Tool Shapening

I have some 1/2 inch square hss and I am attempting to make my own tools from these with some sucess but when I look at the surfaces that I have ground they are not flat they are concave, the grinding wheel is 6 inches in diameter and they have followed the shape of the wheel of course. When I look at tools others have produced the faces seem flat, what am I doing wrong?

John.

John, you are being correct and using the edge of the wheel rather than the flat face!

They're probably correctly using a cup shaped wheel on a tool and cutter grinder, which has a flat working face OR incorrectly using the side of an ordinary wheel.

If I where to use the side of the wheel the surfaces I produce would be flat, but I am using the edge of the wheei as is recommended and as the wheel is of course circular that is why the faces I produce are concave following the convex shape of the grinder. I just wonder why others seem to produce nice flat surfaces on the tools they are grinding. A bigger wheel perhaps.

John

I have watched the proceedure on youtube and the grinders seem similar to mine, one done by Tubalcain.

John

John, the side of the wheel is not a forbidden zone! Do the rough grind as you are doing and then use the side of the wheel to give a flat surface. In 60 years no one has said, 'Do not do that' though its not good practice. They grind drills on the side of the wheel so why not a small lathe tool? Bear in mid that the wheel should be dressed occasionally, either with a diamond or a star wheel. No doubt someone will come along and have a bite at me for saying this.

Clive

Thaks Clive, I would really like to do this without using the side, on the youtube vids. they seem to get it right, one set the tool rest at 15 degrees and was able to do all the sides using ths setting and the finish looked ok, is the knack to set this angle with the the side of the rest at center height and the other side lower to get the 15 degrees, but again some people do not use the rest just do it freehand.

John

I fully agree and have use the sides of grinding wheels for well over 30 years and never had any problems.

The Britan four wheel grinding machine has 'L' shaped tool rests to allow both face and side face grinding.

I would use a diamond wheel dresser as soon as the surface dulls.

Incidentally the grinding wheels on that machine are only around 10mm wide when new.

I remember in the company workshop where the grinding wheels hadn't been dressed for decades and therefore didn't cut well even the best machinists would lean all their weight against a 1/4 in tool to shape it quickly. This kind of attitude applied to the side would not be good. The heat generated in the wheel can cause the contact area a bit inside the very edge to expand and break the rim as it has virtually no tensile strength.

Sensible use of the side is not a problem but with a big tool like yours it is probably best to do the bulk shaping in short sessions on the perifery until you are down to the final shape.

Clive

The only thing I would add is, not having a bite, that I would be very reluctant to dress the side of the grinding wheel with a star wheel. I think that it has the potential to weaken the wheel. I for one have used the side of the wheel but with caution partly due to the lack of the rest.

That said if the face of the wheel is squared up then all the critical edges of the tools can be ground straight/square and any curve from the wheel accommodated on the non critical faces. A quick lap with a honing stone to remove the grinding striations and away you go.

Cheers

Martin

Yes that is one of the reasons I would like to use the edge, I do have a Diamond dresser but not much use on the sides.

John

Sorry Martin we where posting at the same time.

Edited By JOHN BRIDGE 1 on 23/05/2014 22:30:48

I wonder, do those who do some of the grinding on the side of the wheel also dress it on the side?

Alan

I have been in tool rooms and machine-shops for 47years. I have always used the sides of grinding wheels to finish off tools and cutters and haven't broken one yet! It is quite ok to dress the side of the wheel. If you were to grind a shaft between centres and grind a flange face square, you would be using the side of the wheel, so I don't understand what the big fear is.

Be brave ! Roy.

Those diamond dressers on an small handle do a great job of wheel dressing.They are about 1-1/4 inches long about 5/16 or so wide. They are just great and last a long time.

I like using the White wheels for HSS, not sure what they are called to order them. The only issue with using the side of the wheel is being extra careful if there is no side rest support. As been said above, I would not use a star or rotating wheel dresser on the side of any grinding wheel.

Neil

The star wheel breaks up the grit and exposes new sharp edges whereas the diamond stick will give a much smoother surface as it cuts through the grit, sometimes this looks a bit glazed to me and the cutting rate is a bit less. I do not advocate a star wheel on the sides of a wheel ,but I am sure with inginuity an engineer will be able to run a diamond down the wheel side to take out any irregularities and make it flat. A collar on the stick and a clamped bar to run down and gently apply the stick is easy!

