WIDIA - Полный каталог инструмента

Technical Information

Ground Thread Tap Limits

для размещения заказа - zakaz@widiahanita.ru

In addition to the nominal size and pitch of a tap, there is another

important dimensional factor to be considered when selecting a

ground thread tap for a given job. This factor is the pitch diameter

tap limit, “H” and “L”. “H” represents (high) above basic pitch

diameter; “L” (low) is below basic pitch diameter. Tap limits have

been established to provide a choice in the selection of the tap size

best suited to produce the class of thread desired.

Figure 1 Illustrates the numbering system and the .0005" diameter

increment separation between successive limits. Because

the starting point is basic pitch diameter, dividing the limit

number by two establishes, in thousandths of an inch, the

amount the maximum tap pitch diameter is above basic

in the “H” series and the amount the minimum tap pitch

diameter is under basic in the “L” series.

Figure 2 Illustrates the positioning of the tap limits in relation to the

various classes of threads for a 1/4–20 size.

Figure 1

.0050

.0045

.0040

.0035

.0030

.0025

.0020

.0015

.0010

.0005

basic

P.D.

.0005

.0050

This chart shows the

method of designating limits

and does not indicate

available taps in any

particular size.

H10

.0045

.0040

.0035

.0030

H6 .0025

H5 .0020

H4 .0015

.0010

.0005

H1 basic

For taps through 1" inclusive, 8 TPI and finer

For sizes from 1–1-1/2"

inclusive, 6 TPI and finer

P.D.

Figure 2

.2255

.2245

.2235

.2225

.2215

.2205

.2195

.2185

basic

.2175

P.D.

.2165

Class of Thread – 1/4–20 UNC and NC

tap limits

.2248

tapping hole limits

TOL.0005

H2 TOL.0005

H1 TOL.0005

TOL.0005

TOL

.0073

.2248

TOL

.0049

.2211

TOL

.0036

.2211

TOL

.0036

.2201

TOL

.0026

.2255

.2245

.2235

.2225

.2215

.2205

.2195

.2185

.2175

.2165

Y98

zakaz@widiahanita.ru

WIDIA - Полный каталог инструмента - 2017