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General Forestry => General Board => Topic started by: Paschale on September 06, 2008, 08:32:57 PM

Title: Problems threading a rod...
Post by: Paschale on September 06, 2008, 08:32:57 PM
So I just bought my first tap and die set today.  I've got a rod that I'm trying to put some threads on, and I'm really struggling with it.  I can't seem to get it to bite at all, and it wobbles like crazy. 

Any suggestions or tricks to get things rolling, or is it one of those things where you just have got to bear down on it with all your might and hope you get the threads started straight? 
Title: Re: Problems threading a rod...
Post by: TexasTimbers on September 06, 2008, 09:01:07 PM
Paschale, I am no machinist but I can tell you when you are threading on a bare rod by hand the first one or two are challenging. Put the rod in a vise and keep plenty of lube on it and go slow. The "wobble" comes from the die not biting because the teeth aren't being given enough stable encouragement to start the process.

Make sure you use the right size die for the rod you are trying to thread.
Title: Re: Problems threading a rod...
Post by: Fla._Deadheader on September 06, 2008, 09:03:32 PM
 Did you taper the end of the rod, first ???  Is there a "Guide" UNDER the die, to keep the die running straight ???

 Do you have a drill press, to chuck the rod into, and press it down against the die lieing flat on the table ???

 JUST a die, in a holder, with no guide, will not work REAL well.
Title: Re: Problems threading a rod...
Post by: Sawyerfortyish on September 06, 2008, 09:15:28 PM
Are you using the right side of the die with the tapered edge to start?
Title: Re: Problems threading a rod...
Post by: Dan_Shade on September 06, 2008, 09:26:31 PM
it is tough, and takes some practice... also, you can get it going at an angle, which makes it run out...
Title: Re: Problems threading a rod...
Post by: cheyenne on September 06, 2008, 09:49:52 PM
Drill press old machinest trick. If no drill press, Taper the end of the rod, not to much, make sure it's square & use TAP FREE or cutting oil. Keep backing off to clear chips every 1/4 turn. Go slow & have fun. Cheyenne
Title: Re: Problems threading a rod...
Post by: rebocardo on September 07, 2008, 01:38:43 AM
I just want to note that if you bought a cheap set from a big store (under $100) and you have a hard rod (grade 8 or SS) there is a chance the die will not cut the rod. fwiw.

The other thing is to have a rod properly sized for the threads you are trying to cut.
Title: Re: Problems threading a rod...
Post by: Paschale on September 07, 2008, 01:50:47 AM
Quote from: rebocardo on September 07, 2008, 01:38:43 AM

The other thing is to have a rod properly sized for the threads you are trying to cut.


That's actually the question that's been burning in the back of my mind.  If you've got a 1/2 inch rod, for example, should you use a 7/16 die or a 3/8 die?   :P
Title: Re: Problems threading a rod...
Post by: Gary_C on September 07, 2008, 02:18:56 AM
When you are trying to thread a rod, in this case a 1/2 inch rod, use a 1/2 inch die. Thread size is always the large or outside diameter of the threads.

When you are using a tap in a drilled hole, you should use a smaller drill than the thread size because the hole should be about the diameter of the bottom of the thread groves. Technically that diameter is called the minor or root diameter. There are generally tap drill tables either with a tap set or some drill sets with drill sizes for all thread sizes.
Title: Re: Problems threading a rod...
Post by: Slabs on September 07, 2008, 05:40:35 PM
Are you using a "split die"?  If so and if you tightened up the die in the holder that could explain your problem.  On larger rods like 1/2 inch, start with the die barely secured and then tighten up for a final cut.  Also check  to see if the die has a "start from this side" stamp.

Good luck
Title: Re: Problems threading a rod...
Post by: scsmith42 on September 07, 2008, 10:51:07 PM
Paschale, all of the answers you seek have previously been listed.  Once upon a time I owned a machine shop, so I've done my share of threading.  Here is what I'd suggest:

1 - get a good set of dial calipers and a threading chart.  The chart will show you what diameter of hole to drill for each specific size tap, as well as the amount of thread percentage that will result.

2 - Buy a high quality set of drill bits - include fractional, letter, and numeric.  Depending upon the tap size, you will use drills from all three sets.  I've had excellent success with Magnum drills from Eppico.  No matter what, get a good brand used by machinists such as Cleveland Twist, Greenfield, etc.

3 - Rod diameter is usually the same as the bolt diameter.

4 - Buy and keep some high quality tapping oil.  I have both high-sulfer cutting oils as well as "Tap-magic".  Certain materials - such as aluminum or stainless, may require a special oil.

5 - when threading rod, you need to be sure that you have a good chamfer on the end of the rod to allow the die to start.

6 - if possible, obtain oversize (large) die handles.  They make starting threads much easier.  Usually you need to put some pretty good downforce on the die to start the threads, but be careful that you don't push too hard and break the teeth on your die.

7 - Die's are directional.  Usually they will have "this side out" or something like that printed on the threads - if not the side with the taper usually goes against the rod that you're threading (to make it easier to start the die).

8 - keep lots of cutting oil on the die, and every turn or two back it up about 1/2 thread to break up the cuttings.  If threading or tapping starts to get difficult, DO NOT FORCE IT!  Odds are that you'll break the tap or die.  Instead back it out a turn or so and clean out the threads (I use compressed air - wear safety glasses), and then relube it and proceed.

A bench grinder with a wire brush on one side is an excellent accessory to have.  You can clean up threads with the wire brush, as well as debur what you thread.

Additionally, a combination belt / disc sander is an excellent accessory.  I have a 6" belt / 12" disc sander from Grizzly that works well for chamfering, deburring, etc.

Scott
Title: Re: Problems threading a rod...
Post by: Paschale on September 08, 2008, 12:13:38 AM
Thanks for all the replies everyone!  Scott, your post is like an operations manual--I sure appreciate it. 

Since my dad has done some threading, I've decided I'll learn from him too...and that will make sure I don't mess up this project....which is a pretty cool project.

I found an old cast iron wrench that's well over 100 years old.  It's shaped liked a door handle, (as you can see in the picture) and so I decided to make a cool handle for my nephew's tree fort.  I was having a hard time thinking about how best to attach it to a wooden face plate, which I would then screw to the tree house door.  I went to our best hardware store in town and asked for some ideas. 

The guy behind the counter got all fired up about the prospect of using this old wrench for a kid's tree fort, and he came up with the brilliant idea of welding a bolt inside the actual wrench, as well as welding a washer.  What we discovered in trying to find a bolt that would work is that modern day hex bolts wouldn't fit...the box end of the wrench was designed for a square bolt head. 

So we ventured down into the basement, a veritable treasure trove of old hardware.  The only thing we found that would fit were some square headed lug nuts.

We decided that it would be best to use the bolt that fit, then cut off the threads on the lug nut and rethread it. 

As it turned out, the guy who I had hoped would do just some spot welding filled the entire box end of the wrench with steel--so I could have used a regular machined bolt no problem.

Regardless, I think it's a very, very cool handle for my nephew's tree house, who just turned 14 today.

For the face plate that I'm attaching the wrench to, I cut up some wood from my dad's land from an ash tree we milled a few years back from the ancestral land.  My nephew's great, great grandfather would have walked by the wood for the face plate of that handle when the tree was just a sapling.   ;D

Eventually I'll get a picture of the finished handle, but here's a picture after it was welded together.

(https://forestryforum.com/gallery/albums/userpics/10109/Wrench-Handle.jpg)