Member postings for Sonic Escape

Now I'm even more confused about what means a good quality lathe. But for some reason I'm starting to think it's a good idea to buy it. I'm going again this afternoon to see it. I have another steel bar left.

Somebody reverse engineered a 3D model of this lathe: **LINK**

I just saw the lathe this evening. I'm not sure if I've mentioned it before, but this is the first time I've seen a lathe in reality. I think that I spent an hour but I have the feeling that there were a lot of details that I missed or I was completely unaware of. And I have even more questions now ... but here are my remarks so far:

- I put a 6mm mill in the chuck and I measured the concentricity error at 10mm from the jaws. The maximum deviation was 0.1mm (0.0039"

- I fixed a comparator on the compound and put the tip on the bed. Then I set a low speed for the carriage and move it across the whole length. Maximum error was 0.04mm (0.00157"

- I tried to lift the carriage using moderate force and the comparator didn't moved a micron.

- We cut my steel rod from above. First with a 0.1mm cut. The surface was very smooth. Then we cut 1mm deep using a carbide tool. There was a sharp strong noise a lot of smoke from burned oil. It was not something that I would like to replicate. The bar was almost to hot to touch after. The surface also looks nice. Now I realized that I should use a much longer bar. Actually the seller had one prepared but I didn't realized it's purpose. The highest difference in diameter for the 1mm cut is 0.01mm(0.00039"

- I opened the gear box. There was clean oil at the bottom and the edge of the wheels feels sharp. There was no suspicious noise in any gear setting. Both longitudinal and transversal automatic feed is working

- all the slides run smooth and apparently there is no backslash.

- In order to change the speed sometimes you have to manually rotate the chuck. But I suppose this is normal, the wheels are not always aligned.

- The tailstock can be adjusted only horizontally

I think I will return to cut a half a meter bar. I used this comparator.

How do you think are the measurements so far?
If I cut a long bar what is the maximum expected error for a lathe in good condition?

Edited By Sonic Escape on 13/02/2023 19:48:12

Edited By Sonic Escape on 13/02/2023 19:50:55

Edited By Sonic Escape on 13/02/2023 19:55:23

How much would cost a DRO like that? I have no idea

Yes, I'm going to measure with a comparator the concentricity error and all slides. It didn't occur to me to cut some steel. I have this steel bar. How could I stress this lathe with it? What would be the maximum depth at which it should cut? And at what speed?

The machine is three-phase but the seller installed a converter. The chuck has 3 jaws, in that the picture was difficult to see. It has also a new DRO installed. But I want to buy it without. I think I can live without it. It just add to the total price.

It has also the gear wheel for imperial threads. Maybe tomorrow I'll go to see it. I'm still discussing with the seller about the price. Is a little over my budget since I was planning to buy something in the SIEG SC4 or SC6 range.

I'm looking for a lathe and I found this model close to me. It is an Italian lathe with 750mm distance between centers. Anybody had any experience with this model?

It looks like it is possible to change the strip configuration. By desoldering an LED maybe. Then you could divide the 420V strip in two. If the two resulted strips are connected in anti parallel you can connect them directly to 230AC. With only one good quality film capacitor in series to limit the current. A value between 10-15μF should cause the necessary voltage drop at 70mA.

Of course such a circuit will not be safe to touch in any point. And maybe could cause some 50Hz flickering. But in the absence of other options, it is worth trying

Edited By Sonic Escape on 12/02/2023 21:49:54

I knew about epoxy frames. It was one of the first options that I investigated. But I'm not familiar with the materials. What I found here is very expensive for the volume required.
But how about some high grade concrete? A cubic meter of the strongest commonly available concrete here is 80 euro I think.

if I had known that I would be interested in milling machines before the house was ready I could alter the project to incorporate a milling frame. And I would have lived in a milling machine 

Edited By Sonic Escape on 12/02/2023 21:12:31

The cause for the relative lack of rigidity can't be the linear rails? I also wanted to use them because they are widely available but I read somewhere that dovetail slides are more solid.

