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Nicely done!

Next time machining aluminum (drilling too) use Acetone as a lubricant. It works well, but obviously you need a squirt bottle to keep it flowing in.

Gives a nice finish.

Coated tools should be TiCN, not TiN. The gold (TiN) adheres to the molten aluminum. Usually better off with uncoated tools than TiN. Another good lubricant I use is "TapMagic", also for tapping abviously. But it MUST be cleaned off the tools and parts after as it will corrode steel tools and parts. Acetone wash and light oiling of steel (I use SPI spray oil) works great. Threads come out beautiful in gummy aluminum and stainless.

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4 hours ago, Tudor said:

Next time machining aluminum (drilling too) use Acetone as a lubricant.

The most common suggestion is Kerosene, but with the demise of fuel stoves here it has become hard to find. I'll try both on the next part. This one was, I think, 6082 and did not give any problem. 

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Not visible in the pictures above, the bottom of the tool holder counterbore is a bit rough and low. Any normal person wouldn't care, but since my long term goal is precision mechanic, I wanted to fix that with a washer. But, hardware store washers are too large to fit, so I needed to adapt some.

First, a tailstock die holder was turned from leaded steel. The lower section conveniently goes in the rim that the smaller dies of a cheap set. The larger ones are the same diameter w/o a rime, a different holder will be needed. 

DSC_0272_copy_600x1067.thumb.jpg.25992595428527808db0b42b02b98fbd.jpg

Then some sort of mandrel is turned and hand threaded on the lathe. 

DSC_0270_copy_600x1067.thumb.jpg.d5e6233b390ad9fbb487bc54ffbd0819.jpg

Ready to resize OD on five washers. 

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Each washer will have to be deburred individually. Too bad these appear to be zinc galvanized, so can't be blackened as per toolmaking best practices.

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Most supply houses can get "hard" washers, which are thicker, harder and blackened. A bit more, but worth a look to suit your needs for jigs and tooling. 

Or get a chunk or hardenable alloy and make them, sterilize them and blue them.

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17 hours ago, Tudor said:

Or get a chunk or hardenable alloy and make them, sterilize them and blue them.

Drilling, turning an parting bars just to make washers is a lot of work and tool wear. My blacksmith friend has a devilish punching machine, they it use all the time to avoid drilling. It would be just a matter of getting the right dies to make a lot of proper washers from sheet metal. 

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True. You can also expand your search to "type B" washers and other washer profiles, to find "off the shelf" solutions. With the imperial system, sometimes using the "wrong" size washer gives a better fit of the center hole and/or OD.

Where in the world are you? In the states we have several BIG industrial supply houses that give all the details on the products (sizes, thickness, ratings, if applicable), so you can choose wisely. I drive our buyer nuts when I'm ordering "odd" stuff all the time... But the perfect fit makes life better. He actually does appreciate the quality of my work, but is often found scratching his head.

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Your chucks where you need them

A piece of board from the recycling center. Necchi is the famous Italian sewing machines maker. 

DSC_0278_copy_800x450.jpg.1a3878490129e82d151b899b148deab7.jpg

Holes drilled, and posts turned from hard wood. 

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I have few more upgrades planned for the small machine. 

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  • 1 month later...

Another round of improvements

All in all the C0 lathe is not poorly made but there is a lot of room for refinishing and improvement. So I took it completely apart again to correct some defects that bothered me.

 

DSC_0338_copy_648x1152.thumb.jpg.7c00c550e2c91830af9ecb0bff5621d1.jpgStarting with the safety chuck protection shaft mechanism, just cleaning and adjusting. Lots of parts for something that simple. However I think I will remove it completely because it gets in the way.

 

DSC_0340_copy_648x1152.thumb.jpg.d4cada3575e01cf126c1461eb54da036.jpgMany solder joints weren't protected. Not good as some are carrying mains voltage. I placed shrinking tube on all.

