Flattening a Hard Silicon Carbide Honing Stone

[swagman]

A few weeks ago I ordered some 280grt Silicon Carbide Powder to flatten my hard Silicon Carbide Stones; the powder arrived a week ago. I also upgraded my old sheet of float glass to a 12mm (2x laminated); 1250mmL x 300mmD. http://www.glassforeurope.com/en/pro...s-of-glass.php

The stone chosen had a noticeable hollow down its full length; the surface of the glass was 1st sprayed with water, before applying 5 grams of powder within a localized area; its important to bear in mind that these Silicon Carbide Powder's itself break down in size the longer you work it; as a general rule of thumb- when you can no longer hear the sound of the grit working the surface of the stone its an indicator you need to add some additional fresh powder; over a 30 min period; 2 grams of additional powder was added every 10 min. To achieve a totally flat surface over the Silicon Carbide Stone took me 30 min of work; longer than I initially anticipated; most likely that's an indicator that the commensurate grit of 280 is not coarse enough. I have ordered 400g of the 150grt for the next trial.

Random spraying of water over the surface of the Silicon Carbide slurry is a requirement to prevent the effects of air drying. Not difficult to identify, as the drying slurry will start to impede the free movement of the stone across the glass surface.

I should make mention that I previously trialled a Course DMT Diamond Stone to flatten these hard Silicon Carbide Stone's; the diamond grit was non existent after about 10 min of work. imo ; its the bonding agent that adheres the diamond grit to the top surface of the plate that cannot withstand the hardness of these Silicon Carbide Stone's.

Stewie;

 

[Phil Pascoe]

Use water stones - far easier to flatten.







He ducks below the parapet :lol: :lol:

 

[ED65]

To achieve a totally flat surface over the Silicon Carbide Stone took me 30 min of work; longer than I initially anticipated; most likely that's an indicator that the commensurate grit of 280 is not coarse enough. I have ordered 400g of the 150grt for the next trial.

I'd say so, I just had to take about 3-4mm off what I think is a hornfels and I did most of it on 80 grit (alox paper) and it still took longer than I'd have liked.

I should make mention that I previously trialled a Course DMT Diamond Stone to flatten these hard Silicon Carbide Stone's; the diamond grit was non existent after about 10 min of work. imo ; its the bonding agent that adheres the diamond grit to the top surface of the plate that cannot withstand the hardness of these Silicon Carbide Stone's.

I suspect it's the hard matrix of the stones you're working that's the culprit here. I've flattened both sides of a generic Chinese double-sided silicon carbide stone plus recently a small Washita using a diamond plate (a much cheaper one than a DMT) and it wasn't killed by the process. It's definitely smoother than it was, but is still usable as an abrasive in its own right.

 

[bugbear]

I should make mention that I previously trialled a Course DMT Diamond Stone to flatten these hard Silicon Carbide Stone's; the diamond grit was non existent after about 10 min of work. imo ; its the bonding agent that adheres the diamond grit to the top surface of the plate that cannot withstand the hardness of these Silicon Carbide Stone's.

It's possible you were applying too much pressure, which is notorious for stripping the diamonds out of plates.

BugBear

 

[swagman]

Crystolon" is a trademark of Norton Abrasives for man-made stones of Silicon Carbide that are vitreously bonded. In other words, they are heated to such a high temperature that the grains fuse together. Other companies can make similar stones but cannot call them "Crystolon". Silicon Carbide has a mohs hardness of 9.5.

http://keepingfloorsclean.com/wp-conten ... -Scale.jpg

 

[swagman]

The 12mm rubber seals serve the role of containing the flow of the slurry.

 

[essexalan]

Pretty much how I flatten my SiC water stones and what Stu recommends. I usually use a grit twice as coarse as the stone so for a Sigma 120 I use 60 grit which is just about the coarsest grit I can find anyway. I do use 10mm float glass having found that toughened glass is definitely not flat, as in Mk I eyeball not flat. DMT diamond plates are definitely not suitable for flattening SiC stones you will end up with a shiny piece of expensive metal very quickly regardless of how you use them. I use Eze-Lap diamond plates for touching up the edges etc and they do stand up to the abuse. Have heard of folks using plain sand to do this but I have never tried it.

 

[Jacob]

Flattening stones is completely unnecessary.
I've never done it (except once as an experiment).
A waste of time and waste of expensive materials.
It will also dramatically shorten the life of the stone.

 

[Trafalgar]

$300+ worth of kit to flatten a $20 honing stone is just sheer stupidity, not to mention the time involved. Even if you already own this stuff why put the wear and tear on it? Diamond plates and glass and expensive loose diamond grits. What a bunch of hooey.

https://www.sharpeningsupplies.com/Nort ... 179C5.aspx -- standard 8x2x1 Norton SiC combo stone $20.99. Want a single-grit SiC stone? Dollar cheaper, same website.

Don't flatten them. If you learn how to use the whole surface they'll never need it -- 'mind the ends and the corners and the middle will take care of itself' some famous craftsman once said.

And if you can't manage that buy a flippin' new one for, you guessed it, $20.

