O-1 hardness and sharpening

On 25 Nov 2003 06:51:09 -0800, snipped-for-privacy@hotmail.com (Jonathan Ward) brought forth from the murky depths:

Try a diamond plate. I haven't gone back to stones since trying one. I start with a diamond and finish up with 1200grit ScarySharp(tm) paper. (wet-or-dry, available at local paint supply shops, NAPA, WallyWorld, etc.)

- Don't be a possum on the Information Superhighway of life. ----

I think that's about ~55-58Rc, from what I remember. Doesn't sound that hard as far as difficulty in grinding goes... How does it compare to grinding a HSS toolbit (ideally with at least 5% cobalt and NOT from China)?

The further you temper your part, the less capable it will be of holding an edge. On wood, this becomes very important. Also, the harder it is, the less regrinding it will require (pay now or pay later).

I wouldn't be inclined to draw it back further. I know how annoying it is to sit in front of a grinder for 10 minutes grinding a bit (hurts the neck) bit it's worth it when you get a very capable tool.

Regards,

Robin

Get some wooden paint stirrers and rubber cement some strips of wet or dry silicon carbide sandpaper to them and you have sharpeners in every grit that can be made. If you are grinding use a wheel of about "I" hardness.

Or softer. I prefer H for O-1 at RC62 or thereabouts. "I" is ok if the steel is, say, RC58 or below.

Also, if you're using Norton wheels (or their grading codes), the 38A abrasive is good, 32A is slightly cooler, and 32AA even slightly better still.

Jim

How about them fancy "Blue" wheels"?? chuck

Hmm, dunno. Haven't used (or seen) one.

Jim

Look in J&L catalog for a Norton 5SG wheel. Costs about double of a 32A wheel. Suppose to cut hard steel cooler and faster and with less wear and require less dressing.

I have one on my grinder but I don't have enough experience yet. chuck

I have been using one on my surface grinder for a couple of years. It does last longer between dressings. I'd estimate about twice as long as the standard white alox wheel.

Randy

I did quite a bit of grinding yesterday and I used a coarse(46) blue

OK now a tough question. I grind a part and get it close. Now I need to dress the wheel (or change to a finer wheel) for the finish pass. How do you sneek up on the work so you can take off a few tenths???

chuck

I don't know how the pros do it, but I just lower the wheel over the part, while running the table back and forth. As the wheel approaches the work, I slow the advance down to perhaps a tenth or two per second, until it just starts to spark. Then I take a pass, measure the part, set the wheel to the remaining bit and finish it.

Jim

Slowly :-)

Sneaking up: When I raise the spindle to get the dresser under it, I count turns of the crank so I can come close. Once the wheel is dressed, I crank back down to the same place, minus a few thou. Then I use a .0015 feeler gage leaf between the wheel and the work to get within that last couple thou. Finally, I turn the spindle on and bring the spindle down till it starts to make sparks.

I'd be glad to hear how others do it. I usually grind anvil faces, but occasionally do some closer tolerance work. Since I don't want to have to remove the anvil to install the dresser on the table, I have made a more-or-less universal dresser that fits in the hardy hole and only sticks up about 1/4". I have bought a used dresser that will fit on the guard of the wheel, but it will require some modification. I will get that done some day.

Pete Stanaitis

You can actually hear it when the wheel is very close to the work. Some people call it "cutting air". It sounds like a hiss of air as the wheel passes over the work. That's when you need to go slowly.

Or, after some experience, you don't even move the table and just watch for sparks. After machining for some months every day, you hand is capable of stopping real fast after hearing the cutter touch the part...

Regards,

Robin

Grease pencil, when you see it start to be wiped off, it's time to start coming down real slow.