Sharpening a scraper

[JakeS]

I know how you guys love sharpening threads. ;-)

A long while ago I bought myself a cabinet scraper in a local hardware shop - I forget the brand. I took it home and played with it a bit and basically got nowhere, and put it down to my lack of a hard enough burnisher (in fact, I was going off Things I Read On The Internet and trying a screwdriver handle). I wasn't totally unhappy with the finish I was getting after planing alone for the things I was working on at the time, so I put the scraper in a drawer and forgot about it for a bit.

Recently I decided I wanted to go back to it and have another go, so I bought myself one of these, read the instructions, watched the Workshop Heaven video and had a go. And it's certainly working better, at some points along the blade of the scraper I'm getting shavings and a really nice smooth surface, but I'm having a bit of trouble getting a good burr along the entire edge of the scraper. Particularly, in the stage of forming the initial burr, which Matthew called 'ticketing' in his video, I'm frequently finding that there's a sudden resistance to the passage of the burnisher (generally in the centre) and a different noise (which sounds more like... well, scraping). After turning the burr and giving it a go, there's a clear area around the point of said scraping noise that doesn't cut.

It feels almost as if I'm accidentally cutting the burr off partially half-way through the process, but I've tried it several times now, being careful about my actions and it doesn't seem to improve.

One thing I'm wary about is that the burnisher had a small visible mark on the edge when I received it; I don't feel anything running a fingernail along it, so I used it regardless, but maybe there's something there?


I guess my question is: is my problem likely to simply be simply a matter of technique and more practice? Should I worry about the mark on the burnisher and use the other side exclusively and/or clean it up with a diamond plate? Could it be that the cheap scraper is just too soft a metal and the hard burnisher's going through it too quickly?

I don't mind putting the time in and practising if it sounds like it's something I'm doing wrong, but I also don't want to waste time trying to fix my technique if it's really just a crappy scraper or a marred burnisher that's at fault...

 

[Chrispy]

Hi Jake

Have you tried fileing the scraper? As you turn a burr and flat it down and re turn the burr it work hardens the edge untill it gets to hard and brittle, so the time comes when you need to remove the hardened edge and get back to fresh metal, it should only take a few strokes with a good file or coarse oil stone.

 

[JakeS]

Have you tried fileing the scraper? As you turn a burr and flat it down and re turn the burr it work hardens the edge untill it gets to hard and brittle, so the time comes when you need to remove the hardened edge and get back to fresh metal, it should only take a few strokes with a good file or coarse oil stone.

I did that first, yeah - I can try it again, but I got this behaviour immediately after filing and smoothing the first time.

 

[Chrispy]

Then have you honed a nice sharp and square edge all the way along. if you do this you should be able to scrape a small shaving with it even at this stage.

 

[MIGNAL]

Try this. Mount the card scraper in a vice. Using a longish fine file (smooth cut) drawfile the edge, trying to maintain the file at 90 degrees to the flat side of the scraper. You might need to do 5 or 6 strokes with the file. A longish file helps in judging the hrizontal level. Remove the scraper and place it dead flat on a stone, remove the burr. DO NOT stone the top edge. Place the scraper back in the vice and using the back of a gouge (slightly off the 90 degrees) turn the edge in one firm stroke. The scraper should then produce decent shavings.
Then go back to your old method and burnisher to compare results.

The method that I've just described will NOT produce the ultimate in a scraper edge. It should however produce an edge that is good enough for most purposes. It also eliminates some of the problems associated with sharpening scrapers i.e. rounding the cutting edge on sharpening stones. It's a simple method.
If you want a truly sharp scraper you will need to stone the cutting facets of the scraper, producing a smooth and very sharp 90 degrees. The pressure exerted on the burnisher will, to an extent, determine how fine the shavings are.

 

[JakeS]

Then have you honed a nice sharp and square edge all the way along. if you do this you should be able to scrape a small shaving with it even at this stage.

I think so, but maybe my idea of a sharp and square edge isn't good enough... ;-) I can certainly try this part again.

Mignal: Since the only gouges I own are tiny woodcarving or lino-cutting ones, should I assume that any rounded HSS tool will do?

 

[dannykaye]

You might have better luck if you try a hand held scraper first

 

[JakeS]

You might have better luck if you try a hand held scraper first

I'm not sure I follow; the scraper in question is just a rectangle of steel with square edges, it doesn't have a holder or anything if that's what you're thinking?

 

[Chrispy]

When you draw the edge out with the "tickiter" do you remember to lick it first? mine always seems to work better wet.

