Any machinists here ?

[MTT3107]

So, I bought the hose barbs in the picture to install the on the manifolds of my dual carb setup, por a balancing tube.

My tap and die set does not contain a tap with this diameter and thread.

Can anybody here can tell me with tap I have to get to cut those threads ?
OD of the threaded part is a little more than 1/2 in.

thanks !

[busdaddy]

It's called 1/4" NPT, but you may want to upsize the barb end of those to 1/2"+, 1/4" hose between manifolds isn't going to do much.
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[67rustavenger]

Tree'd by BusDaddy. I type slow!
1/4" NPT (National Pipe Thread) tap will do the deed.

But, Your selection for balance tube nipples is on the small side, real small.
See if you can find a larger diameter adapter nipple for your setup.
Also the more rigid the tube, the better. I had a balance tube on one of my engines, I noticed that it tended to collapse while the engine was running.

What carbs are you running?
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[Vanapplebomb]

In agreement with the others, you must use a larger balance pipe. A 1/2 line should work ok.

Tapered threads require a sealant to seal. A good thread dope will work fine. Lately I have been liking the Gasoila Soft Set.
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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[DesertSasquatchXploration]

That is a straight pipe fitting (MIP) You don't want those.

Get some with (1/4 NPT) they are tapered you will see the difference when they are side by side

[Danpa]

McMaster Carr sells these in brass:

They can also get you the 1/4 pipe tap.

A 1/4 pipe tap should take a 7/16 drilled hole if I remember correctly.

Dan
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[DesertSasquatchXploration]

This is my favorite drill chart missing some stuff but its 100% correct has never done me dirty. Yes Danpa 7/16 is correct

[Vanapplebomb]

[oprn]

[Danpa]

Also, one last thing.

Before you start to drill the hole make a good center punch mark in the casting, even if you're using a drill press. You don't want the drill walking around.

Oh, and one more one last thing,

When you're tapping the hole, go in about a third of the way up the tap, take it out, and check your fitting. Go in a few turns each time, repeating the checking until the fitting engages at least a few threads when it's tight.

And don't forget to show the finished job!

Dan
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68 Bay Window Double Cab (gone) sob, sob!
64 Beetle (gone)
77 Scirocco (gone)
73 Squareback (scrapped)
70 Beetle (current, in pieces)

[MTT3107]

OK, thanks for all the answers.
Will show end result when it's done.
But first I have to go and change the fittings, and, buy the respective tap.

[Vanapplebomb]

[oprn]

Yes I am surprised that those fittings pictured don't have either an "O" ring groove or a flat shoulder for a HP gasket. Most of that style of fittings do. How else could they seal? Don't tell me parallel threads seal, they don't.
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[Vanapplebomb]

Yeah, lack of flat shoulder is curious. Usually the o-ring sits in a chamfer at the top of the FIP fitting and is crushed by the shoulder of the MIP
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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[DesertSasquatchXploration]

[mark tucker]

wow this is funny shit!!!! and typickel too. what does npt stand for?? what does mip stand for? what does fip stand for??
as for the OP, take those back and get NPT fittings. thats what you want. not the mip.unless you have the right toold to use them correctly.the set of nos kdog manifolds I have that has the attached line all steel from one steel manifold to the other has a 3/8" /10mm od line.
so now lets see who steps up and either knows what mip is or goobles it and spits out some fodder that may or may not be right. I wood think ray wood be right but....
threads like this are whats rong and so funny and entertaining about the internet exspurts. not limited to vw's at all.
sofar 2 people seem to have a clue...just a clue.

to add....machinest has little to nothing to do with this...sort of.

[Vanapplebomb]

It is a real thing. Done it many times. Like I say, for the high pressure rating, MIP must go into FIP to use the o-ring. For low pressure and vacuum applications, MIP can be used in a female NPT with a thread sealant. Loctite makes an anaerobic hydraulic sealant that I use, but a high solids soft set like Gasoila works well to. Sometimes the female thread needs to be slightly deeper to create the interference as some come quite shallow.

It also isn’t unique to the national pipe thread. There are metric threads that work this way as well. For example, there are quite a few applications where a tapered male threads screw into a straight female thread to create the interference.

It’s rare to see, and not standard. I think it is done by some manufacturers to make a “universal” par, for lack of a better term. The female side is usualy 20thou over or so. So it isn’t quite the same specification, but close enough that both work.
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1800 Type 4 Berrien 295

http://www.thesamba.com/vw/forum/viewtopic.php?t=487021

[DesertSasquatchXploration]

With enough glue sure ok. You can Convince yourself of anything is suppose.

When a Customer pays 500K for a machine they don't want glued fittings with wallered out threads. Just because you can do something don't make it right. You do you to each their own.

[DesertSasquatchXploration]

Now that the OP has their post completely jacked

Like Danpa was saying you tap it a little at a time if you go to much and the fitting is protruding into the ID of the manifold no big deal just file it back so its flush when tight.

[jimmyhoffa]

Fun fact, the drain plug in your transmissions that there are tens of millions of is a straight-thread hole in the magnesium, with a tapered M24x1.5 plug. It's the cheapest way requiring the least care to make work correctly, and happens to work great when the female thread is soft, just like the steel plug in the magnesium trans case. A little Loctite 565 and that thing is GOOD to go for a long time.
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