If you have read some of my earlier projects you'll know that I am busy (that's the wrong word - working towards, would be more accurate) making a pen turning mandrel (or mandrels) and the bits and pieces that will go with it. I would love to spend more time tinkering around in the workshop but other areas of life must go on.
So why don't I just go and buy the kit for about $30 so I can get going with the project? Well, because I am learning to use my mini Chinese lathe and these projects are all useful to understand and learn all kinds of techniques for a variety of machining projects. I am the 1st to admit I make a number of mistakes and have to try again.
One of my mistakes was when trying to thread a 6mm rod for a mandrel was to think I would just hold the rod vertically in the vise and use the standard die kit wrench to cut the thread. I've got a good eye for what's square, and I'd have no problem keeping the die and wrench square with the rod - I've done it before. Yes but with some short threads and I need about an inch of thread on these mandrel ends.
First I tried a length of 6mm stainless steel rod I had. Well the die just went round and round on the end of the rod and made a messy end. Ok, if I'm going to use that again I'll have to thread it on the lathe and I haven't learned to do that yet - using the gears etc.
So I then went back to my FREE salvage of rods I have from old printers. These are really beautifully polished straight rods. You'll see this lot when I get to doing the next instructable. I started the threading and all was going well until I took the die off and found the thread was crooked. At the length of around 25mm (1 inch) the die was hardly marking the one side and deeply cutting into the other. Visibly off course.
So, what to do now? I had to find a way of keeping the die perpendicular (at a true right angle) to the rod. The Internet is a wonderful place these days to find solutions (good and bad) to a problem. There are many videos explaining this tool I'm about to make and I watched a few of them.
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The first thing I needed was a steel or aluminium rod that was larger than my die set. My set of dies are 25mm (1 inch) by 9mm in thickness. I have a few free rods that I have acquired and cut a 50mm (approx) length from one that's around 32mm in diameter. The die is going to be recessed into the one end of this bar and a grub screw, or two, used through the remaining wall to secure the die in place.
The die holder needs to be drilled right through to enable the largest size rod being threaded to travel through its full length(I decided that I would make my hole 10mm). This is because you will be holding this finalised die holder in your hand while the lathe is turning and the rod being threaded. If you are threading a whole length of rob the end will need to exit the back of the die holder.
You will see the images below of the die holder being being held in the hand while it travels up the rod being threaded. I don't have a video in this instructable to show this happening but, if you look online, your will see the process - I don't know if I can mention any names in here but there are number of videos of guys making these die holders on their YouTube channels.
Now, depending on your collection of dies, you will need to make a holder to accommodate the size (diameter) of your dies. Remember to make sure that the diameter of rod you choose must also allow for a grub screw to be inserted to secure the die in place.
The next step needs no real explanation but to machine out a recess 25mm in diameter and 9mm deep.
For this I used one of my boring bars. It's a slow process on the mini lathe because you can't take very big cuts. I managed to feed my compound slide by 15 to 20 units on the gauge wheels. (0.3 - 0.5mm).
When the recess is close to size (use a vernier caliper if you have one - if you don't, and you really do need one when working on lathes, then use a rule, and then trial and error with one of the dies until it just fits) you can clean up all the sharp edges with a file and some emery cloth.
Now we need to drill the hole for the retaining grub screw and tap a thread into it. You'll see that each die has a couple of recesses machined into the side to allow for some for of locking screw, either in the die wrench or in whatever else you would be holding the die in.
I scored (marked) a line around the recessed end at 4.5mm (half of the width of the die) and then slid the tip of a lathe cutting tool across this line to mark a centre point so I could roughly line up the piece and drill in the bench drill press.
As you can see from the photos this is a straight forward process. Because the grub screw thread is very short I felt no real need to worry about the right angle accuracy when tapping this.
I drilled a 4.5mm hole and tapped it with a 5mm thread (M5)
Here is the completed tool (die) holder showing a grub screw inserted. I will find a shorter grub screw as this protrusion could catch your hand when used to thread a rod.
This die holder now needs something to hold it true and square (perpendicular) with the work being threaded while allowing it to slide along the rod being threaded.
Well we now need to use a short piece of rod that is the same diameter as the hole that we chose to drill through the die holder. Remember, I chose to drill the hole out to 10mm. Why? Because I have some free 10mm rods that I salvaged from some discarded printers. Use the size you have - there's no need to machine a rod for this.
The rod needs to be a nice sliding fit in the hole of the die holder. This is what will keep the die perpendicular to make the thread true.
The length of this 10mm rod (in my case) was to be able to fit fully into the die holder (touching the back of the die) and fully into the tailstock chuck, leaving a short gap between the tailstock chuck and the die holder.
You can see from these pictures that I have made a 25mm thread along a 6mm rod which will be used for the mandrel I will make in time to come.
I did use a leather glove when running this thread as I was a bit worried that the protruding grub screw would catch me, but it didn't. I would still use a shorter grub screw and/or make the die holder a little longer.
You do need to play with the speed of the lathe and find the point where the thread runs well (probably around 200-300 rpm. The mini lathe battles if the speed is too slow. A larger lathe will have more power to keep turning a slow speeds.
The beauty of this hand held setup is that you just let go your grip when the thread is long enough and the die holder just spins around with the rod being cut. Grab it again to continue the thread.
I have also shown you a future image of the nut that I have made to be used on the mandrel to tighten up the pen blanks and sleeves while turning the blanks to shape. I would love to be able to knurl that nut, but I don't have the knurling tool in my lathe kit. Maybe it's another project !!
In closing: In the course of these projects we seem to end up with a whole lot more tools and gadgets than what we started out with - but that's the fun of learning these crafts.
Working with tools always has risks, so always be aware of what you are doing.