Dressing wheels seems to frighten people, I have to do this at work as no one else seems to think about it and just carry on pushing tools at the wheel harder and harder. The new surface seems to surprise them, perhaps a lack of knowledge or inexperience there. I have seen a crankshaft grinder wheel go off, it had just started and split in 2 and we only found one half, the other went through the asbestos roof and was never found. Mind you this was a big wheel about 18" dia.. I have never seen a small wheel go yet!

Clive

Make yourself a decent tool rest and you can grind a flat (well almost) surface on the corner of the wheel by sliding the tool across it at one or two degrees to the side of the wheel. Rough it out on the front of the wheel first.

Russell

John,

Why worry about the curve, who says it has to be flat anyway.

The critical bits are getting it the right angles which is where an adjustable tool rest comes into play and getting them sharp which is where the choice of wheel comes into play.

When you start off in this game the learning curve is quite steep, as with any new interest so don't try to read more into this than is necessary.

If you need to account for the curve, puff out your chest and inform the purists that it's hollow ground, a process they have been doing for years on Knives, scissors and slitting saws to get the best shape and cut.

Many even grind a chip breaker groove in the top that forces the chipping to curl up and breakoff and do away with the birds nest stringing.

Remember, right angles and sharp.

Doesn't hurt to have a small motor with a diamond wheel on for lapping. Someone, forget who put one on here only a few weeks ago made out of a central heating pump motor. That would be ideal.

Now some purist is going to tell me that you shouldn't use diamond on HSS as the carbon transfers to the wheel and blocks it. However with these cheap electro deposited ones that doesn't happen. I have been using one for about 7 years now on carbide, HSS, brass where there is a brazed joint, pencils and split finger nails and it's still OK. Put it like this, that £8 ? wheel has probably saved me £500 in tips and other cutters by giving me a second life.

Theory is great but practice rules every time, with lathe tools you need to grind one and try it, that's what gives you experience.

In another thread on chamfering someone posted they hadn't finished a tool and cutter grinder so they couldn't grind a tool to a given shape. What's wrong with freehand grinding ? You don't need a machine for everything.

If you have had to complete the UK abrasive wheel course, you would have been instructed never to use the side of a general purpose wheel designed to grind on the circumference. Unless the wheel was designed to grind on the side (IE. with a depressed mounting on the side/sides) or other manufacturers instructions. That was the training I was given which was the same as the training I was given by the RAF and later by the engineering college. Will I use the side of the wheel - no, but hey, it's your grinder and your choice and plenty do but it doesn't make it right.

Bear in mind though that a wheel coming apart is a sudden release of lots of sharp stone fragments right in front of your face and you are not going to have time to duck. At the very least make certain you always wear safety glasses even for the quickest of "touch up" jobs - in industry you get sacked for not doing so but many people will do just that if they are only doing a "quick" job because they have always done it and never had a problem....

Mark

The only disadvantage to teh "hollow ground" tool faces you get from using the wheel perimeter is that the resulting fine edge will wear quicker than flat-ground faces. The actual angle at the cutting edge is sharper, due to the curve.

I was taught as an apprentice toolmaker never to use the side of the wheel and never have done, much.

Yet I see the classic old model engineering books by the likes of Duplex and LH Sparey recommend using the side of the wheel, and in fact supply plans for sharpening jigs for both tool bits and drills that use the side of the wheel. And these were old timers who knew their stuff. Really knew their stuff. (Although workplace health and safety then was not quite as overbearing as it is now.)

So maybe the answer is as suggested already, compromise. Grind your tools on the perimeter of the wheel, then a light final touch up on the side to take the curve out in the area of the cutting edge. That's what I do -- but don't tell anyone. Specially my old foreman.

I've never had a issue with the curve and to some extent use it as the clearance angle, if the tool rest is set slightly above centre height on a 10mm square tool you will get a clearance angle of around 5 degrees on a 150mm wheel, less angle if the wheel is bigger.

 Wheels are not expensive so when they start to look a bit past their best before date change them. No good trying to get your moneys worth out of the wheel by letting it get too thin or to small in diameter.

Always ensure the tool rest has the minimal gap to the wheel, the number of times I have seen big gaps because people are too lazy to move it.....

Some do's and don'ts c/o Norton http://www.nortonconstructionproducts.com/uploadedFiles/Safety-BenchGrindingWheelDosDonts-Norton.pdf not the motorcycle people.

Edited By Bob Brown 1 on 24/05/2014 10:25:32