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CLOSE THIS BOOKRipping and Mortising - Course: Manual woodworking techniques. Trainees' handbook of lessons (Institut fr Berufliche Entwicklung, 21 p.)
VIEW THE DOCUMENT(introduction...)
VIEW THE DOCUMENT1. Purpose and Application of Mortising and Ripping
VIEW THE DOCUMENT2. Types, Construction and Mode of Action of Mortising and Ripping Tools
VIEW THE DOCUMENT3. Preparation for Mortising and Ripping
VIEW THE DOCUMENT4. Precutting of Recess Edges by Means of Ripping Tools
VIEW THE DOCUMENT5. Chiselling out Recesses
VIEW THE DOCUMENT6. Ripping of Faces, Edges and Corners

5. Chiselling out Recesses

The chiselling out of recesses (openings) for wood joints and for the mounting of fittings is carried out according to:

- the position of the workpiece area to be worked,
- length and width,
- depth and
- the shape of the recess.

With recesses

- being manufactured on outer surfaces of the entire width or thickness of the workpiece (e.g. overlapping joints, dovetail joints, slots) two of the recess edges can be cut in by means of sawing tools. The third one is to be chiselled.


Figure 12 Cutting in two recess edges by means of sawing

1 to be cut by sawing, 2 to be chiselled out

- where all the five edges are inside the workpiece (e.g. covered mortises, fittings) all faces are to be chiselled out up to the working depth.


Figure 13 Depth limited recesses within the workpiece

- through the entire width or thickness of the workpiece (e.g. for through mortises) two recesses should be chiselled out (from the two opposite working faces, up to the half of the working depth each).


Figure 14 Recess chiselled through the workpiece (mortise)

The cutting through of holes from one face to the opposite face will result in size deviations and fraying of wood fibres at the edges!

When mortising

- the trainee encloses with one hand the haft of the mortising tool and guides it to the area to be worked,

- the other hand grasps the striking tool for beating the mortising tool.


Figure 15 Handling of the mortising and ripping tools

5.1. Chiselling out Recesses (Overlap Joints)

The manufacturing of larger (longer) recesses comprises the following operations:

- clamp the workpiece,

- give a cut with the saw close to the limiting lines across the grain up to the marked working depth (cf. Fig. 12). In addition to it, cut in longer recesses sectionally,

- drive in the firmer chisel (from the centre of the recess, with the grain and in an acute angle to the working face.) Tilt the cutting edge of the blade slightly upwards!

- Split off the wood chips by bending the firmer chisel backwards and down,


Figure 16 Driving in and bending the firmer chisel

1 driving in with the grain, 2 bending backwards and downwards

- work the recess in the opposite direction,

- repeat the alternate splitting off of the wood until the required recess depth is reached.



Figure 17 Chiselled recess
- flatten and smooth the prechiselled surface by reworking with the ripping chisel across and diagonally to the grain,

· the cutting edge of the ripping chisel blade is pointed at the working face,
· guide and push the ripping chisel with both hands.


Figure 18 Reworking of the chiselled surface with the ripping chisel

Chiselling out and reworking of smaller (narrow) recesses can only be done with narrow firmer chisel blades across the grain. In doing so

- first cut off the thicker wood fibres,

- then (before reaching the envisaged working depth) cut off thinner chips from outside to inside.

Do not guide the cutting edge of the firmer chisel beyond the recess edge, in order to avoid fraying of wood fibres!


Figure 19 Chiselling of narrow recesses and reworking with the ripping chisel

5.2. Chiselling out Recesses (Openings) at the Edge of the Workpiece (e.g. Slots, Dovetail Holes)

The chiselling out of through holes and depth limited openings at the edge of the workpiece is divided into the following operations:

- give a cut with the saw close to the scribed lines in parallel to the grain, up to the transverse limiting lines (cf. Fig. 12),

- precut and notch at the limiting line across the grain (see Fig. 9 to Fig. 11),

- drive in the chisel at the precut scribed line and cut off the wood fibres. The cutting edge of the chisel blade

· is pointed outwards at the scribed line,
· is guided parallel to the face to be chiselled,


Figure 20 Driving in the firmer chisel at the scribed line and cutting off the wood fibres

- drive in the chisel close to the scribed line diagonally to the grain and split off the wood chips,


Figure 21 Splitting off the wood chips

- enlarge the funnel-shaped hollow by repeatedly cutting and splitting off wood fibres up to half the working depth (the centre of the workpiece).

In case of through holes: Stop chiselling out just before reaching the margin. Leave 1/3 of the remaining length as support for working from the opposite side!


Figure 22 Recess chiselled from the first working surface of the workpiece

1 half the working depth (centre of the workpiece), 2 supporting surface for working from the opposite side

For through holes:

- reclamp the workpiece and chisel out its opening in the same way from the opposite side,

- drive in the chisel from the end-grained narrow face with the grain and split off wood layers,

- cut through the opening up to the centre of the workpiece and cut off the remaining wood chips.


Figure 23 Chiselling of the recess from the second working surface

1 cutting off the wood layers, 2 cutting through up to the centre of the workpiece

On which side of the scribed line must you guide the saw blade, in order to manufacture the opening to be chiselled out true to size?
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Why must through holes not be chiselled out from one side only?
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5.3. Chiselling out Recesses in the Centre of the Workpiece, (e.g. Mortises, Holes for Fittings)

When chiselling out depth limited openings and through holes in the centre of the workpiece, perform the following operations:

- precut and notch at the limiting line across the grain (see Fig. 9 to Fig. 11),

- drive in the chisel along the limiting line with the grain. In doing so

· the cutting edge of the chisel blade is pointed outwards,
· the cutting edge of the blade is driven in at a distance of approx. 1 to 2 mm from the scribed line towards the opening’s side,


Figure 24 Cutting the wood fibres with the grain

- cut a notch in the centre of the opening by:

· alternately driving in the ripping chisel diagonally to the grain and
· splitting off wood chips,

- enlarge the funnel-shaped hole up to a distance of 3 to 5 mm from the precut transverse limiting line,


Figure 25 Caulking a notch in the centre of the opening

1 diagonally to the grain, 2 splitting off the wood chips, 3 distance from the transverse limiting lines

- drive in the chisel at the transverse limiting lines and cut off the wood fibres (see “Chiselling out Recesses at the Edge of the Workpiece”),

- cut and split off wood chips by:

· alternately driving in the chisel from the centre of the opening, with the grain and
· bending it backwards and downwards,


Figure 26 Alternately chiselling out the opening

1 cutting the wood fibres, 2 cutting and splitting off the wood chips, 3 bending the firmer chisel backwards and downwards

- the lateral cutting of the wood fibres at the 4 limiting lines and the subsequent splitting off of the wood chips is carried out

· with depth limited openings until the required depth is reached,
· with through holes up to the centre of the workpiece,

- rework the chiselled faces up to the envisaged size of the hole by guiding the ripping chisel diagonally and across (in case of narrow holes) the grain,

- when chiselling out through holes

· reclamp the workpiece with the opposite side on top,
· cut through the hole in the same way.

Before being chiselled out, depth limited and through holes may also be predrilled.
When chiselling out predrilled holes

- first rework with the firmer chisel the surfaces at the 4 lateral limiting lines,
- then cut off the wood chips and
- finally rework the surfaces with the ripping chisel.


Figure 27 Chiselling out predrilled holes

1 cutting the wood fibres with and across the grain, 2 splitting off the wood chips

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