Plain pins are solid cylindrical pins which have a cold drawn finish. Plain pins with diameters up to 1/8″ have a tolerance of +.000/-.001 in. and diameters 1/8″ and over have a tolerance of +.000/-.002 in.Dowels are solid cylindrical pins which have a centerless ground finish with total precision tolerances.

All plain pins and dowels are special-order items. Various materials, diameters, lengths, end configurations, heat treatment, and finishes are available.

DRIV-LOK’S engineering department will work with customers to provide technical assistance.

Plain and dowel pins are held in place by interference created around the entire pin circumference when it is
pressed into a hole. The insertion, holding, and radial forces generated by these pins are very sensitive to hole diameter variation and usually require the use of a reamed hole.

DRIV-LOK’s split hollow dowels are designed and manufactured to provide excellent retention forces and ease of assembly. They can also be auto-inserted.

Split hollow dowels are ideal for use in conjunction with bolts that pass through the center of the dowel after it has been installed. This offers a weight savings over conventional locating dowels, which require separate drilled and reamed holes. The expense and labor involved in providing separate locating dowels and their holes in
assemblies is eliminated. The bolt hole is counterbored on both halves of the assembly. The dowel is then installed into one of the counterbores and used to locate the other half of the assembly. “Split” hollow dowels offer additional cost savings over hollow dowels machined from tube or bar stock.

A DRIV-LOK split hollow dowel is also used as a Compression Limiter to protect plastic from being crushed or yielding past its elastic limit. When properly designed the bolt head or washer will allow proper seating of the bolt to hold the component in place and the compression limiter will absorb the clamping pressure.

Another application of a DRIV-LOK split hollow dowel is when used as a spacer or standoff to space components apart from one another. They have been used over shafts or bolts to give a set distance between component assemblies.

SITUATION

A leading automotive manufacturer requested engineering assistance from Driv-Lok to solve an assembly problem on one of their transmission lines. The problem was defined as an occasional mis-feed of threaded fasteners during the assembly of a wear plate to the housing. The mis-feed caused the fasteners to fall into the gears and cause failure of the entire assembly. The threaded fastener’s only function was to hold the wear plate to the housing so it could be inverted for assembly completion.

SOLUTION

This application was already using Driv-Lok split hollow dowel pins as a partial holding system. Driv-Lok’s ENGINOMICS team reviewed the situation and added a locking feature to the center of the split hollow dowel, which held the wear plate in place. This feature was then patented under patent #US 7,241,095 B2. This upgrade eliminated the use of the threaded fastener, provided the customer with cost savings, solved the problem, and prevented future defects.

ADVANTAGES

• IMPROVED ASSEMBLY METHODS
• REDUCED COSTS OF OVERALL ASSEMBLY
• ELIMINATION OF ASSEMBLY PROBLEM
• REDUCED NUMBER OF THREADED FASTENERS REQUIRED

Tubular slotted spring pins are manufactured by progressive roll forming flat strips of high carbon steel or heat treatable 420 stainless steel. After forming, the pins are deburred to remove sharp edges, then heat treated to a spring temper. High-carbon (1070-1095) steel spring pins are hardened to Rc 46-53 and 420 stainless steel spring pins are hardened to Rc 43-52.

Spring pins are manufactured to an oversize dimension so that when the pin is inserted into a hole, radial forces are generated against the hole wall holding the spring pin securely in place.

The barbs are located at 120° intervals on the diameter of the pin. The number of barbs along the length of the pin, and the distance between the barbs are determined by pin diameter and customer requirements. The crests of the barbs constitute the expanded diameter. The expanded diameter of the barbed pin is measured on the second barb from the end of the pin and is measured with a ring gage.

BARB-LOK Pins and Studs are made from low carbon steel or aluminum. Low carbon BARB-LOK Pins and Studs are zinc platedfor corrosion resistance. Other finishes are available upon request.

Barbed pin holding power is affected by the pin diameter relative to the hole diameter and material hardness. The recommended hole size for most soft plastic applications is .001 to .005 below the nominal pin diameter. Hole sizes for hard plastic and aluminum applications should be greater than the nominal pin diameter. Specific hole sizes should be determined for each individual application. Ideal product for tamper-resistant applications.

