A Lorch Micro-Mill that never was ...

[wefalck]

Actually, I wanted to continue with my SMS WESPE model, but run into some technical difficulties and then this project came my way ...

 

The complex manual machining of very small parts on a milling machine requires smooth and precise movements of the slides as well as small masses to be moved. The slides of a watchmakers lathe fulfill these requirements. In addition, work-pieces and tools should be visible very well during machining.

 

Milling machines such as the Aciere F1 (or the older F12) or Sixis 101 are ideal for working on small parts, but are still far too large for my workshop (and have a too big price tag ...). Interesting from a design point of view would be also jig-borer and milling-machines by SIP (Société Genevoise d'Instruments de Physique), but they are very rare and difficult to come by. All these machines are massive and heavily constructed in order minimise vibrations by their inertia during the machining of precision parts for watches and instruments – too massive for my small workshop.

 

Aciera F1 milling machine (Source: http://www.lathes.co.uk/aciera/)

 

Sixis 101 milling machine (Source: http://www.lathes.co.uk/sixis/)

 

SIP jig-borer and milling machine  (Quelle: http://www.lathes.co.uk/sip/)

 

A special feature of these machines is that the x-slide is not arranged horizontally under the milling spindle, but vertically in front of the main column. This permits the easy installation of a fourth and fifth machining axis.  However, this arrangement means that the movement in the y-axis is not effected by the cross-slide, but by the milling head. This in turn means that milling head and motor should ideally form a unit. A belt-drive is more difficult to arrange, because the angle between the pulleys changes, when the milling head moves along. The SIP jig-borer for these reason originally was driven through a flexible shaft.

A watchmakers lathe is a good starting point owing to the precision of the slides and spindles, but it lacks the z-axis. In more recent years kits became available to convert Chinese-made watchmakers lathes into small vertical milling machines, but the milling table on them is arranged in a conventional way.

 

Conversion of a modern Chinese watchmakers lathe into a vertical milling machine

 

In my stock of watchmakers lathe bits and pieces I have collected over the years parts for several D-bed lathes of variable state of conservation. Some ‘scrap’ was also bought on purpose. From this parts I now want to construct a micro-milling machine with as little work as possible.

As design specifications I decided that the mill should be able to machine in a space of u 20 mm x 20 mm x 20 mm. This requires movements along the x-, y-, and z-axes of around 40 mm. There should be a fourth axis with a 360° rotation, that should be able to rotated under load. This axis should also be able to be moved from the vertical into the horizontal (5^th axis). All those movements should be realised with parts from watchmakers lathes, so that no dove-tail slides need to be machined from scratch.

The back-bone of the mill will be a special D-bed that I obtained recently. It was originally meant for the conversion of a lathe into a small precision pillar-drill. Its lower end is turned down to a diameter that fits into a lathe foot. The foot that I am going to use probably came from a British Pultra-lathe (http://www.lathes.co.uk/pultra/page8.html).

 

Column and foot

 

Another key part is an old and somewhat battered cross-slide from a Lorch, Schmidt & Co. D-bed lathe. This will be the x- and z-axis of the new milling machine.

 

Cross-slide from a D-bed watchmakers lathe

 

The y-axis will be constructed with the help of a nearly scrap lower-slide from the cross-slide of a Lorch, Schmidt & Co. WW-lathe that I was able to buy cheaply. The spindle and micrometer-dial will have to be made from scratch. A 6 mm-grinding spindle of unknown make will serve as milling spindle. This limits somewhat the maximum diameter of cutters that can be used to ones with about a 4 mm-shaft, but the machine is meant for light work after all. On the other hand, many years ago I made an adapter for 6 mm end-mill for use in the lathe together with a vertical slide (before I owned a milling machine).

 

Lower slide from a WW-lathe cross-slide and grinding spindle

 

Future arrangement for the y-axis of the micro-mill

 

The fourth and fifth axis will be formed by the dividing head that I made some years ago from a 6 mm-watchmakers lathe grinding-spindle. For the moment it will be simply screwed onto the cross-slide as for use with a lathe. This gives considerable flexibility for the positioning at any angle between vertical and horizontal. The setting will be a bit time-consuming and has to be done with templates.

 

Column, cross-slide and dividing head assembled

 

Column, cross-slide and dividing head assembled

 

So far the existing parts that need to be re-conditioned somewhat at a later point in time.

 

To be continued ...

[aviaamator]

Our man!!! Similar tasks lead to similar solutions.

