Thread: Time for a new marking knife.

Nice knife but remember to get that poor dog a new bone.
Regards
John

Rob?

Fantastic, looks great, I might need too steal your design, but I’m just concerned if you drop it said dog might want his bone back!.

Cheers Matt.

That dog (Minnie) would take off with it if she had half a chance. Shes fun. A 6 month old bundle of trouble . Keeps dragging my brooms out of the workshop to play with them. Or comes in dragging a foot rug from the house 90 meters away.
Here she is chewing on a horse dropping. And a Peg, With her best friend Toby.

Image-1a.jpg Image-1aa.jpg

Ticks all the boxes, Rob.

Really good and innovative design and great execution. I predict that it will be copied ... Repeatedly.

Already copied into the ideas and inspiration folder [emoji16]

Fantastic knife!

Sent from my SM-G781B using Tapatalk

Rob, I saved a bit of well-cleaned bone some time ago with a similar application in mind. Boiling gets rid of most of the fat & other organic matter, and a tip from the technicians who used to prepare skeletons for anatomy teaching: chuck a bit of onion in with the bones during the boiling, it makes the process a bit more pleasant! Haven't used it yet, & not sure I could find it or I'd be tempted to flatter with some imitation too...

Marking knives are so easy to make with a variety of cast-off or recycled blade materials - can't imagine why you'd ever buy one, but I guess some folks are chronically short of time. For donkey's years I used an old hacksaw blade epoxied into a handle. There were several iterations, with a bit more attention paid on successive models to finishing the wood: Simple knife .jpg

About 10 years back, Derek Cohen gifted me with one of his knives & I find I use that most often, but the blade is a bit thick for very fine work so occasionally I have to pull out the old hacksaw-blade model....

Cheers,

Rob

Great job and very innovative re-purposing of materials. I often find myself looking at broken drill bits and other high carbon steel such as your reciprocating blade and think "Where else would I source that quality steel?" and then, of course the corollary is, "What purpose can I use it for? " That is where my philosophy lets me down a bit.

You have done well.

Regards
Paul

Onion Ian . Worth a try. It’d start smelling like soup!
I have a box of prepared bone that I did a good way . I keep it for escutcheons and knob inserts . I read how to do it on a link I saw while I went through my Guitar making stage. I’ll try and put it up later. I think it was boiling the bones with detergent in the mix then soaking in a jar of Shellite for a month. This was for luthiers who are only using hide glue as well . On construction or museum grade restoration. Imagine hide glue if the bone wasn’t prepared right. I wouldn’t last long. It’l be interesting to see how the poly holds. It has some fantastic uses . Specially on dissimilar materials.

Im thinking if you give your bone a go you would never consider going the imitation way unless you had to. Imitation melts and smokes as you’re sanding it with a machine like a linisher. Bone doesn’t . There is just a fine white dust that smells like bone which isn’t great . So door open and a fan is a good idea. And a mask. You can also buff bone beautifully where as the imitation I’ve used melts quite quickly. The good thing about imitation is it has fake growth brings which looks more like Ivory possibly ? And its size is much better of course.

This is my box of prepared cow bone . And a bone drawer bottom gauge I made some years back .

EAE97D90-6F00-462B-8589-BC912B6E31A1.jpeg FA52D188-27BE-42DE-BEF3-BB484670BC0C.jpeg

Edit . Here is the bone cleaning link.

Cleaning Bone for Use in Lutherie



Rob

Rob, not sure why you'd need to do much more than boil the bone. You obviously want to get rid of fat which isn't too compatible with most glues (a little detergent would certainly help there). Fat is mostly in the marrow, so if you push most of that out you'll have gotten rid of a good proportion mechanically. I would think the other residual organic matter is unlikely to interfere with hide glue - the organic matrix on which the mineral is deposited is collagen, which is what hide glue is made of...

