Help - Chisel Tip Fail

[RedpentacleB]

Hello, new Tormek user. I'm using a new T8 with SG-250 and SE-77. I sharpened a chisel for a friend. First I flattened and honed the back, then sharpened it following the original 25 degree bevel. The chisel was hair-popping sharp. My friend said he was chiseling out a hinge on a pine door and this happened - see attached picture.

The chisel is a Marples 1", stamped Chrome Vanadium.

Does the slight hollow grind of the Tormek weaken the edge?
Should I use a 30 degree bevel?
What did I do wrong? Ideas?

Thanks in advance,
Red

[Ken S]

Welcome to the forum, Red. Your poor chisel resembles some of mine......

Noted woodworking expert, Ernie Conover, suggested adding three degrees to the bevel angle to compensate for the hollow produced by the 250mm Tormek wheel.

On a whim in my home shop, I reground an old butt chisel to a thirty degree bevel. After I had ground about half the bevel, I realized that only a micro bevel was necessary. Based on my unscientific anecdotal usage, the thirty degree bevel seems to hold up better. I had ground off more chisel length than necessary.

With that in mind, I would suggest you reset your chisel to thirty degrees and grind off the chipped area. Stop when you reach clean metal. Consider yourself part of the test group.

"Fortune favors the brave."

Good luck, and keep us posted.

Ken

[Elden]

I wonder what the tree that board came from ate?

[Ken S]

Elden,

Haven't you ever heard of petrified pine?   

I knew an elderly carpenter who had worked in Florida during "the boom" (1920s). He jokingly told me that he could install a white pine door in fifteen minutes, and a yellow pine door in that many days.

Cliff,

Using a chisel with a mallet is hard on the edge. A chisel used with only hand pressure will work well with a very acute angle, especially in soft wood. Being struck by a mallet requires a stronger edge. Heavy mortise chisels generally require at least 35°. Try 30°, and be sure to post the results either way.

Ken

[RedpentacleB]

I put a 30 degree on it and will report back the results.
Thanks for the support guys (girls?)
-Red

[RichColvin]

Red,

I also wonder if the chisel was previously sharpened on a high speed grinder and the temper of the metal was lost.

Rich

[Elden]

   True Ken, yellow pine is much more tough. I like to keep old bed slats because they are much better boards than what is generally available now, possibly because they were first growth lumber?
   The mallet question passed through my thoughts as well. That is kind of like pounding your best hunting knife through the sternum of is beef with a hammer when butchering. Knots in the wood would provide more of a challenge, also.
   You raise a good point, Rich.

[Ken S]

Good thought, Rich. That flew under my radar. It would be a good explanation. Let's check with Red and get some history of the chisel. I still like the idea of a 30° Tormek bevel, just grinding back to good metal.

Ken

[Ken S]

Elden,

My fondness for Leonard Lee's Sharpening book and DVD has been posted numerous times. In addition to his solid and practical advice, I really enjoy his sense of humor. He mentioned having "a great gathering" of chisels for rough work, The example he gives is giving a chisel a quick touch up with his belt grinder and heading off to fix the garden gate.

Red,

If you do not have Leonard Lee's book in your personal library, you really should. I enjoy the accompanying DVD, too.

Ken

[RichColvin]

I too recommend The Complete Guide to Sharpening by Leonard Lee.  I have a paper copy, & a Kindle ePub one also.

The other good books (listed alphabetically) are :

• Japanese Woodworking Tools : Their Tradition, Spirit, and Use, by Toshio Odate
• The Perfect Edge : The Ultimate Guide to Sharpening for Wood Workers, by Ron Hock
• Sharpening Made Easy: A Primer on Sharpening Knives and Other Edged Tools, by Steve Bottorff

[RichColvin]

Red,

Last thought :  I'd stay with a 25º primary bevel and a 30º secondary bevel.  30º is pretty high, specially for a chisel which is 1 inch wide. 

Unless the wood is very hard or a mallet is being rigorously used, 25º should be good.

Rich

[Ken S]

Rich,

You have three more excellent choices. All three are part of my reference library.

Red,

Rich and I are essentially saying the same thing. Once the micro (secondary) bevel bevomes large, I leave it up to your judgement to decide between regrinding it 25 or 30°. Either will  work. The 25-30° combination makes less resharpening work with bench stones. Either works well with the Tormek.

Ken

[RedpentacleB]

Just following up. Thanks to everyone for the help.

My friend (now customer) is happy with the 30 degree on the Marples chisels. I will be redoing the set, but only as a micro-bevel. They were basically slightly used and never sharpened, so maybe just a lower quality steel (?). Its interesting that the factory bevel was 25 degrees and they seemed okay. I guess the Tormek hollow grind at 25 was enough to weaken the edge.

I will get the Leonard Lee book and DVD. The only sharpening book I ever read was by John Juranitch. To tell you the truth, I purchased the Tormek T8 because I was tired of having dull knives and dull chisels and a dull hatchet, and it took a long time to sharpen by hand and my ability to get the same precise angle wasn't very good. Reviews for the knock-off sharpeners were pretty bad. I had a 25% off coupon from Zoro, so I told myself if I get the best I won't have anything to complain about and I ordered the T8 Hand Tool Bundle. I found I enjoy sharpening with the T8 and I'm thinking it will make a nice retirement business to bring in some extra cash.

Thanks again,
-Red

[Jan]

Red, if we exclude that the wood was extremely hard and also that the malleting was extremely strong, than I am wondering about chisel tip hardness.

Previous high speed sharpening could heated up the chisel tip so intensively that it lost its tempering** and now it is not hard and strong enough to withstand the malleting.

Jan

**P.S.: Colour changes at the tip are witnesses that the tip was overheated during grinding/sharpening. The reason for the colour changes are iron and chromium oxides which form on the tip. The daylight interferes in this layer and its colour tells us about oxide layer thickness and temperature exposure. 

[Ken S]

I remember a piece of working advice from my dry grinding days (pre 2009). If a tool gets overheated and changes color, just finish sharpening it and use it. It will work, however, it will not retain its sharpness as long. Eventually you will grind/sharpen through the weakened steel and get back to well tempered steel.

I had a set of Marples Blue Chip chisels for many years. I liked them; they were good chisels. They were not premium quality tools. Priced at $20 US for a set of four, they were very popular. (Lie-Nielsen premium chisels cost $55 each; Japanese chisels were even higher.) Sadly the fine old firm of Joseph Marples was sold. The products were rebranded and production was moved from Sheffield to overseas.

Sharp and thirty degrees can make up for much of less than premium steel. I suggested grinding only enough to clear the damaged tip to conserve steel. For future sharpenings, I would use just the thirty degree setting. In my opinion, for bench chisels, micro or secondary bevels are bench stone thinking. When sharpening by hand, they are expedient. They serve no purpose with the Tormek.

I also think that hollow grinding is another left over idea from small diameter dry grinders (six inches or less). In theory, the larger diameter Tormek wheels leave a hollow grind, which I find more theoretical than problematic. I would just use thirty degrees and keep the chisels sharp.

The newly introduced diamond wheels have grit on the side of the wheels for flat grinding. I will be curious to see (after the new product hype wears off) how many tools will be reground flat and how many will remain "hollow ground".

Ken

I know a couple very capable professional carpenters whose method of sharpening chisels is buying new ones at the local big box hardware store.