I'm trying to tap my inline pro manifold for an EGT and I've drilled a hole w/ a 5/16 bit. However, I can't get the 1/8 NPT tap I'm using to catch and start making threads. I'm using a tap wrench to do this.

Anybody have any tips or insight as to what I might be doing wrong?

Thanks,
Keith

 

I believe the correct bit is a size "R" drill bit. They are hard to find, but an 11/32 can also be used.

 

Another option is to use a weld-on 1/8" female adapter (ATM-2260 is the only one I know of thus far).

 

What kind of tap are you using? A taper style tap has a lead of about 8 threads, this helps with "bite".

 

I think the 5/16 bit is just a hair too small, thus making it difficult to start the tap

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bluebullet &raquo;</TD></TR><TR><TD CLASS="quote">I think the 5/16 bit is just a hair too small, thus making it difficult to start the tap</TD></TR></TABLE>

yup

 

get 11/32 bit and use plenty of lubricant when you tap it

stan

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Flamenco-T &raquo;</TD></TR><TR><TD CLASS="quote">get 11/32 bit and use plenty of lubricant when you tap it

stan</TD></TR></TABLE>
Yeah, I'll be using 11/32 bit when I'm ready to drill my full-race mani. with Defi BF gauge.

 

Thanks guys for all the help. You guys were right, the bit was a little too small.