INSTRUCTIONS for
F-11-964-G
October, 2013
Be sure this information reaches the operator.
You can get extra copies through your supplier.
ST-21M
MIG WELDING TORCH
P/N 690509
These INSTRUCTIONS are for experienced operators. If you are not fully familiar with the principles of operation and safe prac-
tices for arc welding equipment, we urge you to read our booklet, “Precautions and Safe Practices for Arc Welding, Cutting,
and Gouging”, Form 52-529. Do NOT permit untrained persons to install, operate, or maintain this equipment. Do NOT attempt
to install or operate this equipment until you have read and fully understand these instructions. If you do not fully understand
these instructions, contact your supplier for further information. Be sure to read the Safety Precautions on page 2 before
installing or operating this equipment.
I. INTRODUCTION
The ST-21M (P/N 690509) is a liquid-cooled, in-line body
style, machine torch designed exclusively for mecha-
nized mig welding installations. The current carrying
capacity of this torch is 600 amperes continuous duty,
using all types of welding wire in sizes ranging from .030
inches (0.8 mm) through 7/64-inch (2.8 mm) diameters,
including flux cored wires.
The torch can be mounted directly to an EH-10A welding
head, and can be easily adapted for remote mounting.
The ST-21M is attached to the welding head by means
of an accessory mounting adaptor. To facilitate maneu-
verability and installation fixturing, all service lines are
internally connected to the torch body and exit from the
rear of the torch barrel.
The torch is designed for use with either threadless
type contact tubes which are secured by a collet nut,
or threaded contact tips (see Table 2). The threadless
contact tube can be quickly and easily replaced by un-
screwing the metal nozzle and collet nut (in that order),
and then slipping the contact tube out. The threaded
tips can be replaced by removing the metal nozzle and
unscrewing the tip. Six metal nozzles (one for spot
welding use) are available for use with this torch (see
Table 1). Nozzle sizes 8 and 10 require a spatter liner.
NOTE: Due to the high electrical conductivity, use of tap
water or commercial anti-freeze is NOT recom-
mended for torch cooling. Use of the a coolant
circulator using a specially formulated torch
coolant (P/N 0560950312, 1 gal. container) is
recommended for torch cooling. The coolant
also provides anti-freeze protection down to
-34° F.
II. ACCESSORY EQUIPMENT
A. REQUIRED EQUIPMENT
1. Torch Mounting Bracket, P/N 633885.
The bracket
includes as insulator sleeve which insulates the torch
from the welding head. See Figs. 1 and 2.
2. Nozzle and Wire Feed Accessories.
The ST-21M
also requires a nozzle, a nozzle spatter liner, and
several wire feed accessories (contact tube or tip,
liner, and inlet guide tip) of the proper size for the wire
being used. These accessories are listed in Tables0
1 and 2 following.
3. Service Line Connections and Extensions.
De-
pending on mounting arrangements or welding head
to be used, there are several methods for connecting
the torch service lines to the gas, coolant, and power
supplies (see Fig. 4).
a. Connection block assembly (P/N 58V74) is avail-
able for mounting on the EH-10A welding head.
b. The following service lines and couplings are avail-
able:
Coolant Hose, 3-ft....................................................... 20634
Coolant Hose, 12-1/2-ft. .............................................40V76
Coolant Hose, 25-ft................................................... 406196
Gas Hose, 3-ft. ........................................................... 31504
Gas Hose, 12-1/2-ft. ...................................................40V77
Gas Hose, 25-ft. .........................................................34V38
Power Cable, 12-1/2-ft................................................40V78
Coolant Hose Coupling...............................................11N18
Gas Hose Coupling ....................................................11N17
Power Coolant Out Coupling ......................................11N19
Power Cable Adaptor.................................................. 45V11
Coolant Adaptor (connects hose to 1/4-in. NPT) ........11N16
4. Welding Head Accessories.
Two other accessories
whose selection depends upon wire size and type,
are the feed roll and inlet guide insert on the welding
head. Selection of these accessories is covered in
the instruction booklet supplied with the welding head.
Mounting bracket, Part No. 996497, can be used to
mount an EH-10 to adjustable slide P/N 25V39 (Fig.
2) or to user designed set-up.
