How Scraper Tools Work
The blade of both tools is held in the body with a wedge. The wedge comes almost to the throat of the tool so that the blade is supported to the maximum extent possible to visually eliminate vibration.
The blade is set to protrude beyond the bottom of the tool. The amount of protrusion will depend on personal preference, but no more than one millimetre would be advised.
When working, the brass nose in front of the blade will be in contact with the wood to be scraped. The tool is then pivoted about that contact point to adjust the amount of pressure on the following blade. As the contact point with the wood approaches the blade, the control of the cutting action will increase.
If the blade protrudes a long way beyond the bottom of the tool, then the distance between the contact point and the blade will also be large. As the amount of protrusion decreases, so the distance between the contact and the blade also decreases, leading to more control. However, when the blade is level with the bottom of the tool then it will cease to cut!
The setup of the tool is therefore a matter of taste and also a tradeoff between coarseness of cut and control.