Adding a QCTP to a 9×20 Lathe

It took me a while to find much information on this, so I’m paying it forward to hopefully make it more likely that the information finds its way to someone who needs it! If you’re fairly new to machining, I’m going to discuss toolposts in general a little bit. If you just want to see the 9×20 process, feel free to skip below!

What is a QCTP?

A QCTP, or Quick Change Tool Post, is a type of toolpost for a machine lathe which, as the name implies, allows for much faster tool changes than traditional lantern or turret type toolposts.

Four way turret toolpost
Four way turret toolpost boring out the stainless NN-14 barrel

It’s a pretty standard upgrade for most lathes which are used in any kind of production capacity, since the ability to move through a rapid sequence of tooling allows for efficient machining of multiple identical parts.

There are two main types of QCTP that tend to be used: two position “Aloris”, and 40 position “Swiss-type” or “Multifix” styles. The US tends to use the two position, and Europe the 40-position, though that’s not an absolute. They all use a lever that cam-locks a variety of toolholders in position against a post which dictates the angle they’re at.

The 40-position uses a spline pattern around the entire post which allows a tool to be set every 9°, and a loose pair of arms with pins on the end that engage with slots in the toolholders. The cam operates at the root of the arm joint, pushing the back of the joint apart, squeezing the pins together and drawing them back, pulling the toolholder (with a matching 9° spline) into the post spline. This is extremely accurate and repeatable (repeatability of a toolpost is defined by how close the tip of the tool is to its original position when the toolholder is removed, replaced, and re-locked). When I get a new, bigger lathe in future, this is the type I’ll put on it.

For now, I got a relatively low-cost two-position type. These have square bodies with dovetails on the inside and spindle faces (assuming it’s set square on the lathe, which they usually are). There are two variants of these; piston and wedge type. The piston has a cam inside the body which pushes a piston out of the center of the dovetail against the toolholder, forcing the dovetails to mesh in tension. These tend to be around 20-30% cheaper and are generally considered to have lower repeatability

Toolpost wedges
The silver bits are the wedges, and slide up and down by the big lever

The other type is the wedge type, where the cam action is a screw which draws down a tapered “gib” which replaces one side of the male dovetails. When the toolholder is inserted, the wedge is forced down, pulling the toolholder dovetail slot “apart” and drawing the holder into the toolpost body. These are a little more expensive and generally considered to have higher repeatability. This is the type I got, because being able to reliably replace a tool after removing it to measure the workpiece can be useful. Many people don’t much care and will re-touch off on the part on each tool change. Just personal preference.

There are size standards for QCTPs, so that there aren’t an infinite multitude of toolholders to manufacture. They’re generally categorised by lathe swing, with some overlap since the toolholders inherently have some vertical adjustment. Aloris styles have AXA (9-12″ swing), BXA (10-15″) and CXA (13-18″). There’s even a DXA for monster machines. Since the proliferation of mini benchtop lathes, there’s also an 0XA for 7-8″ swing. Most people reading this will need either an 0XA or AXA. I, of course, got an AXA. It looks quite large on a 9×20″ machine, but more is better when it comes to machine mass.

The toolpost looks big on the machine
Looks even more huge than this on the machine in person!

The second nice thing about quick change tool holding is that the holders have a screw stop with a jam nut to adjust the height that they sit on the post. This allows for quick and easy tool height adjustment, no shims required! If you use HSS heavily, this may be even more useful, since quick regrinds for rake angle, etc can be dialled in within seconds. You can also use this height adjustment as y axis indexing for sneaky little single-axis milling jobs- slotting, etc. on small parts that fit the tool holder. I believe some people have even made tiny mill vices with a lug base that can be fixed in a QCTP holder.

Adapting to 9×20″ Import Lathes

Where an old South Bend 9″ may have a traditional T-slotted compound slide, the import 9×20″ lathes (like my Grizzly G4000) have a fixed M8 stud protruding from the top. The QCTPs come with a large block that’s intended to be milled to size for a T-slot. This, of course, isn’t very helpful to someone who doesn’t have a T-slot and may not have a mill.

Machinable T-nut
The idea is to machine this block into a T-nut of the right size. Some just turn it down in the 4-jaw.

While it may be possible to disassemble the compound, remove the stud, and re-drill and tap for the M14-1.5 stud that comes with the AXA toolpost, this was a lot more work than I really wanted to go through- and entirely irreversible!

