JOB REPORTJOB REPORTONON

CARPENTRY SHOPCARPENTRY SHOP

1. NAME OF THE JOB. Preparation of Cross Lap Joint.

2. OBJECTIVE. The objective of this job is to practice the preparation of a Cross Lap Joint in Carpentry Shop with the help of a supplied wood.

3. THEORY.

a. Carpentry. Carpentry is the term applied to that form of wood-work in which the wooden members are subjected to loads or thrusts. It involves cutting, shaping and fastening wood and other materials.

Carpentry deals with:

Timber Various tools used and The art of joinery

b. Qualities of Good Timber.

o Absence of sap wood o Free from knots, twisted fibers, cup and ring shake

etc; o Well seasoned for specific useo Solid, a hammer blow shall indicate this quality o Free from excessive moisture o With regular annual rings

c. Advantages of Good Timber.

o Easily available. o Quick transportation. o Easy to be worked with. o Less cost of construction. o High salvage value.

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o Suitable for soundproof construction.o Non-conductor of heat and electricity.

d. Materials Used For Joint. Wood.

e. Common Carpentry Joints.

All wooden objects whether doors, window, furniture, handicrafts, toys, cots etc. are all assembled with joints. While there are over 100 different kinds of joints, most of them are somewhat alike. Only the following types of joints are really different from each other:

Edge joint

Rabbet joint

Miter joint

Dovetail joint

Butt joint

Dado joint

Lap joint

Mortise and tennon joint

Lap Joint.

Woodworkers commonly use lap joints of various types in their woodworking projects. Lap joints are made in various styles for differing applications. The basic design requires two cuts of wood that overlap. Some variations include half-lap center lap and lap miter and they are cut using a table saw or router.

Things we’ll need.

Table saw or router

Dado head blade

Thickness planer

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Wood glue

Safety eyewear

Gloves

Steps.

Step One.

Run all wood pieces through a thickness planer to ensure uniform thickness. Be aware that using wood with various thicknesses will not produce flush cuts.

Step Two.

Using a test piece of wood, adjust the blade of the saw to a height that cuts exactly through the halfway point of the piece. Repeat the process as many times as necessary to attain the correct setting.

Step Three.

Cut a test lap joint and fit the pieces together. Run your finger across the intersection of the joint to fell for any unevenness across the joint. Adjust the blade accordingly if the face of each piece is not flush.

Figure: Lap Joint

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Step Four.

Start cutting the lap joint pieces by passing the wood over the blade. Do this until the correct shoulder length is met.

Step Five.

Examine each cut joint piece removing any excess shavings or bumps. Pieces must be flush after cutting.

Step Six.

Apply wood glue to each joint piece. Then clamp the joint assembly together unit the glue is dry. 4. Tools Needed.

To do good work, good tools, kept in good condition are needed. It is far better to have a limited number of really good tools than a large number of poor ones. So tools are something to choose with care, and learn how to use properly. The following tools were required to prepare the job:

A Piece of Wood

Cross Cut Saw

Chisel-3/8 inch, 3/4 inch and 1-1/4 inch

Bench Vice

Claw Hammer

Mallet

Smooth Planer

Marking Gauge

Tri Square

5. Diagram of the Job.

445 mm

150 mm45

mm

45 mm

Measurement for preparation of the cross lap joint

6. Working Procedure. The job was prepared as per the following sequence:

Usually, stock for the two members of the cross-lap joint can best be planed to width and thickness in one piece. Place two sets

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Figure: Preparation of the cross lap joint

of face marks on the piece, so that there shall be one set of marks on each member after they are separated. Two methods of making this joint are given. The first is safer for beginners; the second is better for the expert workers.

Directions for Cross-lap Joint, First Method.

Square the two ends, measure from each of these the desired length of each member, square knife lines around, saw apart, finishing the ends square to the lines.

Measure from one end of each member, the required distance to the nearer edge of the joint. Since the corresponding faces of the two members must be on the same side of the piece when the parts are put together, it will be necessary to lay off the groove of one member on the face and of the other member on the side opposite the face. If the joints are to be in the middle of each member but one measurement need be made.

Square sharp knife lines across at these points.

By superposition, locate and knife the second edge of each joint.

If the joints are to be in the middle of each member, before proceeding further, test to see that the lines have been laid out properly. If the members are placed side by side and the ends evened (as in laying out in figure 01) below, the lines will of necessity correspond. Turn one of the members end for end and even the two ends; the lines ought still to correspond. If they do not, points marked midway between the corresponding lines will give the correct position for the new lines. Follow the Figure 01.

