A Lorch Micro-Mill that never was ...

92 posts in this topic

Was kind of working holiday: had to work on finishing off the decoration and furnishing of our part-time home in Spain - putting in/up wardrobes, building a mock fire-place (unfotunately, we can't have real one there), etc.; jumping up and down the ladder at around 30°C made me loose some 4 kg in weight - feeling a lot fitter than before the holidays - but have been to the beach only once ... grilling on the beach in the August heat is for German and British tourists only anyway ;)




The milling spindle will be secured in its place between the two brackets by a lever-actuated excentric bolt that pushes it down. I found a rough excentric bolt in my scrap-box of odd lathe parts, but it would have been as easy to start from scratch. The excentric was worked over holding the bolt in the 3-jaw-chuck with a brass-shim to give the off-set.



Rough and ready method for excentric turning


The head was turned with the help of the shop-made radius-turning tool (which I originally made to be able to turn miniature door-knobs and the likes). The tool-bit diameter was chosen to match the neck and shoulder of the bolt. The turning operation was followed by smoothing with wet-and-dry paper and steel-wool of various grades. Finally, it was polished with polishing paste. The pictures below show the various steps of this machining process:












To be continued ...

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You are a true Master and I doubt anyone would say different. If they do let me know, I got this nickname for a reason LOL. Keep the post and beautiful pictures coming. Thank you for sharing this with all of us,

PeteB, Nirvana and mtaylor like this

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Are you creating this little mill from plans or is this just all from plans in your head?

I am so impressed!

mtaylor and Jack12477 like this

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Thanks for the praise :rolleyes:


At a matter of fact, it is all in my head. These days I don't even make working drawings :o  Sometimes I make dimensioned sketches for machining, literally on the back of envelopes, in order make sure that what I imagined actually works out. Most of the times things seem to come out as I imagined them. Not alway though :(  Just struggeling with the motor mount now, as my original idea would create a too long lever, when clearing various parts of the mill, with the risk of amplifying vibrations ... have to re-think it.

Chasseur, druxey, Jack12477 and 3 others like this

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I should perhaps add that I let myself be guided in the desgin of the various bits and pieces by what was practice for these machines. Surprisingly, since the 1880s all manufacturers seem to have followed largely the same designs with only small variations in detail. For new parts I try to imagine how these manufacturers would have made them. However, as I have no possibility to have iron castings made, I have to fabricate parts.

druxey, mtaylor, WackoWolf and 1 other like this

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Interesting radius turning set-up, wefalck. I've only seen the ones that work in the horizontal plane, mounted in place of a tailstock. Your version makes good sense!

mtaylor and WackoWolf like this

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A radius-turning tool with a vertical axis would be difficult to implement on a watchmakers lathe, as the clearance over the top-slide is only 7 mm ! So you would need to somehow construct a cantilever from which the turning point would be suspended, or the maximum diameter you can work on would be about 10 mm.

Not sure anymore, whether this was my own inspiration or whether I saw it somewhere in a picture, but I had the idea to use a boring-head, which has a built-in micrometer dial, to change the radius.

I also wanted to be able to turn spherical surfaces for which the centre is not necessarily in the axis of the lathe. Therefore, I built the tool around the quick-change tool-post. Essentially, I built a miniature boring-head and an insert for the QCTP with a horizontal bore, into which the shaft of the boring-tool can be inserted.

The design is not perfect. I should have better control of the end-play in the QCTP and started to work on a system of cone-bearings, but did not finish this.

For the relatively big jobs presented here it works well enough, but when it comes to turning door-knobs and the likes with 0.5 mm diameter, I need to have a better control on the play in the tool.

mtaylor, druxey, jud and 1 other like this

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To to continue: The ball-end lever for the locking bolt was fashioned from a short piece of steel in several steps: first the stem that will be a push-fit in a hole of the bolt was turned;




chucking the material with this stem, then the main part of the lever was turned conical, leaving a part cylindrical for the ball-head;




the conical part was given a waist using the free-hand turning rest;




and finally the ball-head was formed using the radius-turning tool.






The tool-bit in this case was a 2 mm HSS-bit in a special holder that allows to form a sphere with a sharp edge at the stem.



The finished ball-lever



Ball-lever actuated locking pin in place


To be continued ....

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Hope you landed safely  ;)




A while ago I had been able to purchase at a good price a 'left-handed' Lorch, Schmidt & Co. cross-slide, which is what was needed for this project. In Germany, watchmakers for some reason traditionally worked with the headstock to the right, and not to the left as is common practice in virtually all other lathes. Some older watchmakers still seem to work like this, but I gather the majority nowadays, prefer to have the headstock to the righ. In consequence, cross-slides that are meant to be mounted to the left of the headstock and operated mainly with the left hand are relatively cheap to come by.