Haven't ever used synthetic bone, but I did try using some synthetic ivory. There was some very pricey stuff that was claimed to be nearly indistinguishable from the real thing (visually) with the 'growth lines' & all. I only wanted a tiny bit & ended up buying some stuff that was a bit cheaper. It was about as much like ivory as a plastic milk bottle! Apart from the very unconvincing colour & texture, when I turned it, the flakes of plastic flew everywhere & clung to anything they hit - I quit after a minute & spent the next hour trying to clean it up!

The bits I needed were very small (for the tips on the arms of my mini Sandusky plough plane), & I remembered I had some Tagua nuts I'd bought on a whim about a hundred years ago. They really do imitate ivory, the colour is very convincing & they have growth lines that are very like the real thing. Only trouble is the nuts always have a large void in the centre so the best you can get is a piece about 10mm cubed. I had to get creative & attach the bits of nut to a mandrel to turn the tips, but was pleased with the result:17 Finished almost.jpg

And I can confidently assure you that no elephant had to die for my plane....

Cheers,

Originally Posted by Bushmiller

Rob

Great job and very innovative re-purposing of materials. I often find myself looking at broken drill bits and other high carbon steel such as your reciprocating blade and think "Where else would I source that quality steel?"

Thanks Paul.

I have a used large Blue power hacksaw blade somewhere in my stash. I wouldn't mind doing an even larger marking knife with that possibly.

Nothing better than re purposing scrap

Rob

Rob

On the subject of bone, a potential source of suitable material is animal "headgear." In other countries there are antlers from moose (some deer in Oz too come to think of it), but even in Oz there are cattle. Although there is a definite trend towards polled cattle, some farmers still have horned cattle and most times they are de-horned so there is a pile of dis-guarded bony type material somewhere. I think the knife makers snap this up if they can. If you can get one of these Texas Longhorns, you have enough material to keep you in markings knives until you are done marking:

Texas longhorn.jpg

We have few Longhorns around our way, but they are kept as pets (not allowed into the house ) and the horns are all intact, but there are still Hereford breeders around (as opposed to Pol Hereford). The horns are only solid towards the tip and I don't recall how far down the horn before it becomes hollow. There is a vet on this forum who may be able to help in that regard.

Anyhow, just a thought. Your thread I think could spark a trend towards a spate of marking knives being made by your readers.

I believe the fishermen use those large power hacksaw blades to make knives. I made one once, but it disappeared into the ether a long time ago.

Regards
Paul

Paul, horn & bone are quite different - horn is keratin & contains no mineral (to speak of). Antlers, oth, are bone, which is mostly a compound called calcium apatite and by the time they are shed naturally, they are pretty free of organic matter & can be used pretty much as-is (at least that's what I found with the single bit of antler I've used). Antler is really solid stuff and has been a traditional knife-handle material for a very long time. Horn is also used for handles etc. (it can be heated & molded, unlike bone) and can be quite attractive, but it's not as hard or as durable as bone. The hollow goes a long way down, almost to the tip, which is why they could be easily converted to "musical" instruments...

This will be more than you want to know, but the difference between the bovidae & the cervidae is that the former have horns made of hard keratin (really just modified skin) which grow continually throughout their lives. The cervidae grow & shed their bony antlers each year - quite a feat when you think about the size of the racks some old stags produce....

Ian

Edit: Tortoise shell is also a type of keratin like horn - but be careful where you get your tortoise shell, most is proscribed by CITES...

Thanks Ian

I did know they were different, but lacked the knowledge to describe that: However, I knew you would step up to fibring us up to speed. The de-horning of cattle is quite controversial as it potentially opens up a hole to the head .

However, that is another story for another platform. I thought the antlers were shed each year, but as you have pointed out it is hard to fathom how that can happen with such a formidable growth.

Apologies Rob as we are digressing from your marking knife, but we await the version on steroids!

Regards
Paul

Originally Posted by IanW

Paul, horn & bone are quite different - horn is keratin ...

Just like our fingernails - keratin.

(Please correct me if I got this wrong, Ian.)