Mini-lathe - first commercial job!

Part of the deal to get the larger lathe feed gears printed was that the owner of Regenerate3D, James, needed some aluminium parts machined for a radio controlled glider. The bit he needed was an adaptor to go between a motor shaft and a printed propeller. I agreed to make the bits to his drawing and we corresponded for a few days refining his design.

One of the most interesting bits of machining anything is working out the best sequence of operations and I'll show you what I did here but I can't pretend it was the best sequence!

The first step was to cut a chunk of 1" 6021 round bar, face one end in the lathe and reduce it a little so that it would go further into the chuck. I then turned it around to machine the other end to something close to the finished state:

Next step was a face knurl, which I had never done before. I used an existing wheel and made a little holder for it with a bit of 10 mm round bar. The washers are there to prevent the wheel contacting the work. The issue is to get the knurl close in to the centre means you cannot have anything protruding beyond the wheel - so there is no room for a nut or screw head to retain the knurling wheel.

I was very pleased with how it came out, and turned the work around to finish the other end to the same standard. At this point I still had a half millimetre oversized on the journal that would carry the propeller.

I replaced the chuck with the ER25 collet to hold the work whilst I parted it off - this was a mistake, because there was not enough length available to hold the work in the collet to withstand the parting off loads. I should have sawn them in two. Fortunately I hadn't taken any of the diameters down to size and I was able to remove the scuff marks caused by the work moving in the collet. 

Once I had the two bits separated, I could drill the holes for the grub screws. There's a chamfer behind that flange which is out of shot here and I made sure that the holes were drilled and tapped before I formed that chamfer, to give me enough room to hold the part for drilling.



This is the 3D printed propeller that will be used to launch the glider into the sky:



Here is the rear view. You can see the chamfer that I was talking about earlier:



The propeller is actually in two parts - there is an M8 nut hidden inside which retains the prop to the aluminium adapter.

Mini Lathe - feed rate upgrade

 As I started to machine the kickstart shaft for the Model A it became apparent that it was painful in several ways - partly due to the hot swarf coming off it and partly due to the fact that it was taking ages!

What I needed was the automatic feed. This is dead easy to engage and is always available on the lathe but I quickly found that the lathe couldn't cope with the feed rate given by the 20:80:20:80 gearing that the standard setup offers. 

The Ted Hanson book suggests replacing the last 80 tooth wheel with a 3D printed 127 tooth wheel - but they are not commercially available. 

Some browsing revealed that reduced feed gear wheels for the mini lathe are not commercially available on this side of the pond in any shape or form. Some posts on the 7x Mini Lathe Facebook group suggested that the best option was to go to Thingiverse.

As predicted I found some suitable STL files which I could print for free. However not being equipped with a 3D printer I resolved to look around Norfolk to see what I could find, and made contact with Regenerate3D in North Walsham who in exchange for some machining work and a spot of cash produced these lovely gears:

The black ones are made from PPA-CF and the orange ones from PA6-GF. They are both very strong and hard. Both sides needed a little bit of fettling to make fit properly - a 12 mm reamer for the lead screw gear and an 8 mm reamer for the intermediate gear.

Contrary to what some folk have written about this gear size, the cover will fit without modification so you do not have to have your gears exposed while working.

The only negative side of this that I have found so far is that with the increased ratio from motor to lead screw, I can no longer turn the hand wheel on the lead screw and so we'll have to remove or disengage the lead screw hand wheel for milling.

FH - test ride

 I took the Huntmaster out on a nice little test ride today, 25 miles around North Norfolk to buy samosas from a nice family run department store in Holt.

It went beautifully - no problems other than the usual sweating from the base gasket! I think we also have to admit that the number two exhaust guide is probably leaking - probably too much clearance. There's wet oil at the silencer.

It's idling very nicely - I stopped to reduce the speed at one point, and to take a few pictures, and the idle is certainly more reliable than it was.

FH - pilot circuit

 No pictures, but this afternoon I've drilled out the fixed size 20 pilot jet in the Huntmaster's MK1 Concentric carburettor.

It's now got a size 30 pilot fitted, which reflects the size 35 specified for the BSA Road Rocket (fitted with a Monobloc) and the fact that Concentrics are supposed to run richer than Monoblocs...

Time for a road test.

Model A - rear brake pedal

 The rear brake pedal shaft is one of those areas where you see the horrors perpetuated on old motorcycles through years of neglect and changes of ownership with varying levels of skill. Having removed this one to rebuild the footrests and replace the brake pedal spring we realise that it is in fact a bit mangled.

