Hi all, I have drilled & tapped the two holes for the eng. cover (on the turbo side) to take 8mm helicoil inserts, the problem is because it's a blind hole (which I've drilled as deep as possible) the taper on the kits tap bottoms out & I don't think the inserts,which are only 8mm long, will go in deep enough. There's plenty of room for more thread but I could do with a 2nd & then plug tap. So does anyone know what size the taps are in these 8mm helicoil kits ? (It's marked 8x1.25, the OD of the 8mm insert is about 10mm so could the tap be 10x1.25) ?
Thanks in advance.

Andy Warren said:

Hi all, I have drilled & tapped the two holes for the eng. cover (on the turbo side) to take 8mm helicoil inserts, the problem is because it's a blind hole (which I've drilled as deep as possible) the taper on the kits tap bottoms out & I don't think the inserts,which are only 8mm long, will go in deep enough. There's plenty of room for more thread but I could do with a 2nd & then plug tap. So does anyone know what size the taps are in these 8mm helicoil kits ? (It's marked 8x1.25, the OD of the 8mm insert is about 10mm so could the tap be 10x1.25) ?
Thanks in advance.

Click to expand...

Can you not just measure the tap and the thread, do you not have a tap and die set?
I've got several and cannot imagine working on cars without one.
They aren't expensive.

Stanleysteamer said:

Can you not just measure the tap and the thread, do you not have a tap and die set?
I've got several and cannot imagine working on cars without one.
They aren't expensive.

Click to expand...

Hi Stan, I do have a set of taps/dies but as the helicoil kits tap isn't marked with it's actual size (why I don't know ) I presumed they were odd sizes. I'll try a 10x1.25 tap tomorrow & see how get on. Hope you're keeping well, all the best.

Andy Warren said:

Hi Stan, I do have a set of taps/dies but as the helicoil kits tap isn't marked with it's actual size (why I don't know ) I presumed they were odd sizes. I'll try a 10x1.25 tap tomorrow & see how get on. Hope you're keeping well, all the best.

Click to expand...

Hi Andy, yes keeping well thanks. Hope you are the same.
If you have a set of taps and dies then I would have thought that you could put yours up against the one you have got for the helicoils, to see if the threads interlock, and use a mic or a caliper to check the diameters.
Best of luck with it.

Hi Stan, I tried the 10x1.25 & pitch interlocks with the kit tap the 10mm is to big ! Using a pitch gauge the thread measures 20 TPI. Measuring the kit tap is awkward as it only has 3 flutes (all mine are 4 fluted) but it's about 9.5ish mm.
So I think I'll grind a bit off the taper of the kit tap as I'd like another 3-4mm of thread to be sure, to be sure . I'm fine wife's back is not brilliant putting pressure on the the nerves causing numbness in her arms & legs , just hope she's OK for the Billing camping weekend, all the best.

Andy Warren said:

Hi Stan, I tried the 10x1.25 & pitch interlocks with the kit tap the 10mm is to big ! Using a pitch gauge the thread measures 20 TPI. Measuring the kit tap is awkward as it only has 3 flutes (all mine are 4 fluted) but it's about 9.5ish mm.
So I think I'll grind a bit off the taper of the kit tap as I'd like another 3-4mm of thread to be sure, to be sure . I'm fine wife's back is not brilliant putting pressure on the the nerves causing numbness in her arms & legs , just hope she's OK for the Billing camping weekend, all the best.

Click to expand...

That's 1.27 in mm do you not have a metric pitch gauge?
I just found this

Which seems to sort of back up the theory. But I quite undestand your desire to make a bottoming tap from the one you have.
TBH, but too late now, if you have that much meat in what you are putting the helicoil in I would have been tempted to drill and tap the existing hole a bit larger and drill out the holes in the cover. I don't know if you find this but I find the three bolts on the engine cover a bit of a pain, especially the one on the other side, where i have had to make up a ridiculous thing to stop the nuts just turning round and round. I only leave it on to hide the missing EGR valve come MOT time!
It's not the doing up of the bolts that is the pain, it's the lining up of them.

We have both been a bit in the wars, like your missus my back plays me up the instant I push it just a litttle too far then I have to be ever so careful for a ridiculous amount of time after. The missus takes so many painkillers it is ridiculous but with them she soldiers on very well considering she is nearly 80! (titanium cage in her back, paralysed left foot, broken ankle still mending from over a year ago. Still we keep banging on!

I do like the idea of trying a nut with the 10mm x1.25 thread on your tap to see if it fits. It may be a tad tight.
all the best and Enjoy Billing when it comes along!