HSS tool steel temper

[Laurence Giglio]

I have two identical Sorby bowl gouges; one 2 months old and the original 5 years old. With lots of use and a learning curve on sharpening freehand for a year before getting the wolverine system, the original tools flute is now down to 2 inches. When I sharpen the old one using the traditional grind; butt end in the V-arm and roll the tool on the grinder, it seems that it is getting shorter faster. This long preface is to ask this question, are HSS tools tempered all the way down? Does the tool steel get softer as it gets shorter? I guess as the tool gets shorter, the V arm has less distance to maintain the same tip angle. When the new tool is sharpened, I can go about 5 or 6 touchups before moving the V rest, the old tool, its more like 2.

 

[Bill Boehme]

It sounds like you are removing a very large amount of metal with each sharpening. Most of my gouges are five to eight years old and are not much shorter than when I got them. Perhaps you are applying too much pressure when touching the tool to the grinding wheel. The tool should just barely contact the wheel with an almost feather-like touch. I probably only remove a few thousandths of an inch of steel with each sharpening.

 

[Laurence Giglio]

I may have early on taken off too much metal, changing tip angles, trying different side grinds etc, but where I am is where I am. OK, so my question remains, is the steel tempered all the way in the entire body, and what i am seeing is just my imagination?

 

[john lucas]

I have always wondered this. On older carbon steel tools they were not hardened all the way. My best friend grew up turning with those and he would reharden the tip when they got shorter.
HSS tools however I don't know. With todays hardening and tempering processes they could easily do either. Call Doug Thompson and ask him. He will tell you about his tools. I don't believe I've ever asked him.
I have one short Sorby gouge that still seems to hold an edge well and is almost down to the point the Wolverine jig won't work. I had a friend bring a gouge over where the flute was too short for the Wolverine. I put it in my mill and created a flat further down the shaft for him. It seemed to be hardened that far down based on the cutting action of my mill.
I'm with Bill, I remove so little metal from my tools nowdays that they last for many years and I sharpen a lot. You may be grinding too forcefully.

 

[dbonertz]

Laurence,

I have recently had this very thing happen with two gouges bought at the same time and manufacturer. I contacted the manufacturer but could not get a straight answer on your very question. I used to be able to rough out two to four bowls without sharpening them when all of a sudden I could not get through one blank. Almost like I hit a soft spot in the gouge or as you say not tempered. It is a shame since I have about five inches of flute still on the gouges. The manufacturer was great and sent me two new gouges but it still makes me wonder (I am a curious sort).

Dale

 

[Dale Bright]

I seem to remember a Sorby rep telling me that their tools were hardened / tempered the full length. He even showed me a dimple from the Rockwell Hardnest Test and if my memory is correct, it was way down the shaft from the flute.

Dale

 

[Laurence Giglio]

Thanks for the feedback. I knoiw that I used quite a bit of tip when I first got the wolverine jig and tried a fingernail grind, floundered with that then brought it back to a standard grind putting down the vari-jig and just using the V arm. When I sharpen now I use little pressure, but it seems that when I check the angle after a few touch-ups, I need to move the arm in a skosh (more than a smidge, less than a tad).

Generally i use a 50 degree angle but when doing deeper bowls will increase that to 55 degrees.

 

[Charlie Knighton]

Larrence, are you using the same gauge with the 50 degree and the 55 degree angles, or are you useing two different gauges , one with 50 degree and the other 55 degrees?

 

[KellyDunn]

This is what Ihave been told. Take a file and if it skips over the metal its hardened. If it digs in that part is not. I think Doug Thompson told me he tempered the full lenght. I also have heard some do not towards the back of the shaft as untempered is not as brittle and can take more abuse. I have a couple short Hamlets that now wont hold and edge for squat. Need to try the file thing.

 

[Bill Boehme]

Let's not confuse tempering with hardening. Tempering is removing hardness after the steel has been quench hardened and is brittle. A file will definitely skip over metal that has been hardened and it also would be difficult to only harden part of the tool because of the very high temperature needed to heat HSS before hardening it. Since we would not want a tool to have a brittle shank in which only the flute portion was tempered to make it tougher, more ductile, and less brittle, I would guess that the entire tool is tempered to bring the tool to the desired hardness (typically around HRc 63 for turning tools I believe). After tempering, a good sharp file will bite into the steel.