The fixed compound stud between the M8 tap and the new 14mm stud.
The fixed compound stud between the M8 tap and the new 14mm stud in progress.

I did eventually find this handy PDF where a guy makes a replacement 14mm stud which screws into the M8 compound stud, but it seemed like a lot of work and the result would be slightly inferior unless I also used a heat-treatable steel to make it, which would result in even more work. Plus it still requires a mill to make the hex head, and I wanted to come up with a way that didn’t (plus I don’t have a hex collet block for the mill, so it’d be rotary table time!). I figured since they gave me an M14 stud in the package, why not just use that? It amounts to the same thing in the end (well, not quite, but I’ll get to that later).

Cutting off almost all of the bottom threads
Cutting off almost all of the bottom threads

So, I chopped off most of the bottom threads on the M14 stud and faced it off level with the beginning of the thread.

Faced off new stud
I love a freshly faced surface!

Next I needed to know what drills I’d need for the actual process, which turned out to be four: one, a 1/8″ for a through-hole to give the tap chips some clearance. The second would obviously be the 6.7mm tap drill for the M8-1.25 internal thread. The third would be something just a little larger than the shank of the tap. I went with 21/64″ or 0.3281″.

Measuring the tap shank with digital micrometers
Digital micrometers are the best.

That would support the tap and stop it wandering while it was so deep in the hole that I couldn’t support it. By definition, the threaded section needs to be concentric, or the toolpost will get tightened down cocked over.

Compound stud measuring
Not sure why they decided to go with a larger shank than thread, but hey.

The fourth would be the actual diameter of the M8 stud shank so that the M14 stud can sleeve all the way down to the compound for maximum support. I went with 25/64″, 0.3906″.

I drilled the 6.7mm hole slightly over-depth so that ideally, the M14 stud could be tightened directly against the compound surface rather than just hanging on to the M8 stud.

Measuring bore depth
Measure the stud, then see if it pushes in further inside the bore. Simple.

If you weren’t already aware, you can use the inner sliding bar of a caliper as a depth gauge. Apparently this is a thing that people are constantly just discovering, so I thought I’d mention it in case it was helpful!

Time to tap. My only tap wrench goes up to 1/4″, so it was crescent wrench time.

Tapping the bore
Tap tap tap.

Yes, I’m using it the “wrong” way here. No, I couldn’t care less. It’s irrelevant in any practically meaningful scenario.

This is why I drilled the base hole twice! Zero external support:

Deep tapping
Yup.

Then it was just time to open up the base bore, and it would be done!

Last drilling step.
Last step!
Fitting the new stud
It vuhrks!

I decided the first thing I tried would be parting off, since it’s the hardest operation to do on a small machine lacking rigidity and typically having a little more slop in the cross slide leadscrew than is ideal. Dialling in the height just took a few minutes, and the results were beautiful:

Fantastic parting tool chips
Those are the best parting chips I’ve ever seen!

Issues

For the most part, this job really is as simple as the pictures make it look. It’s an ideal process if you don’t also have a mill. There were however, a couple of things to note.

One, on the lowest end of the AXA capacity range, the spindle is naturally going to sit quite low. This means that to center up- especially with tooling larger than the 3/8″ typical of this size machine- the tool tip, the toolholder has to go below the level of the toolpost. This means relieving the compound slide itself to allow that room. I happened to have a large indexable mill that made short work of it, but a little time with a Dremel or file would do the job too.

Removing a little off the compound
Doesn’t need much, barely even 1/8″. I need to do it on the other corner when I get a chance

When it came to actually dialling in the toolpost- which I did with a locked-in toolholder and a test indicator- I found the problem I alluded to earlier. Turns out, the bore of the toolpost is not actually 14.05mm or whatever it should be, and tapping the post into squareness doesn’t purely rotate it like tramming a mill vice does, but wobbles it about the axis of the stud by quite a significant amount, which makes both squaring and tightening quite difficult. At some point, I may weld up a portion of the threads and turn it back down to a much more precise diameter, but since- fingers crossed- I’m very rarely going to need to loosen it back up, that may be a while.

The End

Well, that’s it. I hope this was useful to anyone wondering what a quick change tool post is, or debating the merits of getting one for their benchtop machine. Any questions or comments you can hit me up below or on the social feeds you see in the sidebar there.

Happy turning!

~Rob

BR85 Build Skills, Episode 3

The series finale, in fact!

Once again, the purpose of this series has been to demonstrate some individual, self-contained elements of a build that translate well to other builds and materials that elevate a build beyond simple assembly and paint.

