CNC conversion BL250G/700 lathe

[MrCrankyface]

Tweaked the tool a bit more.
Sharpened the blade with a 3000 grit diamond blade and bent the shank down, this made a massive difference to how it cuts and it's now really easy to get consistent scrapes and get them exactly where I want them.
I think the most important thing here is when I push down onto the surface, the blade is still going along the surface whereas before I had to angle the entire machine down and basically punch the carbide into the surface just to reach.


Holding onto the machine and controlling on/off and speed was another huge issue when it came to comforts.
This was a quick'n'dirty fix to that ...
Hoseclamp around the trigger so I can set the speed with a screwdriver and then a new button that overrides the trigger, basically my new on/off button.
Just secured and insulated with hotglue but whatever works so I can get this done, will probably revisit this and make a better machine in the future.


This really helped the comfort factor of using it, the machine new rests along my forearm with the handle going into my elbow crease and my thumb resting on the on/off switch.
With my left hand I can grip way up front on the handle to achieve a really stable and fine control, definitely way more enjoyable than hand scraping.


I think I'm nearing full coverage now and am a lot more careful when looking at what to scrape away, trying to identify what's real low spots and what's not.


Still area scraping rather than going for checkerboard but I suspect I need to change my tactics there soon.
One thing that makes me really happy about the power scraper is that it makes it really easy to get consistent scrapes and not gauge the surface, I can only imagine how much fun it must be with a "proper" power scraper.

 

[MrCrankyface]

Alright I think I've reached the limit to both my patience and skill with the camelback, I get this print with as thin of a layer of ink as I can achieve, any thicker and pretty much entire camelback is coated.
Learnt a lot about scraping so that'll be good now that my attention is back on the lathe ...
It's pretty interesting now because the camelback is basically sliding over the surface plate now whereas before it would have substantial friction, probably due to higher load per contact area.


Did a quick print on the cross-slide and it's basically sitting on 3 points, tapping on the fourth corner would produce a change in sound so obviously tipping.
Measuring it out, the surfaces are all over the place.


Just some photos of the progress, this is basically the starting point, very small contact surface and tippy behavior.


Quite a lot of passes into it and it's not tippy anymore but still far away from full contact.


This is really helping me dial in my roughing technique, both making it go faster and achieve more on each pass.
This is maybe 2 hours into it
I hope to make this really flat so it later can help me align the surfaces it mates against.
Need to double-check it to make sure the top is still flat and parallel towards this "new" surface.

 

[MrCrankyface]

Took a few more passes then put it on the plate and measured how parallel the top was to the bottom.
It doesn’t seem to be very flat but the important surfaces are fairly parallel, at least it's not twisted which I was worried about after all my roughing.


I think my ink is still a bit thick but if I make it thinner than this I get really poor transfers, I should really try some of the "reputable brand stuff" to see if it's me or the ink being hard to use.
At least it's insanely much better than it started.
The lighter pattern along the middle is intentional, hoping this let's it sit stable for longer instead of wearing the outer parts and starting to rock.


So my next spontaneous idea was to do something about the oiling system.
Originally you oil it from above and that goes into one single hole above the gib and is then supposed to spread to all sliding surfaces.
I say "supposed to" because it really doesn't.
I've seen that many 'more expensive' machines use this Z-pattern and have oil enter in the middle so I'm considering milling this in with a ball endmill or something.
Does anyone have experience with oil grooves and can tell me some do's and don'ts? Been googling for a bit but not finding anything definitive.

 

[mattthemuppet2]

I use a small ball end mill (1.5mm or so) and mill to a depth about 80% of the cutter width. I've never bothered to mill the angle in the Z, I just do an H pattern instead.

 

[MrCrankyface]

Ended up making it real easy for myself.
Just took a diamond coated dremel tool and slowly made my way along the lines, worked pretty well but easy to slip if you're not careful.
I measured so the oil path would always be in contact with the lower surface and not be out in open air.
One mistake was not checking where I'd want the actual oil path to be, had to move one of the holes a bit off-set to avoid the gib-relief.
I did check the scraping marks with an indicator and they're on the shallow side according to recommendations I've seen from Richard King, need to work on that.


