Basic Fabrication Flashcards
(58 cards)
What are transitional fittings used for ?
Are used to change the aspect ratio and to move duct for architectural reasons.
Why is the use of transitional fittings avoided?
Time and money
What are the 3 types of joints used to join transitional fittings ?
- Slip and drive
- cp
- proprietary connection
Why must the slip and drive joint be adjusted on transitional fittings ?
Because the 1” slip cannot be at an angle to the next fitting
You must reduce the length of the net pattern by ____ for each slip and drive connection
1”
When developing the piece for a 2 side flat transition. What should determine which sloped side gets pocket allowances ?
The side that has the most amount of slope because there is less angle for transfer of angle notch.
Why would blocking be used when assembling a transitional fitting with raw edges ?
- form seams and edges
- open pittsburgh locks
Why would the throat and heel be fastened to one cheek instead of fastening both cheeks to either the throat or the heel?
The throat or heel can help support the cheek during assembly
What portion of a plan view for a rectangle to round fitting needs to be developed if the round portion is flat on top and centred in the other direction?
1/2 plan view
When is it advisable to use more then 12 element points for a square to round fitting ?
If the diameter is over 12”
When laying out a pattern for a square to round fitting that is centred you need to lay out how much of the pattern ?
1/4 pattern for the fitting
Why should construction lines be on the inside ?
Makes for a neater job
When folding the allowance for a grooved seam what should you always do?
Fold slightly less than its nominal size
What is the first step when completing a groove seam?
Dress the hooked material down to 4 metal thicknesses using a smooth hammer
What is the material removed by the plasma called ?
Kerf
What is the power source of the plasma ?
Silicon controlled rectifiers or inverters called plasma aggregates
What shade of eye protection should be used with the plasma ?
Eye protection or dark goggles that have a shade from 7-9
What is auto nesting ?
Auto nesting allows you to optimize material usage
What is a duty cycle ?
Rated as a percentage of a 10 minute period
What are the consumables on a plasma ?
The nozzle and the electrode
What is a good rule of thumb when cutting with the plasma ?
Choose a machine class that is 2 times your cutting thickness
What is needed to change the size of the plasma arc ?
Amperage, voltage, gas flow and velocity
How are nozzles sized ?
According to amperage rating
What do slow cutting speeds produce ?
Vertical lag lines that are perpendicular to the plane of the plate
