Cast Iron Barrels - thread repair options

[Pigford]

Me Trumpet has a dodgy thread in the barrel.... bolts go down thru the head & screw into the barrel to hold the head on. One of the threads in the cast iron barrel is stripped - they are fine UNF threads (or sumink like that?).
Whats the easiest solution? Helicoil - do they work OK in cast iron?
Not to worried about originality so the replacement bolt can be a metric equivalent.

[hillbilly]

if your not bothered about originality id retap it the next size you can do,just be carefull when tapping it,as cast iron is a little brittle.

[m1ks]

Helicoil will work, just not sure about the physics of tapping cast iron as i've only ever tapped alloy. (I did tap a steel sheet and a die on a steel bar once to attach one to the other, that was painstaking though. It was something like once, twice in, once back out, once twice in, once back out and so on and lubricated with oil down the flutes).
I suspect you might have to get a machine shop to tap it for you, then the choice is do you just use the higher sized bolt or tap it for an insert to use the original, assuming you can get a helicoil for UNF? I don't know if they're all metric

[Pasc]

Piggy, if you can source a Time Sert in the correct size I would use that rather than a helicoil.
http://www.timesert.com/

[Buckle]

Piggy, if you can source a Time Sert in the correct size I would use that rather than a helicoil.
http://www.timesert.com/

+1 for the Time Sert - miles better than Helicoil. Not sure if you will be able to get a UNF one though

[Pigford]

Cheers Pasc & Buckle......

Can a 'timesert' be used to convert the UNC thread to a Metric...... as I ain't sure how them werks

I know you drill out & re-tap (sort of) for a helicoil

[Pasc]

Not sure on that one Piggy but I guess if you say for example used an M10 Time sert which is essentially a threaded solid bush (rather than the springy thread type helicoil) then the outside thread would also be metric so I'm guessing you would just tap the thread in the cylinders to the nearest next metric size up.
I would try and find a uk distributor and have a word in their shell like.

[Steve Cooke]

There is no problem in tapping cast iron as long as the correct size drill/tap is used. Timeserts seem difficult to source and I,m not aware of any conversion sleeves available, personally although both will do the job I would choose the Helicoil over the timesert as I believe it has more strength when fitted properly.

[Pasc]

Available in UNF
http://www.wurth.co.uk/catalogue/pdfs/UK-CD_04_6026.pdf