+Tap & Die Threads, Associated Reference Tables & Hardware
Last updated on Thursday, June 08, 2023 06:36:29 AM Mountain US Time Zone

HOME

Tables, Drill-Tap Sets, Tap-Drill Charts, Thread Measurement,
Hand Tappers, Tap Handles, Cutting Fluids, Tap & Drill Guides,
Tapmatic 30X, Quill Bracket, Die Holders, Fastener Types,
Imperial Bolt Markings, Metric Bolt Markings, Hardware, Bolt Torque

Introduction to Taps
Single-point Threading Section 
How to Drill a Hole tutorial
Hand Tapper Manual
Machinist Calculator

   
Click on linked thumbnails #ad

Tables
Metric & Inch Equivalents
Inch to Millimeter Conversion Table
Millimeter to Inch Conversion Table
Decimal Equivalents of 8ths, 16ths, 32nds, 64ths
Decimal Equivalents of Letter Size Drills
Decimal Equivalents of Number Size Drills
 
American Standard Pipe Thread & Tap Drill Sizes
Tap Drill Sizes For Fractional Size Threads
Millimeter Tap Drill Sizes
National /Unified Coarse/Fine Thread Dimensions & Tap Drill Sizes
American Standard Acme Screw Thread Dimensions
Double Depth of Screw Threads
ISO External Threads Medium Fit

Cutting Speeds & Feeds for Drills
Temperature Conversion
Rules Relative to the Circle
Tapers & Angles
Triangle Chart

Basic Tapping Guidelines:
Each tap requires a specfically sized hole.
The hole size basically depends on the material being
tapped. Softer materials like aluminum, brass, nylon,
Delrin, require having a hole that yields 75% threads.
Harder materials like iron, soft steel, annealed stainless steel,
require a larger corresponding hole to yield 50% threads.
Failure to select the correct tap hole can result in tap breakage.
A tap is almost designed to break as it is made out of
brittle metal & has numerous "scores" on its surface.
Do not use a low-cost tap on a high-value part due to time & materials.
Broken taps can be hard to remove without causing damage.
Note, many commonly found tables are unlabeled but are for
75% so failures often occur when used for harder materials.
The tap hole should firstly be countersunk to ease starting.
The part & tap must be held normal WRT each other.
Proper cutting fluid for a given material must be used.
Chips must be cleared frequently by backing out the tap.
The tap & part must be held rigidly, with no side forces.
Tapping fixtures & guides mitigate most of these conditions.
Take care to not over torque the tap to avoid breakage.
Smaller taps require greatly reduced forces through
the proper selection of the tap handle size & design.
Different tap chamfers (tapered, plug, bottoming, spiral)
are applied for different tapping designs & materials.
E.g., a blind hole requires sequential use of tapered, plug,
then a bottoming tap. Spiral taps clear chips more effectively.

Drill-Tap Sets

Left to right: examples dipicted of
tapered, plug & bottoming taps, 1/2-20 sizes.
Note they differ by the number of chamfer threads.

Taper (7 to 10 threads)
Also known as a starter tap, a taper tap has the
longest standard chamfer & requires less tapping torque.
 
Plug (3 to 5 threads)
The most common chamfer for use by hand or machine in
through or blind holes. The most efficient chamfer available.
 
Modified Bottoming (2 to 2-1/2 threads)
Allows for threading close to the bottom of blind holes.
Due to the slightly longer chamfer & more working teeth,
this chamfer is more efficient than a bottoming chamfer.
 
Bottoming (1 to 2 threads)
Use for threading close to the bottom of blind holes.
The least efficient standard chamfer available.

Drill & taper tap sets (18 pieces each) left to right:
metric, National Fine (NF) & National Coarse (NC).
Metric: M2.5-.45, M3-.5, M3.5-.6, M4-.7, M5-.8, M6-1, M8-1.25, M10-1.5, & M12-1.75.
NF:  6-40, 8-36, 10-24, 10-32, 1/4-28, 5/16-24, 3/8-24, 7/16-20, & 1/2-20.
NC:  6-32, 8-32, 10-24, 10-32, 1/4-20, 5/16-18, 3/8-16, 7/16-14, & 1/2-13.
Note: the drill bit sizes are for 75% threads in aluminum, brass & plastic.