This time, it’s mag catches:

Even shorter again, clocking in at under 15 minutes!

It would indeed have been up by February as promised last time, but some people decided they wanted to pay me to do stuff, so it’s late. Understandable, right?!

The scope, safety selector and paint are being axed. The scope because the LED system in there isn’t sufficiently different to the ammo counter to warrant a video, the safety selector because they ended up being less functional than I’d like and the NN-14 has a much better version so demonstrate when I get that far, and the paint because honestly, the surface prep is 95% the same as for moulding, and the actual paint schemes themselves are pretty obvious in their execution (just slow and tedious!).

Onwards unto better videos on newer, better projects!

~Rob

STAR WARS: Episode VII – The Force Awakens LPA NN-14 Blaster

The Rey gun!
Because, apparently, I’m incapable of being reasonable, I decided for my second trick I’d do the LPA NN-14 that Han gives Rey on Takodana in The Force Awakens. Not in foam or resin, but in metal.
“I think I can handle myself.” “I know you do, that’s why I’m giving it to you!”
 It caught my eye, because despite being objectively fairly unbalanced, lumpy and ugly, it has some individually beautiful design elements, as well generally appearing to be an homage to Original Trilogy lightsabers. It looks to be the only blaster we’ve seen so far manufactured by LPA, which makes sense because it’s heavily divergent from the general design lines common to most of the blasters we see in either Old Republic/Pre-Empire or Empire/First Order settings.
On top of this, it’s relatively simple to machine manually due to its mostly 30’s machine-age aesthetic. This is very appealing to a guy who hasn’t yet built any CNC technology! Similarly important for me right now is that every part of it fits into a 4″ square, which is all the space that my lathe milling attachment gives me- and even then, the extremes are iffy because the dovetail ways and gib on the thing don’t have a lot of grip on each other and can rack under pressure from the cutter. Sometimes it’s better to flip parts around near the end of its travel.
 This isn’t going to be a completely exhaustive build log by any means; that’ll come if I can find the time when I build version 2, hopefully later this year. But I will touch on the highlights, with plenty of pics to break it up. Don’t be fooled, this is still a seriously substantial write-up, should probably grab a beverage of some sort… But there’s a lot more to it than this. Ok, let’s get started.

Continue reading STAR WARS: Episode VII – The Force Awakens LPA NN-14 Blaster

Revamping The Shop!

So I don’t know how well it may have come across on video, I generally tried to frame somewhat carefully, but the shop as it existed from around the middle of 2015 onwards was a nightmare. Stuff- tools, materials, trash…- strewn across every available flat surface, including the floor, piled up against benches and walls, some bench tools on the floor… Working in it was like playing Jenga in a hurricane.

So, this summer I made good on my threats to actually do something about it, and put a good couple weeks’ of effort into really turning the space into something useable. It’s a huge amount of work, and really has to be broken down into two phases, but the first phase (create more workspace, clear most of the floor, give all the tools a permanent home) is now more or less complete.

I did what was supposed to be a quick video giving something vaguely resembling a tour:

Here are a few pics of where it currently stands:

_mg_4174

Continue reading Revamping The Shop!

BR85 Build Skills, Episode 2

New video is live! Yay!

The idea of this series is to focus on a handful of specific, fairly self-contained parts of the build that can easily transfer to other prop builds, kit assemblies, whatever. To look at some of the more “functional” aspects of a prop build that can be used to improve a project beyond good assembly and paint. Check it out:

This one even manages to be about 35% shorter than my usual running time! 😀

One idea I also had was to make an L-shaped slot so that the handle has a point to catch for an empty/missing magazine, and then could be flipped forward after “reloading”. Since the BR85 seems to have a closed-bolt firing position or a floating bolt assembly- it gets fully racked back-and-forth after replacing the mag in the game- this wasn’t really relevant to this build, but there may be some other weapons (particularly pistol slides) that operate that way in-universe.

For a pistol, you’d need a separate lever that could flip the lever (connected to the slide) back up into the main guideway. Alternatively, a spring-loaded crossbow-style wedge, that allows you to rack the slide back, and then pops up into the main cylinder in front of the returning piston head. The wedge itself would be directly connected to the release lever that would allow you to depress it back out of the cylinder. May be easier that way, since you wouldn’t need to allow a floating, rotating bolt to connect to a linear slide. Anyway, random ideas aside…

Continue reading BR85 Build Skills, Episode 2

Round-up, September 2016

The last few months have been some crazy ones (and where did 2016 go, btw?!), but I’ve been getting some positive results and making some good progress, overall. As I try to drill down into photography, propmaking and 3D work (all three? Yes, all three. I know, I’m insane), I’m taking a moment to look back over the last few months and see where things are going!

