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bowl gouges sharpening - "other shapes" graph

Started by JR DUBUY, January 14, 2020, 09:33:37 AM

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Ken S

Quote from: JR DUBUY on January 18, 2020, 10:02:47 PM
After experiments several settings for sharpening the roughing gauge with the SV186 tool, I finally prefer the following :
- JS 6
- hole B
- protrusion 55mm

The result is closer to TORMEK recommandations when using SVS-50  (alpha angle=35° and a positive rake angle)
It works very well and the SV186 is helpful for the repeatability


Ever the adventurous Tormeker, I decided to reshape my 3/4" Sorby roughing gouge to this configuration, using my 80 grit CBN wheel in vertical position and HonoRite Gold in my T8.

To make a long story even longer, I ground on one side for a timed 30 minutes. Except for a small part of the top of the wing, thirty minutes completed the one side. The grind shape looks very much like the original square roughing grind.

Frankly, I am not sure if it is worth another half hour's work to grind the other side. Supposedly, the T8 is rated for "continuous duty", whereas the T4 is allegedly rated for thirty minutes. This evening, this senior citizen was ready for a rest after thirty minutes working continually with the T8. I would conk out before my T4 would!

As I return to this, I will update things. I like the idea of being able to use the SVD-186 with my roughing gouge.




I get it.  That's why I reshape on a bench grinder (using the Tormek jigs) & sharpening on the Tormek.

Kind regards,
Rich Colvin - a reference guide for sharpening

You are born weak & frail, and you die weak & frail.  What you do between those is up to you.

Ken S

Good point, Rich.

In the past, I have resisted using my dry grinder with Tormek jigs. This reshaping seems like enough of a project to warrant converting my old six inch high speed grinder. I already have the conversion components.
I also have a Norton 3X 46 grit wheel on my dry grinder.

Actually, I was grinding on the original roughing gouge I purchased second hand. It was bent when I purchased it. (The larger roughing gouge I really wanted is fine.) For safety, I later purchased an unhandled head. It has the traditional straight across English grind.

Now, my question is do I really want to reshape the roughing gouge or just use the SVS-50?

Either way, I should get my dry grinder out of mothballs and do the conversion. I could also convert my belt grinder. Too many decisions........


Twisted Trees

Spindle roughing gouge is a completely different tool to a spindle gouge, my advice is don't do it! 45° flat profile if you are concerned about the pointy bits on the top risking catching then turn it upside down and just take the corners off, they won't be sharp, but you NEVER want to cut with the corners anyway!

If you want a large spindle gouge, then get a large spindle gouge! don't try to fake it with a spindle roughing gouge which probably needs a new name as it causes too much confusion as to how it should be used.... how about a bent unskew  ;D

Twisted Trees

I am on a 150 unit production run at the moment, should have finished today but granddaughter came round and stopped work! it should be

find centres and set work blank in lathe, set tool rest.
turn on lathe, set speed
Spindle roughing gouge to make square into cylinder
Spindle gouge to shape it
Skew to finesse it
slow lathe down move tool rest, abrasive and oil it
parting tool to part it off...
repeat 150 times

BUT it is 150...  it is

Set centre on 10 blanks
use Steb centre to drive it so I don't have to turn the lathe off
Balance between centres and tighten tailstock until it is driven
Large skew to round of build curves and finesse it
abrasive and oil from behind work at full speed don't move tool rest, don't put down skew, use skew to part off
load next piece, turn lathe off only after 10 are completed

Check clock and try to shave of 30 seconds + on the next 10! plus probably a coffee either needs drinking or making!
Repeat 15 times see much less work  ;)

All tools can be and are used beyond the design, but the spindle roughing gouge does 2 things well parallel or gentle curve on a spindle (e.g. a tool handle) it should be left for that alone.


Quote from: Rob on January 14, 2020, 04:39:53 PM
Hi there and welcome to the forum.

The geometry of elliptically ground gouges is moderately complex.  But it boils down to the fact you need to know that 3 adjustments affect the geometry and by that I mean the bevel angle and the degree to which the wings are swept back. 
They are:

- the distance the tool is protruding from the jig (P)
- the distance between the pivot point and the grinding media (hole A or B with Tormek's quick set jig) which is the distance the USB is from the grinding media
- the angle at which the bevel is presented ie the angle between the tool axis and the grinding medium axis. (knuckle setting in the elliptical grinding jig).  That's what the manual refers to as JS 2 or 3 or 4 etc

If the chart shows the same angle for any of these variables, then one or both of the other 2 variables must have been altered.

To add to that is also an operator component ie the time spent focusing grinding on different parts of the bevel.  This is classically demonstrated by spending too much time on the nose (goes flat and dips) or not enough (gets pointy and is very frisky during turning).  Or too much wing grinding can wear them out at the backs and not enough means they dont sweep right round and have no cutting edge at the back.  But the angles are managed by adjustment of those 3 variables.  That also holds true for every other jig based grinding system in the market.  one has control of these 3 factors.  Tormek just happens to do it very well because of the precision engineering and good design.
Sorry for up and thank you for that. It was really hard to choose the right one's gouges and for sure it's Art how to sharp them right!