Nomenclature Taps and dies

Tap and Die Screw Thread Terminology

Taps and dies terminology for BSW BSF UNC UNF Metric BA BSB ME 32tpi 40 threads BSP BSPT NPT METP Whitform Special in righthand + Lefthand 

 Angle of Thread: Angle included between the side of the thread measured in an axial plane
 Basic Size: Theoretical or nominal standard size from which all variations are made
 Chamfer/Lead:
   For taps:- The taper at the thread end of a tap or the throat of the die, made by cutting away the crests of the first few threads is to distribute the work of cutting, over several threads and act as guide in starting the tap or die. The chamfer is relieved to facilitate cutting and the TAP is classed Taper(T), Second(S) or Bottoming(B), according to the length of chamfer, approximates are:
   Taper tap is 4^o per side (6 to 8 threads)
   Second tap 8^o per side (3.1/2 to 6 threads)
   Bottoming tap 22^o per side (1.1/2 to 2.1/2 threads)
 Note: The name ‘PLUG’ is commonly used to indicate a Bottoming tap. In America it is used to indicate a Second tap. To avoid confusion the terminology that should be used as stated by British Standard 949,1979 is ‘Bottoming’ tap
   For dies:  stamped-size side is 45^o   and   back side is 60^o
 Clearance Hole: Holes in the die that provide the cutting rake and chip clearance
 Cutting Edge: Leading edge of the land in the direction of rotation for cutting and which does the actual cutting.
 Crest: The top surface joining the two flanks of a thread
 Depth of Thread: The depth of thread, in profile is the distance between the crest and the root of the thread measured normal to the axis
 Effective Diameter: On a parallel screw thread the diameter of an imaginary cylinder which would pass through the threads at such points as to make width of the thread at these points equal
 Flute:   The grooves in the tap that provide the cutting rake and chip clearance
 Helix Angle:   The angle made by the helix of a thread at the pitch diameter with a plane perpendicular to the axis.  The helix angle increases continuously from the crest to the root of the thread
 Land:   That portion of the thread not cut away by the flutes or clearance holes.
 Land Width: The chordal width of the land between the cutting edge and the heel measured normal to the cutting edge
 Lead / Pitch:   Distance a screw thread advances axially in one complete turn. On a single thread the lead and pitch are identical
 Major Diameter:   Largest diameter on a parallel screw thread or tap. The term ‘Major Diameter’replaces the term ‘Full Diameter’as applied to the thread of a nut
 Minor Diameter:   Smallest diameter on a parallel screw thread or a tap. The term ‘Minor Diameter’ replaces the term ‘Core Diameter’ and ‘Root Diameter’as applied to the thread of a screw and also the term ‘Inside Diameter’ as applied to the thread of a nut
 Number of Threads / Tpi: The number of threads in a length of one inch (threads per inch)
 Tapping Drill Sizes: We will show you here how to calculate tapping-drill sizes: (generally)
For Metric (mm) threads a tapping-drill size is calculated by subtracting ‘pitch’ from diameter of the thread eg. for 4x.7mm thread: tapping-drill sizes is 4mm dia - .7 pitch = 3.3mm
For Imperial (inch) threads a tapping-drill size is calculated by subtracting ‘pitch’ from diameter of the thread eg. for 3/4 x 10 UNC thread is 3/4= .75 dia & 10 pitch=1/10 = 0.1 
Tapping-drill sizes is .75 dia - 0.1 pitch = 0.65  x 25.4 = 16.5mm    (Note: 25.4mm=1 inch)
 Tolerance:   Taps: General Dimensions to BSS 949 & American series NC NF NS to ASA standard -
                       Dies circular: Basic dimensions to BSS 1127 

http://donsnotes.com/home_garden/bolts-tap-sizes.html  shows taps and drill size  

September 7/13

Leo, Paul, Brian, Rick and Jim Hiltz spent a strenuous day preparing the Accacia wood for bowl turning.

This was a tree that had been on a property next to Leo's and which had been cut down by the owner.
We salvaged the large pieces and rolled them over to The Workshop.
We split them in halves and bagged them under a tarpaulin until we could begin work on them next session.

Rick, Chris, Jim Hiltz, Jim MacLean, Brian, Wilson, Miles.Paul

Leo spent a lot of time explaining the steps in gold leafing the vase:
Supplies needed:
Gesso, made from the following ingredients:
Yellow ochre pigment: Whiting (sifted limestone)
(Not much yellow is needed)
Fish glue
Good brushes
Gold leaf
Transfer paper for real gold leaf
Eraser (rubber)
Paper towel
Paint the vase: brush it on well: spend a long time at this and do several coats
Sand between coats using paint thinner on the sand paper: start at 320
Spray on lacquer
Cut out the grooves again to expose the wood
Brush on concrete bond: let dry
Brush on the yellow pigment:whiting , mixing it with bond: this gives a very hard surface
Sand out the groove and recoat
Then brush on fish glue (or sizing)
Let it dry
The gold leaf is brushed lightly with water and laid in the groove.
The water melts the fish glue!
Apply the goldleaf gingerly and press it down using a rubber
Let it dry
Can do a second layer
Then burnish with agate

Tips: 
Don’t use Tempura pigment for this project
Try to get turpentine to soak your brushes in: it is better than paint thinner
A good brush springs back after the paint stroke

Leo demonstrated how to cut thin veneer using two saw blades: the inside blade cuts: the outside blade is put on backwards: this prevents the blade from wandering and planes the wood.

First cut a veneer about 1/8 thickness
Then run this through the two blade set up.

Bring the blade close to the table insert edge: use a cardboard washer if necessary to get the teeth very close to the edge of the insert so the thin veneer does not drop down into the space

January 2014

Veneer making

February 25/14

Jim Hiltz, Jim Maclean, Chris, Miles, Brian, Wilson, Rick

We started work on the jewelery box project. Leo went over cutting up stock for veneer. Choose straight grain wood. Birch and Maple are best for this project.

Th thickness planer was used with a platform to carry in the thin strips.

Leo demonstrated how to use a thin kerf swedged blade on the table saw to rip. The teeth cut, whereas carbide teeth tend to push the wood and use a lot more power to accomplish the rip.

To rip a thin piece, dress the wood, run it through the blade, raising the blade gradually and turning the wood end for end to cut almost through.

Finish the job on the bandsaw. Make a cut across the end of the board on the table saw and this allows the band saw blade to get started more easily.

Rick showed a beautiful bowl he did on an irregular birch burl. He showed how to set legs on the irregular side and make the four legs level.

Leo challenged us to figure out this:

The earth revolves around the sun every  364 1/4 days but the year has 365 days.

How is this?