 

 

 

 

 

 
Left-hand taps
Click on linked thumbnails #ad

Spiral Tap Sets

 Plug & bottom tap sets (USA).
The spiral flutes effectively remove
swarf, especially from blind holes.

HSS combination drill bit & tap, Imperial sizes:
4-40, 6-32, 8-32, 10-32, 10-24, 1/4-28,
1/4-20, 5/16-18, 3/8-16 & 1/2-13.

Combination drill bit, tap, & deburr/countersink.
Metric sizes: M3x.5, M4x.7, M5x.8, M6x1, M8x1.25, & M10x1.5
Each HSS bit has an integral deburr/countersink & quick-change hex shaft.
Note the taper after the threading that prevents over drilling.

Imperial sizes: 6-32, 8-32,
10-24, 10-32, 12-24 & 1/4-20.
Variable quality in an import.

For this 10-24, I disconnected the fine down
feed & used the spring-loaded quill lever.
The mill was turning at 110 RPM.
Don't forget proper lubrication.

 
Click on linked thumbnails #ad

Unified Tap-drill Chart: Tap-drill bit references for imperial, metric, & pipe threads.  Also, 60% & 75% thread tap-drill charts, here. 

Thread diameter.

Taper pipe thread tapping requires greater accuracy & it subjects the tools to higher stresses.
Pipe threads must be formed more accurately, because 100% of the thread height must be cut by
the tap or other pipe-threading tool to maintain the standard thread profile. A machinist looking at a
1/2-14 pipe tap is likely to note that the tap diameter is larger than 1/2". In fact, the tap's diameter at
the large end is 0.865". The tap's designation refers to the inner diameter (ID) of the standard iron
pipe it is designed to thread. Therefore, a 1/2-14 taper pipe thread tap is designed to tap a 1/2" ID
pipe. The external thread on a pipe with a 1/2" ID is at least the size of the ID plus the amount of
two wall thicknesses. To achieve the basic thread depth, drive the tap into the work piece 12 turns.

Trapezoidal (metric) screw thread has a 30 deg included angle. ACME screw thread has a 29 deg included angle.
Trapezoidal screw thread is made & measured in millimeters. ACME screw thread is made & measured in inches.
Trapezoidal screw thread pitch is stated in millimeters of pitch. ACME screw thread pitch is stated in threads per inch.

Formula for tap drill bit (round to closest available drill bit size): D1+(0.05 * p).
Where: D1 = minimum internal thread minor diameter, p = pitch

Thread Measurement

Screw thread micrometer with five different
anvil pairs to measure both unified &
metric external pitch diameter. 0" to 1"
measurement range with a 0.0001" scale.

SCREW THREAD MICROMETER ANVILS
ANVIL #	1	2	3	4	5
TPI RANGE	64 - 48	44 - 28	24 - 14	13 - 9	8 - 5
METRIC RANGE	0.4 - 0.5	0.6 - 0.9	1 - 1.75	2 - 3	3.5 - 5

Anvil pairs are clearly marked for pitch range.

Example measurement of a 1/4-20 screw.
The micrometer reading is 0.2160".
Table pitch value is 0.2164" max.
A fast & accurate thread measurement tool.
The bolt can freely rotate around
the micrometer's anvil axis.

Standard Unified & metric thread gauges.

29 deg ACME (1n - 12n) & 30 deg
ISO (2p - 20p) thread gauges.

Thin-plate type screw thread checkers.
ISO Metric Thread Checker 

Metric (black) & Imperial (silver) nut & bolt thread
checker. Note the lower middle set screw is verified.
This is the best method as you measure multiple threads
instead of just a few like the thin-plate type of gage.
For example, you can easily thread a metric screw
(M5-0.8) into an imperial thread (10-32) using the
thin-plate type but the nut & bolt checker will catch the
mistake as it will cross-thread as the screw goes in deeper.

