TD 0.049 venturi thread?

[Andrew Tinsley]

The header says it all. I need to buy some taps so that I can make up some adapters using the TD 0.049 venture. I have done this before and I have forgotten the thread size and cant find the taps!
  Can anyone help with this age related problem?

Thanks,

Andrew.

[BillLee]

1/4-32. same as a glowplug

[Andrew Tinsley]

Thanks Bill!
Now to buy some more taps and guess what? As soon as I buy them, I shall find the old ones.

Regards,

Andrew.

[Andrew Tinsley]

Just tried ordering a tap for 1/4 x 32 tpi. I thought it was a standard UNF thread, but apparently 1/4 x 28 is the UNF standard! The only thread I know of that is 1/4 x32 is a model engineering thread. Assuming this is the correct thread form, it seems odd that an unusual British thread standard was used for miniature spark plugs, that were made and used mainly in the US! Anyone got an explanation?

Regards,

Andrew.

[BillLee]

I believe 1/4-32 is classified as UNEF. The threads for a glow plug and for the Cox .049 venturi are not something odd.

There's a jillion hits on a Google search for
             1/4-32 thread

Bill

[John Rist]

McMaster-Carr has 1/4 32 tap

http://www.mcmaster.com/#hand-taps/=r86vhi

[Paul Smith]

Getting glow plug tap & dies was a pain in the butt 60 years ago.  As the writer says, 1/4-28 is the common size.  1/4-32 is rare.   With the internet we don't have to rely on hardware stores within bicycle range.

[Andrew Tinsley]

I still have to find a UNEF thread table in my books but no doubt I can find it on the net. I will try a search and see if the thread form is the same as 1/4 x 32 Model engineering thread. Those taps can be had easily in the UK finding a UNEF 1/4 x 28 may not be so easy. However we probably have one of the best shops worldwide, they never seem to be beaten. I have even got taps from them for threading the inner and outer firebox wrappers on full size steam locos! That is one very odd size!
  It was mainly curiosity that drove my query. I will get back to you if I find a difference between the UNEF and ME thread form.

Thanks, 

Andrew.

[GGeezer]

Andrew,
1/4-32 model engineering thread has a 55 degree angle, whereas UNEF 1/4-32 thread is 60 degrees.

Orv.

[Tim Wescott]

http://en.wikipedia.org/wiki/Unified_Thread_Standard  Search for "UNEF".

All unified thread standard threads have a 60-degree thread form like Orv said.  You may be able to force a glowplug into a hole tapped to your brit standard, but it really won't be right.

I know you can get the taps here in the states from McMaster-Carr.  I don't know if they'd ship to the UK or not.

(I think the 55 degree vs. 60 degree thing is because 55 degrees is technically better for some reason or another, but in the way-back-time it was much easier to manufacture taps and dies with a 60 degree angle.  In other words, it's a typical Brit vs. American engineering difference of opinion.)

[Brett Buck]

I still have to find a UNEF thread table in my books but no doubt I can find it on the net. I will try a search and see if the thread form is the same as 1/4 x 32 Model engineering thread. Those taps can be had easily in the UK finding a UNEF 1/4 x 28 may not be so easy. However we probably have one of the best shops worldwide, they never seem to be beaten. I have even got taps from them for threading the inner and outer firebox wrappers on full size steam locos! That is one very odd size!
  It was mainly curiosity that drove my query. I will get back to you if I find a difference between the UNEF and ME thread form.

     I found any number of 1/4-32 UNEF taps for around $2.50 with a quick google search and I am sure someone would be happy to mail it to you. 1/4-28 is UNF and also trivial to find, just about every hardware store in the US would have that, for around $2. Order 100 of them and corner the British market!

    Brett

[Brett Buck]

I believe 1/4-32 is classified as UNEF. The threads for a glow plug and for the Cox .049 venturi are not something odd.

There's a jillion hits on a Google search for
             1/4-32 thread

Bill

    Well, odd in the sense that you can't go to your corner hardware store and buy them. Not odd in the form.

    Brett

[Andrew Tinsley]

Thanks guys, now I know the difference in thread form between the ME thread and the UNEF thread, I have emailed the best store in the UK for taps. In the unlikely event they cannot get the UNEF thread form, then I will get some in the US and sent to a friend of mine on the East coast. Maybe I will corner the Brit market as Brett suggests!

Thanks again,

Andrew.

[John Rist]

Thanks guys, now I know the difference in thread form between the ME thread and the UNEF thread, I have emailed the best store in the UK for taps. In the unlikely event they cannot get the UNEF thread form, then I will get some in the US and sent to a friend of mine on the East coast. Maybe I will corner the Brit market as Brett suggests!

Thanks again,

Andrew.

I just called McMaster-Carr.  They do not ship to UK.  So your best bet is to have a US friend buy and ship them.  Makes it a bit pricey.

[John Rist]

The answer is eBay !!!      Hundreds of listings for 1/4-32 tap.  Lots of China sources that ship world wide.  Cheep!!!

[Andrew Tinsley]

Hello Everyone,
I just ordered a set of 1/4 x 32 UNEF taps from my usual source here in the UK. Thanks to everyone that offered help, it is much appreciated.

Regards,

Andrew.

[Dan McEntee]

  Harry Higgley products offers a 1/4-32 tap.  I think we have them on a hook at the hobby shop. I know you got yours, but will be a source for others that might be needing one.
  Type at you later,
    Dan McEntee

[Andrew Tinsley]

Thanks Dan,
 I did see during my browsing that Harry Higly stocked the taps. I also noted that Sig had taken over his operation.

Regards,

Andrew.

[George]

Thanks Dan,
 I did see during my browsing that Harry Higly stocked the taps. I also noted that Sig had taken over his operation.

Regards,

Andrew.

HH also makes or made a nice die in 1/4 x 32 size. It is a good idea to chase glow plug threads in case the threads have a flaw...before ruining an irreplaceable head on an old engine.

George