Please tell me shat you know about burnishing.

Crayola

Crayola

Joined
Sep 23, 1999
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Hello folks! Nearer to the end of the summer, I hope to try a project that may require some burnishing. Actually, it doesn't NEED burnishing, but I want to learn me some new skillz! So, Can anyone give me tips on burnishing? Also, is it best just to make one's own burnishing tools? Any tips would be great!
 
What I understand burnishing to is,using a hard object to polish an object. For example using a brass rod to polish the edge of a leather sheath. Or using a piece of antler (smooth of course) to polish a piece of wood. In the simplest of terms;using a somewhat harder smooth object to smooth another object. When I was a kid we used to make wooden spears and we would fire-harden the green wood on the tip,then we would "burnish" the tip with another green/smooth piece of wood. It made the tips strong enough to stick in trees (just once). Anyhow thats my essay on the subject.
 
In Nihonto polishing, they (now-a-days) use a tungsten-carbide rod to do the burnishing on the shinogi-ji of the blade. There was a good thread on this over on SFI a few weeks ago...
 
Using a harder object to flaten or lower high spots. Makes the surface smoother but perhaps not perfectly flat. An example: using ball bearing type objects in a tumbler lightly beating upon the work piece.

RL
 
in machining
 you'd burnish the sharp edge off something that was machined
 ( the machined edge.)
 you also burnish a wire edge from your knife with a leather strap.
 and yes thus polishing the edge.:)
 
Thanks guys!

Andrew: I noticed that mistake right away, but it is funny! So I thought I'd leave my shat where it lays :)
 
Steel that has been burnished has a bright reflective color to it that is different from the effect of a mirror polish. From what I understand this is often the final surface treatment after polishing for the unhardened backs and spines of Japanese swords and tantos. And thats about the extent of my knowledge of burnishing!
 
Used to burnish jewelry with a hard steel tool that was oval in cross section, ground to point and bent towards the tip. They still carry them in Jewelry Supply catalogs. Its a great way to set stones, moving the metal, hardening it and forcing a polish so bezel edges don't chance degrade blemishes from a polishing wheel. Some Jewelry is burnished as a surface finish in a rotary or vibrating tumbler with stainless shot/small shapes.

They use big vibrating vats 4 to 6 feet across for high volume commercial machine shop deburing/finishing, sometimes with plastic or ceramic pieces with or without abrasive. I use a rotary tumbler with soap and water to burnish/clean my brass before reloading, forget the corn cob or walnut shells, no abrasive needed. One of the local Blacksmiths made a big rotary tumbler for burnishing his work with pieces of small steel scraps, it makes a huge racket, but saves endless work with a hand grinder/rotary brush.

For knives, the idea of a tungsten carbide rod would solve the problem of finding something harder to use. Cobalt alloys would probably work also, I buy it in square bars to make cutting tools.
 
The essence of burnishing is that NO abrasives are used (that's why it was so widely used in jewelry).
If you use abrasives it's polishing, not burnishing.
Burnishing on steel is made with extra-hard carbide rods polished to a perfect glasslike smoothness or agate rods finished in the same way.
Polishing removes material in increasingly small amounts, until the metal is shiny. Burnishing moves metal around so that high points are smoothed down, and the finished surface is perfectly smooth.
Before burnshing a certain degree of polishing is usually needed. If the polishing and burnishing are done propelry the final surface will be finished to a degree analogous to that of the burnishing tool (i.e. a perfectly flat surface).
Burnishing tools come also in curved versions, with rounded points to burnish in crevices or sharp corners.
Oh... burnishing tools are exceptionally fragile...
 
I have a couple of burnishing tools in the shop. One is about 7" in blade? length, triangular, with the sharp corner edges flattened. The other is 31/2" with sharp corners, both tapering to points, like old daggers.
It took me awhile to find out what they were, after I got them up at a garage sale.
I did use them a couple of times, on the spine area, but as most of my stuff is satin finished, I keep them for curiosity value more than anything.
 
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