Lyman Mag 20 Furnace Instructions Manual

							Mag 20 Furnace Assembly, Operation and Parts
Assembly
The main body of your furnace is fully assembled and factory-tested. To facilitate packag-
ing, the valve rod and operating lever have not been factory-installed and you must do so,
prior to using the furnace as follows: Attach the operating lever spring to the operating lever.
Slide the valve rod on the operating lever as shown in Figure 19. Next, place the valve rod
and operating lever, into position as shown in Figure 20. Fasten the operating lever using the
furnished 5/8 6/32 screw. Insert the lever adjusting screw and hex locknut as shown. Your
furnace is now ready for use.
Handling Lead
Lead, a substance known to cause birth defects, reproductive harm and other severe physi-
cal injury, must be handled with extreme care. Handle lead bullets or lead shot only in a well
ventilated area and ALWAYS wash hands after handling lead and before eating. Discharging
firearms in poorly ventilated areas, cleaning firearms, or handling ammunition, also may
result in exposure to lead. Have adequate ventilation at all times.
Figure 19.Figure 20.
WARNING: Melting lead and casting lead objects will
expose you and others in the area to lead, which is known to
cause birth defects, other reproductive harm and cancer.
REDUCING EXPOSURE:
Lead contamination in the air, in dust, and on your
skin is invisible.
Keep children and pregnant women away during use and until cleanup is complete.
Risk can be reduced — but not eliminated — with strong ventilation; washing hands imme-
diately after use of these products before eating or smoking; and careful cleaning of surfaces
and floors with disposable wipes, after lead dust has had a chance to settle. Use a lead spe-
cific cleaner with EDTA, or a high-phosphate detergent (like most detergents sold for electric
dishwashers) and bag used wipes for disposal.
Use Strong VentilationMag 20 Furnace Mag Dipper Furnace 
						

							Safety Precautions:
1) No casting should be done without basic safety garb. This would include long pants and long sleeves, sturdy
gloves, eye protection and closed top shoes.
2) Keep all flammable items away from casting area. Do not operate unit on flammable materials such as paper,
wood or carpeting.
3) Casting should be done in a well ventilated area. Avoid breathing fumes and dust from furnace.
4) Never allow moisture near molten lead. When moisture is introduced to molten lead, a terrific steam explosion
occurs and molten metal is sprayed not only over the immediate area but also over the bullet caster. This moisture
could be introduced by a wet ladle or dipper.
5) Keep children away from casting and reloading areas.
6) Never pick up unit when heated.
7. Do not continue to cast if distracted.
8. Do not smoke or eat while handling lead.
9. Do not run dry without lead. (Except initial warm-up period.)
10) Keep plug dry.
11) Wash hands after handling lead.
12) Use caution when adding bullet metal to furnace or pot containing molten metal to avoid splashing.
Operating your Furnace
Be certain that the thermostat control knob is turned fully counterclockwise to the stop.
This means your furnace is “off”. Next, plug in the electrical cord to an appropriate wall
socket and, once your pot is loaded with up to 20 lbs. of cold bullet metal, you are ready to
apply heat and begin casting.
Note: Before using your new furnace for the first time, we suggest you turn it on, empty,
for 10 or 15 minutes in a well ventilated area (better yet, outdoors) to burn off preservatives.
The unit usually smokes a bit at first which can be a problem inside your house.
The temperature of your furnace is controlled by a positive action thermostat that senses
the lead alloy temperature of the furnace. The thermostat will cycle power to the furnace to
maintain the desired casting temperature. This furnace is equipped with a pilot light located
adjacent to the thermostat control knob. When this pilot light comes on, it means the furnace
is heating the bullet metal. When the light goes off, the furnace is not heating the bullet metal
as it has reached the set temperature.
When you have determined the casting temperature best for you, mark the control dial
plate for future reference. The Lyman casting thermometer is particularly useful here.
Melting Cold Bullet Metal
After loading the furnace pot with up to 20 pounds of bullet metal, turn the thermostat control
knob to the desired temperature setting. The thermostat will deliver maximum power to the heating
coil until the pot contents reach the designated temperature - usually about 15 minutes.
At that time, the heating system will begin cycling as the thermostat maintains a consistent tem-
perature. The blinking pilot light tells you the furnace is cycling at the dialed temperature level.
The numbers on the thermostat control knob are for reference only and do not relate to the tem-
perature of the bullet metal. You will need to experiment with different thermostat settings in order
to find the temperature that works best with your bullet metal and mould combination. If you have a
casting thermometer, 700 degrees F is a good starting point. Once you find your best temperature,
mark the dial so you can return to it in subsequent casting sessions.
Mag 20 (continued) 
						