[captainbob]

I've been dreaming of something similar.  I will continue dreaming while I watch you.

 

bob

[aviaamator]

Hi, Bob! It's my dream, but real... It's lathe TV-16, 1964 year, made in Soviet Union.

[Gerhardvienna]

Hi Eberhard

 

I will be watching this , high interesting machine!

Regards

Gerhard

[druxey]

Lorch lurches! The monster lives!! I look forward to you progress with this re-build.

[Moxis]

Hello wefalck! This is the PROJECT I will definitely follow. For long I have been trying to find a small accurate milling machine to be able to make very small filigrane parts, but never found exactly the right one. I have same ideas as you about the Aciera and other machines, but being too big and especially too expensive, they have never catched my interest.

 

But to make your own machine using the parts of old watchmaker's lathes is a great and new idea that I have never seen before. I wish a lot of luck to your project, and perhaps will follow your example in the future to make my own too.

[aviaamator]

Here's a lathe waiting for recovery, and Jung learns to work on it.

[BANYAN]

I'll take a seat also mate; these engineering exemplars of yours are not only informative but mouth watering results.

 

cheers

 

Pat

[Q A's Revenge]

I'd like one of these, a fully functional miniature Bridgeport!

 

[hof00]

Hi,

Considered Proxxon Stuff?

 

Am thinking of making the investment.

(Might be talking through "A hole in my head" regarding machining/milling.)

 

Cheers....HOF.

[wefalck]

The maker of the miniature Bridgeport is the British model engineer Barry Jordan: http://www.craftsmanshipmuseum.com/jordan.htm

 

@hof00: Proxxon (and all the other makers of small milling machines) don't make a machine of the Aciera/Sixis/SIP type as I discussed above. They all are conventional 3-axis-machines, to which perhaps a fourth axis can be added by deploying a rotary table or a dividing head. Even the smallest Proxxon, the MF70, still is somewhat bigger than what I am building here.

 

Updates will follow over the weekend, didn't have time to take and process the pictures yet.

[wefalck]

Some travel got into the way of progressing this project and on reporting on it ….

 

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In order to mount the y-axis to the column, an adapter is needed. This adapter is fashioned from a small aluminium-block that was bored for the 20 mm column. The top-side was milled to a close fit on the lower slide from the WW-lathe, which is clamped down with a bolt. In this way the lower slide can be moved by about 15 mm, giving a greater depth of throat, if needed. It was planned to use a rectangular key to lock the adapter to the column. However, it appears that the two set-screws lock it sufficiently secure to the column. Practical experience will show whether this is true.

 

Drilling the adapter for the y-axis

 

The 20 mm-hole was drilled and bored on a face-plate in the lathe to ensure that it is exactly vertical to the top and bottom of the adapter block. The aluminium-block was srewed down onto the face-plate using a 6 mm hexagonal bolt. Luckily, a suitable hole was needed anyway for the locking bolt of the slide. Other hexagonal bolts prevent the block from moving during the machining operations and act as counter-weights.

 

Boring the adapter for the y-axis

 

After the functional machining was complete, the adapter was 'beautified' by giving the edges a half-round camfer. For occasional jobs on aluminium like this, I use cheap woodworking router bits ... don't tell any real mechanic.

 

Camfering the adapter for the y-axis

 

Finished adapter block

The Lorch, Schmidt & Co. milling attachment will be held between two angle-irons screwed-down onto the slide. The locking will be effected by an excentric bolt acting as a cam. I had hoped to use the threaded holes that a previous owner of the slide had made, but they did not fit the angle-iron I had in my stock, so new holes had to be drilled and tapped. The pair of angle-irons was squared and trued on the mill using a fly-cutter.

 

Squaring and trueing angle-irons in pairs

 

Angle-irons to hold milling-head

 

Angle-irons to hold milling-head

 

The above picture shows also the drive unit made for the toolpost-grinder of the WW-lathe, which in fact looks very similar to what the future motorised milling head will look like.

 

Provisional set-up of motorised milling head

 

 

To be continued ...

[wefalck]

Thanks for the 'likes' !

 

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... these day I really became angry – some time ago the nice Sherline-motor (https://www.sherlinedirect.com/index.cfm?fuseaction=product.display&Product_ID=405]) for my Wolf, Jahn & Co. milling machine (http://www.maritima-et-mechanika.org/tools/horologicalmillers.html) that I had imported from the USA some 15 years ago began to make strange noises.

