Hi again ;)
Here we go for another big project: I own a chinese made 250x550 lathe for about 4 years, but there where some points that upset me from the beginning, and now I found the courage to do something, to make it a better lathe.
Thats the lathe in its shape bevor the disassembly:
![](http://gtwr.de/hbm/IMG_0086.jpg)
Overall a nice little lathe, a bit chinese, but ok for the money.
A few contact patterns:
Tailstock to bed:
![](http://gtwr.de/hbm/IMG_0092.jpg)
Hmmm..
Crossslide
![](http://gtwr.de/hbm/IMG_0099.jpg)
Uhm...
Topslide
![](http://gtwr.de/hbm/IMG_0100.jpg)
Maybe...
Headstock to bed:
![](http://gtwr.de/hbm/IMG_0102.jpg)
There is a hint of blue on the left...
Bedslide to bed:
![](http://gtwr.de/hbm/IMG_0110.jpg)
Ok, there is a lot of work coming towards me...
Dirt of four years working on that lathe:
![](http://gtwr.de/hbm/IMG_0115.jpg)
This will be a lathe again, some day...
![](http://gtwr.de/hbm/IMG_0116.jpg)
Some parts could be cleaned and primed right away, after I have cleaned em with a pressure washer in a nearby car wash:
![](http://gtwr.de/hbm/IMG_0124.jpg)
Here we go with the Topslide, measuring the thickness from the lower sliding way to the surface which will hold the toolholder, numbers are in 1/100mm:
![](http://gtwr.de/hbm/IMG_0125.jpg)
I put the topslide in the milling vice and machined that surface over. I also cut a relief on the boss, which will make scraping the surface easier:
![](http://gtwr.de/hbm/IMG_0127.jpg)
For the gib, I drilled a few more holes:
![](http://gtwr.de/hbm/IMG_0128.jpg)
The top surface was scaped afterwards. For touching of, i made a ring-type micro-surfaceplate:
![](http://gtwr.de/hbm/IMG_0132.jpg)
Finished:
![](http://gtwr.de/hbm/IMG_0134.jpg)
Then, the topslide was fliped over and pockets where machined in the lower sliding surfaces. They will be filled with moglice, a special epoxy resin thats used for guideways and sliding surfaces.
![](http://gtwr.de/hbm/IMG_0135.jpg)
With the moglice, I can use my surface plate as a reference to cast from. Only thing thats left to do before casting, is to adjust the height of the remaining material on the slideway. It is done with a file.
After a bit filling i get that measurements, this time in 1/1000 of a mm:
![](http://gtwr.de/hbm/IMG_0136.jpg)
The Pockets are filled with the resin, a release agent is applied to the surface plate, and the top slide is put on the surface plate. I mixed a bit to much of the moglice and it squeezes out on the side, but thats no big deal.
![](http://gtwr.de/hbm/IMG_0137.jpg)
The moglice takes 24hours to cure, after that time the part can be released with a blow from a softfaced mallet, and we get that: A perfect even sliding surface with excellent properties:
![](http://gtwr.de/hbm/IMG_0139.jpg)
The "burr" will be filed of.
Lower part of the top slide, its also pretty off, the measurements range from -0,07 to +0,04mm
![](http://gtwr.de/hbm/IMG_0143.jpg)
Again, scraping:
![](http://gtwr.de/hbm/IMG_0150.jpg)
Finished, only 2/1000mm difference left:
![](http://gtwr.de/hbm/IMG_0152.jpg)
The angular surface will also be coated with moglice, so a pocket is machined again:
![](http://gtwr.de/hbm/IMG_0168.jpg)
This time a scraped master is used for casting:
![](http://gtwr.de/hbm/IMG_0170.jpg)
![](http://gtwr.de/hbm/IMG_0171.jpg)
Came out nice:
![](http://gtwr.de/hbm/IMG_0179.jpg)
Scraping the mating surface on the upper part of the top slide:
![](http://gtwr.de/hbm/IMG_0188.jpg)
Measuring the parallelism with a pair of pins and a mic:
![](http://gtwr.de/hbm/IMG_0196.jpg)
Machining a new gib from hot rolled steel, as the original one was badly warped:
![](http://gtwr.de/hbm/IMG_0200.jpg)
Chucking the partly finished gib into the topslide to machine the 60° angle:
![](http://gtwr.de/hbm/IMG_0201.jpg)
Skinny original gib on the right, manly new gib on the left:
![](http://gtwr.de/hbm/IMG_0205.jpg)
As i dont like drilling blind holes into a gib to hold it with the setting screws, I went another route. I assembled the whole top slide, inserted the gib and fixtured it with two wedges. Then I drilled two 2mm holes trough the side of the topslide and into the gib. Two dowel pins will hold the gib in position:
![](http://gtwr.de/hbm/IMG_0209.jpg)
Clearance, only contacting the angular surfaces:
![](http://gtwr.de/hbm/IMG_0210.jpg)
Here the pins can be seen:
![](http://gtwr.de/hbm/IMG_0213.jpg)
I also made those little pieces, with an angular cut, that will go into the threaded holes in front of the set screws, that push the gib:
![](http://gtwr.de/hbm/IMG_0214.jpg)
As the original bearing of the topslides spindle only was a hole, I went for two ball bearings. Machining a block of aluminum to size and boring it:
![](http://gtwr.de/hbm/IMG_0219.jpg)
Flip around, mill a step and bore the other side:
![](http://gtwr.de/hbm/IMG_0222.jpg)
Finished top slide, with the new bearing block I also gained 15mm extra travel.
![](http://gtwr.de/hbm/IMG_0224.jpg)
Another problem was the headstock, the original bearing seats where not very precise machined..so what could I do?
But first, pulling the spindle out of the headstock:
![](http://gtwr.de/hbm/IMG_0107.jpg)
I decided to machine a cardrige with two bearing seats, bore out the old seats in the headstock and glue it into place.
A friend allowed me, to use his lathe:
![](http://gtwr.de/hbm/IMG_0153.jpg)
bearing seat on the first side:
![](http://gtwr.de/hbm/IMG_0154.jpg)
Then it was flipped arround, and the other seat was machined.
Headstock and finished spindle cardrige:
![](http://gtwr.de/hbm/IMG_0156.jpg)
Machining away the old bearing seat, roughing:
![](http://gtwr.de/hbm/IMG_0157.jpg)
Boring to size, got a nice Wohlhaupter UPA1 boring head short time ago
![:D](https://madmodder.net/Smileys/default/Bounce.gif)
![](http://gtwr.de/hbm/IMG_0158.jpg)
Same was done on the other side, and the cardrige slipped in pretty fine:
![](http://gtwr.de/hbm/IMG_0162.jpg)
Cardrige glued in place, bearings and spindle installed, first check, everything ok. Final alignment will be done, when the bed is leveled.
![](http://gtwr.de/hbm/IMG_0216.jpg)
Speaking of the bed, I need a new support frame and cooleant tray for it, so I went outside and weldet a bit steel together.
That will be the main support beam:
![](http://gtwr.de/hbm/IMG_0247.jpg)
It is supported by the cooleant tray:
![](http://gtwr.de/hbm/IMG_0248.jpg)
Primed..:
![](http://gtwr.de/hbm/IMG_0252.jpg)
Back in the shop, the fresh painted bed and cooleanttray-bedsupport conraption got bolted together.
![](http://gtwr.de/hbm/IMG_0259.jpg)
Thats all right now, I will continue tomorrow
![:)](https://madmodder.net/Smileys/default/side2side.gif)
Regards,
Stefan