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:
Overall a nice little lathe, a bit chinese, but ok for the money.
A few contact patterns:
Tailstock to bed:
Hmmm..
Crossslide
Uhm...
Topslide
Maybe...
Headstock to bed:
There is a hint of blue on the left...
Bedslide to bed:
Ok, there is a lot of work coming towards me...
Dirt of four years working on that lathe:
This will be a lathe again, some day...
Some parts could be cleaned and primed right away, after I have cleaned em with a pressure washer in a nearby car wash:
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:
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:
For the gib, I drilled a few more holes:
The top surface was scaped afterwards. For touching of, i made a ring-type micro-surfaceplate:
Finished:
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.
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:
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.
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:
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
Again, scraping:
Finished, only 2/1000mm difference left:
The angular surface will also be coated with moglice, so a pocket is machined again:
This time a scraped master is used for casting:
Came out nice:
Scraping the mating surface on the upper part of the top slide:
Measuring the parallelism with a pair of pins and a mic:
Machining a new gib from hot rolled steel, as the original one was badly warped:
Chucking the partly finished gib into the topslide to machine the 60° angle:
Skinny original gib on the right, manly new gib on the left:
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:
Clearance, only contacting the angular surfaces:
Here the pins can be seen:
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:
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:
Flip around, mill a step and bore the other side:
Finished top slide, with the new bearing block I also gained 15mm extra travel.
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:
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:
bearing seat on the first side:
Then it was flipped arround, and the other seat was machined.
Headstock and finished spindle cardrige:
Machining away the old bearing seat, roughing:
Boring to size, got a nice Wohlhaupter UPA1 boring head short time ago
Same was done on the other side, and the cardrige slipped in pretty fine:
Cardrige glued in place, bearings and spindle installed, first check, everything ok. Final alignment will be done, when the bed is leveled.
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:
It is supported by the cooleant tray:
Primed..:
Back in the shop, the fresh painted bed and cooleanttray-bedsupport conraption got bolted together.
Thats all right now, I will continue tomorrow
Regards,
Stefan
