Thread: You flatten my back...

I know I've mentioned this before, but I have found that I can flatten even extremely unflat blades using a reference plate, bearing blue and a small grinding wheel on a drill, together with the Sigma 120, 220 and 400 grit stones. The most time I've had to spend on a single stone is about fifteen minutes, when I've been really sloppy with the grinder and have to clean up. I have a big Stanley No.8 SW iron that's badly deformed from being clamped in place for 80 years - no way I'd try and fix this with stones alone. I'll start on it tomorrow and post the process. I am convinced I am on to something magic here, damnit...

LOL, well post some pics Eddie. I'm open to new ideas on this one.

But I have to say there's a big diff. between CS and M2 and esp. this species of M2.

If I hadn't run out of belts on the Pro-Edge and if I'd jointed the edge to get rid of the BB first up, this would've been a much simpler job. Live and learn.

I'll be very interested to see a WIP with pictures.

I don't think I have ever seen someone say they spent 3 hours leveling a tabletop with a LN #4 ... but I've often read people saying they spent x number of hours to flatten ... a chisel, a hand-plane, planing iron ...

It naively struck me that ... shouldn't there be an appropriate medium for every job, like The Schwarz said previously "Course, Medium, Fine" ... so that you use something that whacks off a bunch of material, then something that refines that, and then smoother still if required?

I only have CS and D2 steel in any of my stuff, and maybe our end goals are different, ... and I think I am going to have to start describing myself as impatient ..., but I've never spent more than 5 or 10 minutes with any of my plane blades for instance. On old oilstones.

I don't assume I have the answers ... I do assume I am missing whole continents of info on the subject ... so ... as I said, I'll be looking forward to it.

Cheers,
Paul

Well, when you look at the abrasives we're using, we're starting coarse and working through some finer grits.

Before starting in on mic-d's blade I tested my equiv. (another Helmut special) starting with a #60 Ceramic belt. That went gangbusters but was excessive for the job. If left scratches deeper than those on mic-d's blade.

Bear in mind that of course you only have to flatten once, and the polish need go no further than you can register the back on a stone. For me that's about 30mm and on an M2 blade like these that's going to last a long time.

Originally Posted by pmcgee

... but I've often read people saying they spent x number of hours to flatten ... a chisel, a hand-plane, planing iron ...

Paul, HSS M2 is a whole new realm of hardness. I'm the opposite of you - mostly M2 with hardly any normal tool steel.

Yep.

Actually no

Have just tried a poor man's Rockwell test, with an automatic centre punch.

On my blade from Helmut and on a quality Sheffield HSS turning tool.

And on Veritas 01 and A2 blades. Two punches in each sample.

The dimples were noticeably deeper on both HSS samples!

So what we're talking about is not hardness if this test is any guide but abrasion resistance. Which is what you'd expect given the elements added to HSS at manufacture. And so the abrasive chosen is critical to efficient flattening and 'polishing'. Ceramics IME are clearly superior to AlOx and SiC* and they're advertised as such.

* (Added) Both in coated forms I should've said.

Footnote on the Sigma Power #400 for Schtoo:

I'd cleaned this with your Atoma #400 diamond plate and it made no diff to the glazing rate.

Have just now taken it to a glass sheet with #90 SiC grains and will see if that helps to repair the test damage done to my Helmut special blade.

The drill grinder I use is, apparently diamond embedded. Whether that actually means that, in practice, it will work well with super abrasion resistant steels, I don't know. I have used it on HSS and it worked fine though.

Yeah; I do minor touch ups of my V10 turning tools with a diamond paddle hone and it works quickly. But it's not taking off much metal.

It occurred to me that test #1 may have been faulty, as heat treatment of some blades is only applied at the business end.

At mic-d's suggestion that it be repeated further down the blades (on the tops) the results are pretty much reversed.

Helmut's special clearly showed the least compression (ie. the hardest; yep, Brett I'm eating my words publicly).

The Veritas A2 and O1 showed the most, while the Sheffield HSS was marginally better than those.

Pls note that I'm making these judgements by eyeball, but with higher than normal mag'n reading glasses . I don't have the means for proper measurement.

The matter raises again the importance of understanding the various properties of tool steel and how they're labelled and related.

Brent Beach used to have a good bar chart of comparative properties on his site but I can't find it now; next best is Crucible Tool Steel and Specialty Alloy General Information

This had quite a few scratches left from #60 when I had to reserve the #120 belt for mic-d's.

Took it up through the stones:

#120 Shapton, cut fast and dulled really fast. Not a good stone for this steel.
Sigma PS II #240: lovely; raised a slurry quickly and kept it; water control not critical.
Sigma Power #400: after dressing it with the #90 SiC grains this was back to the performance I'm used to. Cut well. No clogging. Water control a bit more important.
Sigma PS II #1000: like the #240. Left a hazed finish.

That's enough at this stage.