Actuall a right-handed cross-slide but the used was in similar condition (forgot to take a ‘before’ picture)


The one I received looked a bit worn on the outside, but mechanically was still in a good condition. Spindles and spindle-nut were tight. However, the nickel plating was chipped and peeling off. I completely diassembled the cross-slide and ground-off the remaining nickel with fine wet-and-dry paper and polished the surfaces. Then all parts were thoroughly cleaned.



Cross-slide taken apart


The spindles have the 0.75 mm pitch commonly found on cross-slides for D-bed lathes. Not very convenient for calculations, but I got actually used to it on my D-bed lathe. The dial on the y-axis (the future z-axis of the mill) was actually graduated with 15 divisions, giving the diameter reduction when turning, though it has the same pitch as the x-axis. On the mill this graduation would be confusing and I also wanted to have a conical dial on the z-axis. So I moved the x-axis dial to the y-axis, which is the future x-axis of the mill, and made a new dial for the future z-axis.



Taper-turning for the new cross-slide dial


For this, a 20 mm piece of brass was drilled and reamed for the 4 mm-spindle. It was then taken onto a 4 mm-arbor for further machining. The lathe top-slide was off-set by 45° for turning the conical shape. In the same set-up the lines on the dial were engraved using a pointed tool-bit - the lathe head-stock, as for all watchmakers lathes, can be used for simple dividing. There are 60 stop-holes, which was convenient for the 15 stops needed here.





Engraving the cross-slide dial on the lathe


The engraved dial was then moved to a special jig I made some years ago, that allows to punch numbers onto conical dials. After punching, the dial was moved back to the arbor, the exact position had been marked before removal, and the burrs thrown up by the engraving and punching were removed by a light cut, leaving behind crisp lines and numbers.



Set-up for stamping the numbers onto the dial



Cleaning up the engraved dial



To be continued ....

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Thanks again, gentlemen :)




As for the other dial fabricated earlier, a pressure pad provides for an adjustable friction stop. The outside rim was also given a treatment with the concave knurling tool described earlier.






Knurling the rim of the dial


The engravings on all dials were filled-in with black paint and when the paint was dry, the dials were slightly rubbed-over with fine wet-and-dry paper to leave crisp black engravings on a satin surface. 



The finished dial at its place


Finally, the cleaned cross-slide was re-assembled with the new dial.



Re-assembled cross-slide



To be continued ....

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Trying to keep up standards ;)




Some time ago I purchased a 12V motor from a Chinese source that is supposed to run at a nominal speed of 3000 rpm. Considering is length of 71 mm and a diameter of 51 mm with an 8 mm drive shaft I expect it to have sufficient torque for the purpose. The data given by the seller were rather cryptic. The mounting of the motor caused me some head-scratching. The original intention was to use a bracket similar to the one used on the lathe toolpost-grinder shown below as the mock-up.



Self-contained drive unit as used on the toolpost-grinder


This would have resulted in a self-contained drive unit. However, the motor would have fouled the cross-slide, when the y-slide is fully run out. Making the bracket longer would have solved this problem, but I was afraid of the vibrations this long lever might transmit and the distortions to the y-slide. Another possibility would have been to mount it upside-down over top of the y-slide, but this would have raised the centre of gravity of the whole machine considerably and transmitted vibrations to the system. In the end I make, for the time being, a simple bracket that uses the two screws with which the extension of the y-slide is screwed down.



Motor mount


The lathe and grinding spindles were meant to run at maximum speeds of around 4000 to 5000 rpm. Therefore, a slight stepping-up compared to the motor speed would be permissible. As the motor bracket does not provide for any adjustment of the belt-tension, I copied the pulley on the grinding spindle for use as a motor pulley as exactly as possible. It will be put upside-down onto the motor, so that the belt can be shifted for stepping up (1 : 1.4) or stepping down (1 : 0.7) speeds without the need for adjusting the tension. Most of the speed control will come from the electronics in the power-supply.

The pulley on the grinding spindle has a 75° V-groove for 3 mm round belts. A V-groove can be cut by either setting over the top-slide, or using a pointed tool with the appropriate angle. I had to grind a HSS-toolbit with this angle, checking it against a template. The two grooves were cut using a stepping method. Cutting it full depth would not be possible. I order to ensure concentricity between the pulley-bore and the groove, first the step in which the set-screw is located was turned and then the piece turned around for drilling/reaming the bore and cutting the grooves in the same set-up. For cutting the grooves the pulley was supported with a revolving tailstock centre.