 

DSC_0341_copy_648x364.jpg.b7c988b6eb952f943b686874819fc108.jpg

This is the bottom of the bed ways, where the gibs slide. No wonder I had to readjust hem often, which was not immediate as one has to remove the control board as well the mounting base.

 

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I used a piece of wood with emery cloth around to smooth them the best I could. Not the easiest task given the small space.

 

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On the ways I gave a very light polishing with paste sliding the carriage with even motion. I must  say these are quite hard.


DSC_0352_copy_648x1152.thumb.jpg.6ce2137a139d9769692b86b67de238cf.jpgNoticing that the wear on the gibs was not even as if they were flexing a bit, I added each one a third fastener to the carriage. This is the most critical adjustment, you must be sure that the carriage does not lift or rotate at all, and both pressing screws are presing the same amount. The resulting action at the leadscrew will result slightly hard still absolutely useable. This is how you can get the most precision, finishing, and repeatability from this small machine.

Finally I drilled a suitable hole in the supporting base so I can reach the gibs without taking anything apart. No worries about loss of rigidity as the base plays no role in that, and is made of thick sheet metal anyway.

 

DSC_0353_copy_648x1152.thumb.jpg.a205b452383fa77d4e506d89dbce1391.jpgThis is the other critical improvement, I have virtually eliminated any backlash on the cross slide simply adding a nut and spring. It is the original one which I had replaced due to premature wear, with the threading section for the slide cut off. Thanks to Axminster that sent me one free of charge at first request.

 

DSC_0346_copy_648x1152.thumb.jpg.73d6993d056c9ddee603337b69527cd7.jpgMore on the cross slide. I sanded all  the non-working surfaces, which were very rough, and rounded the edges a bit. Then went to the gib, which had a terrible fitting - I am seeing from YouTubbers that is very common on bigger Chinese lathes also. Basically it is too thin to remain parallel, an the screw tip does not help in that. I shimmed the the gib with an holed feeler blade, but I hope to make a better one from bronze in the future. Again one must adjust this precisely so that doesn't move at all under pressure. Now with all square and smooth it's much easier to do that without making the cross  slide" become too hard to move.

 

DSC_0373_copy_648x1152.thumb.jpg.005658fd9dc80bee389ee381fc288fb0.jpg

Last for this article is a spacer for the chips guard. Now the 4 jaws chuck can swing even when fully opened. I only had 6082 aluminum of the right size, which is too much luxury for that use, so I will replace it with square tubing later on.

I still have one major upgrade planned, which I had to postpone until now, but I should be able to make it happen soon.

 

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I'm sure those improvements help! Backlash in a leadscrew is often unavoidable. It is best to make sure you are always "pushing" into the work. So, if you make an adjustment, you back out past where you want to be and always move forward into the dimension you want. Backing out, even on a high quality lathe, can often lead to poor finish (at best) or incorrect dimensions. But, excessive lash will cause the carriage to be pulled into the work under certain circumstances, so it is best to keep it tight. The spring may "feel" good, but you may be better served with a bronze washer and double nuts. See how it goes.

Be sure to keep the ways always wet with oil when in use (and a good idea when not, to keep rust at bay). This helps with cleanup but also prevents wear to the ways- you want there to be no metal on metal, it should float on oil film, unless locked in position. To that end, you may want to research "way scraping" to improve longevity. Basically it creates a bunch of small pockets which act as ball bearings when filled with oil. Probably overkill for a small lathe like this. A lost art, like watchmaking...

If you do get rust forming on the ways, be sure to use a way stone to clean it off. Using a file or even emery paper can easily take it out of true.

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2 hours ago, oldhippy said:

I wouldn’t want that in a lathe. Looks like the Chinese made it minus precision. I don't think that lathe will ever be precise. 

Luckily the lathe is precise enough ?, as the corrections were for non-critical aspects. Have a look at this short video, already posted before

 

1 hour ago, Tudor said:

I'm sure those improvements help! Backlash in a leadscrew is often unavoidable.