To start with, we can see that the thread has been cut to a BSW form - Ariel would not have used BSW here, the thread would originally have been CEI. We will build it up with weld and cut a new thread to the right size.

That pin across the right hand end as we look at it forms both the stop and the fixing point for the end of the spring. Part of it, the fixing point for the spring, has broken off. It proves impossible to knock out though it is listed in the parts book as a separate component, so we drill it out.

Here it is, illustrated in the 1930 parts book:

The other curiosity which I didn't understand initially is how the shaft is lubricated. There was no obvious grease nipple but under all the gunge a hole appears half way along the shaft, which is clearly to let grease into the central reduced area - and an ex-nipple on the end which has had some attention from a hammer.

I've said many times that the AOMCC is a wonderful club to be associated with and a few questions posted on the Facebook page yielded this drawing from 1925 and signed by Val Page himself. The drawing clearly shows the same formed nipple on the end of the shaft that the later Ariels used until the end of four-stroke production in 1958.

The difference between this and the later bikes is that whilst the later bikes use a nut to retain the brake pedal on a parallel fixed shaft, this application uses a nut on a taper to retain the pedal on a rotating shaft. Therefore when you want to remove the pedal for adjustment, you have to undo the nut and knock the end of the shaft to free the taper. Guess what happens? The nipple gets flattened...

To start with we're making a new pin on the lathe. I didn't intend to use a piece of stainless, but at the time I couldn't find a quarter inch piece of mild steel round bar - but no one will ever see this, so it doesn't matter if it's the wrong colour.

I've cut a semi-circular channel in the end of the short bar to locate the brake pedal spring. It's a simple matter to chamfer both ends and press it into the pedal shaft.

This is how it looks.

This is apparently the correct spring - I got it from AOMCC Black Ariel spares some while ago and I'm assured it is the right one, though it looks very stretched when it's in position.

See what I mean?

The next step is to build up the mangled thread and nipple. This is none too tidy but hopefully there will be enough material to turn it to 7/16" without firing up the TIG set again.

The first pass at turning to size shows, as it often does, that more building up is required:

That done, we can start forming the shapes according to the drawing with a radius tool to form the curve and shape the grease nipple:

I seem to have missed out a step here - I've forgotten to photograph the drilling out of the grease hole, which is 5/32" per the drawing. The next step is to cut the 7/16" CEI thread. 

Here it is on the bike with the brake pedal attached:

We will need to be very careful when moving the pedal - using a socket or something over the nut to avoid damaging the nipple!

Here's an overall view. That pedal is very high!

Mini-lathe - angle plate

 Some while back we looked at an arrangement to use the compound slide vertically to cut some slots in some screw heads. At the time I had this angle plate with a shim to put the compound slide exactly perpendicular to the bed. 

Now that I have my MIG welder working again I have overlayed the angle to some extent and I'm using a fly cutter to create the perpendicular surface. It looks horrible at the moment because I did the overlay with the MIG at night, with the inverter protesting at the low voltage.

I've made a couple of passes with the fly cutter and we can see where the welding is low.

We will do some more passes with the fly cutter and then fill in some of the holes.

Meanwhile, we need to make this angle plate as stiff as possible so we will put a brace in each end:

One of the functions of the angle plate is to carry the rotary table. Whilst this has its own 90° mount, it takes up a lot of space and for the purposes of the kickstart shaft we would have to extend the cross slide considerably to get it in the right place. A better alternative is to use the angle plate to mount the important part of the rotary table like this:

We will progress the rotary table mounting a bit further when we have finished making the back of the angle plate flat:

Flat, cleaned up and almost finished. The surface is perpendicular to the cross slide top!

In this next picture there is a quarter inch end mill in the collet chuck and we are using the vertical slide to mill one of the retaining bolt holes into a slot, so that we can perfectly adjust the rotary table to align with the lathe centre.

What you can't see is that I have used a 3/8 inch end mill to clean up the bottom edge of the overlay weld on the other side. This is pretty much finished now, but it may require a couple more holes to bolt down to the cross slide. We will look at that when we set it up to mill the slots in the kickstart shaft.

Model A - kickstart shaft

 We're making chips! After a few test cuts, I've settled on a spindle speed of 750 rpm using carbide with oil mix cutting fluid and I'm getting a great finish. 

