India Stones

[SteveHGraham]

Is there any point in having a Norton India stone if you already have a bunch of DMT diamond stones?

[Duder321]

You can shape them into something other than flat which can help hone or debur certain geometries. I have a couple 1/2" ones that I broke in 1/3s and formed to fit some different curvatures. They are also available in already curved/contoured shapes. Otherwise, I find my diamond "stone" performs better, lasts longer, stays flat, and gives a better final finish on 98.63% of the things I'd take a stone to.

[SteveHGraham]

I thought no one had answered! Thanks for the reply.

I saw a guy on Youtube selling India stones he had flattened on a surface grinder. I scratched my head over that one. Since these stones wear and change shape as soon as you use them, I wonder what good it does to pay someone to flatten one.

[neanderman]

No need to pay someone to flatten one. There is a well known process to flatten any surface using a total of three 'flat' objects. I can't recall the details, but if you google 'flatten surface,' I suspect you'll find it.

[tornitore45]

I took a mini-seminar on sharpening wood planes. The abrasive stone is "flattened" with plate glass sprinkled with carbide grit and some oil.
In this case, Flattened must not be taken literally. It get flat enough for the purpose by removing the inevitable steps and gauges left by last use.

As an aside, I got a neat rotary planing tool at a flea market, a 3" disk with two blades. Now I do my planing on the mill and rarely use my hand planes.

[SteveHGraham]

I found a video about it. Apparently, they are used like burr files, to remove irregularities from precision surfaces.

[pete]

Those surface ground stones are meant to be used on high precision surfaces and never used as a general honing stone.There designed to remove any high points on ground or lapped surfaces and not touch the surrounding metal.They come as a set so rubbing the two together both cleans and helps to maintain both stones as flat surfaces a lot longer. Unfortunately using the 3 plate method as used on say cast iron surface plates would be tough to impossible to get 3 flat stones since constantly rotating each plate is part of the method of getting the 3 plates flat. Rectangular shapes with a high length to width ratio and flattening them by hand using the 3 plate technique is well past what most humans could manage. My guess is rubbing the stones together will slowly start to wear them most probably convex and then they need grinding again.

Most gauge block manufacturer's offer maintenance stones for the blocks to remove any damage and given the prices and what those smaller one's are designed to do I'd bet there surface ground as well. The ideas not new and the larger bench sized surface ground stones been around quite awhile from at least one supplier but weren't well known until they hit YouTube. I believe ROBRENZ was the first to show them on his channel and given his intelligence and very high level of experience I'd say there's some logical benefit's to using them. Likely there's no point in having them unless your doing high precision surface grinding and working into the 10ths range. Or you've got any gauge blocks and other metrology surfaces that need touching up. There's some threads about them on various forums and some think they don't make any sense, others think they do.

Mauro I've been using those rotary planers on my mill for a long time. They work a whole lot better that way than in a drill press they were designed for.