Monday 30 October 2023

D1-3 adaptor - dimensional cockup!

Trial fitting of the adaptor body to the Tree spindle nose reveals a problemette - the adaptor bottoms out on the taper nose before it seats on the actual taper. The nose seems to be longer than the taper bore. 

  • What's the problem here?
  • Why have I only just found out?
  • What can I do to resolve it?
The actual stickout from the mounting face of the Tree spindle nose measures at ~14.3mm. But the technical standard for the tapers states the stickout as 13.00mm. So the Tree's nose is too long!

The reason I haven't spotted it until now is due to the fact that I machined the adaptor taper on the Tree with the Vertex 4-jaw fitted to the spindle. I have avoided disturbing the chuck until the last possible moment. So it's only now that I have removed the Vertex chuck that I am able to do a test fit. And my CAD model was created from the BS ISO standard, not measurements taken from the machine. Doh.

All is not lost, apart from my temper for a few minutes. I can counterbore the adaptor axially by an additional 2mm to provide clearance for the tip of the spindle nose. As this will be a clearance (non functional), the concentricity and perpendicularity are not critical. I can do this on the Bantam. Still, it's fair to say this is rather annoying.

Saturday 28 October 2023

D1-3 spindle nose adaptor for the Tree lathe - what's going on with that?

I started out on this project some time ago. The aim is to allow me to reuse all the D1-3 spindle tooling I have accumulated over the years for the Colchester Bantam on my Tree CNC lathe which has a different (A2-5) taper nose. This will mean I won't need to spend squillions on acquiring all manner of chucks etc for the Tree. This is my design for a "D1-3 to A2-5" adaptor. I've made most of the components now and am keen to get this wrapped up and in use before the sun freezes over.

Previously, I made and hardened the cam pieces for the D1-3 adaptor Having made the body and cam pieces, I must surely be approaching the point of completion for this particular project. 

Where are we? This looks like the sequence of outstanding actions:

  • Drill and tap the holes for the cam retainers. 
  • Machine up the cam retainer screws. These are M8 grub screws, machined down to a ~2mm nose - they mate with slots in the cam pieces. I will use a mild threadlock adhesive to hold them in position.
  • Mount the adaptor on the Tree's spindle nose and machine the D1-3 taper to final size in position. IIRC, I left it marginally oversize.
  • Clean it up, finally fit the cam retainers and consider it job done.

The scheme looks like this. I've opted to fit the modified grubscrews from the front face, so that I can remove the cam pieces without needing to dismantle the adaptor from the machine spindle, rather than follow the original plan to screw them in from the rear. This change of plan makes them rather short and stubby but I think it's a sensible change.

This is what the final assembly should look like:

To fit the retainer grub screws in their correct positions, I will need to locate the centre coordinates. For this, a 2D drawing is the simplest approach. I can read off the coordinates and simply type them into the Centroid CNC12 MDI.

But it would be almost impossible to set up the stock at exactly the correct orientation without a significant amount of trial and error. 

Luckily, the Centroid s/w includes a "CSR" (Coordinate System Rotation) function which probes a plane surface and rotates the machine's coordinate system so that it is aligned with that plane rather than the machine's axes. This allows you to set up the workpiece without needing to worry about aligning it perfectly with the table. For this, you need to use existing features on the workpiece - in this case, I can pick up from 2 of the mounting holes using a couple of drills and a precision parallel. The drills are a nice fit in their holes. Like this:

Job done:

Holes drilled and tapped M8:

That looks reasonably convincing when a std pointed grub screw is fitted:

Now I need to machine up the grub screws. They need to be shortened as well as being machined down to a pin at one end. Holding this will require a small fixture.

It can be quite simple. In this case, a 30mm length of mystery loominum tapped M8 all the way through:

I can then lock the grub screw in position by tightening another grub screw up from behind. This looks encouraging:

And it even seems to fit the slot:

And here we are finally:

Now I'll remove the cams and retainers, clean up the adaptor body and prepare to fit it to the machine spindle nose for final in situ machining. It's starting to look as if I may almost be approaching completion....

Sunday 24 September 2023

Rust eater?


I've had to do some derusting on a variety of components recently and it seems to be an expensive and/or hazardous and/or labour intensive business.

The most obvious solution(!) is to choose from a choice of acids such as hydrochloric (muriatic to our Mercan cousins), acetic (vinegar), phosphoric (cola), citric (lemon juice) or perhaps oxalic. To be any good, these would need to be reasonably strong, with the risk of dissolving the test piece if left in too long and also the possibility of some remaining if not fully neutralised. 

