Help threading correctly...

[saefroch]

I can tap threads just fine, but have a look at my sad attempt at making male threads to connect to the pump head (whose female threads are fine)...

My crooked attempt is on the right, with the threads from a same-size carriage bolt on the left:


Help?

[jrrdw]

If the rod diameter is to thick....

[saefroch]

I'm pretty sure it's the correct diameter rod, since the threads I made fit correctly into the threads I made with the matching tap in the set.

If you want to check, go ahead. It's 5/16" threads onto 1/4" rod.

[ramses]

there's your problem. Do you have a 1/4-20 tap and die?

With the smaller thread sizes, I generally turn the rod to the spec'ed major diameter in a lathe, slap a drill chuck in the tailstock, and use it to apply pressure along the axis of the lathe to keep the die straight I turn the chuck by hand, and brace the handle of the die holder on the saddle. If I get daring, I turn on the power feed

never had a problem, except for single point threading(but we won't go there)

[jhalek90]

quick tip that learned in the shop.

Stick the un-threaded rod into a drill, and sand the end that you want to thread, just a little bit, to give it a nice taper.


Then hold the rod as straight as you can, (i used a vice, and a square), and while keeping the thread cutter (die) as level as you can (small bubble level works great), apply a bit of downwards force, before you begin to slowly turn the die.

The tapered rod end will help quite a bit. also, make the threaded portion of the rod slightly longer than necessary, and trim the taper off later.

Hope that helpped.

[saefroch]

I think I do have a 1/4"-20 tap and die, but wouldn't that be even smaller than the 5/16"-18? Would I even be able to get the threads started? I don't have a lathe, so I have to do it by hand.

@jhalek90: I'll try that. Might have a chance to try again tonight, if I'm lucky. At least now I have some practice stock I can try on.

[Fnord]

The tapered rod end will help quite a bit. also, make the threaded portion of the rod slightly longer than necessary, and trim the taper off later.

That's exactly how I do it and I've had good results. Note that even copper is a PITA to thread unless you have a nice tap wrench. I made one with 1" foot handles and it works fine. Use lots of grease.

[saefroch]

Use lots of grease.

Grease?

[jrrdw]

Use lots of grease.

Grease?

Oh yes, you have to keep the cutter lubed during the process.

[ramses]

I think I do have a 1/4"-20 tap and die, but wouldn't that be even smaller than the 5/16"-18? Would I even be able to get the threads started? I don't have a lathe, so I have to do it by hand.

@jhalek90: I'll try that. Might have a chance to try again tonight, if I'm lucky. At least now I have some practice stock I can try on.

wow. that was quite stupid of me. 1/4-20 (or 1/4-28) would be the correct size for your rod.

As was said, taper the end of the rod. Also try reversing the die; some(the good ones) start tapered at one end to facilitate starting, not unlike most (non-blind) taps. It can be turned around to thread closer to a shoulder where necessary.

[saefroch]

So I can reverse a die that IS tapered? Would I do that when I start threading the rod?

[inonickname]

So I can reverse a die that IS tapered? Would I do that when I start threading the rod?

You want to start, and cut all of the threads with the tapered end cutting first. If you need to cut closer to a shoulder, you should then reverse it to cut the last few threads the taper could not reach.

A lathe will help a lot with alignment. Personally, I don't use grease but I prefer a very light cutting oil such as kerosene.

[Gippeto]

Start with stock of the correct diameter...

http://www.engineersedge.com/screw_threads_chart.htm

I use a product called "Rapid Tap" for steel and stainless...works well enough.

http://www.relton.com/pdf/nrtds.pdf

On aluminum, I was using wd-40, but USGF and another fellow (sry can't recall...french Canadian guy.) suggested mineral spirits...don't stock that, but varsol works GREAT!.

Alignment is your major issue...judging from the pic. Have a drill press? Hold the stock in the chuck, place the die flat on the drill press table, turn by hand for as many turns as can be managed. Then move to the vise. Remember to back up (reverse direction) every 1/2 turn or less to break the chip. Helps a lot.

[saefroch]

Alignment is your major issue...judging from the pic. Have a drill press? Hold the stock in the chuck, place the die flat on the drill press table, turn by hand for as many turns as can be managed.

I would... If the stock didn't have 2" of threads on the other end and was 36" long. I'd be lying on the floor in the most awkward position imaginable, crushing the threads I somehow managed to get level on the other side in the chuck.

I'll try to decipher the table when I get home. Thanks for the link.

I really wish I had a lathe... but I don't.

[ramses]

in the future, you can thread a nut onto the threads that exist up to the stop of the threads, and grasp that in a 3 or 6 jaw chuck. As you thread the other end, it will tighten the nut into the shoulder.

leaving a nut on threads helps regardless, that way if you screw up the threaded slightly, when you remove the nut, it will sort of reform them.

The vice, bubble level, square idea sounds good.

I use WD40 for aluminum and Tapmatic gold for everything else. That smells really good.

On second thought, is the tap HSS or carbon steel? if it's carbon steel and you're threading steel, you'll dull it quite quickly.

The thread a bit, back out, thread a bit more approach is also recommended.