Click on linked thumbnails #ad
 

 
Click on linked thumbnails #ad

Hand Tappers

PhaseII+ Hand Tapper No. 265-110 Manual

Points to consider for a successful tapping operation:
Proper tap hole size for a given material.
Aluminum is typically 75% thread whilst soft steel
is 50%. Unless specified, most tap tables
are for 75%. Use a properly sized, quality
tap handle or guide that matches the tap's size.
The smaller the tap the smaller the handle must
be to reduce max torque. Tap must be coaxial
to the tap hole. Proper cutting fluid for a given
material (aluminum, steel, brass, bronze) should
be used in good quantity. The tap hole needs to be
chamfered first to allow an easier start to the initial
cutting action. Swarf removal is essential by
repeatedly cutting then backing out the tap.
Spiral taps excel at removal especially in a blind
hole. Use tapered, plug & bottoming tap sets
for blind holes. The tap & part must be rigidly
held. Side forces on a tap can quickly cause
breakage, after all, it is brittle metal & "scored".
Guides/fixtures help mitigate side forces.

A hand tapping fixture allows fast, precise,
perpendicular, tap-to-hole alignment plus it reduces
 tap breakage that can easily occur when too
much torque and/or side forces are applied.
This hand tapper includes a set of adapters: #6, #8,
#10, 1/4", 5/16", 3/8", 7/16", 1/2" & 5/8".

The tap is first fixed to the adapter &
then snapped into the spindle.
The handle has two different lengths to
modulate the hand torque & it can be easily
removed as it is held in by a tapered pin. For
small taps, the knurled finger knob is used.
The adjustable counter-weight applies a slight
upward force that aids unthreading the tap.
If the adapter is snapped in without a tap,
it can be more easily removed by
first rotating the flat detent spring to
release the ball bearing detent.
Be careful to not lose the ball detent.

Detail of the spring-loaded ball bearing detent for
adapter retention in the precision ground spindle.
The flat spring has been rotated to expose the ball
bearing detent. The vise is designed to float in two
 directions enabling easy tap/hole alignment. The
example shows tapping eight, #7 holes, with 1/4-20
threads. A rotary table was used to drill every 45
deg. A semi-automatic machine tapper is faster.

To steady the hand tapper, 5/16-18
SS bolts screw into bench hard points.
The 3/4" holes were drilled using a Forstner bit.
The hard points are held in underneath by wood screws.
I remove the tapper when not in use & screw
the bolts up from the bottom until they are flush.
The bolt-down hole has also been 3/8-16
threaded to use the clamping studs, as needed.

Always chamfer the hole first &
use the proper thread-cutting fluid.
CAUTION: For soft materials (aluminum, brass, plastic)
use a smaller hole for 75% threads & for harder
materials (steel, SS) use a larger tap hole for 50%
threads to reduce tap breakage. See tap hole tables.
Certain materials, e.g., cast iron, can
crumble, so coarse threads are easier to
cut more successfully than fine. Softer steels
can have higher percentage threads (in the 60s).
There are formulae for calculating any desired
percentage threads or use the Machinist Calculator.

The set of hand tapper adapters: The leftmost is a
custom made, aluminum adapter for a 1/8-27 NPT tap.
Then left to right are 5/8", 1/2", 3/8" (2), 7/16", 5/16" (2),
1/4", #10, #8, & #6 hardened steel tap adapters.


Wooden holders tend to wick moisture
away from metal thus minimizing rust.


Each adapter has a round hole with a set
screw to hold the tap in & a square hole at the end that
positively engages the tap in order to prevent rotation.
Note the recess for the spring-loaded detent.
A spiral-fluted bottoming tap is shown.

Note the two drilled tap holes are chamfered, first.

 
Click on linked thumbnails #ad

Cedarberg (USA) hand tappers are the best & most
costly models while the others are lower-cost copies.
This is a small hand tapper with adapters for
seven different tap sizes 0-80 through 5/16-18.
Each hex-shaped adapter has a square hole & a
set screw to securely engage & hold the tap shank.
The shaft rotates in a pressed-in, reamed brass
bearing. The chromed stop pin can be removed to
provide more table room for the vise/part. The pin's hole
can also be used to bolt-down to a bench hard point.
The finger knob is used with smaller taps to allow better
feel & lower torque thus reducing chances of breakage.
The steel table is 8.5" x 6", the clearance height is 3.75",
the throat depth is 4.5", & the overall height is 9".

