every few minutes when grinding some tool steels (T-15 for example). They can be very hard and abrasion resistant. Instead of cutting the abrasive grains dull and generate heat of friction.

90% of all perplexing grinding problems can be solved via wheel dressing. Even ones on a Sears grinder in a home shop,

Congrats, by the way, for digging into home ground tools. Not all machining problems can be solved economically with carbide inserts.

BadDog
10-12-2008, 03:57 AM
My thoughts, formed from both reading and my subjective experience.

Star wheels: Best for ejecting accumulated loading and dull grit. Leaves the wheel very "open" and "sharp". Sometimes too much so.

Diamond (single or cluster): Best for shaping/truing the wheel. But the diamond will also tend to shear grit particles and may leave the wheel too smooth.

Norbide stick: Best for "finishing" the freshly dressed wheel or touching up an otherwise good wheel while in use, but can also be used for truing and some shaping. I generally use it after either star wheel is used to "open" the wheel, or after diamond true/shape. Most wheels seem to just work better after being "finished" with the stick. Actual magnitude of results seems to depend on wheel composition. I particularly notice this on my most coarse wheel which is far to aggressive after dressing with a star wheel, so much so that it leaves pretty bad burs on mild steel and "feels rough" if you don't finish with the stick.

But I'm far from an expert and still frequently change my "preferred" wheel maintenance based on "gut feeling" based on how it is working at the time.

Peter.
10-12-2008, 08:01 AM
Another option (which I use) is to use a nearly-spent small diameter diamond core drill (for core-drilling concrete or brick). I use a 32mm diameter one but any small size will do. You could even make a tool by brazing a sawblade-tooth onto a holder, but you'd need to know someone in the trade to find a spare segment.