Or, if not going the strong acid route, there's the use of "chelating" agents. These combine with metal ions and take them out of solution. They are often used to absorb and remove toxic metal salts from (medical) patients or materials without the use of strong acids. There are many to choose from - this interesting patent shows some of the ones in common use.

Put it down to my Scottish blood or my Yorkshire upbringing but I bridle at paying through the nose for rust removers and I don't want to rely on strong acids for rust removal. 

As often seems to be the case, when you look more closely at the formulation of some of these US-originated products, they turn out to be pretty mundane. In the case of Evapo-Rust, they make a big song and dance about their special formulation and even claim to have a patent - but when you search for said patent, none is forthcoming. It's all a big mirage and I'd bet in the end they concluded they wouldn't be able to get a patent granted and/or it simply wouldn't be worth the cost and effort. 

The US and EU MSDS datasheets are allowed to hide the chemical makeup of the product - they talk of "trade secrets" but funnily enough, the Australian MSDS seems to give the game away. However, as the market leaders, they have good presence and momentum, so clearly the lack of an actual patent shouldn't actually be a major concern to them.

Either way, it shouldn't be a major challenge to come up with a reasonably effective pH neutral rust remover of my own. There are various examples to learn from, such as discussed in the Garage Journal forum, which links to this YT video 

What's the plan, Fatty?

Let's get some raw ingredients, starting with Tetrasodium EDTA which is available at £22/kg inc vat
and some sodium gluconate which is available at £18/kg inc vat.
If I use 5% of each, that works out at ~£1.10 per litre for EDTA and £0.90 per litre for sodium gluconate ie £2 per litre. Evapo-rust costs £35 for 5 litres ie £7 per litre.

How about this for a test piece? 

It's got a lot of dust and loose rust but I reckon this will require more than a wire brush to clean up.

And here's a mild steel faceplate I made over 40 years ago for my first lathe. Having sat in my parents garden shed, it's seriously rusted.

With the vise in pieces, I can see that the handle would be a good place to start.

And these cutters have suffered from being stored out in my M-I-L's garage for years.

You are making stuff up again!
Indeed - and here are the raw ingredients - Na4EDTA and sodium gluconate. £22 and £18 per kg respectively.

Typically we see around 5% concentration in the various MSDS and patent information, although the solubility is quite a bit higher. Interestingly, as EDTA dissolves, it increases the alkalinity which in turn increases the solubility. Apparently. 

I'll start out with 2 litres of warm water. For 5% w/w concentration, that requires 100g of each ie 10% of my total stash. I don't plan on blowing the lot in one trial.

Once dissolved, we have a highly alkaline solution, which requires some neutralisation if I am to avoid getting hurt.

So I can use citric acid, which is easily available and cheap. Apparently it is also a chelating agent in its own right.

Trial and error:

Finally, a reasonably neutral solution:

So, into the bucket with the vise handle, faceplate and cutters:

Let's give it some time and see how that goes down...


That lot went in at 4:30pm and now it's midday the next day, so coming up to 20 hours. No agitation, just sitting there. Thought I'd take a look, perhaps brush off some of the loose rust and put them back.

But funnily enough, simply brushing it down under the tap with an old paint brush removes ALL of the rust from the faceplate. The vise handle has some way to go still but now there is clear metal visible in places and the handle now moves freely. After brushing any loose oxide clear with the paint brush, it's gone back in. Similarly, the cutters are much better but the white pair are still seized solid. I will check on them this evening (~30 hours) or tomorrow morning (~40h).

And here we are. Simply scrubbing the loose oxide off with a paint brush and washing it off under the tap results in this:

Those remnants of rust in the slots are the result of not reaching in with the brush. This looks pretty encouraging....

What about the other stuff? Well the brass bar cleaned up nicely too, notwithstanding the fact that it's clearly got some sort of varnish / lacquer protection. But yes, this isn't just for rust removal, it removes other forms of tarnishing / oxidisation.

The vise handle didn't look quite so impressive but for really badly rusted parts, you need to help the crud off with something like a pot scrubber or sanding pad.  The EvapoRust instructions tell you to do this - it's not some miracle product, despite the marketing bumf. Once this was done, the results are pretty impressive. I've put this back in again and expect it will look even better without much time or effort needed.

The vise jaws were only just immersed (the depth of the fluid was only about 2" or so) but again, when cleaned up with a sanding pad, the results are pretty good:

It's not exactly a precision product, so I doubt I will go overboard and renovate this vise but it has served its purpose.