Holes down to the grooves are 2mm whilst the 'throghhole' is 4.5mm, I hope the restricted flow down to the oil grooves will help balancing how much oil each groove gets.
Since the crosslide is too wide I had to drill from both sides and plug one end.
Lower row of holes here is for the gib adjustment.
I'm waiting with the dovetails for now.


Figured I'd flatten out the saddle first so everything sits flat on the ways.
I have hand-scraped this before just to remove some really rough surfaces but man, it still looks like something out of the trash.
Bottom left is very irregular and looks like a cast/unmachined surface, despite being a mounting surface.
Machining marks are evident everywhere.


Since it can be a bit tricky understanding it upside down.
Blue is where the apron mounts.
Red are where the front and rear gib mounts.
Finally the yellow is the rear sliding surface.
I've already went at it with the dremel and slotted out the oil grooves, before it was just a hole on top.
I think this will coat the ways better by letting the oil slide down a bit more.


Much like the cross slide, this entire piece was touching on 3 different spots ...
Wasted maybe an hour scraping before I realized I was better of milling off the surface.
Since my mill is difficult to tram accurately, I did my best and then used a small endmill to sweep the entire surface to minimize angular issues.
On the left of the prism, I lowered the shiny surface by a millimeter as it has no real function and was interfering with the bluing process(reddening process in my case? )
On the far right, on the thin 'ledge', I milled down half a millimeter just to get clearance, no point in scraping this surface and it was just making things more difficult.
To not create stress raisers I moved down to depth over 10mm of travel to get a ramp of sorts then cleaned this up with some 400 grit sandpapper.
That is on top of the 0.2mm I removed from all the surfaces just to clean up casting remnants.
Just a few scraping passes in and already printing way better than before.
Every few passes I also put it "right side up" and measure against the sliding surfaces on top to check if things are still parallel.


Eventually I felt like I was chasing my own tail and instead of improving the pattern, I was just constantly getting a different pattern.
...Turns out doing things correctly would've worked better ...
After inking and inspecting the surface I decided to lightly rub it against a clean portion of the surface plate, suddenly I have several REALLY obvious high spots, shiny like little mirrors.
It's interesting how much ink the part is picking up despite almost only sitting on the dark red spots, I've filled all shiny spots with a red marker to help scrape them off later.
I've gotten this far with my shoddy DIY-power scraper but will move on to hand scraping now.

 

[mattthemuppet2]

fabulous work! One tip about the cross slide oil gallery - add an oiler on both sides. I did what you did on my SB heavy 9, with a ball oiler on the tailstock side. Unfortunately, that's the slide that gets the most oil. It's nicely oiled whereas the chuck side gets very little, enough of a difference that I need to remove the ball oiler and drill through to the other side. Just a hassle to take everything off.

 

[MrCrankyface]

Thank you! I will be wary of that and modify if I notice the same issue! I would really prefer not having oilers on both sides of it.
It will be filled through one of those one-shot pumps so I hope it will create pressure high enough to "split the load", will definitely need to test it out and evaluate.

Kept scraping the saddle but got tired of the handscraping on such, relatively, large surfaces. At the same time the "power scraper" linear bushing has noticeably worn already, clearly not made for this kind of abuse.
Figured I'd take another detour by making sure the power scraper will last at least for the rest of the project, and benefit it more.
Took everything apart again and flycut the main gear, got rid of the bearing pin and the entire plateau that used to be around it.
Drilled a hole pattern for my next step.. Went way easier doing this on the CNC-mill with flood coolant compared to the drill press.


These little pieces were a ridicilous amount of work due to the worn out screws and slideways of my mill.
Managed to get the slide ~0.05mm smaller than the slot so the fit is really nice, but it was a lot of work.
The little screwhead hidden in the smaller slot will push/pull the slide in and out.


Bolted onto the main gear, got really lucky with this fit, can't feel any slop at all and pleasant amount of friction when adjusting it through the screw.
Fully extended the stroke should be around 25mm, probably more than I ever need but rather have it than not.