This example shows a 0-80 tapping operation
where a 3/64" tap hole is required for a 75% thread.

Tapping 6-32 threads into a brass weight.

Tapping 2-56 threads into the end of a brass rod.

Tap Handles

Differently sized tap handles
correspond to various tap-size ranges.
Top: The two larger handles are Craftsman (USA).
Middle: The one medium-sized handle is from Germany.
Bottom: The two smaller Starrett (USA)
handles are of superior design & quality.

The Starrett tap handles have
smooth, ideal shapes; best in class.
Their tappered handles afford the needed
sensitive touch when hand-tapping threads.
You don't want to break a tap off in a part
you have been working on for many hours.

Click on linked thumbnails #ad

 
Click on linked thumbnails #ad

Large handle is being used to tap 75% 3/8-16
threads in aluminum. The smaller blue vise holds
the part for transfer to different machining setups.

Maximum chuck capacity is 0.502".
This larger tap handle holds up
to the 1-1/16" H hand reamer.

Cutting Fluids

Always use the appropriate cutting fluid.
Some fluids are specific (e.g., for aluminum)
 while others generic. Kerosene works very well for aluminum.
Use an acid brush to dab on small, controlled amounts of fluid.
Cutting fluids have higher flash-points.

Precision mini-oilers.
 

General-purpose oiler.

Click on linked thumbnails #ad
 

     

   

 

    

 

 

 

 

 

 

 

 

 

 

Micro-tap handles for very small
(#0 to #6 & M1.6 to M3.5) sizes.
Affords good feel while cutting threads.

Tap wrenches of various sizes.
The two black wrenches (left) have integral guides
that mount in a drill press, mill, or lathe chucks.
The ratchet-type tap wrench (right of center) is
useful in tight places. Tap wrenches usually have a
center-drilled hole on the end that can be used with
a spring-loaded guide. Smaller taps, themselves,
have a chamfered (pointed) shank end & larger
taps have a center-drilled hole to use with guides.

A large, chrome-plated ratchet-type (CW, lock, CCW)
tap wrench with a capacity of 1/4" ~ 1/2" (M6 ~ M14).
The two handles slide out for added leverage & slide
in (or to one side) allowing use in tight places.

This tap handle holds up to the 3/4" E hand reamer.

Tap handles with sturdy integral end guides (USA).
Top left to right: 1/2" to 3/4" & 1/4" to 1/2". Bottom: 0 to 1/4".

6-32 drilled & tapped (50% threads for steel)
in the 9x20 lathe cross slide table back end.
This particular tap handle worked nicely as it has
a guide that is mounted into the drill press chuck.
The large steel cross slide is 9-3/4-inches long.
Everything securely clamped; column & table are locked.

Drilling a 7/32" hole in the end of a 0.79" x 19.7"
(20mm x 500mm) steel rod in preparation for a 1/4-20 thread.
The long rod passes through the hole & hangs
below the table surface of the large floor drill press.

Smaller tap wrench.
 

Larger tap wrench.
 

The lowest speed can usually keep the chuck from
turning but sometimes I use a Tommy bar in the chuck.

 

Click on linked thumbnails #ad

This tap handle slides on a steel rod & the 1" diameter
handle that does not easily over torque the tap.
The long, precision fitted guide rod gives excellent,
rigid support & tapping range.

Wooden tap wrench holder.

 

My Dad's Yankee No. 251 North Bros Mfg.,
Co., Philadelphia, PA, USA, ratcheting
tap wrench that has a brass body.

Tap & Drill Guides

Shop fabricated steel (left) & aluminum (right) guides
help start perpendicular tapping in difficult locations.
Holes match the US standard tap shank diameters.
The smaller holes are for select drill bit sizes.
 

Clamping when possible helps.

Holes are threaded with a 6-32 tap
for a Taig mill DRO modification.
 

 

 

Steel tap & drill guides for both
standard & metric sizes (USA).

 

The bottom is precision ground & has a V-groove to
allow accurate centering when tapping/drilling round parts.

Click on linked thumbnails #ad
 

 

 

 

 

 

Self-aligning tap & reamer fixture. 
Useful for making tapped holes outside of the
controlled environment of the workshop.

 

Supplied with two sets (small & large) hardened
jaws to accommodate a 0-80 to 1/2-13 tap size range.