Hardly the definitive product development / test process but for now, this feels like a reasonable result.

Sunday 10 September 2023

Let's try that again - and see how it actually measures up

Having been away from the workshop on a family break, I've been itching to run off another example, with a few changes / enhancements made for good measure:

  • Increase the threading speed. Currently 500rpm but it seemed happy when running over 1000rpm - I had no programmed dwell between the 2000rpm turning spindle speed and the lower 500rpm speed used in the subsequent threading operation, yet it seemed to cope fine during the initial phase where the spindle was still decelerating.
  • Slight increase in diameter of the taper. This is a very shallow taper and although the finished dimension seems close to tolerance, there is little visible clearance between the axial faces of the taper and collet when assembled. So a more finite / visible gap would be reassuring.
  • Use a VNGT (polished and honed) insert for the roughing and turning operation, to see if I can get a better surface finish. These are often described as being "aluminium cutting" inserts but some are actually specified as also being suitable for medium to light machining of steel. True, they have no coating but buildup and chip welding doesn't seem to be an issue for light cuts.
First attempt - went fine, if you don't mind a thread that looks like a serrated weapon. The threading was very noisy, so this was due to chatter. I had the tailstock supporting the workpiece, so I concluded that my surface speed was the issue. I can't sensibly try to operate at higher speed (often this is the suggestion to get past chatter), so the solution is presumably to reduce to perhaps 1000rpm.

Let's try again, ideally not stopping the recording part way through, requiring a 2 part video:

That's better. 

Can't see it easily here but it looks to me that there is a small but finite gap between the collet and the adaptor once it's tightened:

But the bottom line is - have I improved the runout at all? Well, not massively. I'm still seeing about 100um (0.1mm) total runout, which is a lot for a small cutter. 

Not massively happy with this outcome. On the upside, it's an improvement on the previous runout (250um / 0.25mm) but it's still pretty miserable.

I will need to look more closely at the assembly, to figure out where the runout is concentrated. Is it the adaptor or have I overlooked something? Could there be insufficient clearance between the collet and adaptor? Is the centre pip in the Autolock collet chuck off centre?

Thursday 17 August 2023

Chip time - let's do it - 16mm Autolock collet to JT1 taper

These are the tools I'll need - roughing / finishing tool and threading.

Firstly, set up the stock. This is 20mm EN8.

Just checking - what is the max dia of the centre drilling? The pip looks like 1/4" diameter, so I need to make certain I don't make it bigger than this. It's responsible for the radial position of the rear of the collet chuck, so the drilling needs to be a good fit on the pip. 

Here's the rather shitty looking live centre that came with the Tree. Some rust but mostly just grease and muck. Got a cleanup in the Bantam, along with various other MT3 chucks and centres.

I don't have a chuck for the turret yet, so the 8mm centre drill will have to go in a boring bar holder.

But hold on - the drill isn't on centre height. It's about 0.5mm above. You can see the path of the drill tip in the inked up area. Not good.

Removed the locating dowels for the drill / boring bar block and was able to "adjust" the height. That's a bit of a bodge but i don't see any better fix in the circumstances. Bottom line - I managed to centre drill the stock without snapping the carbide centre drill. Unlike HSS they don't flex and the pilot drill is very fragile. You are looking at ~£20 worth of drill here.

Quick facing off and chamfer...

...and off we go.

Looks reasonable.

Now for the 20tpi thread. Is it really 16mm x 20tpi?

Seems not. Looks more like 5/8" x 20tpi which sounds reasonable. So a "metric" Autolock collet has a metric (eg 16mm) bore with an imperial thread - that sounds much more credible. Cut the tread 150um deeper by adding -ve 150um of tool wear compensation (should be a nominal 125um difference, which would take it from 16mm to 5/8") and found Nirvana.

Then parted it off. The surface finish isn't perfect but this is EN8 and I was using a general purpose tip at low speed (2000rpm).

It's a fairly convincing result, either way.

So - now I know what is required, I have adjusted the CAD model so we have 5/8" x 20tpi thread (15.875mm OD instead of 16mm) and a shorter threaded portion. Also removed the tool wear compensation, as the thread should be correct now.

So let's set up the stock again and make the part from start to finish....

D1-3 adaptor - dimensional cockup!

Trial fitting of the adaptor body to the Tree spindle nose reveals a problemette - the adaptor bottoms out on the taper nose before it seats...