How To Repair Aluminum Threads

Repair Stripped Threads In Aluminum

(Article and Pictures by Mark Trotta)

One of the commodities pigsty threads had stripped out on this 1965 Ironhead Sportster motor, which prompted engine disassembly and repair.

This article is a step-by-footstep on how to install thread inserts in aluminum. Merely commencement, a quick mention on two other methods of repairing stripped threads.

Weld Hole And Re-Tap

If you happen to exist practiced at aluminum welding, or willing to pay someone that is, damaged threads tin can be repaired by filling upwards the hole, then drilling and re-borer. This is the near permanent style to repair a stripped thread, but also the hardest and virtually time-consuming.

Enlarge Pigsty And Re-Tap

Another option for stripped thread repair is to drill a slightly larger hole so tap new threads into it. Often times, this method may not be an selection because of space constraints. It as well takes a scrap of originality away from the bicycle, and having i unlike size bolt is ofttimes awkward.

Thread Insert Kits

The most common mode to repair stripped threads in aluminum is by installing a thread insert. Thread repair tools are normally sold in kits, which include the inserts, a special tap for the inserts, and an installation tool. Some kits include the required drill bit.

There are many styles and brands out in that location, one of the about well-known beingness HeliCoil.

The HeliCoil installation tool is a black plastic rod with a hook on the threaded end, and a square drive on the other.

I have several older HeliCoil kits with the diamond-way handle. These also work well, but the newer version makes information technology easier to install an insert deeper into a pigsty.

Stainless Steel Thread Inserts

The inserts that come with the kit are made of stainless steel. When installed properly into aluminum, they give the bolt more than grip than the but threads in bare aluminum. And since the insert makes a stronger grip, if at that place are infinite constraints, the insert doesn't demand to be the same exact depth as the original thread.

Proper-Size Drill Scrap

The first step is to drill out the stripped hole with the recommended drill bit size. Some of the thread repair kits require an odd-size drill scrap. The three/viii-sixteen HeliCoil kit I was using required a 25/64" drill bit.

Metal Chips Impale Motors

The small-scale aluminum fries that the drilling action makes are deadly to an engine's oil excursion and bearings. Because of this business concern, most of the Sportster motor was disassembled to make sure none of the metal chips would remain in the motor when washed.

After drilling the required size hole, chuck the square bulldoze of the tap into a tap wrench. You can also employ a crescent wrench or vise grip.

If you have a steady hand and adhered to the right drill fleck size, the tapping will become smoothly. Since I was tapping the new threads slowly past paw, I saw no demand for cut fluid.

Next, install an insert on the bottom end of the installation tool and a tap wrench on the tiptop. Slowly turn it clockwise.

HeliCoil does non suggest adding Loctite to the thread insert, although I suppose there'southward no harm in adding a drop or ii. I have never used any and have never had one come loose.

Blind Hole vs Through Hole

The majority of stripped thread repairs are for bullheaded-holes, significant the bolt does non come out the other side. When a commodities goes completely through (through-hole) the "tang" needs to exist removed. Information technology is not necessary to remove the tang unless it's in the mode.

If a thread insert is as well long, you tin cut information technology or grind information technology down to the length you need. Conversely, if you need more than thread, y'all tin can combine two or more.

Hither are links to the 3 well-nigh common coarse-thread, non-metric kits:

Shop: 1/iv-20 Thread Repair Kit

Shop: 5/16-18 Thread Repair Kit

Shop: three/8-xvi Thread Repair Kit

Helicoil Master Thread Repair Kit (Coarse Thread)

This thread repair kit includes the three sizes in a higher place, plus 7/sixteen-fourteen and 1/2-13, then you go 5 installation tools, five drill bits, and 48 stainless steel inserts. It all comes neatly packaged in a plastic molded case.

Shop: Helicoil Thread Repair Master Kit

Misc Notes

Disassembling the motor was a lot of actress piece of work, just the anaerobic gasket sealer I had initally sealed the engine cases with proved to exist an easy clean-up.

Conclusion

When faced with repairing stripped threads in aluminum, always do what's best for the bike, even if it means disassembling half the motor to do it.

Read: Motorcycle Engine Build

Source: http://www.classic-motorcycle-build.com/repair-stripped-threads-in-aluminum.html

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