SITUATION

A major manufacturer of infant car seats required a more reliable
method of holding the armrest onto the seat. Their former method
was to use a standard screw to fasten the armrest in place. The
movement of the armrest up and down would loosen the screw.
They needed a method that would hold the armrest fi rmly in place,
while still allowing it to rotate as designed.

SOLUTION

Through our ENGINOMICS ®, Driv-Lok Inc. identifi ed a solution to
the problem by using an engineered Ferrol Stud. Ferrols around the
circumference of the pin are designed so the plastic fl ows over
them when the pin is inserted. The ferrols then lock into the plastic,
making removal of the pin virtually impossible. This allows the arm
to rotate freely while maintaining the required tight fit.

ADVANTAGES

• EASE OF ASSEMBLY
• IMPROVES ASSEMBLY JOINT
• TAMPER-PROOF DESIGN
• MULTI-FUNCTIONAL DESIGN

Knurled pins are similar to grooved pins because they have serration around the nominal diameter of the pin. The knurled pin differs from the grooved pin while there are many serrations on a knurled pin. Also, knurled pins are typically roll formed whereas grooved pins are swaged. A knurled section may have either a straight knurl, a helical knurl, or a diamond knurl configuration.

Knurled pins are available with nominal diameters from 3/32″ through 3/8″ and lengths from 3/16″ through 3″.

The serrations on a knurled pin, when compressed by insertion into a hole, result in forces which hold the fastener in place. Radial forces are more evenly distributed around the diameter of a hole for knurled pins than for grooved pins. This is because a knurled pin has more points of contact with a hole than a grooved
pin. The teeth may broach the mating hole when the material is softer and more ductile than the pin material.

The amount of expansion is predicated on the knurl pitch. Coarse knurls provide greater expansion than fine knurls. A knurled pin should have a minimum of 15 teeth to allow proper feed and rolling capability. The number of teeth must be a whole number to allow for proper tracking and avoid slivering. The capability on expanded diameter tolerance is +/-.002. Call for assistance in determining proper knurl pitch for your applications.

SITUATION

A customer was looking for a way to fasten an aluminum extrusion to an aluminum end plate for use in a lighting
application.

SOLUTION

Driv-Lok’s ENGINOMICS® team designed and produced a fastener that combined two of our technologies- a Knurl on one end and a Barb-Lok on the other. This allowed the customer to easily install the plate onto the extrusion,
securely holding it in place while using only one type of fastener.The new fastener also eliminated the need for
expensive driving equipment, saving the customer money.

ADVANTAGES

• Two-way design resists pullout
• Increases speed of assembly
• Reduces boss fractures
• Eliminates expensive driving equipment

The groove of a grooved pin is formed by a swaging operation in which three tools penetrate the nominal diameter of the metal at 120° intervals. This penetration displaces a controlled amount of metal to each side of the grooving tool, forming a raised portion along the side of each groove.

The crest of these raised portions forms the expanded diameter or “Dx” dimension which is shown in Figure 1. The Dx is a few thousandths larger than the nominal diameter “D” of the pin. The amount of expansion varies with the diameter of the pin, the material being grooved, and the style of groove.

When a grooved pin is used, the hole into which the pin is to be inserted is drilled a few thousandths larger than the nominal diameter of the pin. The hole must never be smaller than the nominal diameter of the pin. (See Grooved Pin Drilling Procedures and Hole Tolerances on page 4.)When the expanded portion of the pin is compressed by insertion into the hole, radial holding forces are generated as shown in Figure 2. These radial forces lock the pin securely into the drilled hole.

SITUATION

A heavy equipment manufacturer using a threaded fastener was experiencing loosening of the joint due to vibration in a hinged joint application. in addition, their current assembly method was extremely slow and ineffi cient.

SOLUTION

The Driv-Lok Inc. ENGINOMICS ® team introduced a Type “E” Groove Pin to the design. This pin eliminateD the loosening that the threaded fastener experienced. The team also designed an insertion press to install the pin. This press holds multiple pieces in place, hands free, while the pin is inserted into the application. The design
is such that the pin is installed to the same depth every time. The end result was a complete system to solve both the fastening and installation problems.

ADVANTAGES

• HIGHLY EFFICIENT, HANDS-FREE ASSEMBLY METHOD
• COST EFFECTIVE ASSEMBLY FUNCTION
• LOWER INSTALLATION COSTS
• ONE SOURCE FOR FASTENERS AND INSTALLATION