Thread: A question on card scrapers

That is the normal way to sharpen a cabinet scraper, you only need to file the edge when you can no longer create usable burr.

So I take it this rule applies the same to a card scraper aswell?

Originally Posted by section1

So I take it this rule applies the same to a card scraper aswell?

Yes! I straighten & re-hone the edges of card scrapers only when I can no longer raise a decent burr. Depending on what I'm scraping, I may be able to do that anywhere from 3 or 4 to 8 or 9 times. The edge I start with varies, too. For roughish work (e.g.removing varnish, etc.), I turn a burr after filing. For fine finishing, the edge gets the 'full treatment' & is honed as fine as I can make it.

Another trick is to first turn a small burr the 'wrong' way, then turn it the 'right' way. This serves to both straighten the working edge, and work-hardens it so that it lasts longer.

And finally, if you don't already do this, use a bit of lubricant on the burnisher. The most convenient lubricant is right in front of on your nose. Rub your finger on the side of your nose where it's rich in sebaceous glands, then rub that on the burnisher. It' essentially the same stuff as lanolin, and does a great job!

Cheers,

Thanks Ian I usually use jobo oil as I have plenty of it available to me, interesting to read about creating a burr the wrong then the right way to make it last longer. Why does it last longer? It seems to me that it would do the opposite it's like bending the stel one way then the other therefore weakening it until it breaks off. This is what I understand of the wrong way can you elaborate on this a little.

Originally Posted by section1

..... interesting to read about creating a burr the wrong then the right way to make it last longer. Why does it last longer? It seems to me that it would do the opposite it's like bending the steel one way then the other therefore weakening it until it breaks off. This is what I understand of the wrong way can you elaborate on this a little.

You seem to have understood correctly, section1. While it does seem a little counter-intuitive, steel is pretty plastic in small sections like a burr, and it will tolerate being pushed around much more than if you were to try bending the whole thickness of the scraper, for e.g. The 'pushing around' is akin to hammering, and it 'work hardens' the steel (check a technical source if you wish to have the chemistry/physics of work-hardening explained - it happens with many metals and alloys). But hardening increases brittleness, so after a number of bends (the precise number depends on how much you deform it & the steel alloy, but it will tolerate quite a few if you are using typical scraper steels), the burr may break off, & that's when you need to reform a nice, clean square edge & start over....

Hope that helps?
Cheers,

Yes like tensioning a saw you hammer very clever Ian thanks very much old mate The issue I am having with the card scraper is that it's getting blunt too quickly, 10 strokes and the shaving start to minimise which I don't understand why

Originally Posted by section1

...... 10 strokes and the shaving start to minimise which I don't understand why....

Hmm, that does seem a bit skimpy, alright. If you haven't had this trouble before, maybe it's the wood. Some highly siliceous woods will kill any edge in a few strokes, but ordinarily, I'd expect a scraper to keep cutting for a few minutes, even on Ironbark or similar. I reckon on getting my fingers thoroughly cooked at least 4 times or more between burnishings...

Cheers,

I'm dealing with reversing grain on Tasmainian Blackwood, I won't say that it goes completely dull but you can see and feel the edge going pretty quickly. Shooting the end grain is a pain as well I am seriously considering purchasing myself a dedicated shooting plane. I feel I will be able to shoot timbers like this without a hassle.