Depth of cut is 0.5 to 0.75 mm, and the feed is probably something like 0.002"/rev. The lead screw gives you 0.004"/rev and it's much slower than that, but unfortunately I have to manually feed at the moment.

There are a couple of upgrades you can do to reduce the feed rate, but they both need 3D printed gears which I don't have...

FH - not charging...

 Having learned that the FH will drain it's oil tank through the gear pump into the sump, I try to run it once a week or so during the winter. It was on one of these occasions that I noticed it wasn't charging and my first thought was to look at the dynamo to see if it had broken another chain.

Fortunately not - so I left it alone for a dose of thinking about.

Coming back the next day, I worked through the other electrical systems to see if anything jogged my thoughts and found the rear light wasn't working either: given that the ammeter and the rear light connect through the lighting switch I had a look under the top yoke:

Two wires had pulled out of the five way connector. Harness too tight or connectors not assembled properly in the first place?

Model A - Making the kickstart shaft

From the features and dimensions in the previous post, we have some idea of what we have to make - if we are to avoid cutting the excess length out of the old shaft and welding it up again, with the cotter flat in the correct orientation.

This would be a waste of an original part and wouldn't be half as much fun, but it is worth remembering that what we are trying to here is produce a replica of the 'Panther' shaft we have, but shorter and with the kickstart lever cotter in the right orientation.

We'll start by defining a list of features, so we can talk about making the shaft sensibly and without getting confused. Here we go:

• A - the pawl carrier minor diameter
• B - the hole for the pawl spring
• C - the holes for the pawl pivot pin
• D - the larger 'stop flat'
• E - the smaller 'stop flat'
• F - the bore for the layshaft bearing, and the bearing itself
• G - The flat the pawl sits on
• H - The kickstart lever diameter
• I - The main shaft diameter - 1 1/8"
• J - The flat for the kickstart lever cotter
• K - The pawl carrier major diameter, 2"

Of course the key question is in what sequence do we machine these features?

This is what I'm thinking at the moment:

1. Face and centre both ends of the 150 mm chunk of EN16 round bar (diameter 55 mm) that I've bought from eBay.
2. Holding the stock in the 3-jaw with the end supported in a live centre, machine away the material to make diameters H, J and K
3. Reverse in the chuck and machine a flange on the waste end, with a 5mm hole to register with the pin in the centre of the rotary table.
4. Hold feature I in the milling vice and use the vertical slide and an end mill to machine feature G.
5. Clamp the waste flange to the rotary table and use an end mill to machine features D and E.
6. Use the rotary table to machine feature A.
7. Use a slot drill to machine the tangential hole B.
8. Hold feature I in the chuck and machine off the waste flange.
9. Machine feature F holding feature I in the chuck and supporting the shaft with the fixed steady.
10. Hold feature I in the milling vice and drill feature C.
11. Last job will be the flat for the cotter. We'll assemble the shaft into the box and then work out where the lever wants to be.

The blank we will have after step 3 will look like this:

Excuse the mixed units, and remember that these are approximate dimensions for roughing out only!

Model A - Kickstart Shaft

 The Model A arrived with a complete gearbox, apart from the kickstart spring, cotter, and spring shroud. The kickstart shaft was also strangely long and fitting the lever left the kickstart pedal very low, since the flat for the cotter was in the wrong place.

What we are trying to here is produce a replica of the 'Panther' shaft we have, but shorter and with the kickstart lever cotter in the right orientation.

A close up of the pawl, the pawl spring with it's plunger and the two-diameter pawl pin:

This is the flat for the kickstart lever cotter. The shaft I show here allows the kickstart to sit too low - it's for a bike that has the gearbox fitted horizontally, rather than at the angle used by Ariel and Brough Superior. The shaft is possibly from a Panther, who used these boxes horizontally in 1929.

The flat will have to move for the new shaft.

This is the flat where the pawl sits, with the axial holes for the pawl pin and the tangential hole for the pawl spring:

These two flats engage with the two plates in the gearbox that stop the pedal travel and disengage the pawl:

This is the bore for the layshaft, with it's bush:

A few dimensions to help us choose the stock for the new shaft:

We see here that the total length of the 'Panther' shaft is 164 mm or thereabouts.

This is the 'Panther' shaft fitted to the bike. This is the excess length - just over 47 mm. That means the total length of the new shaft will be 164 - 47 = 117 mm. Our blank is 150 mm long.

Lastly, here are a few pictures from AOMCC member Michael, showing the original arrangement: