Shear Stength :- The shear test procedure is set forth in ISO 8752, SAE J496, and NASM 10971, which are identical in substances.

Shear values specified will only be obtained under the conditions noted in the referenced standards of special note :-

• The clearance at the shear plane cannot exceed 0.15mm or.005".
• The hole has to be nominal pin diameter (tolerance H6) with a hardness of not less than HV 700.
• The Pin must be installed with the slot up.
• The shear planes have to be at least one pin diameter from each end, and at least two diameter apart.

Insertion Loads:- The following tables are an indication of the typical maximum insertion forces that would be required to insert a Spring Pin using a press or air cylinder. The figures quoted may vary in different applications due to hold and pin tolerance.

Recommended Spring Pin Sizes for Various Shaft Diameters
When used as a transverse pin.

When used as a tongitudinal key.

When used a longitudinal key, a Spring Pin, the length of which is 2 and half times its diameter, develops a shear strength equipment to twice the double transverse shear of the pin.

Combination Double Pins:- In usual conditions which demand exceptionally high shear strengths, it is possible to use pins in combination, by driving an inner pin into an already inserted outer pin. Gaps should be staggered by 180 degrees. Insertion of a combination pin is more difficult than a single pin, and it is recommended that hole size be kept to the high side of the recommended tolerance.

Plating and Surface Finishes :- Dowell pins are normally supplied in a lightly oiled condition, which adequately protects the pins from rust in normal storage, and transit conditions.

Additional protection against atmospheric corrosion is possible by a variety of surface finish processes, which are mainly zinc based. Zinc is an excellent protective material, which has a slow rate of corrosion and also provides additional electrochemical protection for the steel even where the coating is scratched of porous. Zinc coatings usually resist normal atmospheric attack at a rate of around 5 microns or .0002" per year. The addition of a chromate passivation to prevent the initial oxidation of zinc by the atmosphere will significantly increases the protection. Most surface treatments are available on Dowell Pins. A general guide to the treatments most commonly requested is detailed below.

Electroplated Zinc with Clear or Yellow Passivation :-

Phosphate Coat and Oil :- This is a zinc phosphate coating produced by a chemical process in a hot bath dip containing phosphate coating gives a combination of corrosion resistance and lubrication, and is widely used in applications which do not require a long term attractive appearance. It is necessary to stove phosphate coated parts to prevent embrittlement.

Non Standard Size Spring Pins:- In addition to standard Spring Pins, other sizes are available to order, usually subject to a minimum order quantity, although many non standard sizes are held in stock for various customers and to required size or a suitable close alternative may already be available.

Special Spacers, Distances Piece Bushes and Ferrules :-

Non Interlocking Pins :-

In some automatic assembly applications it is important to prevent any risk of pins interlocking together due to the large gap inherent in the design of pins to the metric standards ISO 8752 or DIN 1481.

The design of reduced ends is a practically and very economic solution to the problem in which the ends of the pins are closed down by a minimum amount to prevent interlocking. At the ends of the pin there is some reduction in interference compared with a standard pin.
In most practical applications the performance of the reduced end pin is equal to that of a standard pin.

For applications which demand full interference at the end of the pin there is an alternative design with swaged ends which achieves non interlocking whilst maintaining full dimensional capability.
Minimum lengths and range of diameters suitable for non interlocking designs:

Standard pins over 10 mm diameter do not interlock as the material is of greater thickness than the gap size. All non interlocking pins are made to order subject to a minimum quantity.

Heat Treatment :- We heat treat the majority of pins by autempering, widely considered to be superior to the conventional hardening and tempering process.

In quenching austenite the steel changes to denser atomic structure, and carbon atoms are released. In oil quench hardening these carbon atoms become trapped and distort the structure leading to high stress and brittleness, which must then be relieved by tempering. In austempering, the freed carbon has time to diffuse before transformation occurs, the resulting structure being less stressed and giving superior properties.

The heat treatment furnaces are fully automatic continuous lines which are strictly controlled and monitored to ensure maximum quality and consistency.

Materials:-

Straightness Specification :- The straightness over the length of pins shall be such that the pin will pass freely through a ring gauge of the length and diameter as specified below.

Straightness Gauge Specification:-

Hole Preparation :- Holes can be drilled, punched or cast with no need for additional reaming or sizing. Care should be taken to avoid undersized holes to eliminate potential pin damage during insertion. The following points are suggested for consideration:

• Break or debur the edges, particularly in case of hardened holes.
• Countersinking is not recommended as it increases the clearance at the shear plane.
• In case of cast or sintered metal holes, provide a lead-in radius.
• Whenever possible, punched holes should be punched in the same direction of pin insertion.
• Eliminate hole misalignment problems by drilling holes together.
• In case of hardened collars or similar components, flatten the component at the entry of the hole to avoid two-point contact as the pin starts into the hole.