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Casting Repair Products > Crack Repair Tools & Supplies > Metal Stitching Pins > C Series Stitching Pins > C3 Stitching Pins > Steel CASTMASTER™ C3 Stitching Pins > Order # C3B-50  
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Order # C3B-50, Steel CASTMASTER™ C3 Stitching Pins

Specifications  · About C Series Stitching Pins


Shipping Weight

52.00 oz

Thread length

7/8 "





Major Diameter

0.375 '

Shoulder Diameter

0.480 '

Tap Drill Size

0.316" (letter O)

Thread Diameter

0.375 "

Units Per Package


About C Series Stitching Pins
CASTMASTER™ (C Series) stitching pins do not spread the crack! In fact they do the opposite. This pin with its incredible Spiralhook™ threads creates a drawing pressure that actually pulls the sides of a crack together and permanently locks them together. C Series pins exert PULLING pressure.

So why not just always use CASTMASTER™ pins? The installation process requires that every drilled hole receive a recessed spotface to assure some of the shoulder of the pin remains below the surface after grinding or machining. The spotfacing is accomplished with a special piloted tool. The reasons not to choose C Series pins for all your repairs are cost, speed and technical requirements. Because of the spotface, installing the pins at steep angles to the surface usually doesn't leave enough material thickness for the threads.

Almost all repairs to cylinder heads that are made below the seat angle are made with L Series pins. C Series pins can be used from the bottom of the seat angle outward to the end of the crack. A new seat can be ground or three-angle cut right on C Series or L Series pins. Cracks that extend back into a port are repaired by drilling through both walls. C Series pins will seal on both ends.

Cracks that run crosswise on the top of cylinder heads are usually repaired with CASTMASTER™ pins in order to add strength instead of spreading pressure, so the repair will not open when the head is torqued to the block. Cracks that extend from threaded holes, freeze plug holes, pipe plug holes and main bearing holes require CASTMASTER™ pins. Cracks that originate from the corner of the cap fit in a main bearing can be repaired with C Series pins.

You should always choose the largest diameter CASTMASTER™ pins that you can. For repairs in thin sections down to 0.100" use C1 pins. For sections starting at 0.200" in thickness, use C2F pins and for sections 0.750" to 2" use C3 pins.

C2 was the first CASTMASTER™ pin introduced and is now is being replaced with C2F pins. Many improvements, including one of the original design features, have been included in this new version. These changes include a single tap process for through holes, same tap drill size as L6 pins, a hook angle under the shoulder with matching spotface, ability to be used in thinner sections and a large increase in strength and seal.

In extreme structural repairs, locks should be used in conjunction with CASTMASTER™ pins. It is often easiest to use L Series pins next to the locks and then continue the repair with C Series pins.

Steel CASTMASTER™ pins can be used in aluminum castings where heat and corrosion are not a factor. Aluminum CASTMASTER™ pins should be used in combustion chambers when cracks extend below valve seat inserts and when the inserts will be replaced. When seat inserts will be replaced after a crack repair it is not necessary to heat the head and freeze the seat prior to installation. You can simply apply LHC623 to both the seat bore and seat and drive the seat in the way you would in a cast iron head. The sealant will lubricate during installation and then cure for retaining strength.

NOTE: The spotface depth for C Series pins is important. Whenever possible you should try for approximately 50% of the shoulder to be left below the surface. In the combustion chamber this will make the repair more heat-resistant. You must pay close attention to the depth of the spotface to make sure there is enough material left for threads.


·  C Series Stitching Pins

·  Pin, Drill and Tap Chart

 Mini-Kit for C3 Stitching Pins 

C Series Pin Mini-Kits (LMK-C3)
C3 Steel Pin Mini-Kit

 Taps for C3 Stitching Pins 

Taps for C3 Stitching Pins (C3FT)
Taps for C3 Stitching Pins

 Pin Spacing Drill Jig for C3 Stitching Pins 

Pin Spacing Drill Jigs (l8500)
Pin Spacing Drill Jigs