G'day Chris here, and welcome back to Clickspring.
A standard die holder can sometimes be a little awkward to keep aligned with the work.
In this 2 part video, I make a more convenient holder that can be mounted in the tailstock of a Sherline lathe.
This is what I currently use for die threading on my larger lathes, and I'm using it as a guide for the design of this one.
The body of the tool slides up and down on a shaft, to allow the die to be pulled onto the stock as it forms the thread.
And the fact that it sits in the tailstock also makes alignment a little more reliable.
There are recesses at each end to accept different sized dies, and grub screws to hold them in place,
and compress them if needed. The grip pattern I'm using is consistent with
some other Sherline accessories, like this little tool that holds watchmaker collets.
I'm going to put in a series of close milled grooves around the perimeter, to give it a similar straight knurl look.
The shaft needs a zero Morse taper to fit into the tailstock,
and the tool also needs a little handle to finish it off.
Now the fact that it hangs out quite a bit from the tailstock influenced my choice of material.
Solidworks has this great feature called "Mass Properties",
which tells me that if I make it from steel, its going to weight in at almost half a kilo,
which is a bit much to ask of the little Sherline tailstock.
But with aluminium alloy, it comes in at around 150 grams which I think will be fine.
I also need to consider the different dimple patterns that are found on modern split dies.
I think this little holder deals with it best. It has 4 holes spaced to both open or compress any common split die.
The 45 degree spacing takes care of some, and the 90 degree spacing sorts out the rest.
So lets get started!
I cut off a section section of inch and a half rod, and set it up in the lathe for a light facing cut,
and then drilled and reamed the center.
For the tool to work correctly, the die recesses need to be perfectly concentric with this bore.
But there's a fair chance that the drill wandered a bit, while I was making it.
And even if it didn't, I would lose all alignment anyway, when I flip the part to do the second recess
So I roughed out both recesses, but i've left them undersized,
so that I can true them up to the bore using this stub arbor.
Its a piece of drill rod held in a collet, and confirmed to be running true.
Then a few drops of super glue hold the part into place.
From here I took a skim cut of the outside surface, and took the first recess to final dimension.
The part needs to be flipped, and then remounted to take care of the other end.
And heat from a torch breaks the superglue bond, but I'm pretty sure that vapor coming off isn't overly healthy,
so I wear breathing protection whenever I heat super glue.
The part was then remounted on the arbor, and the other recess turned to final size.
Next I marked out and cut the outside profile.
You can see the work is hanging out from the chuck a little more than it should be,
and I probably should have given it a bit of tailstock support,
but I kept the cuts light, and it worked out fine.
One small drawback of stub arbors, is that they are an absolute magnet for long chips!
Without disturbing the part, I set up the vertical slide and dividing gear on the lathe to take care of the outside grooves.
I don't think the cutter profile is overly important,
but I had this 90 degree countersink left over from another job,and it looked like it would do the trick.
So I centered the cutter on the work,
and took extra care to make sure it was clear of the chuck,
and that I had a temporary stop in place to stop me doing anything absent minded.
Please don't ask me why I know this is important!
The first cut is much like the wheel cutting process. I took 2 cuts side by side, to judge the right depth of cut.
As it turns out, I misjudged this, and had it at full depth for that first cut,
so I was kind of lucky I didn't lower it any more, or I would have ruined the part right here.
But what really stood out to me at this point, was the sound of the cutter.
It was making a woody "knocking" sound, and cutting on the return pass.
Definitely not the behaviour of a happy cutter.
Plus the surface finish was terrible.
I was fairly sure the problem was that it was just a bit blunt,
so I gave it a bit of time on the sharpening stone, and from there it cut beautifully.
Off camera, I thinned down that centre section just a little bit more, to make it feel a bit nicer to hold.
I then mounted the part on the mill, held in a dividing head using an ER collet chuck.
The spindle was put in line with the axis of the part, using an edge finder,
and this time I used a bit of support, using this little machinists jack underneath the part.
The downward force from the drill is significant, and I wanted to keep deflection to a minimum.
I then drilled and threaded, the handle and grub screw holes.
A light touch with a countersink, and that's the part complete.
The threading dies fit quite nicely in the recesses; not too tight that they get stuck,
but without too much play either. Also the part feels quite good to hold, which I think
is important for a tool like this, so you can feel what's going on as the thread is being cut.
In the next video, I'll finish off the tool
by making the morse taper shaft, as well as the handle.
Thanks for watching, I'll see you later.
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Thanks again for watching, I'll catch you on the next video.