6Figure 01

Extend the knife lines across the two adjoining surfaces of each member.

Set the gage for the required depth and gage between the knife lines on the surfaces. Though the groove on one member is laid out on the side opposite the face, do not make the mistake of holding the head of the gage against other than the face.

Saw accurately, to the knife lines and to a depth indicated by the gage lines.

Chisel out the waste stock. Test as shown in Figure 02.

A well-made cross-lap joint is one in which the members can be put together with the pressure of the hands and which will not fall apart of their own weight. Figure 03 shows the results of "forcing a fit.

Directions for Cross-lap Joint – Second Method.

The two members are to be planed to width and thickness in one piece but are not to be separated until the grooves have been laid out and cut. The grooves must be laid out by measurement only, since superposition is impossible. The positions of the grooves relative to the faces are, as in the first method, one on the face and one on the side opposite. The gagging for both is done from the faces.

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Figure 02

Figure 03

7. Safety Recommendations During Carpentry Jobs.

Machinery safety.

We should be careful during turning wooden parts with wood working machine

Ripping, cross cutting, leveling must be done by circular saw carefully.

Students must be careful to cut wood with band saw.

To cut internal and external curves on thin wooden piece we must use jig saw carefully.

Electrical powered tools.

Do not use power equipment or tools on which you have not been trained.

Keep power cords away frorsi the path of drills, saws, vacuum cleaners, floor polishers, mowers, slicers, knives, grinders, irons and presses.

Do not carry plugged-in equipment or tools with your finger on the switch.

Do not carry equipment or tools by the cord.

Garage doors.

Do not use undersized rods or other improvised tools to wind garage door springs.

Engage garage door lock in the "locked" position before winding the springs. Do not attempt to adjust winding coils or bars when the garage door is in the full open position.

Hand tools.

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Use tied-off containers to keep tools from falling off of scaffolds and other elevated work platforms.

Keep the blades of all cutting tools sharp.

Carry all sharp tools in sheaths or bolsters.

Tag worn, damaged or defective tools "Out of Service" and do not use them.

Do not use a tool if its handle has splinters, burrs, cracks, splits or if the head of the tool is loose.

Do not use impact tools such as hammers chisels, punches or steel stakes that have mushroomed heads.

Chisels.

Keep the cutting edge of the chisel sharp.

Do not use chisels with damaged striking ferrules.

Hold a chisel with a tool holder if possible.

Clamp a small work piece in a vise and chip towards the stationary jaw when working with a chisel.

Files/Rasps.

Do not use a file as a pry bar, hammer, screwdriver or chisel.

When using a file or a rasp, grasp the handle in one hand and the toe of the file in the other.

Do not hammer on a file.

Hammers.

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Use a claw hammer for pulling nails and driving nails.

Do not strike nails or other objects with the cheek of the hammer.

Do not strike a hardened steel surface, such as a cold chisel, with a claw hammer.

Do not strike one hammer against another hammer.

Knives/Sharp instruments.

When handling knife blades and other cutting tools, direct sharp points and edges away from you.

Store knives in knife blocks or in sheaths after use.

Do not use knives with dull blades.

Do not use honing steels that do not have disc guards.

Do not attempt to catch a failing knife.

Use knives for the operation for which they are named.

Pliers.

Do not attempt to force pliers by using a hammer on them.

Do not slip a pipe over the handles of pliers to increase leverage.

Use pliers with insulated handles for electrical work.

Do not use pliers that are cracked, broken or sprung.

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When using diagonal cutting pliers, shield the loose pieces of cut material from flying into the air by using a cloth or your gloved hand.

Sa ws.

Do not use an adjustable blade saw such as a hacksaw, coping saw, and keyhole saw or bow saw, if the blade is not taut.

Do not use a saw that has dull saw blades.

Keep hands and fingers away from the saw blade while using the saw.

Do not carry a saw by the biade.

Screw drives.

Always match the size and type of screwdriver blade to fit the head of the screw.

Do not hold the work piece against your body while using a screw driver.

Do not put your fingers near the blade of the screwdriver when tightening a screw.

Personal safety.

Correct dress is important, remove rings and watches, roll sleeves above elbows.

Always wear protective eye protection.

Never lean on the lathe.

Never file lathe work unless the file has a handle.

File left-handed if possible.

Use two hands when sanding the work piece.

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9. Conclusions. Carpentry shop provides us the opportunity to learn how to prepare different jobs on ground. This is of immense importance and of extreme practical usefulness to prepare such jobs in the welding shop, which will make the students beneficiary in the long run.

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