Tru-Grind Jig & SAWG Spacers: Angle Questions

[ebf]

Greetings,

I am a newbie turner and am getting to grips with sharpening turning tools - finding that round shapes are slightly more complex in terms of angles than bench chisels :-

I am using the Tru-Grind jig (older version with small notches instead of "teeth" for setting the leg angle), and have also downloaded and made the spacers from the South Auckland Woodturners Guild (SAWG)

Getting some (strange) results, and would appreciate feedback from anyone else familiar with the Tru-Grind jig and SAWG spacers.

Scrapers, parting tool and bowl gouges I'm happy with the results.

Roughing Gouge (Hamlet 3/4)
using the 45-degree spacer, and setting the jig leg to the notch first stop away from parallel
at the bottom of the flue I get a measurement of 50 degrees
at the wing/tip of flue I get a measurement of 35 degrees

when I set the leg parallel to the tool shaft, I end up with wings that are higher than the cutting edge at the bottom of the flue, does not seem right...

http://i303.photobucket.com/albums/nn127/ebfourie/wood_turning/roughing_top.jpg
http://i303.photobucket.com/albums/nn127/ebfourie/wood_turning/roughing_side.jpg

Spindle Gouge (Hamlet 1/2, roundbar type)
using the 30-degree spacer and setting the jig leg to the second last stop away from parallel (8 on old design or ? 4 for new design)
at the bottom of the flue I get a measurement of 45 degrees
at the wing/tip of flue I get a measurement of 30 degrees

http://i303.photobucket.com/albums/nn127/ebfourie/wood_turning/spindle_round_side.jpg

Spindle Gouge (???, 1 inch, flatbar type)
using the 30-degree spacer and setting the jig leg to the second last stop away from parallel (10 on old design or ? 5 for new design)
at the bottom of the flue I get a measurement of 50 degrees
at the wing/tip of flue I get a measurement of 30 degrees

http://i303.photobucket.com/albums/nn127/ebfourie/wood_turning/spindle_flat_profile.jpg
http://i303.photobucket.com/albums/nn127/ebfourie/wood_turning/spindle_flat_side.jpg

- Comments / suggestions about the settings / measurements above
- Am I correct in saying that the further away the jig leg is from parallel, you seem to end up with a 15 or more degree difference between the bottom of the flue and the top/wing ?
- Any suggestions / tips on achieving a "flat across" type grind in a roughing gouge, using the Tru-Grind system ?

Hope this makes sense, thanks in advance,
Eben

[RETIRED]

I will give an answer tonight.

[RETIRED]

I like 45 degrees on all my tools and disregard the settings suggested by jig makers. It is largely by trial and error that you get what you want to suit you but here goes.

before you start, mark all your bevels with a black Texta (marking pen). Leave the grinder off and rotate by hand with the tool in the jig. I sit the tool against the wheel and rotate the wheel backwards just a little.

The shiny part is where the wheel is cutting. Adjust Jig (tool holder) or support bar to get the result you want. Leave the projection the same, 50mm or 2".

Roughing Gouge (Hamlet 3/4) The 3/4 half round Spindle roughing gouge comes out exactly as you describe if you use the Trugrind jig. If you look at the geometry of the tool whilst in the jig it gives you the best clue. Because of the distance from the handle to the jig it has no option but to cut a longer bevel on the edges because it is not describing an arc which the end of the tool actually is.

The tool will still cut sharpened this way but if you are like me, the bevel should be parallel all the way round.

The only way I found to obtain this was with a copy of the Oneway jig here. Grinding Jig (http://www.oneway.ca/index.php?option=com_virtuemart&page=shop.browse&category_id=37&Itemid=2) because it uses the handle as a reference it has no option but to rotate around its own axis, not one offset by an inch.

This is the one I made:196133

The 1/2" Hamlet: Use the 30 Degree space and put the jig parallel with the the handle. Do not rotate the tool too far.

You should have a "thumbnail" shape at the cutting edge. The side angles will alter fractionally but shouldn't be a worry.

The 1" traditional spindle gouge is a different kettle of fish (fush:D) Because of its width it describes a greater arc than the little one so you have to use a slightly different approach. Forget the set-up jigs. That will only give you the angle at centre of the bevel.

If you can roughly hand sharpen, sharpen the bevel to where you want it. If not it is going to take some playing around.

If you hand sharpened it, put the tool in the jig, lay the tool over at approx 60 degrees on the wheel and set the support bar so that the bevel sits on the wheel Using the Texta. Lock in place.

Straighten the jig back up to vertical. NOW SET THE JIG to the bevel angle you have. Do not move the support arm.

Do a trial grind with the grinder running and check the coverage on the bevel for evenness.

The playing around method. Put the tool in the jig, lay the tool over at approx 60 degrees on the wheel. Using the texta to check, alter the support bar in or out to remove either the cutting edge or the heel. My guess is that you will need to move it in to remove material from the heel. Once that is set, follow the above to set the bevel at the centre of the grind.

If you want to copy a grind that you like this is the way it is done.

Remember that the further you lay a tool over the further up the sides the grind will go and it will alter the angles on the sides.

It is pity you live so far away because to show you would take about 10 minutes.

I hope this helps and that you can understand my dribble. Let us know how you go.

[ebf]

Ian, thank you for all the info :2tsup: - really appreciate it - will do further experiments based on your settings and also look at the jig for roughing gouge, and let you know how I get on.

Cheers, Eben