Scraping wrong

[Bob N]

On my current project, an ash bed for my son, I tried to compare using a scraper against a ROS for final surface prep before varnishing (T&T varnish oil). I must be doing it wrong because the scraper results are disappointing. I do get nice, very thin curls off the scraper, but the wood surface is not very smooth and has a lot of high spots that follow the figure as the edges of the winter wood stand out. It also takes an unfair amount of effort and the upper edge of the scraper is slicing my fingers like salami. The ROS with

220 paper worked better - smoother, flatter surface, even after vacuuming the dust out of the pores.

I'm using the Veritas scraper/burnisher set and scary sharpening the edge down to 2000 grit paper, using a scrap block of wood to keep the edge square, before burnishing the edge at 10 degrees. It seems to take at least 6 passes to get a palpable curl on the edge.

So how many things am I doing wrong here? Could it just be that ash doesn't take scraping well?

Thanks.

-- Bob

[A Dog Named Stain]

doesn't take scraping

You're WAAAAYYY overdoing it. Use a flat file and file the edge of the scraper flat. Burnish a hook on it and scrape.

[Donnie Vazquez]

take scraping

I'm no expert by a longshot, but 10 degrees sounds a bit extreme for finishing work. I'd back off to 5-7 degress and see if that helps.

[Roger Jensen]

Bob,

You likely answered your own question. Oak, ash, pecan and other such course woods don't scrape as well as tight grained woods. That said, I most often sand those kinds of wood and sometimes, depending on the finish I am after scrape the in-between coats. The hook is not as critical as you may think, you can scrape a smooth finish with broken glass, a razor blade or most anything with a sharp edge. I am not saying toss your scraper or the techniques you are using, you are doing it very well.

Rog

[Andy Dingley]

I know our (UK) oak is harder than US white oak, but I scrape a lot of it with no trouble. Ash OTOH, is a bit soft. You can do it, but it's more critical of your scraper preparation.

The hook is significant, because it changes the method of chip formation.

A square edge forms Type III chips. Material is compressed ahead of the edge (the "snowplough" effect) and it fails through compression. The waste comes off as dust. The surface can be poor, unless you take a very chin chip. If the surface is inflexible and not too well bonded to the substrate, then this dusty action is fine - so glass scrapers are good at removing old varnish.

A hook forms a Type II chips. The material is lifted and bent by the edge, and it fails along a well defined diagonal plane ahead of the edge. Chips are soft (already folded) shavings.

On a soft timber like ash, compression of a Type III chip tends to rip out of the surface beneath. You're better with a hook and making sure the angle is right to keep making Type II shavings.

-- Die Gotterspammerung - Junkmail of the Gods

[Mo' Sawdust]

How thick is the scraper? If the scraper is following the density of the late/summer wood, it sounds as though you are using a fairly thin scraper. Might want to consider using a thicker one.

Something to also consider using is a Stanley #80 scraper, especially if you are scraping relatively large flat surfaces (table tops and the like).

Thin scrapers are used with a light touch, and are quite useful in scraping finish coats (runs and the like).

[George]

OP is Canadian, no? Could be he's trying F. nigra, which is a real stringy stinker to scrape. It even tears with a good plane.

't believe that bit about no taste or smell. Black ash has both in abundance.

[Andy Dingley]

Thought that stuff was just for basketmaking ? I've rarely seen it, but it's bloody awful timber to use.

-- Die Gotterspammerung - Junkmail of the Gods

[Myxylplyk]

a

wrong

of

scraping

One possibility to consider is that you are working *way* to hard with the scraper. If the scraper edge is smooth and well burnished, and you have experimented with the proper scraping angle, you are probably flexing the thing too much. This causes a lot of wear in a small area, overheating and dulling quickly. (not to mention excessive hand fatigue). This also leaves a lot of small but increasingly noticable furrows in the surface.

I would say to resharpen and curl a fine to moderate hook. Further, I would recomend the non flexing pull method of using a hand scraper. If you're unfamiliar with this, refer to Tage Frid's books on teaching woodworking for a description.

Lastly, practice until you're comfortable on project fall offs before attacking the projects final finishing.

Good luck, Myx

>

[George]

Makes great picture frames with that outrageous grain, though. Knew one guy who made a hooded cradle out of it. No way a kid could fall asleep in anything that noisy.