 

The base has two, 120 deg V's
for centering on round stock.

 

This tap guide (top) has a hardened, reversible tip.
The pointed end fits into a center-drilled tap wrench
end or the cupped end captures/guides the pointed
end of a tap shank. Both have adjustable spring tension
via the set screw. A Taig spring-loaded center is shown
(bottom) that also works well as a tap-wrench pivot.
Spring-loaded guide semi-automatically adjusts
out as the tap cuts deeper into the hole.

This photo shows how each tip type
is used for the spring-loaded guide.

 

 

 

 

 

Use the tap handle to hand cut the thread.

Tapmatic 30X

Tapmatic 30X
It requires a torque bar attached to either the
table or the quill (bracket details are shown, below).
Handy device if many holes need to be tapped
using a mill or drill press. Tapmatic 30X instructions.
 

 

 

The top left knob adjusts tension on a slip-clutch to
reduce tap breakage. The scale is only a positional
reminder. If the tap has a male center, it should be
ground off so as to seat fully into the chuck. Back jaw
set screws engage the tap's square shank. The chuck
assembly floats & taps in/down about 1/2" before
releasing to neutral. The quill stop has to be set
carefully to control depth & release of the tap. Pulling
up on the quill then causes the chuck to reverse at
1.75 times the mill's set RPM. The instructions have
suggested tapping speeds best for high production
output but I use slower mill speeds for small batches.
Bought used on the web. 
 

 

  
Click on linked thumbnails #ad

Quill Bracket

Milling a 3.6" hole on the rotary table. 1/4"
thick material was used; 1/2" would be better.

Tapping an 8-32 thread on one side of the slot
followed by drilling a clearance hole on the other side.

 

Milling a slot for the quill clamp.

 

The torque bar is a 3/8" steel rod
fastened by a 10-32 bolt with a washer.

 

Under heavy use the bracket loosened so the thumb
knob was replaced by a wrench-tightened cap-head.
A second clamping bolt was also added to stiffen the
assembly. A lock washer was also added for the rod.

Die Holders

Die handles: Top one (India) is for 1-1/2" diameter
dies (a split-type is shown), next one is for hex-style dies.
The hex die-to-tap adapter is from the metric set.
One-inch (GER) & 13/16" (USA) round-die holders shown.

Small dies & taps (left to right): 0-80, 1-72, M2-0.4
(in 13/16" die handle) 2-56, 3-48. Small red tap handle.
 

Wooden tap stand being made using the CNC mill.
The part is held by double-sided tape.
 

0-80, 1-64, 1-72, 2-56, 3-48,
4-36, 4-40, 4-48, 5-40, 6-32 taps.

 

A handle that holds 20mm dies.
An M6-1 left-hand (L) die is shown.

 

Metric die & tap set (USA).

 

 

 

 

 

 

 

   

 

 
Click on linked thumbnails #ad


1" & 13/16" round die holder slides on a 9/16" steel
rod with an MT2 adapter for the 9x20 lathe tailstock.
Refer to Machinery's Handbook for the proper
major diameter dimensions for any given threaded rod.

The body is knurled for good grip & the
removable steel bar can be added for more leverage.
Hand use without the bar gives good,
low-torque control for threading delicate parts.

This is a hex & round (two sizes) die holder.
The pockets were CNC fabricated. 

Die holders for threading
whist the part is on the lathe.
The top holder is for 1.5" dies.

Fastener Types

Refer to the Hand Tools Section, too.


Screw-head types. Additionally, there is the
Japanese Industrial Standard (JIS) Driver