 

Sherline-motor, as used on my lathe and milling machine

 

Upon investigating, I disovered the the brushes were completely run down, in fact the motor was running on the copper contact-plates. I contacted the Sherline and they quoted my 25$ plus shipping for a new pair of carbon brushes – the German/Austrian distributor near Vienna just shrugged the shoulders. I trailed the well-known bight up and down and finally found some of about the right size in China. Three weeks of milling-break.

Once arrived, I ground the carbon the the right size and inserted them. The motor was running again, but somewhat noisily. I suspected problems with the ball-bearings. A week later, suddenly during the work loud noises and bang – rien ne va plus. I opened the holder for the brushes and found that they had already worked down by half and the contact-wire ripped off. I dismantled the motor-holder and idle-shaft in order to be able to take the motor out for further investigations. With a doctor’s eye-mirror I tried to look down at the commutator, but couldn’t see much. The only solution was to dismantle the motor. Of course all the nuts and bolts are imperial and had no suitable spanner. Had to go into town and get for some good money a 3/8” spanner for the nut, the screw-head had a 5/16” head, which is almost equal to 8 mm – learned some interesting this way: in the USA screw-heads and matching nuts don’t have the same size, as is the case in the metric system.

The motor turned out to be completely filled with carbon-dust, which then spread around my workshop. After having cleaned the rotor a bit (whereby a good deal of the carbon settled on me) the problem became apparent: several lamellae of the commutator had been ripped out and the end of it was that some of the connectors to the coils had been cut – a total write-off ...

 

Ripped commutator of the Sherline-motor

 

In my ‘scrap’-collection I found an old capacitor-motor that originally came with one of my milling machine. I did not use it, because controlling the speed is difficult and one looses torque (unless one buys an expensive inverter). However, as I had acquired a good idle-shaft since, controlling speed on the motor-side is not so important anymore, as the belts can be shifted to various-sized pulleys. I now had to adapt the motor-mount to the new motor and I was back in business. The good thing about this kind of motor is that it is much quieter than a mechanically commutated motor.

 

Motor running-capacitator (bottom)

 

So, milling began again – but not for very long. After two hours rien ne va plus encore. The motor only hummed with the 50 Hz, but didn’t want to turn. Touched the motor and and shrieked back, it was really hot. Perhaps not enough ventilation in the motor housing of wood to protect the open motor from flying swarf. The heat killed the capacitor that must have been several decades old already. Measured the motor through, but the coils were ok. Back to the bight and trying to find a new 7µF-capacitator. Found one, this time in Ireland, which meant only a few days, rather than weeks break ... got it yesterday and I am back in business again ...

[wefalck]

While sorting out the replacement motor for the mill, I turned my attention to making the spindle for the y-axis. Most WW-lathes seem to have the odd thread of 4.5 mm x 1 mm pitch. The spindles from the old cross-slide I am using were missing, but must have been thinner, probably 4 mm. As I have both, a die and a tap for the usual left-hand thread, I decided to adapt the cross-slide for this.

 

 

Set-up for cutting the thread on the y-axis spindle

 

 

First the spindle was made. Unlike the original desing on watchmakers’ lathes, it will have two ball-races as thrust bearings, but otherwise the design will be similar. The ball-handle crank is a commercial product. I started out with a 5 mm rod and turned it down to 4.5 mm and then set-up the lathe for cutting the left-hand thread.

 

The first pass

 

Almost finished spindle

 

This means cutting proceeds towards the tailstock. As the torque on the WW-lathe transmission system is too low, the thread was cut by hand-cranking. For this purpose I had made an adapter for a ball-handle crank already a long time ago. The thread was cut with full cuts until it was about 90% complete.

 

Calibrating the thread using a 4.5 mm x 1 mm die in the tailstock

 

The final cut then was made with a die in the tailstock die-holder to calibrate the diameter, which might have been a bit bigger in the middle due to the flexing of the long spindle. In order to eliminate the effect of flexing, the cutting bit was run along the thread several times without adavancing it into the work, until no material was taken off anymore.

 

The finished spindle thread

 

To be continued ...

[wefalck]

The long hole for the spindle in the cross-slide was opened up to 5 mm using the Dixi horizontal miller as a boring mill.

 

Drilling out the the spindle hole in the old top-slide

 

However, the travel of the slide was too small, so an extension was made to give the slide a travel of around 50 mm, allowing the milling spindle to reach across a face-plate mounted in the dividing attachment on the mill. The extension is a fairly complex piece, fashioned out of a block of aluminium. This is jointed to the existing top-slide with two location pins and two countersunk screws (the holes used were already made by a previous owner).