 

[Bill Blasic]

I'm with Kelly on this one as I believe that a properly hardened M2 and up should not be affected by a file. There was a problem awhile back with the Benjamin's Best tools and the way to know if you had a bad tool was the file test. If a manufacturer used an induction process to harden tools it could be possible that the entire flute might not be hardened but I have no knowledge of the hardening process of any manufacturer except Thompson Tools in which the process is completed on the entire tool.
Bill

 

[Laurence Giglio]

Larrence, are you using the same gauge with the 50 degree and the 55 degree angles, or are you useing two different gauges , one with 50 degree and the other 55 degrees?

When i first got the wolverine, I only had the one gouge, so i tried a 60, a 45, then a 55, then a 50. Yes, I know that I ground some steel trying to figure out what worked. Thats why i got the second gouge. So now the new one is set at 60 and the older to 50. But as I said, it seems that as I am nearing the end of the flute, the steel seems to grind off faster.

 

[Dale Miner]

Laurence,

Just a thought here.

When using the V pocket to hold the end of the handle and put a conventional grind on the gouge, as the overall length of the gouge gets shorter, the amount of metal that needs to be removed to make a significant change to the bevel angle becomes less and less.

Consider if the gouge and handle were 6 foot long. The point of contact on the grinding wheel determines the bevel angle. If .010" were ground off the tip, the amount that the tool would drop down lower on the wheel would be insignificant, and make only a very little change in the bevel angle. If the overal lenght of the gouge and handle was much shorter, say 6 inches, then the .010" removed would cause the gouge to drop down quite a bit, and make a noticable change to the bevel angle. It could be that what you are noticing is more a function of geometry than steel hardness.

If you have the Wolverine system, and are using the V arm to put a conventional grind on your gouge, try learning to use the platform side of the system, and just roll the gouge on the platform. That way the bevel angle will be determined by the angle the platform is set at, and not dependent on the overall length of the tool.

As to the hardness being from end to end or just most of the flute, I think that varies by manufacturer.

 

[john lucas]

Dale I'm confused. I extend my gouge out of my Wolverine jig 1 3/4". The length of the tool or handle or both don't make any difference other than maybe the excess weight causing problems. Maybe I read your answer wrong since I know you know what your doing.

 

[Dale Miner]

Dale I'm confused. I extend my gouge out of my Wolverine jig 1 3/4". The length of the tool or handle or both don't make any difference other than maybe the excess weight causing problems. Maybe I read your answer wrong since I know you know what your doing.

John,

The OP has stated that he has stopped using the Varigrind, and now just puts the butt end of the handle in the V pocket and uses a traditional grind. My comments about the geometery of the process apply to that procedure. The total length of the gouge then becomes the hypotenuse of the triangle, and if the handle and gouge are very long, the slight change in the overall length makes almost no difference where the bevel makes contact with the wheel. If the combined length is short, then a slight change in the overall length makes the gouge drop down lower on the wheel much faster. Taking into account the curvature of the wheel in addition to the lower contact point, the bevel angle becomes more blunt very quickly.

You are correct in that the use of the Varigrind or other type jig with a constant stick out would not be affected by the overall length of the gouge and handle. Wear on the wheel without moving the V pocket closer to the wheel will cause the bevel angle to become more blunt with the Varigrind or other type jig because as the distance between V pocket and wheel becomes larger, the handle of the gouge needs to be raised to bring the bevel in contact with the wheel. This causes the tip of the gouge to contact the wheel at a lower spot on the wheel resulting in a more blunt bevel angle.

I forgot to put the following in my first reply, so will add it here.

If people are putting the butt end of the gouge in the V pocket and rolling the gouge, make SURE (VERY SURE) that the arm of the V pocket is VERY tight in the base. If the V pocket arm slips away from the grinder, the gouge will drop on the wheel and all hell will break loose. The gouge will 'catch' on the grinding wheel and the combined momentum of both grinding wheels will force the gouge downward and into the grinding wheel. A wheel explosion can result. This is especially true for gouges with a more blunt grind. I have seen someone do this with a roughing gouge. It took a large chunk out of the wheel, and luckily the wheel did not explode. It did however bend the shaft of the grinder enough that it is noticeable (.020"). The reason that it is more critical with a more blunt grind is that the downward force on the gouge from grinding has a much greater mechanical advantage in forcing the V arm away from the grinder.

