SAWMILLING AND WOODWORKING
- Hand sawing is used where machine sawmill cannot be set up.
- Protect from weathering and fungal attack
- Sawing can be done everywhere including rough terrain
- Cheap and economic
- Unfinished productivity
- Big diameter logs cannot be converted
- Unsuitable for large wood conversion
- Sawmills are used for woodworking.
- “This is the plant with different types of machines for sawing logs into planks, scants, etc.”
- Sawmill is one of the most important steps of wood utilization.
- Based on the number and type of saws:
- Band sawmill
- Circular sawmill
- Double band sawmill
- Horizontal sawmill
- Based on small sawmills
- Based on the level of permanency:
- Portable sawmill
- Permanent sawmill
- These are of portable/ semi-portable nature
- Moved from place to place
- Designed fore easy transport from one site to another
- Situated inside forest
- Necessary where timber is difficult to export in log forms where there is difficulty in the log for converting the material
Essentials of Portable Saw mills:
- Must be light as possible
- Machine capable of being taken into parts
- Should be the simplest type
Machines required for potable saw mills:
- One/ two breakdown sawing mills
- Couple of circular saw benches
- Portable steam or diesel engine which in addition can be used as a tractor for handling machinery from site to site.
Work required for portable saw mills:
- Converting logs into sleepers
- These saw mills are permanent in nature
- Situated close or in the cities
- Work of converting the material to the point at which it is ready fro assembling eg cabinet manufacturing, joinery, etc.
Before installing such saw mills, the following points may be given consideration:
- Regular supply of timber
- Delivery of timber at mill site at a reasonable cost
- Should be good market around
- Sufficient demand of sawing
- Reasonable margin of profit
- Cheap motive power ie steam power, water power, etc.
Factors kept in mind while establishing permanent sawmills:
- Location should be near cities
- Adequate supply of raw material
- Suitable market for its produce
- Product should pass by a well through the process from one section of the mill to other
- Minimum expenditure
- There should be regular material supply
- The layout of the mill should be properly designed
- Entrance and exit of mill building should be large for the free movement of logs
- Well lighted and fully ventilated building
- Timber handling operations should be properly managed
- Log transport cost should be minimum
- Storage and seasoning facilities should be available
- Space for future expansion
- Place should be neat and clean so that chances of fungus, insect attack should be minimum.
- Number of staff should be enough and properly distributed according to the working skill and capacity in different sections
- Selection of machine:
- Maximum daily output
- Minimum cost of the machine and its operation cost
- Accuracy of work
- Minimum wastage with max production
- Highest timber grades
- Chief power of sawmill should be the steam power, electric power, water power.
- Fine circulation of winds for seasoning.
VARIOUS TYPES OF SAWS AND SAW MACHINES USED IN SAWMILLS:
Saws are basically cutting tools with toothed edges. They may be reciprocating (it includes various hand operated and machine operated blades which cut in one stroke or both strokes ie backward and forward), revolving or traveling types.
Classification based on Type of work:
- Used in the 1st stage of sawmill process ie break down
- It reduces the log into smaller parts eg planks, scants, etc.
- Circular head saw:
- Inserted toothed saw, mounted on shaft support on beaming
- It has a disc of steel with teeth at regular intervals
- Logs are fastened to a traveling carriage which moves towards saw, that engages with the wood chisels its way through
- Sash/ Frame head saw:
- Consists of one or more saw blades
- Secured to a frame
- Moves either horizontally or vertically
- Blades produce several planks, scantlings, in a single operation
- Nowadays not very common.
Gang head saw:
- Consists of a number of saws mounted parallel to each other on the vertically operated frame
- Recently circular and head saw have been introduced
- Fitted with two saw pulleys
- Set vertically or horizontally
- Steel band having teeth on one/ both sides of the edge
- As the saw pulley revolves, the steel band starts revolving
- Timber on carriage comes in contact with revolving band saw and breaking it down into planks
- The second step of sawing is called re-sawing.
- After breaking down planks, scants, cants, etc, are re-sawn into the timber of required dimensions
- Gang re-saw
- Single –double vertical band re-saw
- Horizontal re-saw
- This is the machine used to turn the finished timber and to remove the wane, or rounded bark edges,
- The machine used to square the edges of timber
- Reduce the timber to the desired size
- Turn out defects in timber
- Trimmers may be single sawing cut off saws or two saw trimmer.
METHODS OF SAWING:
Break down sawing:
- Sawing alive: in which successive cuts are made on the same plane
- Sawing around: in which the log is turned around and cuts are made after two or more planes
- 1st one is more wasteful than the 2nd one but the second one is more time and labor consuming
Plain Sawing/ Ripping:
- Involves sawing in a plane tangential to growth ring
- Widely used and comprises a greater proportion to the output of sawmill
- Greater yield, easier operations
- Involves sawing in a plane which is to be more or less perpendicular to ray and perpendicular to the growth ring of the tree
- It is used for decoration piles
- Used for surface crack wood
Factors facilitate the working of Sawmill:
- Site preparation: Minimum time and money should be spent on site preparation
- Disconnection of the machine: Machine which can be easily disconnected are preferable
- The weight of machine: Light as possible
- Power of sawmill: internal combustion engine or portable electric generators
- Choice of machinery: Depend upon nature of work and output required
- Foundation of machinery: Good foundation is essential for high working machine
Important components of wood workshops:
- Surface Machine: Edge, face, chamber rebate to store up finishing products.
- Thicknessing Machine: Bring the timber down to the given thickness after it has been edged and faced.
- Over wood under Planner: Used as a combined surfacing and thicknessing machine.
- Tenoning Machine: For joints provided with a spindle for cutting lenosn of with shoulder of various length
- Boring Machine: For light boring work. They may be pillar wall, horizontal, vertical boring machine.
- Mortising Machines: For mortising, operated horizontally/ vertically
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