Exhaust port tap

Status
Not open for further replies.
R

rmullett

Joined
Nov 20, 2010
Messages
49
Looking to buy a exhaust port tap to clean up the threads on my latest Norton Commando head. Any leads on where this might be available ?
Please email me directly at: rmullett@shaw.ca
 
I'm guessing that your threads are in rag order. The problem is, any tapping of the threads is going to remove metal and there is probably not much there to start with. A tap that size will be very expensive. You might consider putting that money towards a proper repair. Ernie Hall (Croydon S. London) helicoiled mine in 1975 they have been better than new ever since. I was directed to him by Norton but I doubt if he's still in business. Some people don't like helicoils, probably because they are tricky when that large and only about 4 or 5 threads deep.
 
You might be able to make a tool out of an old exhaust nut by carefully cutting the threads down to their roots with a hacksaw blade,or perhaps a file, in order to make flutes.

I wonder if there isn't a way to slightly expand our exhaust nuts from the inside to get a tighter fit on the OD, similar to those internal expanders that muffler shops use.
 
Exhaust port tap


I think Bwolf has this one.
 
You can use a tool like this one on Ebay
360871381662 (UK site item number)

A hand internal chaser. You mount a handle on the spiked shank just as you would a hand file. Then it is normally used with the job in a lathe but you can carefully use it like a scraper to "improve" the form of the damaged thread. However as already said removing any metal will further weaken the thread an increase chance of its total failure.
Personally i would dress the tread with an item such as this as a cheap short term fix (as a toolroom turner i have done this many times) but in long term i would not buy the expensive tap as the money would be far better spent on a full thread repair (sleeve or helicoil) carried out by someone familiar an equipped to do it.
 
I use an old exhaust nut, cut through with a hacksaw in four places at 90 degree angles. Works pretty well.
 
A really good way to clean up big internal threads when they have been cross threaded or if they are just dirty or dinged up, is to get a tap with the same number of threads per inch as the thread you want to clean up. I can't remember how many threads per inch the Norton exhaust nuts are but for example if they are 14 threads per inch, you would use a 7/16-14 UNC tap. It would be best if you can find a plugging tap. Then you put a handle on it and use it as a scraper. I have done this a few times and found it works amazingly well. Usually I seem to have a tap already in my tool box, but even if you have to buy a small tap like this it is not expensive.

Nigel
 
daveparry said:
This is not exactly a "small" tap Nigel, somewhat bigger (and more expensive!) than a 7/16.
Click to expand...

A much smaller tap can be used as a thread scraper as long as it has the right TPI.
 
Here is what I did to lightly clean up a slightly damaged thread.

Exhaust port tap


Exhaust port tap


The small skinny ones are left hand for bicycle crank arms. The disk is what I cut the slots in the exhaust collar with.
It worked great.
 
Thread files are a cheap way of cleaning up damaged threads and have used them to clean up a mates exhaust threads, I have a few in diffrent sizes from UNC, UNF, BSW and metric, each file has 8 diffrent size threats for internal and exteranl clean ups, after 39 years I have never had any problem with my exhaust threads but have used the files to give then a good clean up.

Ashley
 
Status
Not open for further replies.

Similar threads

C
JS exhaust port fillers
2 3 4 5
Replies
82
Views
3,295
acotrel
acotrel
D
Exhaust port thread repair
2
Replies
24
Views
1,423
Dan1950
Dan1950
D
Norton Exhaust Port Repair
2
Replies
26
Views
1,135
ilikevelos
I
MikeG
Classic British Spares Exhaust port repair
2
Replies
23
Views
1,859
Dzldanz
D
jseng1
Domni exhaust ports
Replies
5
Views
186
kernel65
kernel65
Back
Top