SIZE THREAD TO RE-TAP IT

[disco_thrasher]

URGENT HELP MAYDAY MAYDAY
I am very stuck as when removing my new EGR by pass kit i ****ed the thread ,reason for removing it was to refit it as i had a slight leak now i need to re tap it but dont know the size does anyone know this
thanks Kelvin

[Blknight.aus]

which thread?

[discowhite]

if its urgent find a smaller bolt that goes right the way threw and stick a nut on the back, from memory the 4 egr small bolts are m5x1.25.

cheers phil

[Bigbjorn]

if its urgent find a smaller bolt that goes right the way threw and stick a nut on the back, from memory the 4 egr small bolts are m5x1.25.

cheers phil

Are you sure the pitch is 1.25mm? That is very coarse for a 5mm fastener. More likely to be either 0.8mm or 0.9mm.

If it is then drill to 5mm and tap M6 x 1.0.

[disco_thrasher]

Thanks guys i followed all your instructions i ended up getting a lift to a nut and bolt shop where we took a guess on the sizes i bought 5:1 and 6;1 and 7:1 the 5 :1 was way to small the 6:1 was probarly the orginal size the 7:1 was perfect it was then screwed in very slowly and straight trying to follow the left over thread and it worked so if anyone ever does the thread on there removal of there Egr the original size is 6:1 but if you have a steady straight hand screw in a 7:1 my other optioms if this did not work was to remove the whole inlet manifold drill it out and retap it or heli-coil it

the guy at the speciality bolt shop was a great form of knowledge saying that any pitch over 1.25mm will not work on alloy for the size bolt i needed and 1 mm pitch would be the ideal size for the application it was intended for

thanks again and sorry for the late reply as i needed to get to shop intime before it closed and then once i started working on the car well i didnot stop until 11pm last night

cheers kelvin

[Bigbjorn]

For future reference, the tapping drill size for metric threads is diameter - pitch. This gives 75% thread depth. For Unified threads, the formula is:- (diameter in decimal inches) - (1/pitch in TPI). Use closest commercial drill size.

Metric drills are available in steps of 0.1 mm. but hobby/workshop drill sets are usually only in steps of 0.5 mm. Get yourself a set of number and letter drills and you will be able to find a drill within a couple of thou. of ideal size for most automotive applications which are rarely over 1/2" on passenger vehicles.