Kanna chipbreaker question

**fissionchips** · 28th April 2013, 08:12 AM

I have become a big kanna enthusiast of late, and I've written about some of my experiences here. Every time I pick up a kanna I learn something new about the tool and its uses. Pictured below is my primary 58mm smoothing kanna, a real workhorse of a tool. While working with some figured wood last year I wanted to improve the kanna's performance and reduce tear out, so I installed a kuchi-ire (key insert) made of ipe. The insert gave the plane a great boost, and I've used it extensively since with just the main blade installed.

IMG_8086b2.jpg IMG_8089b2.jpg kanna anatomy 1b.jpg

I'd like to start using the chipbreaker as well, but the new insert poses two challenges that have prevented me from taking the plunge. The first is that I have trouble viewing the leading edge of the chipbreaker to set the height correctly, and the second is that the chipbreaker narrows the opening and causes ships to accumulate.

The mouth opening is ~0.5mm, and the koppa-gaeshi (see diagram from Chris Hall above) is cut at 115deg, 5mm tall. I'm looking for any tips or modifications that might help me use the chipbreaker as intended. It's been quiet lately on this forum, I'm hoping that there are still some regular visitors passing through.

**Sheets** · 29th April 2013, 04:30 AM

I think the best thing to do is make the koppa-gaeshi closer to 90 deg (so just remove material from the part that goes past vertical, so you don't increase the mouth opening). This should (hopefully) make enough room between the chip-breaker bevel and the koppa-gaeshi to allow shavings to pass without getting jammed. It will also allow in more light to make the edge of the chip-breaker visible when you adjust it.

Otherwise, as there's only so much room, you'd be forced to widen the mouth, which wouldn't be desirable in a finish kanna.

Until a regular visitor passes through,
Steve (who can't keep quiet for ever - until I , you know, expire)

**Gadge** · 29th April 2013, 09:22 AM

Hi Fissionchips,

I've modified quite a few kanna with kuchi-ire and have not had any problems.
I agree with Sheets. Just change the angle of the koppa-gaesh until you get enough clearance to allow the shavings to pass. On my kanna I can still see the bottom edge of the chip breaker. I can't remember the exact angles so will take a look at one this evening and give you feedback if there's anything interesting to report.

Regards,
Gadge

**fissionchips** · 29th April 2013, 11:13 AM

Thanks for the feedback Gadge & Steve, it sounds reasonable to take material away from that area of the mouth as it doesn't serve any particular function that I know of.

**Gadge** · 29th April 2013, 11:44 AM

The lower the angel of the koppa-gaeshi, the less the mouth will open as the sole is worn away.

Regards,
Gadge

**Gadge** · 29th April 2013, 11:49 AM

Sorry, that should have been "angle" of the koppa-gaeshi.
My company has a product called Angel, so I must be used to typing it.

Regards,
Gadge

**fissionchips** · 13th May 2013, 04:24 AM

Thanks Gadge, I can visualize the trade off now. With the added durability of the insert I'm not worried about the sole wearing away too quickly, and even as it does the insert can be knocked down to close the mouth back up.

With confidence I made another insert, this time from ebony for a 74mm 'Moto'. The opening angle on this insert is more like 95deg.
IMG_8095b.jpg

**Gadge** · 13th May 2013, 09:28 AM

Hi Fissionchips,

Looks perfect. I'd like to see a photo of the sole though.

Regards,
Gadge

**fissionchips** · 13th May 2013, 10:05 AM

Sure thing:
IMG_8120b.jpg
The insert covers 4mm of the landing at the mouth.

**Gadge** · 13th May 2013, 12:12 PM

It looks good. Should work very well.
Nice looking blade!

Regards,
Gadge

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