There are exceptions, as there no more backlash on my cross slide! I rig a mount for an indicator  and post a video next time.

 

Quote

The spring may "feel" good, but you may be better served with a bronze washer and double nuts.

Maybe I wasn't clear. Mine is now a double nut and spring anti-backlash setup, the same type commonly used on CNC machines, just like the one below:

T8-Lead-Screw-8MM-T8-Anti-Backlash-Nut-Spring-300-330-350-380-400-500MM-Stepper.png.9414d29cb5e088154ebbac34c533c319.png

 

Quote

Be sure to keep the ways always wet with oil when in use (and a good idea when not, to keep rust at bay).

Be reassured, oiling and all the necessary maintenance is done regularly on this machine, just like any other before as well  the many vehicles I owned since a kid ?

Quote

To that end, you may want to research "way scraping" to improve longevity. Basically it creates a bunch of small pockets which act as ball bearings when filled with oil. Probably overkill for a small lathe like this. A lost art, like watchmaking...

Not lost yet. Watch below Abom79 and RotarySMP, two of may favorite YouTubbers, scrap lathe ways respectively in a collective and individual environment.
If I'll ever need to do that mysel that's no problem. I learnt scraping and filing square blocks at the first year of technical school, way back then 

 

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Grinding wheel bushes

With the lathe now shipshape I wanted to try myself on a new (easy) part. I bough a glass-specific wheel for a clock repair but of course the hole size doesn't match the small arbor on my motor. My grinding book says that the adapters must be made like the below, screws included, so I did. For better concentricity I turned and drilled as one piece, then split (not on the lathe, that's out of question) and finished. I retained the plastic blots to reduce the strain on the wheel.

DSC_0370_copy_648x364.jpg.91a74c70e6ab05e8aedf53323893866a.jpg

To be honest I have the impression that a drilled bar section, or a 3D printed piece would have been enough anyway ?

 

DSC_0372_copy_648x1152.thumb.jpg.4116fb3ef4b88a374e2f8e9aa8bf5cdd.jpg

Partly visibile the simple jig that I intend to further modify and to use. I will describe the glass grinding in another posting, with the hope of good results.

 

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On 12/15/2020 at 12:56 PM, AndyHull said:

I've got 500 litres of the stuff in a big green tank in the back garden, its called domestic heating oil.
Your local garden centre probably has it too, its used in green house heaters.

Yes isn't called kerosene anymore, maybe due to regulations. But you can buy a heater fluid called Kerosun. Others use bioethanol and variants.
In the end it's very similar to white petrol, which I find excellent for general cleaning. I keep it in an open can with a brush and doesn't evaporate. Less smelly than diesel fuel, which is also in the same category.
I saw and machine aluminum with it, small parts so it doesn't make an huge difference, but you feel the tool cutting more quietly, and with less pressure needed.
Works for me without the need to buy different stuff for each purpose.

 

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  • 6 months later...

I have an 1/2" tapping guide but is cumbersome to use on the Unimat, one has to hold it in a big chuck on the tailstock, and for some work this setup is too long. So I "designed" and made the below, which use 20mm of length inside the tailstock barrel. It can also be useful with any lathe or drill press having a smaller 10mm chuck.DSC_0472_copy_800x600.jpg.d55978128726c6304039837688322300.jpg

The tips are still to be cut, but I was too tired for this today. The cap is made from a regular M8 bolt and it's knurled so it can be opened by hand to reverse the rod, it has a shallow hole to increase its travel.DSC_0473_copy_800x600.jpg.cb3f9664187c0e96010c7c2d6836e322.jpg

Comparing with the 1/2" guide.DSC_0475_copy_800x600.jpg.35fb9ef62c626f945864b18fa29e0ae0.jpg

The guide can be made with the Unimat itself, but I used my bigger lathe which is more practical, except for refinishing the smaller parts held in a collet chuck.

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  • jdm changed the title to Tapping guide for the Unimat 3 lathe

So, I did some research of my own, and found this video which explains a bit about the manufacture and use. 

