They were probably the correct size before welding...the welding shrunk them.

Probably won't take much to get them to the correct size....use grease on the tap, and clean it often...to keep from getting shavings inside the tank.

 

Thanks fxst1984, we have something in common! When my motor was torn down, the mech comment on how the heads or cylinders were very early and were sand cast? Or something. And how easy they were to skim or something for higher compression or sommat?

Interesting these early softies!

Steve

 

Update! No luck:-(


I have a tap but the stainless is so hard, its not cutting and I'm afraid of going too hard on the tap, I am using lots of lube but the tap is only going in 1/4 of its length, that's after an hour of working slowly and carefully.


Looking at the tap and the oil line fitting side by side, it looks like the tap really needs to go in its full length for the fitting to fit the hole without having many threads left showing. At the moment most of the threads show and only one or 2 threads screw in before going very tight.


Help! What can I do? I am thinking it is easier to machine the fittings down which are not stainless! The die I have in this set which wont screw on the thread of the fitting, maybe I am best to butcher them as they are only €10 each.....! Grind the thread down so the die bites and make them smaller.


Any other suggestions chaps?


Ta


Steve

 

What size is the tap you're trying to use? What is the drill bit size to use for that tap? I would start with that. You may also need a quality tap. I've tapped a lot of 304 stainless in 1/2x20, and you need a quality tap and some good cutting fluid like Tap Magic, plus you need to start out with the right size hole. We don't really know what size hole is in there, do we?

A trip to a machine shop and a "tap these holes this size for me please" might not be a bad idea either. Can't charge you too much for that.

 

I am in rural France and it's not so easy finding a place who can do this for me. I also worry about them scratching the tank...
I bought a 8.5mm drill and it drops through two of the holes nicely so it apears to be the right size hole(at least, not too small)

The tap is 1/8 NPT, and I have a better quality one coming just to be sure!

Cheers

Steve

 

8.5mm should be pretty close. 8.4328mm is spec (0.332"):
http://www.engineershandbook.com/Tables/npttap.htm

So, after that, you just need the proper tap and a proper tap wrench and some good cutting fluid. When you start it, try to start it in the threads that are already cut. Some wiggling, etc., as you ease it in. Make sure it is attached to something so it doesn't move around. Go slow, turning in 1/8 turn, back it out 1/8, turn in 1/4, back out, etc. Use a good tap wrench that you can get good leverage on. Do not ever put force on the tap in any direction but circular. If you bust it off, then you have a real problem. Ask me how I know.

 

Did you solve your problem? I might be able to hook you ip with adapter fittings that might work. Let me knoeUOTE=Greenblood;15081966]Yep, looks like I have to tap it out. Bugger. Not so much a problem tapping it, more the hassle of getting the swarf out after! Grr!

Steve[/QUOTE]

 

hdvespa, thanks for the offer, yes I'd appreciate some help.


What I need are 3x 1/8 NPT to 3/8 hose at 90 degree with a thread smaller than normal so it will screw in the whole way.


Happy to pay if someone can make or modify something for me to use without having to mess any more with the tank.


Cheers


Steve

 

For conversation what are the fittings your using made of?
Have the fittings been chromed?

I'm thinking a brass fitting might be more forgiving in getting screwed in a good amount. Not that it would look good

Just throwing a thought out there

WP

 

The fittings are chromed brass if that helps.
Steve