First up, the last of the BR85 project!

BR85HB-SR Battle Rifle

UNSC finish
UNSC finish

I finally finished up this project and shipped out the last two by about May or so, pushing the entire project to nearly two years!

Continue reading Round-up, September 2016

Video Post! LED Lighting for Props

While I continue to work on the Blender particles-of-particles post (I maybe sorta kinda forgot how I did it so I’m having to reverse-engineer it), here’s a video I published yesterday on installing RGB LEDs and building a diffusion box for light-up screens on prop builds!

 

Yep!

~Rob

The Borderlands Episode: Commercial Recasting

(The following issue was resolved shortly prior to publication, but if you’re interested in the legalities of replica propmaking, feel free to continue!)

Well, that escalated quickly. First from Abby Darkstar, then Harrison Krix (post deleted), and most recently at time of writing is Steven “SoloRoboto” Meissner sharing Steven K “SKS Props” Smith‘s Twitter spat last night with the BusDev and Licensing exec at Gearbox, David Eddings (no, not that one). It started over the image at the top of that back-and-forth, Glitch Gear’s PAX announcement of their “Psycho Mask prototype”, which SKS claims as a recast of his own. I can’t imagine it’s going to get better from here unless the Gearbox marketing department starts swinging, but all’s quiet on the western front, which indicates that emails are privately a-flying.

Naturally, “no recasting” being rule #1 in the cosplay community, everyone piled on Glitch Gear and David Eddings to defend their fellow maker. Is it as simple as that, though? Since I don’t identify specifically as a propmaker but more as a general physical and visual creative, I tried to think my way through the tangled web of our broken IP legal system as best I understand it, with the facts that I’m aware of. I haven’t played Borderlands (though I did rather like the 2003 Halo PC port) and don’t really know Steven in any meaningful way, so I don’t particularly have a horse in this race. The usual “I Am Not A Lawyer” caveats apply, as well as “I am not a long-time professional propmaker” and others. Feel free to disagree with my points.

For the sake of argument, I’m going to assume that the mask IS a recast, since if it’s not, and it’s simply an SLA print of a high-res asset (which would have been the logical way to do it) the entire argument is moot and Steven’s drawn some unwanted attention for naught.

1) The Commission System

Commissions are used in the cosplay community to legally mask the appearance of mass-production of unlicensed works. That may be an unpopular opinion, but as best I can tell it’s a fact. I may even be guilty of it myself, if a run of five- three kits and two builds- from silicone moulds would be judicially considered “mass production”. The idea is that commissions of popular IPs are individual artworks unencumbered by copyright and trademark law, since they’re built from scratch as one-offs by clients who are paying for the skilled labour, not the object. Big difference, legally.

Continue reading The Borderlands Episode: Commercial Recasting

TIL: BR85HB-SR Edition!

AKA. The First Mistakes Post of Many!

_MG_2566

I was just reflecting on some of the things I’ll be doing differently on future builds and/or kits, and realised that it might make an interesting post. Currently I’m in the unique position of being still just about post-first-build, and therefore the things I’m reflecting on now are likely to be “obvious”, overlooked by builders further on in their pursuits.

Here’s the top five that I think about regularly: Continue reading TIL: BR85HB-SR Edition!

The Value Proposition of Craftsmanship

Harrison Krix (Volpin Props) recently tweeted,

which set me to wondering. Not so much about cat condos, as entertaining (and potentially yet slightly disappointingly profitable!) a concept as that may be. But it is distinctly noticeable that the world of propmaking, just like the world of “professional photography” that I also have a foot in, has been becoming increasingly crowded.

Bubbling Up

I think the reasons for these two “bubbles” is both the same and entirely different. Photography has boomed primarily thanks to the democratisation of the hardware. You can pick up a camera that’ll happily compete with the big boys for $500 used (or new, in some cases) and Chinese OEMs have flooded the accessory market with affordable gear- I have three Yongnuo speedlights myself as well as my American-made StudioMax and Einstein strobes. Having the gear is one thing, but it’s the education and sharing that has really accelerated the trend. Continue reading The Value Proposition of Craftsmanship