TARK-3/8 Trailing Arm Drill/Tap Guide Kit for drilling and tapping for 3/8″ studs

$79.99

SKU: TARK-3/8
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A frequent source of frustration for Triumph owners is the stripping of the threads holding the rear hub to the Trailing Arms (TA). The TAs are made of cast aluminum which is both soft and porous and the six studs on each side are threaded at 5/16″-24, which Triumph only rated at 14-16 foot pounds of torque. Anything more then that and you can strip the threads in the aluminum. Some people just drill and re-tap at 3/8″, but you’re still threading a steel stud into aluminum. The better solution is to use a threaded steel insert in the TA that the stud can screw in to, but the problem with doing that is drilling and tapping 12 holes that remain on center and perpendicular to the TA. If you have even one misaligned, the brake back plate and the rear hub won’t fit properly or not at all. More information below.

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Additional information

Make

Triumph

Model

TR250, TR6, TR4A, Stag

Thread Repair

3/8ā€ studs

Description

ARK – 3/8 – Kit for tapping to 3/8-16 for use with larger studs. This kit does not use inserts.Ā This kit can be used when fitting some CV axles and does not useĀ threaded inserts.

The difference between kits 1 & 2 are the insert type you plan on using i.e KeenSerts or Heli-Coils. While the jig back plate is the same for both kits, the drill & tap insert jigs are different so make sure youĀ use the correct insertsĀ with the jig that you are ordering.

These kits DO NOT INCLUDE the drill, bottoming tap or inserts. You will also need a good quality tap lubricant for use in aluminum for both drilling and tapping.

Please note that KeenSerts require an “X” drill size and 7/16-14 bottoming tap. There’s some confusion here because a 7/16-14 tap is supposed to use a “U” drill size,Ā BUT the KeenSerts instructions specify the larger “X” drill size. So don’t make the mistake of using a “U” drill. The KeenSerts directions also call for a countersink but you won’t need one when you use this set-up. If you were “free-handing” the tap, the countersink helps to line you up and get you started. The tap insert used here does all of that for you.

KeenSertsĀ – while these can be sourced at many places, I’ll useĀ www.McMaster.comĀ and their part numbers as these were used for our testing.Ā However……McMaster only ships parts domestically, so anyone outside of the United States may want to order Heli-coils which are more readily available worldwide.

McMaster Part#Ā  Ā  Description

92070A3377 PIECE KIT with TOOLĀ – BLACK-PHOSPHATE STEEL KEY-LOCK THREAD INSERT, 7-PC THIN WALL REPAIR KT,5/16″-24 INT,7/16″-14 EXT T

92070A250
PACKAGE OF 7Ā  ADDITIONAL INSERTSĀ – BLACK-PHOSPHATE STEEL KEY-LOCK THREAD INSERT, THIN WALL, 5/16″-24 INT THRD, 7/16″-14 EXT, 7/16″L,

1413K42
TAP MAGIC CUTTING AND TAPPING FLUID, FOR ALUMINUM, 4-OUNCE CONTAINER

2521A644
GENERAL PURPOSE HIGH-SPEED STEEL HAND TAP, BOTTOMING, 7/16″-14, H3 PITCH DIAMETER, 4 FLUTE

2901A168
“X” SIZE DRILL BIT

Heli-CoilsĀ are also available from many sources but as a former NAPA store owner I’d just recommend you order NAPA part #Ā BKĀ 770-3082. This kit contains 12 inserts, the insertion tool and the tap. It DOES NOT INCLUDE a 21/64″ drill bit or tap lubricant. Additional inserts can be ordered under NAPA part #BK 770-3132.

Please specify the kit based on the threaded inserts that you will be using.

  • Trailing Arm Repair Kit for use withĀ KeenSerts is Part#Ā  TARK-KS
  • Trailing Arm Repair Kit for use withĀ Heli-Coils is Part#Ā  TARK-HC

This kit, TARK-3/8 is for installing 3/8 studs directly into the aluminum rear hub housing, often required for upgrades to rear CV shafts

TARK ā€“ 3/8 ā€“ Kit for tapping to 3/8-16 for use with larger studs. This kit does not use inserts. This kit can be used when fitting some CV axles and does not use threaded inserts.

Trailing Arm Repair Kit for use with 3/8ā€ studs is Part# TARK-3/8

Studs can be purchased from your local auto parts store or from goodparts.com

One (1) Alignment Jig
One (1) Tap guide 3/8 studs
One (1) Drill guide 3/8 studs

Detailed documents, videos and downloads on installation can be found in Product Support under the Trailing Arm Kit section.

Also see:Trailing Arm Repair Kit ā€“ Set-Up | Trailing Arm Repair Kit (TAK) ā€“ Contents.

Download: the ā€œInstallation Tipā€ pdf for useĀ withoutĀ Inserts

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