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View Full Version : Flute shape, preferences, and sharpening



artme
10th December 2012, 11:14 PM
Following on from the debate about the Robert Sorby Pro-edge
sharpening system I was prompted by Ern to start a different thread.

So here it is.

What flute shape do you prefer in a bowl gouge and why?

What method/s of sharpening do you prefer and why?

What style of grind/s do you prefer and why?

vk4
11th December 2012, 09:15 AM
with my bowl gouges , I sharpen with a small back grind on the wings, , I find this reduces my catches and gives a slightly longer side edge.I do not use the finger nail grind.

For grinding / sharpening , I have a *" benchgrinder, with an 80Grit white alox wheel, I have found that 60Grit is too coarse and 100/120 is too fine , for my style of work( when I can get any done).

CBN wheels are another option , 1 which I have not explored, and the TOMEC machines , which I now do give excellent results with very fine sharp edges( though they are a little slower).


Jeff

Paul39
11th December 2012, 12:54 PM
What flute shape do you prefer in a bowl gouge and why?

My first bowl gouge was a Crown, then a Thompson, then Bodger, and recently a $45 mystery metal unhandled one that spark tests HSS.

They are all a variation of a V flute.

What method/s of sharpening do you prefer and why?

I started sharpening screw drivers, bench chisels and old files on a 1 inch wide belt sander with no backing plate. Everything was slightly concave.

When I bought my first "good" lathe it came with an 8 inch 1725 rpm grinder with 80 & 120 grit stones, and a Wolverine sharpening system and a Vari-Grind and the early Oneway fixed bowl gouge jig.I now have a 120 grit stone on both sides so I can grind bowl gouges on one side and everything else on the other without having to move the v jig and platform.

I sharpened the Crown with the Oneway jig. The used Thompson came with almost an Ellsworth grind, so I used the Vari-Grind to keep that profile. I have found the very swept back grind too volatile for my taste, so have been bringing all the bowl gouges back to a slightly swept back grind using the Oneway jig.

My scrapers and Bedan I grind upside down using the platform at about an 80 degree angle. The raised burr cuts clean for a short time for the last slicking before sanding.

The spindle gouges I grind free hand upside down - wheel rotating away from the tip - just a quick swipe.

The accursed skews are not ground unless bought used and mangled. I cleaned one up on the side of the 120 grit wheel. I sharpen them either on a strip of sandpaper on the lathe bed or on one of several grits of diamond plate. I use 400 or 600 grit for the final finishing passes.

Last winter in a weak moment I bought a used Tormek, the predecessor to the T-7. I sharpened friends plane irons, scissors, and eventually a bowl gouge, on which I promptly cut myself. As my shop gets below freezing it was not installed there and due to illness and then coming out of retirement to renovate a building is still not installed in the shop.

I think the best use of a Tormek is to sharpen the bowl gouge for the final passes on a bowl before sanding. Otherwise use a dry grinder as the wonderful Tormek edge is worn off in a few seconds of turning.

The Tormek jigs are superb. I think the best set up is a dry grinder with diamond wheels and a Tormek bench grinder mount.

What style of grind/s do you prefer and why?

Bowl gouges, "Celtic" grind for the sides and outside - left below, fairly blunt with the sharp corners ground back for bowl bottoms - right below, but sharp corners ground back.

http://www.toolpost.co.uk/pages/Turning_Tools/Hamlet_Tools/Hamlet_Gouge/Hamlet_bowl_gouge_grind_comparison.jpg

The blunter grind is easier for me to get smooth flat bottoms. The more swept back grind can be used in many positions to get to anywhere on the inside or outside of the bowl.

The Ellsworth Grind really takes off the timber, but the slightest lack of attention might give me an undesirable spiral feature.

I use a long bread knife for a parting tool that is sharpened upside down on the platform at 80 degrees. I usually leave my grinder running the whole time I am turning. It is one foot from the tail end of the lathe, so it is easy to reach over and give whatever tool a swipe frequently.

I do find that honing the inside of gouges with 200 and then 400 grit paper wrapped around a rod or dowel makes a difference.

Rounding all the sharp edges on the shafts of the tools with sandpaper makes for more comfort. The top edges of the bowl gouges and all corners of scrapers, accursed skews, Bedan, etc. The exception might be the top left edge of a square ended box scraper.

robo hippy
12th December 2012, 06:10 AM
Flute shapes: The more V shape there is to the flute, the less I like it. I like the Thompson V which isn't much of a V, but more of a U. I also like the more open U flute from Doug, and his fluteless gouges, which are similar to the Continental type gouges with flutes more like this ). I tend to hold my tools level, and roll the gouges on their sides for a high shear angle, and the fluteless and continental style gouges are best for this. I mostly use a finger nail grind I guess. Some thing like the 40/40 gouges as in 40 degree bevel, and 40 degree sweep. I don't use the swept back grind much any more. The biggest advantage to it is for the high angle, dropped handle shear cuts, and maybe for roughing as you have a larger edge you can put into the wood, if your lathe has the horses to keep up with that much resistance. I use scrapers for roughing, and for my shear cuts. I do have a couple of 'bottom feeders' types of gouges for the transition and across the bottom of the bowl cuts. ground like a SRG, only with a 60 to 70 degree bevel, and a tiny bit of sweep, maybe 5 degrees. The fluteless gouges are the same angle and maybe a little more sweep.

For sharpening, I have CBN wheels from D Way, 80 and 180 grit. Perfect, and one of those 'best tools I ever got for my shop'. I free hand/platform sharpen, and wouldn't know how to set up a gouge jig any more. It is simple, and much faster than setting up a jig. I have a couple of clips up on You Tube (type in robo hippy) showing how I platform sharpen, and my platform. I learned from Allan Batty. It really is as simple as it looks. Biggest hurdle is getting the idea across to your mind that, yes, it is pretty simple. I have experimented back and forth with gouges and scrapers on the grinding wheels. I really can't detect much difference in how the tools seem to cut with either a coarse or fine wheel finish. Maybe the burr for scrapers is a bit more sturdy on the coarser wheels.

robo hippy

rsser
16th December 2012, 06:56 PM
Between shallow (spindle), really shallow (detail) and deep (bowl), I choose the tool for the application and my skill level.

Any of those can be modded as to cutting edge shape on the grinder.

In the other thread Arthur, you suggested that diff. brands needed diff. treatment at the grinder. And they may do but there's as much diff. within as btwn brands; and variations produced at the grinder will always exceed variation in flute shape (in cross section) alone.

Whatever, as the kids used to say. Find a tool/shape you're comfy with and enjoy honest work at the lathe.