Smoothing planes

[Tom King]

Nice find.  I think you will find that the vast majority hollow grind irons.   I'm probably one of the few that don't use a hollow grind to key off of.  Mine are hollow ground when they get damaged, which is rare, but no extra bevels when sharpening, so the bevel angle of the cutting edge takes over the whole bevel on my plane irons, and very, very rarely touch a grinding wheel.

edited to clarify

[BonPacific]

I don't hollow-grind either. Mostly because I don't trust myself with the bench grinder. I use my belt sander to establish the general angle, and then do the microbevel on my diamond plates.

[Coop]

I looked it up and still don't get it. What is hollow grind, a steeper angle? 

[bleedinblue]

17 minutes ago, K Cooper said:

I looked it up and still don't get it. What is hollow grind, a steeper angle? 

Nope, it's just another way to not have to remove steel along the full length of the bevel of the iron with sharpening stones, just the same as a micro-bevel.  It's done on a bench grinder, literally letting the round grinder stone leave a concave surface along your irons bevel.  This way when you hit your finishing stones, the stone only contacts the tip and back of the bevel, leaving the center of the bevel untouched along the length.  

I've never done it though, and my explanation probably sucks.

[Coop]

Au Contraire Blue, it's not the explanation but the recipient. So the edge is not straight across but has a concave? 

[bleedinblue]

4 minutes ago, K Cooper said:

Au Contraire Blue, it's not the explanation but the recipient. So the edge is not straight across but has a concave? 

Yup, slightly.  In the picture of the bevel i posted, it's not real clear but you can see the center of the bevel has a different sheen as the top and bottom.  In person you can see the coarse lines from the grinder.  The tip and beginning of the bevel is like a mirror, as it was ran over a flat 8000+ stone.

[Coop]

Dang, and that's done on purpose? I'd better stick with the way I know. Thanks Blue for your time.

[bleedinblue]

1 minute ago, K Cooper said:

Dang, and that's done on purpose? I'd better stick with the way I know. Thanks Blue for your time.

I'd have to upgrade my grinder setup and confidence with it a bunch before I'd attempt it...and I probably will never do it with plane irons, but maybe chisels.

[Coop]

Oh s*#t, now another can of worms, but it's your thread, so co-hj away. Why chesels? Life is getting more complicated

[bleedinblue]

Ha...I only knew of hollow grinding because Marc and Shannon have talked about how they hollow grind their chisels.  I never knew anyone did it with plane irons.  I think it would easier to do on a chisel because of the size, plus my chisels are much cheaper than my planes, so if I screw them up it's no big deal.

[Pondhockey]

Hollow grinding is good for ice skates - it gives two edges ("inside" and "outside") on each blade - although the Russian hockey players supposedly play with triangular blades that have only a single edge and so (supposedly) don't take as much time to transition from inside to outside.

Hollow grinding as I know it comes automatically from the curvature of the wheel (you specify 3/8, 1/2, or 5/8 wheel, when you get your skates sharpened).  Of course you could use the side of the wheel to grind your edge, and get a "flat" grind (goalies often use a flat grind).  Still being a novice woodworker, I'll leave  the expert opinions to others, but I sure don't understand why a hollow grind would be a good idea for a plane blade. I flatten the ground edge with a course stone or sandpaper after using a grinding wheel.

[wtnhighlander]

Hollow grinding leaves the middle of the bevel "hollow", so that only the cutting edge and heel contact the flat stone for final honing. This makes it easier to feel the registration when honing without a guide, and also means less material must be removed, so honing is quicker.

[RichardA]

9 hours ago, K Cooper said:

Au Contraire Blue, it's not the explanation but the recipient. So the edge is not straight across but has a concave? 

It's like the back of a Japanese chisel.

[Tom King]

A hollow grind itself has no effect on the camber, or curve of the cutting edge.  Anything ground on the side of a round grinding wheel, like a bench grinder, or Tormek, will have a hollow grind to match the radius of the grinding wheel regardless of the profile of the shape of the cutting edge.  

Some say it helps with feeling when the cutting edge is in contact with a sharpening stone, because the point and heel of the bevel contact the stone, and if one or the other lifts off, you can feel it easier.  If the sharpening stone is perfectly flat, I can't tell the difference to amount to anything between a flat bevel, and a hollow ground bevel.  If the sharpening has only been done by hand, and the bevel has developed a rounded shape the reverse of a hollow grind, there is a big difference in feel of keeping the cutting edge in contact with the sharpening stone.  For this reason, some who only sharpen by hand on stones do a lot of grinding with a grinder.

