I.M.U. USA, Inc. provides free direct pick-up & delivery service with our own cargo van for customers located in the Greater Chicago metropolitan area (including Rockford, IL). Eligibility for free service is determined by quantity of dies to be re-ground and estimated frequency of pick-ups.

Otherwise, customers are asked to ship their dies at their own expense to our facility in Chicago.

On the basis of die quantity & size, we will submit a "FOB delivered" quotation covering all remaining transport costs.

Although IMU re-grinds virtually any used dies, there are cases when re-grinding is not recommended.

D2 steel (or equivalent) dies are not worth re-grinding by IMU, as the re-grinding price we quote would not be much lower than the average market price of the same dies when new. Moreover, die-users have often noted that a re-ground set of D2 dies frequently has a lower die-life than a new set. Lastly, no coating applied so far by IMU has significantly improved die-life for D2 steel dies.

Dies which should also not be re-ground are duplex dies whose corners are chipped beyond two thread depths measured from the thread bottom line (see figure below). This issue is not relevant to the first cut of single face, single entrance dies, as IMU automatically reverses the top side by re-marking the intact bottom side.

Other dies which should not be re-ground are those where stress cracks in the thread are deeper than two thread depths measured from the thread bottom line (see figure below). In many cases, this can be detected only when the worn out thread is ground off at the IMU plant. At this stage, IMU determines whether a further reduction in die-thickness can eliminate the cracks or not.

It is important to remark that IMU can easily deal with deep cracks in threads or chipped corners by reducing die thickness or die face, respectively, through supplementary grinding operations.

In consequence, re-grinding cost is increased. We always communicate to the customer any supplementary cost for additional processing and proceed upon customer authorization.

We definitely recommend re-grinding high speed steel dies in # 20 size & larger. Re-grinding smaller dies (up to & including # 10 size) may not be cost-effective, as the price for processing may not be much less than 20% below the cost of a new set. There are naturally exceptions to this rule of thumb: depending on the quantity of dies involved and their general condition, competitive re-grinding prices may be quoted for some dies in the # 10 size or smaller.

There are 2 main reasons which justify re-grinding high speed steel dies.

1) The price of a set of dies (# 20 size & greater) re-ground by IMU is often near to 50% or less than the price of the same set of new IMU dies. This accompanies the fact that the die-life of IMU dies re-ground by IMU is guaranteed to be equal to the die-life of the same dies when new.

2) A coating is ALWAYS applied on any high speed steel dies re-ground by IMU. The IMU coating enhances the wear resistance of the die. Customers often notice how high speed steel dies not manufactured by IMU yield more parts after the IMU re-grinding operation.

Upon arrival at the IMU headquarters, every lot of dies is isolated by customer. Each lot undergoes the following steps:

1) Correspondence is checked between the actual die sizes and those stated on the purchase order of the customer.

Changes in thread size requested by the customer are also noted. Any discrepancy is promptly referred to the customer whose feedback determines how to proceed.

2) Every single set of dies is subjected to visual inspection, in order to determine its effective "re-grindability". Cracks and chipped corners are evaluated, as well as die material. IMU communicates to the customer any information which may require a change in the purchase order and awaits customer approval before proceeding.

3) The worn-out thread is ground-off on all dies, until a perfectly flat surface is obtained. This operation is crucial to the elimination of stress cracks and tensions. The surface is then checked to determine the presence of any residual cracks. A further grinding operation may be necessary in order to eliminate any superficial cracks not exceeding the size of another thread depth. In case cracks still appear after this second surface grinding operation, the dies are set aside and returned to the customer.

4) All the remaining operations are carried out as they would normally be performed during the manufacturing procedure of new dies.

As re-grinding automatically reduces die thickness, the customer usually provides the shims necessary to compensate for the reduction in thickness once the re-ground dies are re-installed into the die-pockets of the threadroller.

However, the following two alternatives are available:

1) IMU can establish a fixed multiple of reduction in die-thickness (1/8", for example) for each re-grinding operation. This enables the customer to keep pre-measured shims in multiples of 1/8" without having to guess the thickness of the required shim once the re-ground dies have to be used.

2) IMU supplies the shims together with the re-ground dies. Usually, one set of shims is supplied for every ten sets of identical dies.

An extra cost applies for both of these alternatives.

IMU maintains a minimum thickness value of 1/2" for any re-ground die. Thus, a thread-roll die can potentially undergo quite a number of re-grinding operations before being scrapped. However, it is quite safe to say that a set of thread-roll dies would usually allow at least two re-grinding operations.

Keeping this figure in mind, we will quantify the cost reduction achieved by re-grinding one set twice versus purchasing two new sets of dies.

We have stated above that some brands of high speed steel dies may yield more parts when re-ground by IMU than when they were new. According to the hypothesis illustrated below, we will assume that the re-ground dies will yield the same amount of parts as new dies.

Price of 1 new set of dies $ 200

Price of 1 re-grinding operation $ 100

Parts rolled with 1 set of dies (new or re-ground) 50,000

Total amount of parts to be rolled 150,000

Total cost of dies: $ 200 x 3 $ 600

Die cost for each rolled part ($ 600/ 150,000) $ 0.0040

Total cost of dies: ($ 200 x 1) + ($ 100 x 2) $ 400

Die cost for each rolled part ($ 400/ 150,000) $ 0.0026 (minus 35% of die cost)