Please don't tell me that there is anybody on the face of the Earth that would go through all of this angst and effort to save twenty dollars. You'll easily spend more in time and materials than a brand new stone costs.

 

[swagman]

Charles; the word stupid; is derived from a Latin adjective that means “amazed or stunned,” and stupid people are stunned by everything because their minds are numb.

Stewie;

 

[Trafalgar]

Well, yes, I'm stunned at the notion of flattening a $20 SiC honing stone. It's the essence of absurd. It'll cost more than that in loose grits and/or paper to do the job, and of course, time. And beyond that the results stand a decent chance of not being all that great.

This is reminiscent of the stories one occasionally hears of EBay buyers bidding a used Lie-Nielsen plane up over the price they could have paid for a brand new one bought directly from the company. Makes no sense in the real world.

"I should make mention that I previously trialled a Course DMT Diamond Stone to flatten these hard Silicon Carbide Stone's; the diamond grit was non existent after about 10 min of work. imo ; its the bonding agent that adheres the diamond grit to the top surface of the plate that cannot withstand the hardness of these Silicon Carbide Stone's. "

Unfortunately, it sounds like you ruined or severely shortened the life of a DMT diamond stone trying to flatten a $20 SiC stone. I'm pretty sure that DMT diamond stones don't go for twenty bucks.

 

[swagman]

Makes no sense in the real world.

You got that right Charles. Absolute stupidity. http://qz.com/726802/in-much-of-america ... a-protest/

 

[NazNomad]

1. Flattening stones is completely unnecessary.
2. I've never done it (except once as an experiment).

1. Can you explain why?

2. So you have done it?

 

[Trafalgar]

Makes no sense in the real world.

You got that right Charles. Absolute stupidity. http://qz.com/726802/in-much-of-america ... a-protest/

Stewie, this isn't relevant. There are other forums to discuss politics.

What's happening in this thread at this point is keeping another woodworker from ruining a $100+ honing stone by trying to flatten one that costs $20. I think this was just a matter of not understanding where the market is for SiC honing stones. They're obviously cheap and frankly not even worth fooling with if they become a little clogged or slow much less out of flat, if you've determined that flatness is a requirement. You just get a new one and move on. It's like worn out underwear, nobody has it repaired (who'd want that job anyway?) you just buy new.

 

[Trafalgar]

1. Flattening stones is completely unnecessary.
2. I've never done it (except once as an experiment).

1. Can you explain why?

2. So you have done it?

People make the mistake of thinking they need the entire surface of a honing stone when backing off the burr on the face of the tool. You don't. You just need a relatively small area. I back off on the ends of the stone most of the time in order to even out the wear. And if your stone hasn't been cemented into the box you can use one face for backing off the burr and keep it flat if you just can't stand doing it any other way. The other face sees all the other action. I think backing off the burr in very tight circles results in a better edge anyway (anecdotal, don't get excited). You don't need the whole stone for this -- you can move spots from time to time.

 

[Phil Pascoe]

There's someone who agrees with Jacob in my area - I found a boxed stone this morning at the market that was over 1/2" hollow. :shock:
Charles, I don't use oilstones only waterstones but as my mother used to say when getting me to hoover or do the ironing as a child - pay attention to the edges and the corners and the middle will get done. It's years since I flattened one.

 

[Trafalgar]

Yep!

I'll say this for emphasis about hollowed stones -- flip it over and look at the other side. One side is usually allowed to go hollow and the other kept flat or at least as flat as it arrived from the manufacturer. Some stones will be found to have grooves that fit certain carving or turning tools perfectly revealing the previous owner's intent, if not his profession.

With just a touch of ingenuity all six sides (count 'em) of a stone can be used for something. And why not? You paid for the whole thing.

 

[bugbear]

There's someone who agrees with Jacob in my area - I found a boxed stone this morning at the market that was over 1/2" hollow. :shock:

I often find coarse stones are hollow - as long as the hollow is full width, it causes no trouble when working the bevel, but is useless for backing off the burr.

Presumably the owners of the stone either didn't remove the burr (yuck!) or removed it using another (flat) abrasive, either stone, or strop.

s/h fine stones tend to be flatter, I find.

BugBear

 

[woodbrains]

There's someone who agrees with Jacob in my area - I found a boxed stone this morning at the market that was over 1/2" hollow. :shock:

I often find coarse stones are hollow - as long as the hollow is full width, it causes no trouble when working the bevel, but is useless for backing off the burr.

Presumably the owners of the stone either didn't remove the burr (yuck!) or removed it using another (flat) abrasive, either stone, or strop.

s/h fine stones tend to be flatter, I find.

BugBear

Hello,

I always remove the burr with the final stone I intend using. Once the blade back has been polished on a fine stone, it only ever sees the fine one for burr removal. That said, I hate hollowed stones at any stage.

Mike.

 

[Trafalgar]

Norton makes SiC stones in fine grit and these might be just the ticket for some of the relatively exotic alloys that have found their way into woodworking. They even make SiC slip stones for those who might be interested -- also round or axe stones in coarse/fine. I believe it was Robt. Wearing who mentioned using a round stone on scrapers. Could have been somebody else -- I know it was a Brit though. Lovely price points all...