Steps in machining the motor pulley



The finished moto pulley



The two drive pulleys


To be continued ...

aviaamator, WackoWolf, cog and 12 others like this

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With only a few days between the many business-related travels, progresss is very slow ... :(


With most of the machining done, I turned my attention to the finish. I would have preferred to leave the parts in their bright, nickel-plated finish. However, the plating on the foot, for instance, was coming off in large flakes. In addition, the parts fabricated from aluminium have a rather different colour. I wanted to have a unified look. Therefore, I spray-painted most parts in my favourite bottle-green (RAL 6007).










To be continued ...

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Coming ....




The milling spindle was disassembled and given a thorough clean and generously oiled before being put together again. I also replaced the slotted worm screws that lock the pulley in place with Allen ones. Not original, but easier to operate.



Disassembled milling spindle


These milling spindles are intended to be operated horizontally and, therefore, have only a simple oiling hole with no cover. In order to ensure adequate oil supply to the upper bearing surface, I fabricated an oilder that rises to the level of the upper bearing. A piece of 4 mm brass was turned down for a press-fit into the oiling hole.







Steps in manufacturing an oiler


An 1 mm-hole was drilled part-way from this side and a 3 mm-hole from the opposite side. The resulting tube was cut at a 45° angle and the two pieces silver-soldered together to form a 90° knee. From a short piece of brass a cap was turned and bored for a sliding-fit over the oiler. Since the convex knurling worked so well, I applied this also to the cap.



The finished oiler



Re-assembled milling spindle with new oiler


To be continued ...

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Thanks !




The milling spindle was missing the draw-tube. A new one was turned from a piece of 8 mm tube with a 5 mm bore. One end was tapped 5.1 mm x 36 tpi for the collets, for which I am lucky to have a tap. The other end was serrated to provide a positive lock for the hand-wheel. For this machining operation, a pointed tool was mounted with the cutting face vertical in the QCTP and the draw-tube indexed in the head-stock of the lathe.





Serrating the draw-tube on the lathe


The original hand-wheels were made from black or dark-brown Bakelite, a materials that is not easy to buy anymore these days as round stock or thick enough plates. I had to resort to a piece of black POM. As it turned out to be too complicated to set up the radius-turning tool for this, the torus-shaped rim was fashioned by free-hand turning. The POM is rather soft and was best finished with a fine file and steel-wool. The finished hand-wheel was loosly taken into a 3-jaw chuck and the draw-tube, that was held in a collet in the lever-tailstock was pressed in.



Turning the hand-wheel from POM





Finished draw-tube and an original one



To be continued ...

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 The other end was serrated to provide a positive lock for the hand-wheel. For this machining operation, a pointed tool was mounted with the cutting face vertical in the QCTP and the draw-tube indexed in the head-stock of the lathe.


Why didn't you use a straight knurling tool?



donrobinson, WackoWolf and mtaylor like this

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Good point: 1. because I wanted really sharp, 'cutting' serrations to positively lock the draw-tube into the knob, 2. this method is less straining on the lathe, though the cutting is quite tough on the nut of the top-slide.

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Very nice machining Wefalck; these  micro machines you create are miniature work of art in their own right!





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Thanks, gentlemen !


The last three weeks I was barely home for two or three days in a row, just too much business travels - good for the business, but not so good for the private life, including hobbies. I still managed to squeeze-in a couple of hours in the workshop. This is needed from time to time to relax ;)



As indicated at the beginning, the machine will be provided with a fifth axis for rotary milling and dividing operations. Some years ago, I fashioned a geared dividing head from an old Lorch, Schmidt & Co. grinding spindle. This mounts onto the cross-slide of a 6 mm lathe, such as the one used in the milling machine.



Geared dividing head constructed some years ago


These grinding spindles were meant to be bolted down onto the cross-slide using the latern for the turning bits. While this reduced the number of bits and pieces to be provided for the lathe and to be taken care of, it seems to be a rather strange economy. In the present circumstances this method of bolting is also not very satisfactory, as the angle of the spindle, as well its position in the T-slot have to be adjusted at the same time. Too many degrees of freedom.



Elements of the holding-down bolt


Therefore, a mounting bolt was fashioned from a normal M6 screw with a hexagonal head. These fit perfectly into the T-slots, but their heads have to turned thinner. Over the bolt a sleeve with an internal M6 thread screws down, thus keeping the bolt in place.



Geared dividing head in place


Now, the dividing head can be rotated around the bolt without movement up and down in the T-slot. The dividing head is clamped with an standard M6 cap-nut (a nice polished stainless steel one though) and a large washer. The latter also is a commercial stamped product that was cleaned up on the lathe and given a nice polish for aesthetics sake.



Geared dividing head in place


To be continued ...

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This mill is one of those machines that comes under the heading of "art".  Beautiful, functional, working art.   

cog, WackoWolf and michael mott like this

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