 

[MIGNAL]

Any smooth 'harder than Cabinet Scraper steel' will do. You only need to turn the edge.

 

[Ian down london way]

I bought an earlier version (wooden, not plastic) of one of these:
http://www.axminster.co.uk/veritas-veri ... prod22457/

I find it works a treat. The burnishing bar is kept at the correct angle (mine is a fixed angle, this device is adjutable, so they can justify a dearer price!) and as its hidden away inside the device, it doesn't get dinted.

Bloody expensive though.

Oh yes, and I always flatted the sides and the end of the scraper using a diamond stone, rather than an oil stone ,as I think the diamond stones stay flat much better than an oil stone.

 

[johnwc812]

Hi
Nobody has mentioned lubricant, (no naughty comments). I always use a tiny smear of oil on the burnisher.
My dad, a lifelong cabinet maker and now 100 years old, always used the following method to hone the edge of a scraper.
He always had his oilstone in a two half wooden box, he would slide the scraper between the two halves and
sharpen it against the stone edge, this kept the edge of the scraper perfectly square before the burnishing stage.
Cheers John

 

[JakeS]

When you draw the edge out with the "tickiter" do you remember to lick it first? mine always seems to work better wet.

I always use a tiny smear of oil on the burnisher.

I had another go last night, starting from scratch with the filing and smoothing the edges and applied a small bit of oil to the burnisher; I don't know if it was definitely the part that made a difference, but I certainly got less of the scraping noise and a smoother feel to the motion of the burnisher. More to the point, the resulting scraper edge is cutting more consistently across the whole length of the blade - thanks for the tips, guys! I'll continue to practice in the hope that it's just me. ;-)

As it goes, though, since we're on the subject - out of curiousity, how does one go about turning a burr on the curved kind of scraper? Just burnish along the 'top' edge from the beginning several times to work the burr down from there without touching the sides?

 

[bugbear]

When you draw the edge out with the "tickiter" do you remember to lick it first? mine always seems to work better wet.

I always use a tiny smear of oil on the burnisher.

I had another go last night, starting from scratch with the filing and smoothing the edges and applied a small bit of oil to the burnisher; I don't know if it was definitely the part that made a difference, but I certainly got less of the scraping noise and a smoother feel to the motion of the burnisher. More to the point, the resulting scraper edge is cutting more consistently across the whole length of the blade - thanks for the tips, guys! I'll continue to practice in the hope that it's just me. ;-)

Best tip I know is to go easy with the pressure when burnishing the edge. Most scraping tasks (other than removing varnish) need a surprisingly small burr.

BugBear

 

[MIGNAL]

Depends on the radius of the curve. If it's a longer, flowing curve you can turn the edge in one stroke. If it's a much tighter curve you will have to go round in a series of shorter strokes.
Here's a Video of a different kind of scraper from my 'mate' Al carruth. I made a similar one from one of those Chinese HSS block plane blades:

http://www.youtube.com/watch?v=a7XRbfbpXiE

 

[whiskywill]

I once saw a scraper sharpening demonstration at a small wordworking show where, after the edges had been squared by filing and stoning, the edge was first "drawn" with the scraper laid flat on the bench. This edge was then turned over by burnishing with the scraper in the vertical position.
The result was impressive.

 

[MIGNAL]

That gets rid of any residual burr and it supposedly work hardens the metal. Over the years I've tried it numerous times. To be honest I haven't really noticed any improvement, either to how effectively it cuts or the edge retention.

 

[Corneel]

I do that when I freshen up the burr without filing or stoning again.. I think it straightens out any remnants of the old burr, so you start with an almost fresh square edge again. But of course I never really tested all the alternatives, so it might be hogwash.

 

[Peter Sefton]

With any new scraper apart from Veritas and possibly LN you need to file a fresh straight and square edge, then hone the file marks out and hone to flatten both sides of the scraper.

Next use a good quality burnisher to tack the flat sides before turning the wire edge anywhere between 5 and 15 degrees to produce a hook.

Depending on the quality of the scraper and how abrasive the timber is you should be able to tack and re-turn the hook several times before returning to the stone.

You should be able to repeat this process several times before you need to refile and start all over again.
I like my cabinet scraper to be between .6 to .8 mm thick for general use

Cheers Peter

 

[bugbear]

Next use a good quality burnisher...

Yes - whilst several "make do"s will work "near enough", even a good quality burnisher (Hock, Clifton, Two Cherries) is cheap enough that there's no real reason not to have one.

In particular screwdriver shafts are too soft and too rough; anybody who manages to make a decent edge using one is doing it in spite of the tool, not because of it.

BugBear