And the gear mounted back in the powerscraper, adjusted to 0 stroke.
It is possible to adjust it to "negative" stroke to make sure I can adjust it all the way down to 0.
The upper half of the casing will need a hole or slot cut so I can access the hidden allen head screw.
Next step is to make a new linear guide system that will be both stronger and longer-lasting.
Also need to change the mounting screws to countersunk or just sink those down.

 

[MrCrankyface]

Man, I'm always amazed how long time it can take to churn out parts, and how easy it is to make mistakes.
Found a suitable scrap piece of aluminium to build upon, hence some extra holes in it.
After getting some rough positions for the machines bolt pattern and milling out space for the rotating gear/pivot point, I did a quick mock-up of the linear unit.


I think this is what took the most time.
-Facing and threading a suitable piece to hold my workpiece.
-Cleaning up all the hole positions.
-Milling a pocket for the front portion of the machine(which is raised up).
-Milling out room between the bearing blocks
-Drilling hole pattern for the bearing blocks
-Drilling out hole patterns for later reinforcing structures
-And finally milling out a new contour so it's not just a massive block/sheet.


Some countersinks and screws later, almost surprised how well everthing lines up.
Seems promising for the next step when I need to connect the rotating pin to the linear shaft and later make some kind of tool-holding block to sit between the bearing blocks.
Machine looks really long with this addition but the carbide-bit will be around the same place as it used to, a bit of an optical illusion I guess.
For reference, the nose of the machine is roughly under the middle of the rear block, so the carbide bit used to be around the position of the front bearing block.

 

[MrCrankyface]

So quite a few things happened and didn't get a lot of pictures.
-Machined up some sidewalls to straighten and stiffen the entire construction.

-Cut and machined the 12mm shaft to spec. There's a large flat section on it where the tool holder piece sits, fun feature to make.
-Tool holder piece and link between yoke/shaft are currently 3D-printed, seems to hold up fine.
-Machined up an aluminium block to join up with the 12mm shaft on the left of the bearing blocks.
During the process I realized I made the slot way longer than it needs to be, thus making the entire machine longer than necessary, must've just taken a number out of my head when doing that one.


And the underside now with the protruding tool holder.
Need to countersink all those screws to get the heads out of the way.


And with the old tool mounted back on.
Tried putting a bit of rubber between the surfaces, supposed to dampen the blade or something I guess.
All the marks on the left tells the story of how I'm testing this out on the cast iron worktable.
Going to take some time to get used to it but seems incredible already.
Taking 25mm long scrapes with ease and consistency where I before could barely manage 10mm due to instability(when yoke was fixed).
Due to being much more solid, it's also a bit less forgiving, need to test with more rubber and see if it makes it better/worse otherwise I'll just have to be more careful/deliberate.
Next I need to clean everything up, shorten pins that are too long etc and design some covers so I can't get my fingers caught anywhere.

 

[MrCrankyface]

More iterating and I was not satisfied with the strength of the printed tool holder so I made one in aluminium instead.
Quite difficult to make(for me) but so satisfying when done.
Ruined an endmill trying to make a slot in the tool shank so had to open that up with a grinder instead, makes it much easier to just slot in and out when/if I want to change the bar.


Entire thing is a bit bulkier than it needs to be but I'm still very happy with how it's turning out.


Finally added the 'adjustment hole' so I can reach in with an allen key and adjust the stroke.


Some final touches were to add covers for it.
Bottom piece is both grip surface and to cover all the moving parts, wouldn't want to get pinched...
The entire train-carriage-looking-part could be both lowered and shortened quite a bit but at this size it offers quite a good grip for my hands.
Will most likely rework the rear of the machine by removing the grip up to the cylindrical motor since I'm only gripping the machine along the black surfaces anyway.
Left to do is to fix that, make a better speed adjustment and add a new on/off switch in a convinient location.
Then it should hopefully be down to a final teardown, clean, grease and re-assemble so I can get back to scraping the lathe.