My bench grinding disaster - please help?

[fobos8]

Hi all

I recently bought some kit to do some bench grinding. A cheap grinder, Veritas tool rest and straight jig, and a Norton 3x stone.

The reason I bought the stuff was to get rid of nicks out of the ends of my chisels. The plan was to then hone a secondary bevel on my DMT diamond stones.

The results I got from the grinding were dissapointing to say the least!!

The biggest problem I got was that the newly ground bevel is not straight. It has a slight arc in it. I am not talking about the hollow grind. If the chisel is placed flat on a table with back facing up and a try square is butted up against the side you can see that the middle of the cutting edge sticks out more than the sides.

Has anyone got any idea why this is happening? Its a problem for me to use chisels like this as the cutting depth will not be uniform.

Thanks in advance, Fobos

 

[wizer]

you need a Diamond truing tool and/or a better quality wheel such as Norton 3x

 

[Mr Ed]

you need a Diamond truing tool and/or a better quality wheel such as Norton 3x

He's got a Norton 3x

Cheerrs, Ed

 

[fobos8]

I also trued the wheel with a diamond stick

 

[DaveL]

Hi Fobos,

It sounds to me like you could be swinging the chisel across the wheel, in an arc, you need to move in from side to side in a straight line.

 

[fobos8]

thanks Dave

Thats what it would seem to me aswel. Thing is I was using the Veritas jig which is supposed to help you move from side to side in a straight manner??

I dunno what the problem could be.

 

[CHJ]

Is there any play between the guide and the slot, allowing the chisel to pivot slightly as you push from oposite sides to change direction?

 

[DaveL]

So looking at this picture

So you have both bits shown?
Have you mounted the grinder and the jig on a solid base board, eg 1/2" ply or MDF, thicker is better, there must be no slop on any of the fixings and does the guide slide smoothly on the rest? I don't have this jig but I would wax the slot and the bottom on the guide to help with a smooth movement.

How big is the curve on the chisel?

 

[Aled Dafis]

I think that I know what your problem might be.

Firstly have you dressed your wheel to be dead flat? I dress my wheels with a slight camber, so that the centre of the wheel is slightly proud of the edges, i'd say about a milimeter proud is more than enough. This crowned face greatly reduces the chance of catching the edge of your chisels on the stone, and risking burning the edges.

Also, your techinque may add to your problem, I always make sure that the chisel/iron is moved clear of the wheel at the end of every stroke (left/right). If you stop the iron to change direction while it is still in contact with the wheel, the blade is in contact with the wheel for more time at its extremities, than at the middle, and thus more metal is ground away, resulting in a cambered blade.

I hope that helps, if not, feel free to ask more questions.

Cheers

Aled

 

[fobos8]

Hi all

Didn't expect so many replies so quick but judging by whats on TV tonight I'm not surprised!!

The Veritas jig and the grinder are both solidly bolted down to a scrap piece of kitchen worktop (>30mm). I did notice that there is play in the Veritas setup. The square jig slides in a groove in the tool rest. The groove in the tool rest is about 2mm wider than bit which slides in it. This would account for the arcing as the chisel is moved side to side.

When I was moving the chisel from side to side I was moving it clear of the wheel before changing direction.

Any other ideas?

 

[CHJ]

... The square jig slides in a groove in the tool rest. The groove in the tool rest is about 2mm wider than bit which slides in it. This would account for the arcing as the chisel is moved side to side....Any other ideas?

As I suspected, I would suggest you dress the chisels from one side only passing completely passed the wheel.
Keep the pressure the same each time so that you keep the guide pressed to the same side of the slot.

 

[Chems]

Stop wasting money and get a tormek!

But seriously, I was faced with this choice, buy the same bits of kit you have or a tormek. So I shelled out the considerable £224 and got a tormek and its fantastic!

 

[fobos8]

I have tried doing that aswell - just passing in one direction.

 

[Harbo]

I use a small engineer's square and mark a thin straight line near to the edge with a fine perm. marker pen.
I then work to that - it also ensures your grinding at right angles.

Rod

 

[Derek Cohen (Perth Oz)]

Grinding takes practice. You have just begun. Rod has just given you good advice.

Remember, even with the excellent 3X wheel, you want minimum presssure on the edge of the blade. Just tickle the wheel.

Regards from Perth

Derek

 

[gidon]

I'd recommend honing your secondary bevel on your best grinding attempt and not worrying too much about it. Your secondary bevel may be bigger than it needs to be but the next time you grind use this secondary bevel to gauge your grind. Grind keeping the secondary bevel as even as you can across the bevel as you grind - keep checking. Stop grinding when you have roughly a 1/2 mm of secondary bevel left - even in width across as you can. This method also makes sure you don't burn the tip.
Cheers
Gidon

 

[fobos8]

Hi all

I really appreciate all the time you're taking to give me advice. I keep going back and trying again bearing in mind the advice given but to be honest I find the whole thing pretty scary.

My reasoning for using the dry grinder method was to grind out nicks. I know I'm a novice and you guys are gonna hate this but I was looking for a method which I can learn quickly. I don't have a great deal of time to practice. I'm flat out in daytime and have a young family to "entertain" in evening. I've recently got busy doing site secondary fix refurb work and so my chisels are getting more knackered up.

I am finding that if I make a slight error when grinding that my chisels are ending up in a worse state than before! The reason I got the Veritas jig is because its supposed to be easy to get good straight results but I find there is too much play in it for this to happen.

If this is the best way to grind out nicks or is there another easier to learn method. Gidon has mentioned in a previous posting that he sometimes uses the DMT xtra xtra course diamond so I've been thinking about this. Also dare I mention it is the Tormek system any easier??

Thanks again, Fobos

 

[Mr Ed]

Stop wasting money and get a tormek!

But seriously, I was faced with this choice, buy the same bits of kit you have or a tormek. So I shelled out the considerable £224 and got a tormek and its fantastic!

I have a Tormek and personally find getting a perfectly square edge on this is not foolproof. It still requires careful technique to get the result you want. Theres play in the Tormek fixtures just the same as other brands, so they are not the panacea to all sharpening issues that they are sometimes vaunted to be.

Now I've got the Tormek I'll stick with it, but if I was buying again I'm not sure I'd go the same route.

Cheers, Ed

 

[woodbloke]

Have to agree with Ed about the Tormek...there's a knack to using it to get a square edge as you need to press down or raise one end of the jig when it's on the bar as it moves across the stone. A tiny 50mm square as well is also useful to check that the blade is being ground square. Don't take it for granted that you can lob a blade in the appropriate jig and it'll come at square...it won't. Once the initial learning curve had been achieved they're great bits of kit, I wouldn't be without mine - Rob

 

[Dave S]

That's interesting, because I have the much cheaper Sheppach 'copy' of the Tormek and also find it tricky getting a square edge. I assumed that if I'd paid the extra to get the 'proper' version, I would have less difficulty.

The fixture does bend in use but also, to get a square edge, the guide needs to be parallel to the shaft, and the wheel has to be true. Getting the guide parallel to the shaft is the tricky part, I find, given the flex in the guide and the shaft being so short.

I've thought about dispensing the with the guide and using a conventional one - in effect just using the Sheppach as I would a dry grinder. Not tried it yet, though.

Dave