If you are using slow cutting sharpening stones, another advantage of a hollow grind is that you can put more pressure on a smaller amount of metal on only the two sides of the hollow grind, so it will speed up the process compared to honing a complete flat bevel on slow cutting stones.  If you are using really fast cutting stones, the difference doesn't amount to much.  

This is where it gets a little complicated because if you are using really fast cutting stones, they can be pretty soft stones, and using hand alone, it's easy to gouge the surface of the stone. I bought one of my Sigma Selects used off of another woodworking forum from a well respected sharpening guru who preaches hand alone.  I've used that stone for three years now, and I still haven't gotten to the bottom of all the gouges. There are many branches of possibilities to go off in different directions.

There is no one best way for everyone,  The important part is the very cutting edge itself, which is the angle formed by the intersection of the combination of the bevel side, and the back of the cutter, whether chisel or iron.

Having a hollow grind is not an important decision to make one way or another.  The important thing is to have the end goal in mind, and a plan that works for you of how to get there.

[justforfun]

As Ive said in other post Im really new to plains and trying to learn. I got my first plane, a old no 8 and learning with it as Im waiting on another size. I came with a huge convex grind. Very rounded but sharpens at 25 deg. Should I flatten this?

[wtnhighlander]

No. 8 is considered a "jointer", and as such, would usually have a square grind to the iron. I can only imagine the convex grind had a special purpose for a previous owner.

[Tpt life]

Poor feeehand technique leads to convex. 

[Eric.]

Yes you need to regrind that bevel flat.  It's impossible to sharpen freehand that way and any jig will inherently remove the convex anyway.  Just start over.  Takes a couple minutes to regrind a bevel, even without a grinding wheel.  I use a Diaflat and it's plenty fast enough.

I do slightly camber my jointer plane iron (by camber I mean I knock the corners off just slightly) because I don't use my #7 for milling, per se...just final flattening where I'm at a part of the process that I don't want tracks.  The "cambering" is so light and the blade is so wide that I can still joint the edges of 8/4 boards or two 4/4 boards sandwiched together and only the flat part of the blade contacts the wood, and the relieved corners hang off the sides.  This may not be standard practice but it works for me.  Keep in mind that I do all of my initial milling with machines so my needs may be different than yours.  I use all of my planes as tuning and finessing tools post grunt work.

[wtnhighlander]

Perhaps I mis-read the post, is the blade "bellied" between the toe and heel of the bevel, or radiused across the width of the iron?

[Eric.]

9 minutes ago, wtnhighlander said:

Perhaps I mis-read the post, is the blade "bellied" between the toe and heel of the bevel, or radiused across the width of the iron?

Or to put it in basic terms, cambered or f***** up?  It sounds like the latter to me.  A convex bevel is good for nothing.  It was sharpened by someone who doesn't know how to sharpen.

[bleedinblue]

Mine?  Mine was concave but dull.  I need to do a bit more work to the iron, but I removed the hollow grind on a 220 stone very quickly.  I think I can get it sharper than it sits right now, I ran out of time, but it's a lot better than when I brought it home.  It's cutting thin shavings but is taking more effort than it should.

Still yet I think I'm convinced enough to sell my WR...if for no other reason than keeping all of my planes matching brands.  Functionally, I think the WR could match the LN.

[Eric.]

55 minutes ago, bleedinblue said:

Mine?

I was talking about justforfun's.  Not sure if he was talking about a camber or a boogered bevel.

[G S Haydon]

A convex bevel is fine as long as long as it's not a shortcut, or poor method which is often described as rounding over. On thin, Stanley pattern irons or softer chisels, using coarse abrasives it works fine. 

Justforfun, I think you'd benefit from keeping your collection of planes small for now, and investing into a Charlesworth/Sellers DVD and get used to them. You can watch both of their approaches on YouTube, see which one you're drawn to most.

[Eric.]

4 minutes ago, G S Haydon said:

A convex bevel is fine as long as long as it's not a shortcut, or poor method

Just curious, G...how would you arrive at a convex bevel if not for one of these two reasons?

[Tom King]

Bleedingblue, If you have the time to wait a few days for the iron to go and come, send it to me, I'll prep it and sharpen it for you, and then you will get to see in hand what the goal is, and why.  It won't take me long, so don't worry about wasting my time.   If you PM me, I'll give you my mailing address.