Hi Dave,
As Stan says and assuming the thread in the block is still ok, you just need to find the correct insert, as per his advice.
I have used helicoil inserts, and other makes, they are indeed diamond shaped in cross section.
Do pm me if you need any more advice. (phone number in DM)
Please visit the Club's website https://www.dloc.org.uk/ to join. Visit https://www.dloc.org.uk/adhoc to DONATE towards the cost of the forum.
Please don't post someone's email address to avoid it being harvested by spambots and it's against GDPR regulations.
Always look at "ACTIVE TOPICS" to see all posts in date & time order as they are sometimes moved; or look at "Your Posts".
Please add Reg. nrs. when posting a photo or anything about a car as this will help searches. Don't add punctuation next to nr. as this negates search.
CHANGED YOUR EMAIL ADDRESS since registering?, click your username and check your address in User Control Panel, Profile, Account Settings.
If you want help to register, use "contact us" at page bottom for help.
Please don't post someone's email address to avoid it being harvested by spambots and it's against GDPR regulations.
Always look at "ACTIVE TOPICS" to see all posts in date & time order as they are sometimes moved; or look at "Your Posts".
Please add Reg. nrs. when posting a photo or anything about a car as this will help searches. Don't add punctuation next to nr. as this negates search.
CHANGED YOUR EMAIL ADDRESS since registering?, click your username and check your address in User Control Panel, Profile, Account Settings.
If you want help to register, use "contact us" at page bottom for help.
Daimler 15: stripped thread
Re: Daimler 15: stripped thread
Cheers, Henry Curwen
Registrar for Conquest & Century Saloons (DJ250/1, DJ256/7, DJ260/1)
Conquest (Drop Head) Coupe DJ252
Registrar for Conquest & Century Saloons (DJ250/1, DJ256/7, DJ260/1)
Conquest (Drop Head) Coupe DJ252
Re: Daimler 15: stripped thread
It looks like part of a stud that stripped some time ago and wasn’t removed. It proberbly bound just enough to hold a new stud but then give up the fight when you removed it. The way to find out is measure the hole. If its 3/8ths or slightly more then it hasn’t been previously helicoiled.
Colin,
I may be slow but I’m rough as well !
I may be slow but I’m rough as well !
- captain bobo
- Posts: 268
- Joined: Tue Feb 09, 2016 7:32 pm
- Location: Kimbolton, Cambs
Re: Daimler 15: stripped thread
Curioser and curioser! Finally had time to do a proper investigation today with results that surprised me.
The head stud itself is 3/8 inch diameter with 20 tpi threads at each end which are not 3/8 inch BSF threads, but an oversize thread which requires a different (slightly larger) head nut than the other head studs. The block thread is the same oversize, so I imagine that in the past the block thread stripped and a new thread was cut without enlarging the hole to accommodate a thread insert, and a head stud fabricated to fit, but it's a guess.
Question, is there a 20 tpi thread spec that has a fractionally larger external diameter than a 3/8 BSF? The head nut for the problem stud just slips over a 3/8 BSF threaded stud.
Anyway, I've got hold of a thread insert kit for 3/8 BSF and a BSF tap and die set. I've cut the thread on the stud down to 3/8 BSF at each end, drilled out the head stud hole, threaded the hole, inserted 2 x 1.5D thread inserts and installed the head stud. All I need now is to get hold of some 3/8 BSF nuts, then the head can go back on.
Thank you all for your comments and suggestions, they have been helpful in diagnosing and rectifying the problem
The head stud itself is 3/8 inch diameter with 20 tpi threads at each end which are not 3/8 inch BSF threads, but an oversize thread which requires a different (slightly larger) head nut than the other head studs. The block thread is the same oversize, so I imagine that in the past the block thread stripped and a new thread was cut without enlarging the hole to accommodate a thread insert, and a head stud fabricated to fit, but it's a guess.
Question, is there a 20 tpi thread spec that has a fractionally larger external diameter than a 3/8 BSF? The head nut for the problem stud just slips over a 3/8 BSF threaded stud.
Anyway, I've got hold of a thread insert kit for 3/8 BSF and a BSF tap and die set. I've cut the thread on the stud down to 3/8 BSF at each end, drilled out the head stud hole, threaded the hole, inserted 2 x 1.5D thread inserts and installed the head stud. All I need now is to get hold of some 3/8 BSF nuts, then the head can go back on.
Thank you all for your comments and suggestions, they have been helpful in diagnosing and rectifying the problem
Best wishes, Dave B
Re: Daimler 15: stripped thread
7/16 UNF ?captain bobo wrote: ↑Sat Aug 21, 2021 4:07 pm Question, is there a 20 tpi thread spec that has a fractionally larger external diameter than a 3/8 BSF? The head nut for the problem stud just slips over a 3/8 BSF threaded stud.
-
- Helpful Person
- Posts: 404
- Joined: Wed Mar 16, 2016 6:40 pm
- Location: Cheshire
Re: Daimler 15: stripped thread
The 3/8 BSF has a major diameter of 9.525mm , so the nearest slight oversize is probably an M6 fine , which has a major diameter of 10mm and a pitch of 1.25mm which equates to 20.32 per inch . However, the thread angles are probably different ( I can't recall the exact angles) so you need to be very careful about mix and match
- captain bobo
- Posts: 268
- Joined: Tue Feb 09, 2016 7:32 pm
- Location: Kimbolton, Cambs
Re: Daimler 15: stripped thread
The nuts that fitted the correctly threaded head studs didn't properly fit the"rogue" stud - they started to thread ok but then got very tight indeed as the whole nut threaded on. Based on what Chris wrote in that last post I suspect the rogue stud could have had M6 fine thread - my 20 tpi thread gauge best fit showed it having nominally 20 tpi.
I've cut a proper 3/8 BSF thread onto each end of the rogue stud and installed it with a thread insert into the block - it's a good tight fit now.
Just need some new replacement 3/8 BSF nuts and then I can put the head back on.
I've cut a proper 3/8 BSF thread onto each end of the rogue stud and installed it with a thread insert into the block - it's a good tight fit now.
Just need some new replacement 3/8 BSF nuts and then I can put the head back on.
Best wishes, Dave B
- captain bobo
- Posts: 268
- Joined: Tue Feb 09, 2016 7:32 pm
- Location: Kimbolton, Cambs
Re: Daimler 15: stripped thread
Update: new 3/8 BSF nuts arrived, I decided to use new nuts all round. The head studs have all tightened up to the recommended 41 lb ft (ft lb?), the helicoil did the trick. The head is back on, I'm cleaning and polishing the inlet manifold, carburettor and rocker cover, making up new exhaust and inlet gaskets, degreased the block and repainted while I had good access, replaced the rubber hoses and associated clips, cleaned out the waterways with a pressure washer. Next I'll flush the radiator and then reassemble everything.
Thank you all for your interest and comments.
Thank you all for your interest and comments.
Best wishes, Dave B