 

Top-slide extension (under side)

 

Top-slide extension (upper side)

 

To it screws the housing for the y-spindle bearing. Watchmakers lathes usually have simple sliding bearings there, the end-play of which is controlled by a nut with a very fine thread. The elements of this arrangement would have been ground to give a smooth sliding. I decided instead to use miniature thrust-bearings with I.D. of 5 mm and an O.D. of just 10 mm. Two are needed, with the thrust-collar on the spindle in between. This gives an arrangement of 12 mm in length.

Centering the future y-slide spindle bearing-plate in large 4-jaw-chuck

 

Turning stub for spindle bearing-plate

 

The bearing-housing was made from a piece of 15 mm x 15 mm aluminium bar. The section was centred in the large 4-jaw-chuck on the lathe and the stub turned on. The piece then was reversed and taken into a 3-jaw-chuck so that the face that screws down onto the slide extension could be turned flat and perpendicular to the axis. The through-hole was drilled and reamed for the spindle. In the next step the seat for the bearings was bored out to exactly 10 mm diameter and a tad unter 12 mm depth.

Reaming bearing for y- spindle

 

Boring-out seats for thrust ball-bearings

 

Finally some cosmetic milling operations gave the bearing housing a more elegant shape.

Shape milling of the spindle bearing-plate

 

To be continued ...

[druxey]

I was wondering about the limited travel on the Lorch cross-slide bed. Nice solution! Sorry to read about your motor woes, but hopefully they are behind you now.  Alors, on y va!

[wefalck]

The original bronze spindle-nut seems to have had a left-hand thread of 4 mm x 1 mm, so it was drilled out 3.7 mm for the 4.5 mm x 1 mm thread and the thread re-cut with the appropriate tap. The odd digs and dents were removed by a light cut on both ends in the lathe.

 

Parts of the spindle and its bearings

 

A test assembly showed that everything worked as planned. The ball-handle crank has been bought-in and is fixed by set-screws, rather than being pinned as was the Lorch-practice.

 

Spindle in place, but micro-meter sleeve still to be made

 

To be continued ...

[BANYAN]

Very nice Wefalck; I drool every time I visit your tools pages, engineering art!

 

cheers

 

Pat

[wefalck]

Thanks Pat and I hope you have enough Kleenex around

 

*****************************************************************************

 

After some disruptions due to travelling (spent inter alia a couple of days in Pisa for work ) I tackled a job I had never done before:

 

Digression: making a concave knurling wheel

 

Today, concave knurls to produce the convex knurling seen on many older high-end precision machines are obtainable only at prohibitive costs. Therefore, I embarked on making my own knurl, encouraged by a few examples on the Internet. Knurling wheels normally have to have a certain diameter in order to prevent their bore from being distorted under the stress of the knurling process. I choose a blank of only 10 mm diameter for a bore of 6 mm in order to reduce the mass to be heated, when attempting to harden the knurl with my rather limited heating capabilities. I also had a cut-off from a Schaublin collet-blank available, which I assumed would harden nicely.

 

Hobbing the knurl on the milling machine

 

The proposed process of creating the knurling wheel employs an ordinary threading tap as an improvised hob. This, stricly speaking, would result in a 'rope' knurl, but the helical angle of a, say, 0.4 mm pitch tap is barely perceptible. The easiest way to hold the blank for cutting seemed to hold it in the knurling-holder for the watchmakers lathe that I made a few years ago. This means, however, that the process could not be done on the lathe, because it would have been not so easy to mount the holder on its side. Cutting the knurl on the lathe would have been better, as the end of the tap could have been supported in the tailstock in order to eliminate flexing. Unfortunaly, the DIXI horizontal mill does not have an overarm, which then would make it the ideal machine for the job. So the job was done on the vertical mill.

 

Hobbing process in detail

 

The blank was drilled and reamed for the arbor of the knurling tool holder. Some polishing ensured that it spun freely. A M2 tap was chucked in a collet as short as possible and offered to the blank with its uppermost end in order to keep flexing to a minimum. Initially, the mill was run at slow speed and with a small feed. After each incremental feed, the blank was allowed to make several revolutions until no chips were produced anymore. Once the pattern was created, the mill was run at a somewhat higher speed and the amount of incremental feed increased from around 0.03 mm to 0.05 mm. Every time blank and tap were flooded with WD40 in order to wash out the chips that then were wiped off. A first failed trial showed, how important it is to wash-out chips. The second attempt was successful.