I didn't know that some taps have a female cone at the rear end for just this purpose.

I just checked, and I have one set of taps from M3 to M12. The M3 to M6 taps in the set have a male cone on the end. Above that, the ends are squared off and plain (no female cone / dimple). My watchmaking taps 0.7 to 2mm have been roughly ground on the ends to break the edge, forming a rough approximation of a cone.

I will look out for this feature the next time I am buying. Thanks @jdm!

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17 hours ago, Klassiker said:

Above that, the ends are squared off and plain (no female cone / dimple).

Yes, I have an M14 set which is like that. So to use it with the guide I bored a short cylinder which covers only a portion of the tap so it can be turned with a spanner, the other face is center drilled.

About my guide since I'm not super happy with the diamond knurling results I've got another idea, I hope to be able to show it soon.

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  • jdm changed the title to It's Turning Fun

Dressing Chuck Jaws

That is probably the oldest machinist's trick but I never did it before. The Total Indicated Runout dropped from from .08 - .10mm to  .01. Then the test point is moved away from the chuck and the runout there is corrected tightening the chuck nuts. 

I'm about to undertake a new part which will require some precision, probably the 4 jaws would be better but I thought, what if I didn't had one?

I'm also fond of the tool holder hanger which I made from recycled wood using the milling column of the same machine.

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My first precision taper

Here's the part for which I've adjusted the big lathe chuck. It's a B10 chuck arbor for the Sieg C0 (Unimat 3). The original tailstock chuck is stupidly expensive for such a trivial part, I bought instead the precision chuck in the picture, which I will be able to use somewhere else too.

558307672_Immaginiridimensionate-1.thumb.jpg.648379abcfd98aadd123f2b6bb0d68e1.jpg

 

Making the part was not difficult per se, and it could have been made on the C0 as well. but as the usual the devil is in details. On the last taper cut I ended making it a bit too small, so it slides in the chuck a couple of mm more than ideal, as a consequence I had to cut the relieve shaft a bit longer than desired. I have now to see how accurately it drills, if all good I have a job already lined up for it.

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Sleeve it once, sleeve it twice...

While making the chuck arbor in the previous post I realized to my dismay than one of my new small bore gauges came faulty from the factory, the female threading was totally borked as if it was drilled wrong. These are not expensive, but only sold in a set of four, so worth to repair. Fortunately, the arbor I made before proved to be sufficiently precise for the ensuing work.

First, the shaft is placed in the C0 lathe and the end is parted off - bottom left. It has a lip that keeps the inner shaft (which is solid with the thimble knob) in place, and I wanted to save all of that.
DSC_0521_copy_600x800.thumb.jpg.48694d161ecee3f9de042b5a2bd53911.jpg 

 

The inner shaft is placed on a collet and drilled 2.90mm. A brass rod is turned to some interference and the drilled shaft is pressed around the rod using the tailstock chuck. Then the extra portion is parted off.

DSC_0517_copy_800x600.jpg.8b1fbe87f87ab2e235188c94e1265ade.jpg

 

Now the inner shaft goes back into the chuck, the rod is faced flush, center drilled, drilled 1.6mm, and tapped M2. Even if not a super-small diameter, tapping requires slow work and feeling. Below that being done with the help of my custom tapping guide that I've described in another post.
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The shaft has now a new soul!
DSC_0520_copy_800x600.jpg.9bb8012ac27e4407a1d8317fbc8a4c7f.jpg

 

Last issue is how to reattach the two parts of the main shaft. Another friction sleeve was the answer, as I happen to have a small assortment of bushing tubes.
DSC_0522_copy_800x600.jpg.62781a80a2b663995452aa199aa53967.jpg

 

The best matching one was adapted to size, and pressed into action with the same method as before. Work finished, here it is with its natural companion.
DSC_0523_copy_800x600.jpg.52a7b7a254ef7904d4228ecd2e14b40c.jpg
 

 

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