HVAC Flashcards
Major diameter of a fastener
Largest diameter of a screw head
Minor diameter of a screw head
Smallest diameter of a screw head
Root diameter of a fastener
Diameter of a screw head measured from the inner edge of the thread
Screw thread
A flexible form that has been wrapped around cylinder at a uniform rate of advance
External thread
Thread on the outside of a member
Internal thread
Thread on the inside of a member
Nominal diameter
Diameter by which the fastener is named
Pitch diameter (simple effective diameter)
Diameter to where the thread thickness is equal to the space between the threads
Pitch
Distance from a point on a screw thread to a corresponding point on the next thread measured parallel to the axis
Lead
The distance a thread advances actually in one turn
Crest
The flat or straight edge of the top of a single thread
Root
The bottom surface between two threads
Flank or side
The surface of the thread from the root to the crest
Single depth of a thread
The distance from the root to the crest measured on a perpendicular axis
Thickness of the thread
The distance between the two adjacent sides of a single thread measured from the pitch line
Fit
The looseness or tightness between two mating threads
Tolerance
Total permissible variation. Maximum or minimum sizes of the parts
Allowance
Internationally agreed difference in the dimensions of mating parts
Thread angle
Angle formed by the sides or flanks of a screw head most are 60degrees
Helix angle
Angle formed by the helix of a thread
Left hand thread
Winds in a counter clockwise direction
Right hand thread
Clockwise
UNF
Unified national fine. Used for materials of high tensile strength. 60 degrees
UNC
Unified national coarse. Low tensile strength. Deep grooves with greater distance between the crests. 60 degrees
NPT
Tapered thread that seals the joint
Type K
Colour coated green, thickest wall. Available in both hard and soft temper. For underground and interior service.
Type L
Colour coated blue. Thinner walls than K but thicker walls than L. Available in both soft and hard temper and applicable for above ground service
Type M
Colour coated Red. Thinner than both K and L. Available in hard temper only suited for above ground service and water lines.
DMV
Colour coated yellow. Suitable for only above ground drains waste and vent piping. Cannot carry any water pressure
How is pipe measured?
By it’s inside diameter
How is tube measured
By it’s inside diameter
SAE flared tube fittings
Nut is threaded internally and the body is threaded externally. The body is tapered and designed to fit against the flared tube. The angle of the taper is 45 degrees.
Inverted flared tub fittings
The nut has an external thread and the body has a internal thread. Meant to be used with SAE
JIC flared tubings
Joint industry conference. Similar to the SAE but has a 37 degrees flare. Used for hydraulic fittings and steel tubing. Reduced angle reduces the chance for a split flare
Double compression fitting
Has two parts: nut and the body. Body has tapered internal thread and is designed to fit over the end of tubing
Solderless compression fittings
Consists of three parts: body nut and sleeve.
Bushing Vs coupling
Bushing goes into the fitting coupling goes over each of the tubing
How big of a hole do you need to drill before you use a stud extractor
1/8”
Soft solder
Lead and Tin, alloys that have a melting temp below 800 degrees
Hard solder
Silver soldering. Brazing, higher temp for joining. Uses silver 1100 to 1600 degrees.
Sil-Fos
15% silver 80% copper 5% phosphorus flows freely at 1300degrees
95-5
95%tin 5%antimony melts at 464degrees
What is a flux
A liquid solid or gaseous material that helps capillary action and prevents oxides.
