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On a different tack, why do you need a 20mm.
I have an RF31 and use a 16mm screw with no problems.
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When I bought this mill a year ago, I decided to just DRO it and keep it manual as I thought it would be a good learning experience. I'd say it has been - I've got to know this mill pretty well, and have finally done a 'proper' and very scary job on it: machining valve reliefs into my car's engine block!
But, it is a big mill, and I've grown pretty tired of handle cranking, and getting showered in hot chips, and I miss being able to cut arbitary profiles in 3D, so it's time to CNC it
If I had the time/space/money, I think I'd probably just buy another WM18 and convert it - you need a mill to make the conversion parts, and it's a load easier if you don't have to keep disassembling and reassembling. I don't however have that luxury, so I had to take a different tack. Looking at the other BF30/WMD30/WM18 conversions people have done, the hardest bit seems to be fitting the X-axis screw under the table. There isn't much room between the saddle and the table so it's a bit of a squeeze.
My hunch has always been that it might be possible to modify the saddle to get a 20mm ballscrew in there - the Opti conversion package uses them - but it's not really feasible to mill the saddle on the mill itself.
So a few months ago, I looked into getting a spare saddle. It took a few emails and calls to suppliers, but eventually I ordered one for £70 odd, and sat back and waited 3 months for it to travel over on a slow boat from China.
It's a bit different from my mill's original one here in green:
You can see that the blue one has far more metal on the top of the saddle - the milled flat at the base of the dovetails is almost flush with the rough cast surface between them:
Looking at the Opti CNC conversion manuals though, they seem to have even more metal removed, to lower the axis of the screw, and the ballscrew mounts onto the top-face of the saddle in a shallow pocket, rather than being mounted through the slot as on my saddle.
My plan is to try milling out some metal from the blue saddle to allow me to fit a ballscrew on the X-axis. I'd really appreciate it if someone with a real Opti BF30 could measure the depth of the ballscrew's pocket from the top of the X-axis dovetails on the saddle.
I need to choose a ballscrew and do some maths/CAD before I start cutting, but I thought it'd be worth starting this thread anyway.
Cheers.
On a different tack, why do you need a 20mm.
I have an RF31 and use a 16mm screw with no problems.
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I guess I don't 'need' a 20mm screw, but that's what the orginal ACME's are and what Optimum use for their CNC conversion. Looking at most of the datasheets I've seen, there doesn't look like there's enough room for a 16mm screw without modifying the ballnut or saddle anyway...Originally Posted by M250cnc
Have you got any pics of your conversion you could share?
Cheers.
Unfortunately not, but I just copied the supplied housing to fit the new ballnuts. It was pretty straight forward.
Phil
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Thought you might end up doing this
Looking to sell your DROs?
FWIW, my mill is running nicely on its 16mm X-screw. But it is literally almost touching the table. If you are in a position to HAVE to machine the saddle, I think it is worth trying to fit a 20mm screw.
Yes, LongRat - you were right all along! I'm still not 100% sold on gibs and dovetails for CNC but this is a pretty capable machine, and should be lots more fun CNC'ed...Thought you might end up doing this
Looking to sell your DROs?
FWIW, my mill is running nicely on its 16mm X-screw. But it is literally almost touching the table. If you are in a position to HAVE to machine the saddle, I think it is worth trying to fit a 20mm screw.
I have no plans to sell my DRO right now - I can't understand how anyone can use a manual mill without one, and I'm still half tempted to buy a bigger manual lathe so I might move it over.
I really should start CAD modelling this spare saddle - but I've got lots of tedious computery things to sort out first.
I'm not sure what I'm going to do for the controls - I've still got my old WinXP machine with Mach 3 on it but I'd rather go over to EMC2 in the long run - just got to get my finger out on finishing the PCB's I need...
I'm obviously going to shamelessly steal all the best ideas from your conversion thread - but I'd rather machine this soft cast-iron saddle than hardended ballscrew-casing.
I machined a little off my Hiwin ball nut the other day with my Weiss 30 and it did just fine.
I did have a really nice MA ford 8mm cutter though.
I removed the ball nut flange on mine with a bench grinder. Ugly, but it got the job done.
The difference between 16mm and 20mm surfaces at high table speeds (or the related ramps). During brakeing or accelerating on push, the spindle wants to flex sidewards. This can be a wear issue on long spindles. On the other side, this is no production machine.
There are calculating tools from makers/suppliers. But why not throw in a 20 if it fits... a little stiffness never hurts.
Cheers,
Johann
I did some measurements and some CAD, and it's looking very,very tight getting a 20mm screw in on X. From what I can see, I'd have to drop the entire body of the ballnut into the saddle some way - the saddle->table gap is ~28mm and the OD of most 20mm ballnuts is about 36mm.
I am toying with the idea of mounting the ballnut from the underside of the saddle, and cutting the topside so that I can drop the screw itself about 5mm into the saddle. Looking at the Opti pictures, their X-screw axis is way below that of the Warco/Amadeal ones...
What about the linear rail option? That would jack the whole lot right up - I believe you suggested it to me when I was at exactly this point in my own conversion. As long as cutting so much out of the saddle doesn't hurt the rigidity, I doubt that 16 or 20mm screws with these low power machines makes a lot of difference.
Well remembered
I'm not discounting linear rails - I really do like them a lot, but on a machine with a 2500 rpm spindle, I can't really see it ever needing to move particularly fast.
A 16mm screw would probably be fine - I'm planning to order screws in early December, so I still haven't made my mind up yet.
At the moment, I really need to work on the electronics to drive it all - what I really like about the manual-ness of this mill is the user interface! DRO's are excellent for knowing where you are, and handwheels are excellent for sneaking up on the stock or for carefully putting a drill back in an existing hole to take a measurement or set a reference position. So, I don't think I'm going to be happy with CNC on joysticks/keyboards/mice again - I need a real MPG on my EMC2 setup.
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