Sawing. Reciprocating saws (power hack saw) being replaced by horiz band saws only cuts in one...

Sawing

Reciprocating saws (power hack saw)

• being replaced by horiz band saws

• only cuts in one direction

• up to 24” x 24”

Band machines

• continuous band = high cutting efficiency

• blade has large number of cutting points so wear is distributed

• no limit to length, limitation is frame size

• 3 types

1. Horizontal band saw• mainstay of production stock cutoff

Swing stock stop clear before cutting so work does

not bind

If possible, don’t cut short pieces

Support both ends of vise for short pieces

Proper clamping

2. Vertical band saw

Cuts narrow kerf

Cuts circular patterns (contours)

Table can be tilted 10 degrees left and 45 degrees

right

Feed can be by hand or mechanical

• generally not used to cut round stock

Keep guidepost guard about 1/4” above work piece

Cutting a blade to insert in a hole in a work piece

3. Tilt frame band saw

• band blade is vertical and tilts from side to side

• good for angle cuts

Cold saw - circular saw accurate cuts to within .002”

Abrasive cutoff saw• uses circular abrasive wheel

• abrasive particles act like a saw tooth

• seldom used for general stock cutting

• used more for very hard materials

Advantages of abrasive cutoff saw

• speed (up to 20,000 sfpm)

• ability to cut non metals

Abrasive wheels made from:

• a. aluminum oxide - for most metals

• b. silicone carbide - non metallic materials such as stone

• c. diamond abrasives - hard materials like glass

Feed Rates

• too fast - heat generated by friction will dull tool

• too slow - results in early dulling

Setting feeds and speeds

• Generally harder tougher materials = lower cutting speeds

• Charts

• Experience

Saw blades• at least 3 teeth in contact with work thin

material = more teeth per inch

• thick = fewer teeth per inch

Blade materials

• carbon steels

• high alloy steels

• tungsten carbide tipped teeth

Terms

Kerf = width of cut

Width = distance from tip of the tooth to the back of

blade

Gage = thickness behind set (teeth) of blade

• reciprocating saw blades - up to .250” thick

• band saw blades - up to .035” thick

• pitch = teeth per inch

Pitch = Teeth per inch

Tooth forms• standard - accurate & smooth finish

• skip - gives additional chip clearance

• hook - faster cutting due to positive rake angle

Set

• Total distance from tip of tooth on one side to tip of tooth on other side

• Provide clearance for back of blade

Set patterns

• raker - for general sawing

• straight

• wave - where cross sectional shape of the work piece varies

• raker and wave most common

Selecting a blade depends on:

• material to cut

• thickness of material

• cross sectional shape

• some machines have a job selector for assisting

Cutting fluids are important for:

• carrying chips away

• cooling

• lubricating

Installing blades

• tighten until a ring is heard when tapping

• make sure teeth point in proper direction

• check for proper tracking

• recheck band tension after a few cuts because blade will seat and stretch during break-in period

Installing blades (cont.)

• adjust blade guides close to the blade

• chip brushes functioning properly?

• wear gloves when installing blades (usually don’t wear gloves in machine shop)

Blades can be ordered already welded or you can

cut and weld your own from a spool

Misc. Operations:

Band filing

Spiral saw blades - intricate contours in any direction

Friction sawing