							When replenishing a near-empty pot, there is no need to adjust the control knob since the
furnace automatically increases its heating efforts until the designated pot temperature is
reached. The blinking pilot light indicates the furnace is at temperature.
The bottom pour spout valve system of the furnace has been designed to provide efficient
trouble-free casting. Valve leakage is usually caused by dirt and grit, suspended in the molten
metal, jamming the valve partially open.
Opening that valve to “full open” will usually clear such debris. When this does not work,
drain the furnace and allow it to cool. Then dismount and clean the shutoff rod valve and
internal bottom pour spout drain.
If the drain channel is seriously clogged, heat the furnace to the melting temperature. Hold
an unbent paperclip with pliers and feed the wire up through the drain channel to dislodge any
obstruction. Be careful to wear heat resistant leather gloves when performing the above pro-
cedure.
How to Use the Warming Shelf
The warming shelf is located on the rear rim of the inner pot and allows you to pre-heat
your mould blocks while the furnace is bringing your bullet metal up to casting temperature.
Single and double cavity moulds are best stood on end with the handles straight up. Four
cavity blocks are best positioned horizontally on the warming shelf.
Use of the warming shelf and the foregoing placement techniques will greatly reduce the
block warmup time to produce a good bullet - and keep the handles cool, too.
The Thermostat
Your new Lyman electric furnace provides a full range of temperature adjustments. The
thermostat employed is one of the finest available and allows you to control the melt tempera-
ture to within 20 degrees repeatability.
In time, your original thermostat and/or heating coil will age to the point where it needs
replacement. In the interest of safety, replacement thermostats and heating coils must be
installed in our factory. A minimum charge (plus shipping) is made for this service.
Remove all bullet metal before shipping your furnace to the factory for service.
Preserving your Furnace’s Heating System
To realize the longest possible life from your furnace, follow these precautions:
I . Disconnect your furnace when it is not in use.
2. Do not operate your furnace above rated voltage (115 Volts, AC or 240 Volts, AC).
3.For maximum life, run the furnace at the lowest temperature that provides satisfactory
casting. Establish appropriate temperatures by trial for each type of bullet metal. Normally
a 650˚-720˚ F temperature range proves adequate for most bullet casting.
Lyman Mould Guide - Alignment and Use
The proven and popular Lyman Mould Guide is an assembled part of your new electric furnace. Please
read the following for details on how to adjust the mould guide for optimum performance for your applica-
tion.
Place your bullet mould in the track of the mould guide and raise the entire mould guide assembly until 
Mag 20 (continued) 
						

							there is about 1/4 between the pouring spout of the furnace and the top of the mould block. Tighten the
elevation adjustment screws against the support posts so the mould guide will remain in this position.
To align the sprue hole in the mould with the pouring spout on the furnace, you must
loosen the carriage bolt in the adjustable mould guide slide. Loosening this bolt will allow the
adjustable slide to be moved backward and forward. This also allows the horizontal alignment
of the track. On multiple cavity moulds, align the sprue hole closest to the operator. When the
sprue hole is aligned, slide the adjustable slide tight against the front of the mould block and
tighten the carriage bolt.
When using the mould guide with a multiple cavity mould, the mould is set into the track
and slid forward until it touches the adjustable slide.
Then, the cavity closest to the operator is filled with molten bullet metal first. Remaining
cavities require visual alignment and are filled (each in order) as the mould is slowly drawn
toward the operator. When all cavities are full, allow the mould to rest on the track for sever-
al, seconds until the sprue solidifies.
If an ingot mould is to be used with the furnace while the mould guide is in place, set the
ingot mould (length-wise) either on top of (it may be necessary to remove the mould stop), or
beneath the track and fill the cavity closest to the operator first. Remaining cavities are filled
by slowly drawing the ingot mould toward the operator. Pliers should be used to handle the
ingot mould and care taken to avoid accidental spilling of hot bullet metal.
Note: Be a safe bullet caster. Wear protective glasses, gloves, long-sleeve shirt, long pants
and closed top shoes when casting. Do not allow moisture, in any form whatever above or
near your furnace filled with molten lead. When moisture is introduced to molten bullet
metal, a terrific steam explosion occurs and molten metal is sprayed not only over the imme-
diate area but also over the bullet caster.
1Carriage Bolt 2990503
2Adjusting Slide 2990502
3Rivet* 2990724
4Channel* 2800095
5Base Plate* 2990515
6Elevation Adjustment 
Screw (2) 2999048
7Post Support* (2) 2990696
8Washer 03236R
9Plated Hex Nut 2990075
10 Complete Mould Guide 
Assembly 2837515
*Not Available Separately
Mould Guide Parts ListKey  Part Description  Part #
Mag 20 (continued)
WARNING! See Safety
Instructions Page 57 
						

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MAG 20 (upper)
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www.lymanproducts.com
See Page 63 for parts Description 
						

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MAG 20 (lower)
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							MAG 20 PARTS LIST
1Lever Stud* 2999081
2Rd. Hd. Screw #6-32 x 5/8** 2800029
3Limit Screw** 2999092
4Hex Bolt 
1⁄4-20 x 1” (4)* 2800079
5Valve Guide Plate* 2999080
6Inner Pot* 2800074
7
1⁄4-20 Hex Nut* 8094080
8Self Tapping Screw (8)* 2800080
9Upper Body* 2800081
10 Heating Element 110V* 2800073
11 Probe Retainer* 2800084
12 Hex Nut 10-24 (6)* 03324R
13 Lower Body* 2800086
14 Carriage Bolt** 2990503
15 Adjusting Slide** 2990502
16 Lower Post (3)* 2800004
17 Washer** 03236R
18 Base* 2800087
19 Hex Bolt 
1⁄4-20 x 1⁄2” (3)* 2800088
20 Shut Off Rod** 2999085
21 Lever Spring**** 2999087
22 Lever**** 2999086
23 Knob Stud**** 7994420
24 Lever Knob**** 7994419
25 Indicator Light* 2800072
26 Pan Head Screw #6-32 x 
1⁄4”* 2800089
27 Thermostat Knob** 2800077
28 Thermostat 110V* 2800071
29 Washer (5)* 2800091
30 Strain Relief Bushing* 2800094
31 Channel*** 2800095
32 Electric Cord 110V* 2800070
33 Hex Nut #10-24 2990075
34 Post Support (2)*** 2990696
35 Elevation Adjustment Screw*** 2999048
36 Base Plate***   2990515
37 Rivet*** 2990724
38 Insulation* 2800078
39 Hex Nut 2800043
*Factory Serviced Part Only
**Part Supplied for Customer Service
***Available as an inseparable sub-assembly 2837515
****Available as an inseparable sub-assembly 2999093