Theoben Rapid Forum

Everything Technical About Rapid => Technical => Topic started by: etiam viviens on October 18, 2025, 01:42:47 PM

Title: Stripped thread M3 valve retaining screw
Post by: etiam viviens on October 18, 2025, 01:42:47 PM
Did some testing over the chrony and noticed some air leaking. And after a short investigation I noticed that valve retaing screw is missing  :-[ after checking the thread of the screw it appears it is stripped.

My plan is to place a helicoil or make the hole M 3.5. Think the Helicoil option is the best option. Is there someone who has done it before and has some tips?
Title: Re: Stripped thread M3 valve retaining screw
Post by: Ca_Varminter on October 18, 2025, 04:48:15 PM
Well there is not a lot of Meat work with!!
HeliCoil can work...
But tapping out to the next size would be better....
INHO...
Stuart
Title: Re: Stripped thread M3 valve retaining screw
Post by: etiam viviens on October 18, 2025, 04:58:28 PM
Next size would be M3.5 or M4 will look into that.
With Helicoil you have steel on steel contact and no more aluminium on steel

drill size for M3 helicoil is 3,1/3,2 depending on brand
drill size for M3.5 is 2.9 but I think this is not an option as the hole is al ready 3 or bigger.
drill size for M4 is 3.3 so this should be good to go.
Title: Re: Stripped thread M3 valve retaining screw
Post by: KevG on October 19, 2025, 11:54:07 PM
ive had to do a few
no drilling necessary.4ba tap in original hole then use a 4ba cap head bolt.
kevG
Title: Re: Stripped thread M3 valve retaining screw
Post by: etiam viviens on October 20, 2025, 05:40:46 AM
Thanks for the tip KevG.
As the drill size for 4ba is 3mm this would also work, but the only tap sets I could find is in the UK and cost over 100 euro to get it here in Holland.

At the moment I have ordered a helicoil set m3, I have m4 tap.

Title: Re: Stripped thread M3 valve retaining screw
Post by: etiam viviens on October 21, 2025, 09:32:32 AM
Did some measuring and as the material thickness is only 2.6 mm and its ends in a round chamber of the valve.
The option are tapping 4BA and M4 as it looks now.

Now is BA tap sets and screws not very common in Holland and I do have a hard time finding these.
Hope I can find these or it will be M4
Title: Re: Stripped thread M3 valve retaining screw
Post by: etiam viviens on November 04, 2025, 06:55:59 PM
The BA sets are very expensive in Holland so it has become M4.
Not the best screw but it is shooting again.
Title: Re: Stripped thread M3 valve retaining screw
Post by: DB.20 on November 04, 2025, 09:28:25 PM
Needs must, as the saying goes. Glad you got it sorted and shooting again.
Title: Re: Stripped thread M3 valve retaining screw
Post by: Brooksy on November 06, 2025, 07:57:35 PM
Does it still slide into the stock? An M4 grub screw would be better.
Title: Re: Stripped thread M3 valve retaining screw
Post by: etiam viviens on November 07, 2025, 01:53:33 PM
I have a chassis so its fits, also the reason the screw could fly out when the thread was stripped.
It would not fit a wooden stock I would think.