Surgical chisel turned kerfing chisel. Love it!

[Malcolm Schweizer]

297586297587297588I have used card scrapers to finish the kerf on half-blind dovetails; then I saw Derek Cohen's shop-made kerfing chisel and loved the idea. I had seen surgical chisels before (used for chiseling bones- ouch) and remembered they are rather thin, so I figured that was a good start. I went on eBay and bought a really good one 1.25" wide, with a hefty handle cast as part of the chisel. It is HEAVY! It's also thin as I had hoped, and stainless too!

I used a WorkSharp 2000 with 80 grit to get it to proper thickness. I am posting a bit soon, as it still needs finish sanding, but it worked beautiful. I took it down to 1/32" and stopped there to try it out. I hammered it into some end-grain pine and it made a perfect kerf. Heck, who needs a saw? You can almost just hammer the whole thing with this. (I kid- probably not a good idea.) Final sanding will thin it a bit more.

I still need to grind a bit off the business end to ensure it is flat. I will dress the face to 2000 grit or so as well; perhaps polish it. The pics with hardwood floors as backdrop are the before. The pic with maple table as background are after. The pic of the kerf is where I just hammered it into some wood, sans saw kerf, and it made a perfect kerf.

Regards from a dimly lit room that smells of metal shavings,

[Derek Cohen]

Brilliant Malcolm.

Just a word of caution - I always place a clamp across the tail board when hammering in the kerf chisel. This guards against splitting in some woods. Also I do not hammer in the full width of the kerf, but take it about 1/4" at a time.

Regards from Perth

Derek

[Malcolm Schweizer]

Thanks Derek,
I saw your tutorial and will keep in mind to clamp the wood. I owe you for the suggestion in the tutorial to make the business end flat. I would otherwise have sharpened it to a point, but you are right that it is better to be flat so it doesn't wedge.
Cheers,
Malcolm

[Sean Hughto]

The purpose of this is to provide a guide for starting/placement of your rip saw on pins and tenons?

[Jim Koepke]

The purpose of this is to provide a guide for starting/placement of your rip saw on pins and tenons?

My recollection is Derek posted about using a similar tool for making kerfs on half blind dovetails instead of a saw.

His kerf chisel is in the third post of this thread:

http://www.sawmillcreek.org/showthread.php?173762-Half-blinds-revisited

jtk

[george wilson]

I do not know about ALL surgical chisels,but I bought one that was quite soft. The doctor said they like them soft so they will heave a ragged cut on bone,which promotes healing better than a smooth cut.

[Sean Hughto]

Oh, thanks. I would be pretty much certain to split the board - I'll stick with chopping and carving.

[David Weaver]

I do not know about ALL surgical chisels,but I bought one that was quite soft. The doctor said they like them soft so they will heave a ragged cut on bone,which promotes healing better than a smooth cut.

Surgical chisels and straight razors are both soft. But soft in this case is probably a good thing.

[george wilson]

But,mine was too soft to hold an edge

[David Weaver]

Yes, they're too soft to hold an edge. I thought they were specified in the high 40s or 50 hardness, but they look nice when they're new!

There was a rash of excitement about surgical razors (wapienica or something) starting about 6 or 7 years ago, I think mostly because they were cheap (eastern europe origin) and people don't know much about things like that so they are a novelty. They quickly went from $5 to $60, and they were soft, with ugly steel scales (so that they could be autoclaved) and often not straight or hard all the way through.

I don't know where that excitement is at this point.

I'll admit that I only knew about surgical chisels because someone had a whole set of new surgical chisels with nice bevel edges on ebay once for cheap and I thought about buying them until I read up on them. they looked really nice. Wouldn't be very inviting to use in a cold shop, though, even if they were hard enough.

(i was smart enough to not buy the razors!!)

Given all of that, I think ground at 90 degrees to use as a kerfing chisel, the medical chisels would be fine. I've always sawn those dovetails and then worked the chisel down from the mark on the diagonal, though (pares easily). Tried a card scraper a few times, but it seems like an even proposition, and most of what they remove is hidden, anyway.

[Malcolm Schweizer]

I appear to have gotten the hard version. It took forever to grind with 80 grit at 2000 RPM.

[Malcolm Schweizer]

The purpose of this is to provide a guide for starting/placement of your rip saw on pins and tenons?
It is to finish the kerf on half-blind dovetails. You saw first at an angle, as normal, then chisel the kerf flat. This way paring out the waste is a snap. The kerf in the image in the original post above was a test just using the chisel alone to make the kerf- just to see how well it did. I was amazed. If doing an actual piece I would clamp it to be sure it didn't split, but the test went way better than expected. That was one very light tap with a 19oz round mallet and it sank in like a hot knife in butter.

I was afraid the blade would either be flexy or would crack, but this thing is solid. I think you have to get a good chisel to start. I spent $40 on this one; a bit pricey, but the quality is very apparent, and the steel is very hard.

[Sean Hughto]

Yeah, I wouldn't be worried about the steel ... I'd be worried about the wood.

[george wilson]

I used to sharpen a plastic surgeon's nose chisels years ago. They were hard. The bone chisel I got from Ebay was soft.

[Malcolm Schweizer]

I used to sharpen a plastic surgeon's nose chisels years ago. They were hard. The bone chisel I got from Ebay was soft.

When I first read this, I thought you were saying it was a plastic chisel!