Washer types

Nut types

Setscrew Types


Slotted round-head machine screw


Combo round-head (Phillips/slotted) machine screw

Phillips pan-head machine screw

Slotted flat-head machine screw


Phillips truss machine screw

Socket drive, knurled-head bolt with shoulder

Socket drive flat-head machine screw

Socket drive flat-head machine screw with shoulder

Socket-drive, knurled head, shoulder bolt

Hex-head, fully threaded bolt

Hex-head bolt with shoulder

Hex flange bolt with shoulder

Slotted hex-head with washer machine screw

Carriage bolt with shoulder

Timber bolt with shoulder

Combo head sex truss bolt

Combo head truss mating screw

Truss head, one-way mating screw

Phillips flat-head wood screw

Slotted flat-head wood screw

Phillips round-head wood screw

Slotted oval-head wood screw

Phillips pan-head sheet metal screw

Phillips oval-head sheet metal screw

Phillips truss sheet metal screw

Phillips flat-head sheet metal screw

Slotted flat-head sheet metal screw

Hex-head sheet metal screw

Phillips pan-head self-drilling sheet metal screw

Phillips or square-drive, flat-head self-drilling sheet metal screw

Hex-head with washer, self-drilling sheet metal screw

Modified truss with washer self-drilling sheet metal screw

Hanger bolt

Hex flange lag bolt

Forged-eye lag bolt

Forged-eye bolt

Wire eye-bolt

J-bolt

L-bolt

U-bolt

Phillips flat-head concrete screw

Hex-head concrete screw

Hex-head with washer conrete screw

Slotted flat-head sleeve-type anchor

Concrete sleeve-type anchor

Machine screw concrete anchor

Wood screw concrete anchor

IMPERIAL Head markings & mechanical properties

METRIC Head markings & mechanical properties


Hardware

It takes over 440 bins to keep it all sorted.

The newer polypropylene drawers are much
stronger & won't crack/break like the clear ones.

Click on linked thumbnails #ad
   

   

 

 

 

 

 

 

 

 

 

 

 

 
Dowel Pins

   

 

 

 

 

 

Spherical Washers 

   

 

 

 

 

Metric threaded rod, SS, 250mm (10") long.
RH Sizes: M4x0.4, M5x0.8, M6x1.0, M10x1.5,
M12x1.75, M14x2.0, M16x2.0, M18x2.5,
M20x2.5, M22x2.5, M24x3.0

 
Imperial threaded rod, zinc-coated,
6" (152mm) long, 10-pack.
RH sizes: 4-40, 6-32, 8-32, 10-32, 1/2-13, 5/8-11

 

 

 

   

  

 
Blue Loctite has medium grip whereas Red is stronger.
Loctite is a thermal plastic so heat always loosens it.
Loctite Liquid Threadlockers Properties Chart

 

 
Click on linked thumbnails #ad
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 
Metric Sizes
M4-12, M4-16, M4-20, M4-32,
M5-12, M5-16, M5-20, M5-25,
M6-12, M6-16, M12-50 (2 pack)

Lazy Susan heavy duty ball
bearings, available in nine diameters:
6" (140mm),8" (200mm), 10" (250mm),
12" (300mm), 14" (350mm), 16" (400mm),
18" (448mm), 20" (490mm), 24" (600mm) sizes.

 

  

 

 

 

Click to See Ball Bearing Section.

 

 

 

 

 

 

 

 
Click on linked thumbnails #ad

Brother P-Touch label maker; TZe Tape Type.
Brother PT-1400 P-Touch Labeler Manual

Bolt Torque
Torque is the tendency of a force to rotate
an object about an axis, fulcrum, or pivot.

A torque screwdriver set to 20 in-lb

Torque ranges are specified for different screw & bolt types.
It varies as a function of size, material, number of threads,
hardness, plating, lubrication, etc. There are numerous torque reference tables
available on the web; it's common to over-torque. Store torque
wrenches at the lowest setting to help maintain long-term accuracy.
Torque screwdriver instructions

 

 

 

 

 

 

Click on linked thumbnails #ad


Selecting a hollow-ground bit that fits a given screw
greatly reduces damage. Gunsmithing screwdriver set

1/2", 3/8", & 1/4" drive torque wrenches.
Store torque wrenches at the lowest
setting to help maintain accuracy.
The top 3 wrenches measure ft- lb or Newton-meters;
the bottom 1/4" drive wrench measures in-lb or cm-kg.

Tables, Drill-Tap Sets, Tap-Drill Charts, Thread Measurement,
Hand Tappers, Tap Handles, Cutting Fluids, Tap & Drill Guides,
Tapmatic 30X, Quill Bracket, Die Holders, Fastener Types,
Imperial Bolt Markings, Metric Bolt Markings, Hardware, Bolt Torque

HOME