Thank you for all suggestions. I suppose that a stronger bench drill would work better. After all even with my Bosch drill I was able to cut a steel nut and a bolt. But I want to build one just because I find it an interesting project. It doesn't matter if in the end it might end up more expensive that a used machine. The cost will be spread over a long time.
However I'm considering also the option of buying an used milling machine in bad shape, if the cost is reasonable, and to restore it. If it is a serious machine, >600kg. That would be and equally interesting project I think. In my region there are often in the used market old Romanian milling machines. My favorite is this one, a FUS22:

It weights 800kg. But it costs 2000€. Because the seller insists in selling it together with a large rotating table, a divider head and an additional slotting head. If they are in worst shape, like what I'm looking for, they end up in the scrap yard not on Internet. And even without accessories they don't drop bellow 1500€. This days I'm also looking for a lathe and such a milling machine would consume too much from that budget.

In my ignorant view, all I need is a way to move the spindle vertically as rigid as possible. I'm happy even with locking the spindle after I set the height. To be more rigid. I don't plan to adjust it during the milling. It is not a CNC.
The rest is relatively easy. For the frame I can weld something heavy enough. Steel is cheap. I dropped the requirement to be able to move the machine alone. I can build it directly where it will stand. There is plenty of space around. It is also a well ventilated place to use MMA welding there. The electronics part like speed regulator is not a problem.
I started some talks to see how much it would cost for somebody to drop a large boulder in my yard. I heard that some high end milling machines are made from granite. I could carve the boulder outside and then move it somehow in the garage. But this is not my first choice. Or at least not yet

The table is moving horizontally over a dovetail?

I continued to think about the options and currently I have two dilemmas. First, what spindle to use. The one that I posted above I don't like it. Seems difficult to adapt a pulley to it. And also I don't know in what condition it is. From my research I concluded that there are two widely available options. One is a combination of air or water cooled high RPM motor that include ER collet:

The second option is only a large cast iron block with an BT30 tool holder:

This one is limited to lower RPM. But I don't need high speed if I'm not in a hurry, right? The green one looks more solid to me. But the first is easier to use.

The second dilemma is the vertical movement. I'm thinking to use a solid vertical tube. Something > 4" in diameter and very thick walls. Similar to this home made contraption:

But I'm not sure how to make that piece that slides up/down over the column. Maybe another pipe with interior diameter just a little larger than the column diameter? I could slotted it to be able to clamp it over the column before milling.

Hi An,

I don't have any type of work in mind. I just find it interesting to build one. I have some vague requirements like to be able to move it alone, up to 10cm of vertical movement and should work with mills up to 7-8mm. Cutting speed is not an important factor. But I would like to be as precise and vibration free as possible.
My current idea is to make a frame from half inch thick metal plates. There are plasma cutting companies in my area and I can weld reasonably well. But I have to check the precision of this cutting method. Because they usually cut metal sheets for fences...

Also I found this in the local used market, a kind of milling head:

This thing has an ISO 50 cone and I estimate to weight around 60kg. It is larger than what I was planning but the price is ok and I'm wondering how difficult could be to use it. Maybe to replace that teeth wheel with a pulley for a belt?

Hi,

I want to build a milling machine. Just for fun. I have no experience so I was looking for something simple. I bought a Bosch PBD 40 bench drill, a milling table and this precision vise.
The milling table was full of rust, had a lot of play and was covered in a bad smelling grease. I cleaned it and painted. Fortunately it was possible to adjust it to remove the play. I stacked everything together like this:

The table is moving smooth but unfortunately I underestimated the rigidity required to mill metal. I have a 5mm carbide mill and I was able to cut the top of a nut. But I think I was lucky that the mill didn't snap. There were a lot of vibrations. This is the result:

I like the table so I will keep it but I want to replace the column drill. So I'm evaluating different options for building a more solid frame. I'm open to any option, from steel to concrete.

Hi,

I recently started to be interested in lathes, milling machines and various mechanical devices and I was looking for a forum that covers this topics. I have no experience in this domain. So far my hobbies were electronics and programming. But I want to try something new. Preferably without involving a screen.

Cheers

Andrei