Thread: Setting accurate bevel angles on grinder...help please

Hi Anthony,

I have an aluminium angle fitted to my grinder tool rest to act as a fence for a simple wooden jig that sandwiches the blade (two pieces of wood held together by t-nuts and screws. Initially I think I fitted a blade with a known angle and set the position of the jig on the blade so the hollow grind sat nicely on the wheel. That setback was noted by holding the jig against a board and marking the position of the edge with a line on the board. Might have been a bit of fine tuning back and forward to get the exact angle correct. Different angle settings can be recorded in the same way. It is indepedent of blade thickness. Hope this makes sense!

There's a piccie of my simple setup here:
http://woodworkforums.ubeaut.com.au/...ad.php?t=31492

Cheers
Michael

Anthony

Try this ..

http://www.inthewoodshop.com/Woodwor...ryGrinder.html

Regards from Perth

Derek

Michael, Derek,

Thank you both for the responses, they will do the trick nicely.

Anthony

I think that it is also worth keeping in mind that accurate angles are not important, what is important is "repeatable" angles. It doesn't matter wether it is 24, 25 or26degrees, so long as it is the same each and every time.

Denn

Originally Posted by derekcohen

Anthony

Try this ..

http://www.inthewoodshop.com/Woodwor...ryGrinder.html

Regards from Perth

Derek

Nice jig.
Rather than have the whole inside surface of the arc fully in contact with the wheel, if there were only two contact points, one at the beginning of the arc and the other at the end, then there may not need to remake the jig should the wheel wear, providing one of the contact points is adjustable for jig angle relative to the wheel.

Zelk

Denn,

I agree with you about repeatability, and that is the problem with setting the bevel angle for me....one time it is 25 degrees, next 28-30.

I will have a go at Derek's suggestion, quick, simple and should be repeatable.

Thanks everybody.

Anthony

All,

I still need some help. I made the jig as described by Derek, as follows:
1) I cut a scrap of mdf parralell and square to the ends;
2) I then cut one corner off at 25 degrees;
3) I scribed, very accurately, the wheel dimension;
4) I filed away the MDF until it was almost to the line;
5) I made the MDF match the profile of the wheel by giving it a run against the wheel for 30 seconds or so.

I then set the jig against the blade and then against the grinder rest and ground the old blade I have for practice. The resultant blade angle was 43-45 degrees......much different from that on my setting jig.

I thought I must have made a mistake, so made a new one, no change. I then went back to Derek's web site and noticed on his picture the protractor was set at 15 degrees not 25. Is this where I am going wrong??

Any help gratefully accepted.

Regards,

Anthony

Anthony

You are right! I need new specs.

OK, here is another and foolproof method ..

Do the same as in the tutorial, but instead of measuring off the angle to grind, 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.

Now replace the blade with a blank template - the wood - and hollow grind that. This will give you a template to reproduce that angle. Do another for 30 degrees.

Remember to use it on top of the blade you plan to hollow grind.

In the meantime I will check the angles on my templates while wearing my glasses!

Regards from Perth

Derek

Originally Posted by Wooden Luddite

All,


I thought I must have made a mistake, so made a new one, no change. I then went back to Derek's web site and noticed on his picture the protractor was set at 15 degrees not 25. Is this where I am going wrong??

Any help gratefully accepted.

Regards,

Anthony

I actually noticed the same and thought it was some mistake. However, looking at the geometry, I realised that the protractor had to be at 15 deg to get the resultant 25 deg or there abouts. So it may not be an issue of Derek requiring his Rx after all.

Zelk

Thanks again for your responses Zelk and Derek. I will have another go. I am committed to this idea, in the long run it will create far more repeatable bevels in quick time too.

Happy Christmas,

Anthony

I think that where you're going wrong with Derek's jig is that you're measuring the angle for the thickness of the jig, not for the thickness of the blade you're sharpening.

ie. you're not taking the hollow grind into account. We all know that a thin blade will always end up at a steeper angle than a thick blade for the same setting of the table.

If the table on your grinder has a quick release, I'd be inclined to offer up the blade to the grinder so that the heel of the bevel rubs first, then slowly decrease the angle until the moment you see the sparks coming off the cutting edge. (Which is how most of us turners freehand their chisels. )

Once that's done, lock the table at that position. To make it easily & quickly reproducable, place a strip of MDF or ply on the table so that it runs past the side of the wheel and scribe the wheel outline. Then you can cut it away and end up with Derk's jig but one that you know is at the right angle for the blade you used to set the table.

It'd probably be best to repeat this, making a seperate jig for each blade of significantly different thickness...

(Of course, Derek's jig would lose accuracy as the wheel wears, but I guess you could also make different sets of jigs for the different wheel diameters if you want to be anal about accuracy... )

With an adjustable support, has anybody tried just grinding a test piece ie a piece of timber the same thickness as the blade, until the desired angle is reached?
Zelk

^^^
That's pretty much what I do. Get a chisel of similar length and thickness, and use that to set the grind rest. Check the results with a bevel guage.

Guys,

I actually have the (completely useless) Triton wet grinder. The only thing I liked about that system was setting the blade angle using the angle jig.

The problem with the bench grinder is that the Triton bevel jig does not fit against the wheel because the guard is in the way. What I decided to do was cut a small slot into the guard so that the jig now sits on top of the wheel and I set the grind angle from that, as you do with the Triton / Tormek wheels.

The guard is still in place, just has a slot cut out of it......easy, accurate and safe.

Thanks for your interest.

Anthony