Grinder angle jig

[Dan T Jones]

In my neanderthal education rehabbing old Stanley planes I want to start by grinding to 25 degrees. I have a Wolverine jig and I want to be able to set the platform jig to get the 25 degrees.

I can't figure out a jig to get the platform to a consistent 25 (or whatever else degrees) degrees. Anyone out there have any ideas??

Thanks for the help.

Dan

[Derek Cohen]

Dan, here's a short article from my website (2008):


Adjusting the tool rest for a specific angle needs to take into account two factors, the diameter of the wheel and the thickness of the blade.


As the diameter of the wheel becomes significantly smaller, it will be necessary to make a fresh jig (I emphasise “significantly” smaller since a little bit here-or-there is not important in the grand scheme of things). The only jig I am aware of that adjusts for different diameter wheels is the Tormek. However the is not enough room to use one on a dry grinder with wheel guards.


Each time the jig is used, it must account for the thickness of the blade. This is done by placing the blade on the tool rest, and then the jig on top of the blade.


Tighten the tool rest setting once it is set up as in the above picture.




The Jig

http://www.inthewoodshop.com/WoodworkTechniques/AngleSettingJigForDryGrinder_html_m10e41ef0.jpg




Making the Jig

The dimensions are not relevant and may be made any size you please. The jig in the picture will grind a 25-degree hollow.




Use a blade with a known bevel angle (say 25 degrees).

Set this up to grind such that it will create a hollow at the middle of the bevel. To test this, use a felt tip marker (texta, magic marker) and colour the bevel. Place the blade on the rest and – with the power off – move the wheel back-and-forth to create a slight scratch pattern. Adjust the rest until the scratch is in the centre of the thickness of the bevel.



Retract the blade on the rest until it no longer touches the wheel (you may wany to clampit here so that it does not move).

Place a block of wood on top of the blade and hollow grind that. This will give you a template to reproduce that angle.





Do another for 30 degrees (and any others you wish).









Regards from Perth


Derek

[Kees Heiden]

That's a smart idea Derek. I'm always guessing but would like a little more accuracy on this point, so I'll make one too.

[Chuck Hart]

Derek what do you use for a tool rest? Do you still use the one you designed with the CBN wheels. By the way how are they working out for you? I am curious how the flat wheels work for you. I am getting ready to buy a couple of wheels and you influenced my decision a lot.

[Dan T Jones]

Derek,
Thank you! That is exactly what I was trying to figure out in my mechanically challenged brain. I've marked a piece of wood with the outline and plan to band saw to the curve and then touch it up with the grinder.
Dan

[Stewie Simpson]

https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcTSuS5Uqh1zmlgM8AmUVeHrxRYjq0Jou BxbN81bOlhvKE9vKGJn

Question; if the grinders tool rest was set to 25*, using a digital protractor, would that result in a hollow ground primary angle of 25*

[Jim Ritter]

Not necessarily Stew. Only in one ideal spot in relation to the wheel.
Jim

[Stewie Simpson]

Thanks for the reply Jim; could you add some further detail.

I have just placed an order for 2 x 6 inch cbn grinding wheels; with the following tool rests. An accurate means of setting the tool rest to a given grinding angle is what I am currently searching for.

Stewie;

http://www.cwsonline.com.au/shop/item/tru-grind-sturdy-rest-base-left-hand
http://www.cwsonline.com.au/shop/item/tru-grind-sturdy-rest-base-right-hand

[Jim Ritter]

It's all in relation to the approach to the wheel. The rest may be set at 25° but if it is low say on center line of the wheel it will be too steep an angle. If you approach near the top of the wheel the angle will be way less than 25°. Only in one sweet spot will it be the desired angle. Does that make sense? Not sure I can draw something up and post it. If not I'll try again.
Jim

[Stewie Simpson]

Thanks Jim. That makes perfect sense.

[Don Dorn]

I use the Ian Kirby approach with my own modification. I made a short video of it on Amazon regarding a view to his book on sharpening. Here it is:
http://vid111.photobucket.com/albums/n124/djdorn/Grindingplaneironto25degrees_zpse6a3bd46.mp4

I made a couple of minor mistakes in speech but it's just a different method - to each their own.

[Stewie Simpson]

http://www3.telus.net/BrentBeach/Sharpen/grinder.html#grinderset

If you scroll down to Calculator - Hollow Grinding Angles ; there is a formula available; I have not trialled this method.

[Derek Cohen]

Derek what do you use for a tool rest? Do you still use the one you designed with the CBN wheels. By the way how are they working out for you? I am curious how the flat wheels work for you. I am getting ready to buy a couple of wheels and you influenced my decision a lot.

Hi Chuck

Another way to do this - which is my current method - is to use the Tormek angle setter (this only works if you do not have guards in the way). That makes sense for my set up since I have the Tormek BGM - 100 on my grinder., and all guards are removed (these are either aluminium or steel wheels and cannot shatter). Note that one side uses a flat plate/rest.

http://i13.photobucket.com/albums/a262/Derek50/Sharpening/f_182_big.jpg

My grinder set up ...

http://www.inthewoodshop.com/WoodworkTechniques/UltimateGrindingSharpeningSetUp_html_5c5d41f4.jpg

The flat wheels are perfect. I really recommend the use of CBN wheels. Maintenance is a thing of the past.

Regards from Perth

Derek

[Tom M King]

I use a couple of these on the 8" CBN wheel: http://www.amazon.com/Stuart-Batty-Angle-Gauge-One/dp/B0083SH7KC

They show a method to use them on other diameter wheels, but it looks to me like there is still some guess work involved. I like Derek's better anyway.