Tap & Drill For EGT Fitment 1/8 PT - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• Tap & Drill For EGT Fitment 1/8 PT by Gernster on 02 Oct, 2008 01:06
• Sorry to harp on, but there is a lt of expertise on this board, am I'm very grateful for your advice!
  
  The fixing for my EGt guage, says the connector is 1/8" PT which I'm assuming is 1/8" plug tap, but Ive always been a bit confused by BSW/ INF/ UNC etc etc...
  
  Is this what I want? and also what size drill bit do I need?
  
  http://cgi.ebay.co.uk/Presto-1-8-BSW-Plug-Tap-Made-in-England_W0QQitemZ170231131139QQcmdZViewItem?hash=item170231131139&_trkparms=39%3A1%7C66%3A2%7C65%3A2%7C240%3A1318&_trksid=p3286.c0.m14
• #1 by dillenger1 on 02 Oct, 2008 03:15
• You need pipe thread.that one doesnt look tapered.
• #2 by Gernster on 02 Oct, 2008 03:48
• ah, so it does need to be tapered then?
  
  the thread on the fitting doesnt look tapered.....
• #3 by Turbinepowered on 02 Oct, 2008 04:29
• Does it call for 1/8" NPT, BPT... or is it just "PT" all by itself.
  
  NPT is the American standard National Pipe Taper, which seals better than straight threads.
• #4 by saurkraut on 02 Oct, 2008 04:59
• What thermocouple are you useing.  The Spruce thermoucouples come in 1/8 and 1/4 NPT and some metric sizes.
  
  aircraftspruce.com
  
  The larger NPT taps I have do have the drill size noted right on the shank of the tap.  Otherwise, its typically on the label of the package that the tap comes in.
• #5 by Gernster on 02 Oct, 2008 12:04
• Its a cheap chineese guage Ive bought for £25, comes complete with thermocouple. Instructions just say 1/8" PT
  
  
  
  And do you know what, now I look at it more closeley the thread DOES look tapered!
  
  Sorry my cameras crap at closeup!
  
  
• #6 by arb on 02 Oct, 2008 13:04
• Even if the threads on the probe are not tapered, if they are PT the tap will be tapered and it will still have the same sealing effect. Also, the photo looks like a capilary probe rather than a thermo couple.
• #7 by Jet A on 02 Oct, 2008 16:04
• If your turboed, dont stick that preturbo.
  
  Most common is NPT as mentioned before. Can be found at most hardware stores (US) for a couple of bucks. otherwise, online. or order a thread gauge.
• #8 by Gernster on 03 Oct, 2008 06:24
• I am turbo'ed, watercooled garret T2, (1.6GTD) which is the reason why Ive bought the EGT, so i can start to wind the boost up a little and play with the fuelling.
  
  Conflicting advice here then, so why not pre-turbo when another guys is saying it has to be pre-turbo??
• #9 by arb on 03 Oct, 2008 07:02
• To be sure if you don't have a thread gauge, take the probe to the hardware / tool store. Compare the threads with the 1/8" NPT tap, they should interweave perfectly. Check the diameter as well. One way is with an NPT 1/8" die for cutting the threads on the pipe.
  
  I cut my probe pre-turbo as TIT (turbine inlet temp) is critical to the life of the turbo. You've not going to find an aircraft with turbine exit or exhaust temp.... it does not matter.
  
  If you are concerned the probe will be ingested by the turbine (catastrophic event) get a quality probe like from Aircraft Spruce.
• #10 by 53 willys on 03 Oct, 2008 07:11
• go pre turbo.....I have NEVER heard of anybody having a probe break off or rust off...highly unlikely.....post turbo does not give very accurate temps.
• #11 by Gernster on 04 Oct, 2008 11:53
• done the job, 1/8" NPT tap, £10 from a local engineering shop plus a fiver for the 11/32 drill bit.
  
  stuck it out on number 4 next becuase I was worried about of fouling stuff.
  
  Nice easy job, no dramas.
  
  Should have the engine back together tomorrow so hopefull back on the road!
  
  thanks for the help guys.