 

The finished concave knurl

 

After the machining, the knurl was hardened by heating it to a cherry-red colour and quenching it in ice-cold water. As I don't have a very strong torch, the knurl was pre-heated to 450°C using the hot-air soldering gun and then brought to temperature with the gas-torch. The knurl was also rubbed in soap to prevent scaling. After some cleaning, the hardened knurl was tempered to a straw-yellow colour using the the hot-air gun. A test with a file showed that the hardening was successful.

The knurl in the tool-holder for the watchmakers’ lathe

 

... well, it actually worked as you will see in the next contribution

 

To be continued ...

Edited July 10, 2016 by wefalck

[Nirvana]

Okay, not that we are supposed to used cursing words in this forum.

but what the $#@$#&*%$ have I missed!

These machines are absolutely crazy!

What is the pricetag of the Micro Mill?

Not that I can afford a regular one as of today, but I am curious. Must be in the price of an Aston Martin Db5 Vintage

[wefalck]

Per, as it never was, the mill doesn't have a price-tag   ... unless you were indeed prepared to pay me at my commercial rates, which means that you would have to trade-in a decent car, may not quite an Aston Martin (but I would gladly exchange it for the mill, BTW)

 

***********************************

 

For the dial on the y-slide I had a piece of 21 mm diameter brass to hand. This was faced in the 3-jaw-chuck, drilled and reamed for the 5 mm spindle, and then bored out to fit over the spindle bearing-plate.

 

Preparing the blank for the dial

 

The blank was the mounted on an arbor with a 5 mm stem so that I could turn the outside shape. At one end there is the notorious convex knurled ring. For this, a ring of 1.2 mm width and 1 mm height was left standing with edges slightly chamfered.

 

Turning the blank for the dial

 

For the next machining step the knurling tool with the concave knurl was mounted to the cross-slide. The knurling tool was fed slowly into the slowly rotating blank. It catches quite quickly at the edges and the pattern evolves fast. As expected, the processes is both, a cutting as well as a shaping one – the relatively soft being squeezed into the indentations of the knurling wheel. While generously lubricating with WD40 the knurl was fed into the faster rotating blank until the pattern had developed fully.

 

Knurling the dial

 

To be continued ...

[BANYAN]

Another tantalising update Eberhardt - I have stocked up on the tissues so ready for the main installments

 

That knurling tool does a great job.

 

cheers

 

Pat

[wefalck]

Thanks, Pat. I was actually surprised myself, that it turned out so well

[wefalck]

The blank on its arbor was then transfered to the dividing apparatus on the milling machine for engraving the dial. For this a 15° engraving bit was used. in the same set-up the hole for the friction brake of the dial was pre-drilled.

 

Set-up for engraving the dial

 

Engraving the dial

 

The numbers were stamped in a make-shift set-up in a vice. In order to ensure that the number-stamps were applied exactly radially a purpuse-made guide-block was used.

Set-up for stamping the dial

 

Finally, the dial was mounted back on the arbor and the burrs from engraving and stamping cleaned up with a couple of light cuts in the lathe.

 

Cleaning up the engraved and stamped dial

 

The two parts were separated on the lathe with a jewelers saw substituting for a parting tool. The dial then was degreased and the engravings laid out in black enamel paint. After the generously applied paint had dried, the dial was cleaned up with very fine wet-and-dry sanding paper.

 

Painting the dial

 

To be continued ...

[Nirvana]

Pure artistic, I have no words on how to compliment you for this amazing tool build. Beautiful!

[druxey]

Beautifully machined, Wefalck!

[wefalck]

Now, with the summer holidays behind me, I am back in the fora and in the workshop   However, first a little postscript on things that were completed before the vacations:

 

A couple of pictures that show the different components of the y-axis spindle. Also visible on the first picture are the parts of the friction brake for the dial, short piece of acrylic rod that is pressed down on the spindle with a set-screw. Tightening or loosing the screw allows to adjust the friction.

 

The parts of the y-axis spindle

 

Spindle assembled

 

Spindle in its working place

 

To be continued ...

Edited September 5, 2016 by wefalck

[druxey]

Welcome back, wefalck!

[BANYAN]

Hope you enjoyed the holiday mate; welcome back.

 

cheers

 

Pat