It is much safer and in my opinion better to roll the gouge on the platform for traditional grinds and for roughing gouges than to put the butt end of the handle in the V pocket. In my opinion, the only thing that the V pocket should be used for it the Varigrind, everything else should be sharpend either on the platform or freehand. I would never attempt to sharpen a bowl bottom blunt grind gouge with the V pocket method. To my way of thinking, that is inviting disaster.

 

[john lucas]

Dale I thought that might be the case. I also think when you use the V jig it's very easy to put too much pressure on the tool which of course removes too much metal.
When using the Vari grind jig I have some wooden jigs that set the V arm to the wheel for each tool. This way no matter how much the wheel wears down the angle on the gouge stays the same all the time. This lets me remove the least amount of metal and makes a very repeatable angle.
I will second the warning on letting the tool get too low on the wheel when grinding. This is especially dangerous with spindle roughing gouges if you grind them really blunt. ONce you get the tool edge too close to the center line of the wheel it can be pulled into the wheel and can cause a wheel explosion. Very very dangerous.

 

[Bill Boehme]

Dale I'm confused....

Initially, I was too, but after a couple reads, I figured out what he meant. It was the first sentence that threw me off because there is more than one way to interpret it. Once I got past that sticking point, I saw that what he was wanting to say to the OP had to do with the reason that he needs to adjust the Wolverine arm more frequently as the tool gets shorter. However, assuming that we are always keeping the bevel angle the same, I don't see the mentioned danger of going below center and jamming the tool when using real world examples (six inch tool and steep bevel angle, yes -- twenty-two inch tool length and 50° bevel angle, no).

I understand the reason for the exaggerated examples to make things more intuitive without dragging math into the fray, but I am just curious how observable this might be in a real world situation. I might do a CAD analysis to satisfy my own curiosity. The human part of observability is that the change in length takes place over several years -- I don't know about others, but my memory isn't good enough to retain that sort of stuff.

 

[hockenbery]

John,
It is much safer and in my opinion better to roll the gouge on the platform for traditional grinds and for roughing gouges than to put the butt end of the handle in the V pocket. In my opinion, the only thing that the V pocket should be used for it the Varigrind, everything else should be sharpend either on the platform or freehand. I would never attempt to sharpen a bowl bottom blunt grind gouge with the V pocket method. To my way of thinking, that is inviting disaster.

I would second this
Any steep angle 70-80 degrees should be sharpened on the platform.

Using Pocket alone or with the Veri- grind both run the risk of pulling the gouge and attached body parts into the wheel should anything slip.
I saw a severe hand injury when the gouge was pulled down over the wheel.

Keep the arms tight!

With 30-60 degree angle the gouge is on top of the wheel. Less likely to move a not so tight arm and if it does you have time to pull away.

Turn safe,
Al

 

[Bill Boehme]

I would second this
Any steep angle 70-80 degrees should be sharpened on the platform.

Using Pocket alone or with the Veri- grind both run the risk of pulling the gouge and attached body parts into the wheel should anything slip.
I saw a severe hand injury when the gouge was pulled down over the wheel.

Keep the arms tight!

With 30-60 degree angle the gouge is on top of the wheel. Less likely to move a not so tight arm and if it does you have time to pull away.

Turn safe,
Al

I had a safety thought -- how about a stop that prevents the tool from dropping below a certain distance. This is sort of tongue-in-cheek because we shouldn't be allowing such a situation in the first place where a tool gets jammed and besides such a stop already exists -- it is the built-in tool rest that comes with every store-bought grinder. I've noticed that a few people have removed these rests where they wind up relegated to the same fate as the safety cage on a Powermatic lathe. Leaving the rest on the grinder is at least worth thinking about.

I assume that most of us would never get in a situation where we would even come close to sharpening the tool on the hairy edge of going "down under" -- just the thought give me the willies. But, it is not too much of a stretch to imagine that even the most safety conscious among us might someday accidentally poke the tip of a tool into a grinding wheel while the Wolverine arm is not sufficiently locked down. Things can go south in a big hurry and some folks might be able to continue a normal life without a head, but it would, at the very least, complicate eating.

I hope that the person who experienced the bent motor shaft, broken grinding wheel, and bent SRG appreciates how fortunate he is that only tools and machinery were trashed.