Plane iron/chisel back flattening

[Joe]

Is there a general consensus of opinion about whether or not it's a good idea to use a whetstone grinder to flatten the back of plane blades and chisels (i.e. grinding on the side of the whetstone and then buffing on the honing wheel)? I do find it very time consuming and tedious doing it by hand on waterstones.

 

[Woody Alan]

My experiences only for what they are worth....
I don't know about consensus, but my experience of that method has been poor i.e. not flat. I have tried diamond coarse stones but found them slow (surprisingly). To date my best success has been a lapping plate and it's cheap.
http://www.axminster.co.uk/product-Hari ... -20855.htm
Too be fair though this has only been neccessary on some seriously dodgy plane blades. Coarse waterstones wear too fast so as soon as you start trying to flatten the blade the stone wears and it's already not flat.
Also a good cheap india coarse stone is surprisingly good for fairly quick metal removal often undervalued I think.
http://www.axminster.co.uk/product-Nort ... -22390.htm
Hmmm well OK not as cheap as they used to be, they will stay flat longer and can be flattened fairly easy on a paving slad with water and silver sand ..as can any oilstone.

Alan My experiences only for what they are worth

 

[woodbloke]

A way that the now departed Alf showed me in the summer was to use a piece of flat 10mm acrylic (perspex) onto which is placed the grinding medium. Alf used a diamond paste (which I wiped off on a rag ) for the demo. Not having any diamonds to hand, I used some coarse valve grinding paste, the idea being that it 'beds' into the acrylic and forms a cutting surface. This works very well and is perhaps too brutal (good for renovating rusted and pitted blade backs) as it removes a lot of material fairly smartly...better I think to use a finer grade of paste, just takes a little longer...but not much :wink: - Rob

 

[AHoman]

A way that the now departed Alf showed me in the summer was to use a piece of flat 10mm acrylic (perspex) onto which is placed the grinding medium.

I've tried the side of the Tormek wheel and haven't been too impressed by the results.
Where is Alf, anyway?
-Andy

 

[Digit]

When I were a lad, (he's off again!) anybody in the shop could use the grinder, but then the bleeding hearts brigade decided that they, from behind their office desks, knew more about the task than us skilled men. They decided that in future users had to be certificated, (certified?) and told us that in future the use of the side of the wheel was far to dangerous and was now Verbotten!
You have been warned!
I use grinding paste and a piece of float glass.

Roy.

 

[Philly]

Joe
When you say "Back" you do mean the "non-bevel" face??
I certainly wouldn't use the whetstone to flatten it (I assume you are talking powered grinder?) While it works you will probably find the back is not flat - I know, I've tried!!
A very easy and effective method is to use sandpaper slapped on a flat surface (table saw?). I use 120 grit, works real good to get things started. After that use finer grades or jump over to your favorite sharpening media (oil, water, diamond stones) to grind up to a mirror finish.
I find a real coarse grit is needed initially or you just spend ages polishing away minute amounts of metal, never actually getting a flat surface and getting board.
Hope this helps
Philly
Who spends too much time making irons..........

 

[Joe]

Thanks everyone for the advice. It seems the general opinion is that a (powered) whetstone grinder is far from an ideal tool for the job in question. Being cursed with a complete lack of flat surfaces in my workshop/studio (I don't have a table saw, just a small, not very flat bandsaw table) I think I might invest in a granite surface plate and a pile of sandpaper. The problem I can imagine having with glass/acrylic/mdf impregnated with diamond paste is that this surface will flex a little if not placed on a flat surface (something I've experienced when trying to flatten waterstones).

 

[Philly]

Joe - you're right. A flat subsurface is necessary to prevent the acrylic flexing.
The small granite surface plate from Axminster is superb - well worth the money.
Let us know how you get on.
Best regards
Philly

 

[Digit]

That's why I use float glass, fridge shelves are the easiest source.

Roy.

 

[woodbloke]

Joe wrote:

The problem I can imagine having with glass/acrylic/mdf impregnated with diamond paste is that this surface will flex a little if not placed on a flat surface

You're right of course, there is a little bit of flexing if the acrylic isn't properly supported...that's why mine is screwed to a bit of 18mm mdf which is then used on top of my thickish sharpening bench - Rob

 

[Joe]

Roy, do you find a fridge shelf rigid enough? I have a small piece of plate glass (comes with the Veritas stone pond) but it flexes under pressure.

 

[Digit]

I've had no problems with it at all, I suppose if you put in on a bowed enough surface you might have a problem, but a piece of kitchen work surface has been okay for me.

Roy.

 

[DaveL]

One source of flat glass is old mirrors, they often come up on freecycle.

 

[Philly]

Don't forget you need "float glass" - this is made by pouring molten glass onto a bed of molten tin and produces very a flat product.
Toughened and other types of glass are not so flat.
Hope this helps,
TriviaPhilly

 

[woodbloke]

Float glass is the stuff to get hold of...this is my latest 'plane sole flattening' jig made from a piece of 1000x200x10mm thick float glass:

The underside is a lump of 18mm mdf and the sandpaper (or similar) is trapped under and held securely by the two 10mm thick side pieces, the two smaller end pieces are thinner than the 10mm glass so there's no danger of anything catching in use - Rob

 

[Joe]

I've just bought Rutland's granite surface plate. Costing about £40 and made in the PRC, it claims to be accurate to 0.0001" (really) and comes with a test certificate. This proves nothing of course, but I tried testing it with my Veritas steel straight edge and a strong light and it looks very good - only a minute amount of light visible in places (couldn't slip a blue Rizla paper under). It is great for flattening waterstones and blade backs - possibly a bit small for plane soles (probably just about ok for No.4's and anything smaller).

 

[Philly]

Pretty impressive plates for the money, Joe. And they certainly are the flattest things in my 'shop :lol:
Philly

 

[woodbloke]

I was in WHS having a gander at the woodworky mags...(what else is there to look at? :roll and I happened to pick up a copy of GW in which was a piece about getting the backs of chisels to a mirror finish. Having committed most of the relevant bits of the article to memory, notwithstanding the fast diminishing amount of grey matter available, I'm going to have a go later on with my LNs' and will report back on progress - Rob

 

[bugbear]

I've just bought Rutland's granite surface plate....possibly a bit small for plane soles (probably just about ok for No.4's and anything smaller).

It's fine all the up to a #5 - if you use it right

http://www.geocities.com/plybench/flatten.html

BugBear (with a similar size plate)