Engine - Thread Reconditioning: Overview
DATE: Feb. -95SECTION: 2
GROUP: 21
NO.: 820
Threads, reconditioning
850
REFERENCE: TP 2102201, SECTION 2 (21), ENGINE B5202, B5204, B5234, B5254, 850 1992- Threads, reconditioning
This Service bulletin replaces the earlier Service Bulletin: 21 - 803, and sections H1-7 in Service Manual: Section 2 (21) Repair.
IMPORTANT
If the thread damage is in conical threads, then the part must be replaced with a new one.
WARNING
Use protective eyewear when drilling.
THREAD INSERTS, GENERAL
^ Damaged threads can in most cases be reconditioned using HELI-COIL(R) thread inserts.
^ Thread inserts are available in a variety of sizes, pitches and lengths of thread.
^ A correctly reconditioned thread will increase the strength of a joint.
TOOLS REQUIRED FOR INSTALLATION
^ The tools are delivered in kits which include a number of thread inserts.
^ The tools can also be ordered separately according to the part numbers table illustrated
MEASURING TO DETERMINE WHICH THREAD INSERT TO USE
Measure the threads and thread length in the hole
A: Thread
B: Thread length
DRILLING AND TAPPING NEW THREAD IN THE HOLE
Drill out the damaged threads with the correct drill, (see tables for reconditioning threads on the cylinder head etc.).
Cover openings, then blow hole clean.
Tap new thread with correct tap and blow hole clean.
Note
The thread taps are specially made for use with HELI-COIL(R).
Use denatured alcohol or similar to lubricate the threading operation.
Tap longer threads in stages, back out the tap and blow the tap and hole clean.
Thread hole to the proper depth or through the hole if it is open and to be threaded throughout.
C: Drill depth
D: Cutting pitch