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Oster Power Threading Handbook

Common Machine Problems

The following are some of the more general machine problems encountered by users in the pursuit of good threads.


Most electrical problems encountered in the field have to do with the loss of threading power. Machines are susceptible to power losses when an extension cord is used. If it cannot be avoided, use a cord with at least 12 gauge wire up to 10 feet and 10 gauge wire for extension cords over 10 feet. In any case it is not a good idea to go over 50 feet in length with any extension cord. Other electrical problems have to do with the amount of current being used. On machines that use 120 volts this is especially sensitive. When cutting the last few threads on a 2 inch pipe, current usually rises to the 30 amp level at the set point of the average 120 volt breaker. This is not a problem if the machine is alone on the circuit, but if any other machines are on the same circuit then overloading can occur. In general, operate your threading machine alone on its own circuit and look to see that the circuit breakers are sufficient to handle the loads your machine will place on that circuit. on machines with plugs, never defeat the grounding pin as serious personal injury could result. Insure that all machines are properly grounded.

Dirt And Grit

A multitude of problems are caused by dirt and grit getting in between metal surfaces which causes rapid wear of even hardened steel. This also causes smooth working surfaces to bind up, resulting in poor threads and early machine failure. Much of the dirt and grit comes from the environment in which the machines are used. Attention should be used to limit the amount of foreign matter that is carried into the machine by the material being threaded. Cleaning the material before it enters the threader is always a good idea. One not so obvious source of dirt and grit is the coating on the pipe. This coating is a varnish type of material that breaks into a very fine grit when the pipe is being threaded. If left to accumulate, it will cause early wear and failure. It also tends to cause the die head to bind up and not operate freely.

A lot depends on the type of material that you are threading. Cast pipe will produce a fine chip and the oil should be filtered more frequently than when threading stainless steel that has a large chip. Common sense should be used, so that the oil does not become contaminated with sand, dirt or rain water.

BESTOIL never loses its ability to provide the proper metal film-lubricity and cooling that is so necessary to threading, but it does need to be filtered once in a while, depending on the usage. just strain the oil through a cloth and put it back in the machine.


There are two types of ways, round and flat. The round ways are used on the smaller portable machines and the flat ways are used on larger machines. The problems that arise in the round ways are from dirt, grit and misuse. An occasional drop of lubricating oil (NOT CUTTING OIL) will do a world of good. Misuse of the round ways comes from their being used as handles. This is one of their functions but care should be taken not to bend or dent the ways as they are what align the dies with the material.

Flat ways are more susceptible to dirt and grit wear than round ways and therefore should be wiped off with a rag more often, and small amounts of thin lubricating oil placed on them.

Die Heads

Stationary - This type of die head does not turn, it moves, usually on a carriage, axially along the material. The majority of these are adjustable, in that they can cut a range of pipe or bolt by aligning pre-set marks. The majority of these type of die heads are quick opening. That means that when the length of thread has been cut, a handle is lifted and the dies move away from the material (some die heads open automatically). The dies are usually inserted in the die head by aligning the "change dies" marks. NEVER force the dies either in or out. Stop and find out why they do not slide easily. It is better to disassemble a die head than to hammer a set of dies out of it. Most problems in this area are caused by dirt and grit or chips. Always use a brush to clean out the slots before inserting a set of dies. When setting for correct size, remember that very small movements along the size marks move the dies in and out relatively large amounts.

Problems involving inconsistent size are usually die head problems and can be traced to three places. 1. Bolts in the die head are loose and need to be tightened. 2. The dies are hanging up in the slots and need to be removed and the slots cleaned (never file the slots). 3. The die head is worn in either the slots or the linkage. The linkage can be replaced; however worn slots dictate a new die head.

Periodically remove the die head from the machine and disassemble it, then wash it in a cleaning solvent, and add a small amount of lubricating oil.

With a little care the average stationary die head should last many thousands of threads.

Rotary - The rotary die head differs from the stationary die head in that it rotates instead of the material. The material is clamped in a vise and only moves axially into the rotating head. This type of die head is generally used for production type work. All of the housekeeping precautions that were taken on the stationary die head apply to the rotary head. The only difference is that rotary die heads do not adjust from one size to another, although small adjustments of diameter can be made involving a few thousandths of an inch. Rotating die heads require a different set of dies for each size and pitch of pipe or bolt. Dirt and grit are this die head's worst enemy, but with proper care and cleaning they are an excellent way to thread.


There are two types of carriages. One carries the die head and one carries the material in a vise. In operation these are similar to each other, and consequently fall prey to the same problems. The majority of carriage problems are from wear, causing alignment difficulties. Some play should be felt from side to side but when the amount is in question the manufacturer should be consulted to find out if it is excessive. Some carriages (with flat ways) have adjustable gibs that can be tightened to take up excessive wear.


The alignment of the spindle, chucks, die head and material is critical to the threading operation in that it insures the material is being guided into the center of the dies. If the machine components are misaligned, poor threads will result. An easy test to check alignment is to, (with the machine off), place the material in the chuck, close to the die head, then bring the two together. The material should touch all the throats of the die segments at the same time. If it does not, the machine is out of alignment.


It is important that the threading machine is kept as level as possible. Large machines should be mounted per the manufacturer's instructions. Portable machines are often used outside on construction sites. Care should be used to keep them on as level and stable a surface as possible.


Transmissions are found on the mid-sized to larger threading machines. As with any other machine tools periodic care should be taken to maintain the proper level of lubrication oil in the cases. Your owner's manual should list the type of oil and frequency of replacement.

Chucking Of Material

Frequently long sections of material are placed in threaders. When their length creates a force loading one end down, they should be supported by an auxiliary stand.

On machines with stationary die heads, the chucks rotate with the material. The clamping device located closest to the die head is usually the chuck. Most chucks on threaders are the hammer type. The rear chuck is a centering chuck and should not be tightened down, just brought to the point of touching the material.

If trouble is encountered gripping the material with these types of chucks, check the replaceable jaw inserts to see if they are cracked, broken, or worn. On machines with rotating die heads the chucks do not turn. Problems incurred with gripping in these devices are usually due to worn jaws.


Cutting fluids are not good machine lubricants. Knowing this, having a can of lubricating oil by your threader is a good idea. An occasional drop of oil on the ways and die head will help preserve the machine. As with other machine tools, a program of greasing and lubrication, using your owners manual as a guide, is a must for trouble-free operation.