PDA

View Full Version : How flat is flat?



daveb
09-27-2012, 01:49 PM
I've been fooling around with getting the stones "flatter". I can get within 2mm variance and remove visible dishing by eyeballing stone. I measured stone below after initial flattening.

10271

Question is would you flatten further to reduce the variance? I tried with one stone (even found a feeler gauge in the back of the toolbox) and got it to less than 1 mm variance overall and reduced dishing to less than .25mm. But I washed a lot of stone down the drain doing so. I'm thinking this is past the point of diminishing returns and the calipers and feeler gauge can go back to the toolbox.

Curious as to how others flatten.

Regards,

Dave

bluntcut
09-27-2012, 01:59 PM
For me, flatten is done when the dished part is gone. I figure that angle wobbling & pressure deltas are way more destructive than a surface flatness variances.

Cutty Sharp
09-27-2012, 02:28 PM
For me, flatten is done when the dished part is gone. I figure that angle wobbling & pressure deltas are way more destructive than a surface flatness variances.

Wow - 'angle wobbling & pressure deltas' - I have to say that's some impressive vocabulary. :)

Well done. That about sums it up!

chinacats
09-27-2012, 02:49 PM
I mark mine with a pencil and flatten until I no longer see any pencil marks--don't lose too much stone that way and it finishes flat every time.

Cheers!

Zwiefel
09-27-2012, 02:54 PM
I mark mine with a pencil and flatten until I no longer see any pencil marks--don't lose too much stone that way and it finishes flat every time.

Cheers!

+1....probably nobody here is going to learn anything from me though!

Cutty Sharp
09-27-2012, 02:59 PM
I use an Atoma 400 and find that feel is better than markings. I haven't used a DMT, but have read how it sticks a bit when flattenting. I've found with my Atoma that it only does that when I've really hit the flat point, generally speaking. If dished it doesn't stick and I can feel the uneveness. If flat, it has a stuck all-contact feeling, and testing with pencils has helped prove this.

daveb
09-27-2012, 03:46 PM
Wow - 'angle wobbling & pressure deltas'

I knew zactly what he meant and he's prob right.

Thanks all for feed back so far.

Lefty
09-27-2012, 03:54 PM
I hate flattening, and it hates me! For knives, I'm in the Carter camp. Razors...I hate my life.

Birnando
09-27-2012, 04:14 PM
I'll do a proper initial lapping of all new hones.
After that I only do a few figure 8's with a Shapton DGLP or a DMT.
That way the stones always stay clean, and reasonable flat.
I do this both with my razor and knife stones.

Lefty
09-27-2012, 04:18 PM
I need to start doing that. My rhomboids and lower pectorals still hurt from my two hour flattening session.

Canadian
09-27-2012, 04:20 PM
I hate flattening, and it hates me! For knives, I'm in the Carter camp. Razors...I hate my life.

x2.

I use x stroke on coticule for razors so no issues there either.

bieniek
09-27-2012, 06:49 PM
If we talk only knives, i dont flatten.

Unfortunately must clean off the JNS 1K sometimes. Sometimes must sharpen stainless and that is what I hate.

JBroida
09-27-2012, 08:08 PM
also, one thing to keep in mind is that the surface may be flat, but the plane may not be parallel to the bottom of the stone or your worktable. Honestly thought, its not that important. We're not sharpening razors here... mostly flat will do.

Mike9
09-27-2012, 10:21 PM
Pencil all over - when the pencil is gone stone is flat enough. Parallel is another story and there is no reason for a stone to be flat and parallel IMO. Parallel would require an accurate jig.

I think a better question might be whether stones change dimension when soaked. If you flatten when wet do they retain that flatness after drying and re-wetting? This could become scientific to the point of ridiculous.

Lefty
09-27-2012, 11:11 PM
Parallel is overkill, definitely. That's why God created bar coasters.

Cutty Sharp
09-28-2012, 12:15 AM
I need to start doing that. My rhomboids and lower pectorals still hurt from my two hour flattening session.

I don't get how that's possible, Lefty. Maybe it helps that I check flatness frequently, but 1 stone shouldn't take me more than a minute. You're joking?

Yes, I don't think parallel matters and some people prefer to haave the stone at an angle anyway.

ecchef
09-28-2012, 02:14 AM
also, one thing to keep in mind is that the surface may be flat, but the plane may not be parallel to the bottom of the stone or your worktable.

I run into that all the time. Drives me nuts.

NO ChoP!
09-28-2012, 09:00 AM
I lap my stones frequently during use to remove clogging and build up mud. Rarely need actual flattening....

bkdc
09-28-2012, 10:12 AM
For hand-sharpening, as long as the surface is flat and the dish is gone.....

The only time I worry about whether one side of the stone is thicker than another is on my Edge Pro Shaptons.

tk59
09-30-2012, 02:56 PM
For routine knife work, I use pencil and an Atoma 140 to find the high spots and try to work the stone so it's roughly flat. I still end up grinding down the ends on occasion.