Can anyone explain what shear scraping is?

[=Adam=]

Hi guys,

I have been watching a few videos online and many of them talk about shear scraping with a bowl gouge, they seem to put the tool with the flute facing the work and pull it across the surface, is this correct?

Could someone please explain the technique and also tell me why it would be useful as compared to swapping to a traditional scraper?

Sorry if this is a silly question but I thought I would ask

Cheers

 

[CHJ]

Basically the person is using the cutting edge to SLICE across the surface, using the fact that they can get a sharper edge on the gouge that will last longer than a scraper Burr edge on a conventional flat scraper.
Regardless of tool the concept of Slicing (shearing) as opposed to Chopping is the key to its use in shear mode.

Using a bowl gouge to do this is not as easy as those proficient at doing it would have you believe, as there is a very fine line between shaving the surface with minimal bevel pressure and the gouge diving in for a deeper cut if it rotates at all in your grip or presentation. With a Burred Flat scraper it is much harder to get it to dive in deeper than the burr because the top surface acts as a stop.

Think of using a razor blade without it being in a safety carrier holder, if you can use a cuthroat razor then you should understand the concept.

 

[Mark Hancock]

With traditional scraping the cutting edge of the tool is held horizontal and trailing against the timber.

With shear scraping the cutting edge of the tool is held at at angle to the timber of about 30 to 45 degrees and in a trailing fashion.

This can be done with a bowl gouge in the manner you described: by putting the flute of the gouge to the timber at about 45 degree (handle low), the bottom cutting edge is then trailing against the timber because of the profile of the flute. The easiest way to maintain the shear scrape is to keep a 1 mm gap between the top cutting edge which you can see and the timber.

Shear scraping can also be done with a traditional scraper inclined at 45 degrees. Most shear scrapers sold have the edges of the tool rounded to allow a smooth movement along the tool rest.

Chas, I'm afraid I'll have to disagree with your "minimal bevel pressure" comment. There is no bevel contact with shear scraping. However there is with shear cutting.

Shear scraping is used to refine the surface of the timber or form of the piece.

 

[jpt]

The how to is explained very well above the why is a different matter.

Once you have mastered the technique it is much quicker to use the gouge than change to another tool. If you are doing it for fun the time element doesnt matter but if you are trying to earn a living every second counts.

john

 

[henton49er]

I find that shear scraping with my fingernail profile 1/2" bowl gouge gives a better finish than using a scraper. However, I find it difficult or impossible to use the bowl gouge in this way on any tight concave curves (e.g. inside a bowl) whilst convex curves (e.g. the outide of a bowl) are relatively easy. Shear scraping with my bowl gouge is my preferred method of cleaning up any tool marks as a final finishing cut. I always sharpen the tool before starting to shear scrape. I revert to scrapers on the insides of bowls.

 

[CHJ]

.....Chas, I'm afraid I'll have to disagree with your "minimal bevel pressure" comment. There is .....

Agreed Mark, I should have said no bevel support hence my comment about not allowing the tool to rotate resulting in the cutting edge diving in to the piece.

 

[Richard Findley]

I think most of it has been said. It might be considered a slightly more advanced technique but it really is quite easy and most of my students are doing it straight after being shown.

The technique is handle low, flute closed to the wood and cutting with the lower wing of the gouge at around 45deg. There is no bevel contact.

The thing that is important is the shape of the grind, the wing must be ground back somewhat but most importantly the wing must be ground with a convex shape, if the shape of the wing is straight or concave you will struggle. This will also help to reach those concave curves on the outside of a bowl. It is not a cut for the inside of a bowl.

The reason a shear scrape works better than a standard scrape because you are presenting a sharper edge. An example would be, by holding the tool as a standard scraper and running your finger down it vertically as if it were the wood (don't do it, just imagine it!) it wouldn't cut you much, by holing it at a more shear angle and doing the same there would certainly be blood! Point proven I hope!

HTH

Richard

 

[Noggsy]

I've used (and am about to purchase) the Tracey Owen fine finishing tools which are shear scrapers par excellence. I find them superb to use as they are so easy to control and they work inside and outside the bowl. I never got on with flat scrapers really, finding them difficult to control, but the TO tools have a really thick bar, which makes them very rigid. I've also got a Sorby teardrop scraper which is useless in flat mode, but gives a good finish at 45 degrees. The only issue there is the thin bar holding the scraper - I should really make a thicker tool for it to go on.

 

[henton49er]

..... but it really is quite easy and most of my students are doing it straight after being shown.

Must be relatively easy if I can do it!!! :lol: :lol:

 

[Richard Findley]

Another benefit of shear scraping for the finishing cut on the outside of a bowl with a bowl gouge is the position that you stand. With the traditional push cut you tend to focus really on the shape you are making near the tip of the tool, rather than the shape overall, with the shear scrape with the BG, because the tool is tucked next to your body you stand I front of the bowl and have a really clear over sight of exactly what is going on the the shape of the bowl.

Cheers

Richard