Ideas Needed To Get Smooth Bore On Tees Removing Pipe Threads

B

Big Bob

Registered
Registered
Joined
Dec 24, 2012
Messages
43
I need to machine a sliding 3/4 or 1 inch diameter in a pipe tee and fit same diameters in the tee, thus needing to remove the pipe threads. I tried several ways to locate in lathe or mill, but lack of reference surfaces on the rough casting exterior of the tees is challenging and I have not figured it out yet. Pipe thread also makes locating difficult. I am going to try to put a threaded pipe in one end and turn the other, but then what do I do to locate to do the other two bores and hole a +/- 0.010 tolerance and perpendicularity.

My other option is to use a two inch diameter rod and bore both and weld. Tees would be easier and cheaper.

Suggestions?

Bob
 
Sounds like a good job for a 4 jaw chuck on the lathe. Use a piece of brass pipe to indicate off of. I think that will meet your tolerance requirements. Use a center in your tail stock to help.
Dave
 
Interesting project. Probably several wayst to get'er done.

I think you have a good plan for the first one: cut a pipe thread in a piece of bar - then you can machine away the thread on the other side of the straight through (and face the end off pretty too). Make a second support stub that is just a close clearance fit to the portion you have just bored - loctite the fitting to the bar and machine away the thread on the other side of the straight through (and face it pretty too) - heat the fitting out of the loctite. Then grip in the 4 jaw (on the two surfaces you just faced) - using that first mounting bar threaded into the branch to index off.

Sort of depends on how many you want to do.
 
Remember, you're machining low grade cast iron, you'll never get a good finish. It's take solder, or be welded, but it won't be pretty, like steel.
 
You can do the bull head part in the four jaw one of the ends with a nipple to indicate from for the first run the second run you might use a face plate with a angle plate. It all depends on how good you must have it.
 
I have never had any problems turning galvanized fittings.
Pipe threads in cast galvanized fittings are rarely straight, makes it very difficult to know where to index.
If I understand your project, the side of the tee stays threaded and there needs to be a straight through bore perpendicular to the pipe threaded into the side of the fitting.
Do you have a milling attachment for the lathe?

If not you may want to consider this:

Make a threaded stub to fit the side of the tee. The shank of the stub should be turned to fit a ¾ or 1 inch boring bar holder.

Pre-align the boring bar holder on the compound to be perpendicular to the spindle axis and at center height.

Screw the stub into a tee fitting good and tight.

Mount the stub in the boring bar holder and level the tee fitting. Tighten the boring bar holder.

Mount a boring bar in a scroll chuck on the spindle.

Bore out the tee fitting as required.
 
Last edited:
Good suggestions. I have a 4-jaw on Colchester round head 13x36 and will use nipple in the tee. I did not think of putting the cutter in the chuck and this lets me drill/bore/ream through. I knew of this technique, but just did not think of it for this and I appreciate all your suggestions. Thanks. Bob
 
Make a solid internal T that threads together. If the cast T is one inch ID, take a piece of 1 inch bar stock that sticks out on each end of the cast T by 2 inches. Thread it in the middle for another piece of bar staock to screw in @ 90 degrees. The other piece also sticks out of the cast T by 2 inches. Slide the long bar into the tee and then stick the other bar into the T and thread it into the long piece. Now you have the T captured in every direction with a 2 inch stub sticking out so you can chuck it to machine off all 3 threads. If the 1 inch bar stock is a loose fit you'll have to use bigger stock and machine it for a tight fit.
 
Bob, just a caution if you plan on using a standard hardware store nipple to chuck the tee. There is no guarantee that the nipple will be threaded straight. Actually my money says that the threads on the nipple will be cocked quite a bit unless you get very lucky.
Consider the merits of making your own stub so it will be threaded concentric.
 
Again good ideas. One problem I have is that I do not have a taper attachment (anyone have one at good price for me?) so cannot make pipe thread on the lathe.
 
You must log in or register to reply here.
Back
Top