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Flat vs Hollow Grind Bevels

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There have been several threads recently where folks have said they prefer a bevel flat grind to a hollow grind. I’ve tried a flat grind on skews but no other tools. What are the purported advantages of a flat grind, in particular gouges? Include other tools as well. Let the debate begin!
 

hockenbery

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For spindle turning it is easier for me to roll beads and cut coves with a flat grind or even a slightly convex grind.
a micro bevel is an easy way to undo the concave grind
on my small 3/8 diameter bowl gouge I use a michelsom grind - a convex bevel. Great tool for hollowing small openings.

I hone skews a concave grind makes it easier for me to hone. I hone many many times before regrinding a skew.

my bowl gouge I use from the grinder with a concave bevel. for hollowing I grind off the heel To make a partial micro bevel.

bevel drag is the enemy of a clean cut. The flat, convex, and micro bevel have less bevel drag.
the convex bevel makes the cutting edge want to cut a little deeper and it increases the bevel drag slightly.
 
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Very interesting, and something I have thought about. I have hand-honed my Alan Lacer Uber Skew so many times that it is going to need regrinding soon. Given that I am still a newer turner, would you take it back to a wheel for the original concave grind, or try to flat-grind such a huge skew?

If it makes any difference, I use that beast for many turning steps, even on pens and sometimes cleaning up tear-out on bowl exteriors-I know that is against the rules, so I'm always super-careful doing it (though lately I have been using my new D-Way round-nose NRS for that duty with great results-it's like a tear-out slayer!).

Just curious what you experienced turners think?
 
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For spindle turning it is easier for me to roll beads and cut coves with a flat grind or even a slightly convex grind.
a micro bevel is an easy way to undo the concave grind
on my small 3/8 diameter bowl gouge I use a michelsom grind - a convex bevel. Great tool for hollowing small openings.

I hone skews a concave grind makes it easier for me to hone. I hone many many times before regrinding a skew.

my bowl gouge I use from the grinder with a concave bevel. for hollowing I grind off the heel To make a partial micro bevel.

bevel drag is the enemy of a clean cut. The flat, convex, and micro bevel have less bevel drag.
the convex bevel makes the cutting edge want to cut a little deeper and it increases the bevel drag slightly.
Al, I can't ever seem to find a technique for sharpening a skew that doesn't leave me queasy. Over the years I have come to the technique of just about exclusively honing the things on a diamond card and I rarely rarely ever touch it to a grinding wheel. Things go wrong when I put a skew on a round grinding wheel. Do you have a video out there somewhere that shows you sharpening a skew?
 

hockenbery

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Al, I can't ever seem to find a technique for sharpening a skew that doesn't leave me queasy. Over the years I have come to the technique of just about exclusively honing the things on a diamond card and I rarely rarely ever touch it to a grinding wheel. Things go wrong when I put a skew on a round grinding wheel. Do you have a video out there somewhere that shows you sharpening a skew?
no videos
if I’m doing a bunch of spindle turning I set up the tormek. It has a jig the clamps the skew at a set position.
then hone. The tormek has leather wheel that I use for honing With a charming compound.

if I’m doing a tool handle or one finial and the skew needs grinding
i use a platform with CBN 180 wheels . when I had Norton 3x wheels I would dress 120 wheel Before using it.
set the platform angle to match the bevel angle on the skew.
I just slide the skew across the platform lightly touching the wheel. For me 3 light passes is better than 1 heavy.
honing begins with a soft & hard Arkansas stone then the diamond hone. Then I’ll just use the hone until I roll over the edge then back to the grinder - maybe hundreds of times.

im not an expert with the skew but I get by Pretty well.
 

john lucas

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I find no difference. It's only the first millimeter that does the cutting. When I set up my strip sander I played with flat friends on gouges a d skews and really could not tell the difference. Also played with convex grinds. There were subtle differences there but I think it takes a skilled hand to really tell the difference.?
 
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Al, I can't ever seem to find a technique for sharpening a skew that doesn't leave me queasy. Over the years I have come to the technique of just about exclusively honing the things on a diamond card and I rarely rarely ever touch it to a grinding wheel. Things go wrong when I put a skew on a round grinding wheel. Do you have a video out there somewhere that shows you sharpening a skew?
Sharpening a skew is not hard--if I can do it, anybody can do it. If you can sharpen a parting tool, you can do a skew. Set up your platform for the right angle. For straight skew, apply bevel to wheel with edge straight across the wheel face, slide back and forth, flip and do again. For a radiused skew, put skew on platform with thumb on top of skew in the rough center of the curve, apply heel part of edge to grinding wheel and rotate, flip over and do again.
 
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Some CBN wheels have a flat side (4-in-1 CBN Wheels). Its very easy and safe to set the platform to 90 degrees and use the side of the wheel to cut the flat by holding the tool at a 45 degree angle to the wheel while the bar is flat on the platform then flip the tool and do the other side.
Al
 
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Note: Per Allan Lacer and common sense when you hone a hollow ground skew you ride both edges of grind arc and that way there will not be any micro bevel on the cutting edge where as a flat grind can only be honed with a micro bevel. The micro bevel will affect the quality and the control of the cut.
 

Roger Wiegand

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I hone all of my turning tools, so prefer a hollow grind. None of my plane or chisel blades ever see a powered grinder, so they are ground flat on a water stone (I don't find that takes any significant time, but they get a whole lot less wear between sharpenings than a turning tool does.) My carving tools have not yet seen any sort of grinder in my hands, they came sharp and I power hone them on a leather wheel with a polishing compound; some are now fairly convex, but still seem to work fine. It's something I've been meaning to ask my carving mentor about. I've never seen him use a grinder or stone, though he's told me he really learned to sharpen when he was hired to "fix" several thousand bungled tools for a major retailer.
 

john lucas

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Note: Per Allan Lacer and common sense when you hone a hollow ground skew you ride both edges of grind arc and that way there will not be any micro bevel on the cutting edge where as a flat grind can only be honed with a micro bevel. The micro bevel will affect the quality and the control of the cut.
When you hone a hollow grind you are creating micro bevel. It could easily be the exact same angle as the micro bevel on a flat skew depending on the included angle of the grind.
 
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