Loctite advice

[Colin Wilks]

I am building up my sports crankcase and need to rework the rearmost crankcase to block stud hole. In the past this has been tapped 7/16 bsf and stepped to 5/16. Unfortunately, whoever did this managed to tap the hole out of true and so I have made up a 7/16 threaded plug in 6082 aluminium which I will install and then drill and tap in situ.
The threads on the new plug are good, and those in the crankcase are acceptable, but I don't want to make extraction of the plug in the future a destructive event as there's not enough meat to take it out to 1/2".
I intend using loctite on the plug thread, but the more I read up about the many different Loctites out there, the more choice there seems to be. I have both 243 and 248 on the shelf, but am after something that will fill any small voids in the thread form as strongly as possible but not make the whole thing permanent.
Recommendations from those with experience very welcome please. 
Photo shows the old stud.

[Colin Reed]

Hi Colin,
I Would use 262 Studlock
Any of the thread lockers can be removed by applying Heat about 230 Degrees C
so no need to worry about them being permanent
 One other thing looking at the photo i would have a light Skim taken of the top of crankcase
(PS) also a small counter sink to the stud hole so that it does not pull up when fitted

Hope that is of some help

Colin
NZ

[Stuart Giles]

I use this stuff instead of the Loctite product. It's slightly thicker than their 638 and is very strong, as Colin says blowlamp heat will melt any of the Loctite type retaining compounds. https://www.ebay.co.uk/itm/203089075645?...SwdJlfRkiI

[Robert Foreman]

Colin,
 I would use Loctite 638 retainer for the insert.  Put the 638 on the insert, screw it in flush. Remove any excess. Then place a tube over the stud bigger than the 7/16" insert with washers and pull up with a 5/16" nut. This way the Loctite is filling the thread on the back flank and you have metal to metal on the thrust side.

[Colin Wilks]

Many thanks for the replies. I have to plug the 7/16" tapped hole and then drill and tap this plug 5/16" due to the hole being skew and I want the new stud perpendicular to the casing.

In the end I decided to make the plug a permanent part of the crankcase and have installed it with JB Weld. I squared off the end of the plug and used a 12" tap wrench to wind it hard down. Once it's cured I shall drill a pilot hole to retain the centre, remove the material proud of the casing and finish off by lapping the entire surface on a granite worktop with Timesaver.

Hopefully a permanent fix ready for drilling and tapping back to 5/16" BSF.

[Ivor Hawkins]

Looks like someone’s pillar drill was particularly perpendicular!

[Nick Turley]

Looks like a nice job in the making Colin.