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Casting Repair Products > Crack Repair Tools & Supplies > Metal Stitching Pins > L Series Stitching Pins > L6 Stitching Pins > Steel L Series L6 Stitching Pins > Order # L6B-25  
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Order # L6B-25, Steel L Series L6 Stitching Pins

Specifications  · About L Series Stitching Pins


Shipping Weight

7.20 oz

Thread length

5/8 "



Thread Diameter

0.246 "

Units Per Package


About L Series Stitching Pins
When considering which stitching pin to choose for a particular repair, you will want to understand the functions of our two types of pins.

The most important thing to remember about the L Series pins is that when tightened into the casting they seal on the threads because the pin is bigger than the tapped hole. This results in spreading pressure on the crack. If the casting doesn't have enough structural strength to contain the spreading pressure, extension of the crack can occur. REMEMBER, L Series pins create spreading pressure.

Our L Series pins consist of three different diameters, several different thread lengths, and are made of either steel or aluminum. The L4 pins are very small and have extra fine threads for use in thin material and in tight places. L6 pins are about 1/4" in diameter, have coarser threads, and are the most popular of all pins for many cracks in cylinder heads. Our L8 pins are larger and have the same pitch as the L6 pins. They are used in many casting repairs up to 1" in thickness.

The steel pins are made of a soft machinable steel that has the same expansion rate as cast iron with about the same hardness and corrosion resistance. Our aluminum pins are made of 2024 T4 aluminum. This is a harder, stronger grade of aluminum than most castings are made of.

All LOCK-N-STITCH® pins are designed to be installed up to the shoulder so the head can twist off while leaving a small amount above the surface to grind or machine off. This means that in order to completely fill the drilled hole without more than 1/8" of the pin protruding on the other side, you will have to inventory an assortment of different lengths to accommodate different thicknesses of castings.

Because these pins seal on the threads, it is possible to install them at steep angles to the surface. This is why they are so popular for repairing cylinder heads. The combustion chambers of cylinder heads are, in most cases, very strong structural shapes. The L Series pins perform extremely well in these applications. There are some specific repairs where the CASTMASTER™ pins are required, but for most cases L Series pins really do a good job.

It is not necessary for the tapered shoulder of the L Series pin to contact the surface evenly. In fact, in most cases it doesn’t. In the places a perfect finish is required, such as on a machined surface, the shoulder will crush into the surface and leave a flawless finish when machined. When extra material is to be machined from the repaired surface or when the cast iron is hard (such as exhaust seats), use a countersink to enable the pin to seat deeper.

We recommend that whenever possible you stitch across cast iron intake and exhaust seats and remachine the new seat right over the pin without installing a seat ring. Many repairs can be made to aluminum heads with our L4 aluminum pins without removing the seats. The tap can cut right into the side of the seat.

If your repair doesn't run along an inside or outside corner, or doesn't run into a freeze plug hole or bolt hole, and doesn't require the addition of structural strength, the L Series pins can seal a leak or fill a gap faster and easier than anything else you've ever seen.


·  L Series Stitching Pins

·  Pin, Drill and Tap Chart

 Mini-Kit for L6 Stitching Pins 

L Series Pin Mini-Kits (LMK-L6)
L6 Steel Pin Mini-Kit

 Taps for L6 Stitching Pins 

POWERTAP™ L Series Taps
POWERTAP™ Taps for L6 Stitching Pins

Tough Duty™ Taps for L4 Stitching Pins (LT4ST)
Tough Duty™ Taps for L6 Stitching Pins

 Tap Extractor & Fingers for L6 and C2F Taps 

Tap Extractors for L Series and CASTMASTER™ Taps
Tap Extractors for L Series and CASTMASTER™ Taps

Tap Extractor Replacement Fingers for L Series and CASTMASTER™ Taps (set of 4)
Tap Extractor Replacement Fingers for L Series and CASTMASTER™ Taps (Set of 4)

 Drill Guide & Tap Extension for L6 and C2F Stitching Pins 

Drill Guide & Tap Extension Kit & Components (L6XK)
Drill Guide & Tap Extension Kit & Components

 Pin Spacing Drill Jig for L6 and C2F Stitching Pins 

Pin Spacing Drill Jigs (L6500)
Pin Spacing Drill Jigs

 Quick Change Adapter for L6 and C2F Taps 

Quick Change Tap Adapters (C2TA)
Quick Change Tap Adapters