Thread: Back flattening - horse power rather than hand power

Just talked to the local glass supplies guy.

They can arrange water-jet cutting a disc and a hole and then tempering.

He was pulling figures out of the air on the spot for 150mm OD and 10mm hole ... $50 - $60.

Do the research on US supplied WS discs; would have to be transhipped as last I looked they wouldn't supply direct.

HTH

I've been reading "The Handplane Book".

The author suggests using a small grindstone attached to an angle grinder to remove high spots when flattening backs. The high spots are identified by using a fine waterstone for a few strokes, as usual.

This is apparently done freehand in the picture provided in the book, but I think it would be wise to clamp the blade, at least.

This sounds like good fun (although probably dangerous). But, I suspect that it would be easy to go too far and leave slight "dimples" in the backs of your blades which would be an enormous pain to remove later.

Has anybody tried this method?

Agree, dangerous but fun.

But it shouldn't matter if you then put a back bevel on a BD plane blade and by that commit to honing at the same angle.

....

To add to the above: Andy came around for a session with a pitted-back firmer and a cheap plane blade with lousy surface grinding.

The coarse WS discs mounted on the lathe made light work of them and a simple arbour and drill press would do as well.

The trouble with these discs is that local replacement cost is about six bucks each and then only in a pack of several grits.

So for fun (again) I've got some coarse Norton W&D PSA discs from the Sandpaperman and will give them a run. There are a number of reasons to be sceptical about them but maybe for the heavy lifting they'll pass muster.

Other than that, the good stuff in coarse grades is available in various forms from Workshop Heaven (UK) and Rio Grande (US).

Hj Ern,

have you ever considered a set up like this?

Heiniger Grinder

The pendulum jig could probably be adapted for use on the lathe.

A bit of an idea of how it works:

grinding shearing gear, grinding combs, grinding cutters, grinding gear, grinding, sharpening shearing gear

Interesting idea. Thanks. Similar principle as horizontal grinders like the Worksharp 3000 (about USD 200 in the US and about triple that here!).

For lapping, holding the blade is no drama. Can be done with finger pressure and pivoting the edge in to start.

Update: it's now possible to source Worksharp abrasive discs via Amazon.com but the postage costs are steep.

G'day Ern,

Happy New Year.

Instead of Worksharp's glass disc and abrasive discs, did you consider the 8 inch aluminum platter used in their "Veritas® Mk.II Power Sharpening System"?

I am thinking the aluminum would dissipate heat build up better than glass, though I am not sure if it matters.

I am considering it for a 3/4 hp motor I salvaged from a washing machine. Not sure if it is possible to source 200 mm diameter PSA discs locally. I'll drop the Sandpaper Man an email to enquire.

Just a thought.

Regards,

Gunn

Same to you Gunn.

Yeah, worth a try. Wasn't aware you could buy one.

The heat builds up enough with the glass discs to mean you need to take a break now and then but it's not such an issue.

SPM has 150 mm PSA discs in SiC; don't recall 200 mm.

Maybe buy sheets and apply with spray adhesive.

At a bit of a tangent (since it's still handpower) I've had good results using a hand grinder with white wheel to grind the belly off an especially bad blade - it's just a matter of not going very deep and returning to the stones nice and often. I was concerned about leaving little "dimples" with an angle grinder, but the large diameter of the hand grinding wheel, and the slow speed, makes it difficult to mess up too badly.

i havnt read all the posts but from the picture it looks a bit like what i have used on my lathe for years to good effect, abrasive glued to MDF or similar which is attached to a face plate on the end of the lathe, i use a old woodfast lathe table attachment that changes angle so i can a flat grind the front bevel (my preference for good reasons) grind as well..i've updated to a dedicated flat grind machine now but i played around with those sorts of things for years, belt sanders for flat grinds, also made a belt sander attachment once out of thick plywood a few bearings and a couple of axels (for lack of a better word that escapes me atm) that uses the drill press to drive it, very effective, advantage with the lathe and drill press opposed to the belt sanders is being able to reduce the speed

cheers
chippy

Originally Posted by snafuspyramid

At a bit of a tangent (since it's still handpower) I've had good results using a hand grinder with white wheel to grind the belly off an especially bad blade - it's just a matter of not going very deep and returning to the stones nice and often. I was concerned about leaving little "dimples" with an angle grinder, but the large diameter of the hand grinding wheel, and the slow speed, makes it difficult to mess up too badly.

sounds like you are describing hollowing out part of the back, a bit like japanese chisels and some plane blades, their purpose is to save time or make it easier to hone the back to a fine finish as they use hard laminated steel, it has its advantages the hollowed out backs also have some disadvantages though..your brave, cant say i would want to take to my plane blades with a powered hand grinder, to ugly a finish for me

It doesn't affect the finish on the chisel, because only a very small amount of material is removed. By the time the entire back is flat, the grind marks will have been removed by the waterstones. The grinder just speeds up the work for the stones a little, it doesn't replace them or create a hollow as in Japanese chisels (while that's an interesting idea, I wouldn't have enough control to do it properly). I wouldn't use an electric grinder, though, that's for sure. And it's only when it's a choice between grinder and bin that I'd recommend this option.

Using the sides of a wetgrinder wheel can also work very well lapping big chisels or plane blades. The trouble is dressing the sides once they're clogged.

I've had yet another of my inspired, strictly OHS friendly ideas...

I'm gonna use a coping saw to cut out a flat piece of Oriented Strand Board (as that's what I have around - the sad remains of an Officeworks job), in a roughly circular shape, then stick on some WD sheets I haven't known what to do with. I'll have to sacrifice an old pair of scissors to get the sheets into shape. I don't have a decent adhesive to hand, so I'm thinking I might just use a glue-stick...

Then I'll attach the OSB disk to my hand-cranked grinder in the same way as I would a traditional wheel, i.e. lightly clamped between metal disks.

Now obviously some decent WD or other adhesive would be better, as would glass or even MDF as a base. And there's a risk that my trusty office glue-stick isn't going to be the perfect adhesive for the job. But hey, necessity is the mother of all invention (or workplace accidents).

I'm rather hoping that the very slow speed of the hand grinder will overcome the obvious safety issues...


EDIT: Severe fail. I couldn't drill a sufficiently clean, accurate hole in the very "flaky" OSB, so I couldn't mount the disk true.

My next options are to experiment with the side of a highly friable wheel (in the hope that this'll overcome the problem with clogging to some extent) or to find a glass or steel disc...