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|kbn| · 03-10-2004, 04:24 PM

I am a bit lost looking for the right type of tap and drill. First for the thread used on 1/2" barbs, would I need 1/4", 3/4" tap? the blocks I have use 1/4 while my 1250 eheim pump uses 3/4 on inlet.
I know the type is BSP but my dad has said there are four types.
The type I would need is tappered, so that its at an angle, allowing the barb to bite into all of the thread and making it harder for high pressure to push the barb out. then there are three types of parrelell tap, whiere the first is slightly tappered and is used first, then the other two (second and plug) are used so that the thread is made parrelell. Using parrelell threads with tappered barbs wouldnt be very good becuase only the top of the barb would bite into the thread.
I thought maybe the tappered one listed on there site is fully tappered while the other two are for making tappered into parrelel?
What size drill would I need? I thought 11.5 or 12mm but it seems the BSPT barbs have 16.5mm diameter threads? ....... <edit>16.5mm was from a 3/4" bspt thread, ill need 1/4" threads, although I *could* use 3/4".
Ive measured a 1/4" thread. The smallest part of it (as its tappered) is 11mm while the biggest is 14mm. this means its probabaly best to drill and 11m hole and then a 12mm hole but with this only 3/4 of the way in, so that the bottom part of the tap is still used instead of wasted by using too large a drill... and then tap it with a 1/4" fully tappered tap.
Chronos dont seem to have 11.8mm drill bits on there shop?

03-10-2004, 04:24 PM	#14
\|kbn\| Cooling Savant Join Date: Feb 2004 Location: W. Sussex, UK Posts: 329	I am a bit lost looking for the right type of tap and drill. First for the thread used on 1/2" barbs, would I need 1/4", 3/4" tap? the blocks I have use 1/4 while my 1250 eheim pump uses 3/4 on inlet. I know the type is BSP but my dad has said there are four types. The type I would need is tappered, so that its at an angle, allowing the barb to bite into all of the thread and making it harder for high pressure to push the barb out. then there are three types of parrelell tap, whiere the first is slightly tappered and is used first, then the other two (second and plug) are used so that the thread is made parrelell. Using parrelell threads with tappered barbs wouldnt be very good becuase only the top of the barb would bite into the thread. I thought maybe the tappered one listed on there site is fully tappered while the other two are for making tappered into parrelel? What size drill would I need? I thought 11.5 or 12mm but it seems the BSPT barbs have 16.5mm diameter threads? ....... <edit>16.5mm was from a 3/4" bspt thread, ill need 1/4" threads, although I could use 3/4". Ive measured a 1/4" thread. The smallest part of it (as its tappered) is 11mm while the biggest is 14mm. this means its probabaly best to drill and 11m hole and then a 12mm hole but with this only 3/4 of the way in, so that the bottom part of the tap is still used instead of wasted by using too large a drill... and then tap it with a 1/4" fully tappered tap. Chronos dont seem to have 11.8mm drill bits on there shop? Last edited by \|kbn\|; 03-10-2004 at 04:37 PM.