Weiss WMD30LV conversion project

[LongRat]

Good to hear. I'll check the tram when my conversion is complete.

[LongRat]

I am back in the house and back on the mill. Got the X ball nut mount finished and mounted up to the nut. I'm now in a position to fit the screws onto the mill, but for the end bearing blocks.
This is disappointingly rough after several spindle stalls on the X2, because I am using a very dull cutter. Should get the job done though.

[digits]

That's a nice looking part LongRat!

So, do you think you'll be CNC'ed this side of the New Year?

[LongRat]

There is a good chance of that, as long as I don't get too many things to do with the X2 in the mean time.

[LongRat]

Completed my Oldham couplers. Cost about £5 for the plastic parts from Farnell, so I saved a lot by machining the hubs myself.

[digits]

Looking good LongRat! Do those couplers have 2-lobes per hub, and is there any advantage to that over the 3-lobe 'nuke-sign' style ones?

[LongRat]

The 3 lobe style are not true Oldham couplers. I'm not sure exactly what the name of those is. They rely on compression of the spider section for their operation. My opinion is that this means they will allow backlash under a high enough force. Oldhams are made of 2 perpendicular slides which means that, if made accurately, should be more resistant to backlash under load. Plus, they can tolerate a LOT of radial and axial misalignment.
Nice animation of the concept here: http://en.wikipedia.org/wiki/Oldham_coupling

[digits]

Thanks for the link LongRat - that animation is great!

[BobWarfield]

Very nice couplers, and project overall!

Cheers,

BW

[LongRat]

Thanks Bob.
Got to give some respect for your site, I've been reading through a lot of it and found it very informative. And it always seems to have a lot of updates!
I'm feeling pretty good because I made a ton of progress today.

1) Bearing block test fitting
I measured up the bearing journals carefully with a digital mic. All were between 15 and 30µm oversize on diameter. I'm not sure what the spec is for fitting shafts to these bearings but to my mind that's too far out. It would be a very tight press fit and almost impossible to remove again if needed.
I ended up loading the screws into the 9x20 and polishing the journals down to size. I centre drilled and supported the end, then coated the journal in machine oil and wrapped a strip of 800 grit wet and dry paper around, running the lathe at a low speed and pulling the paper strip tight. I've read about this technique for getting shafts dead-on, when making model engine crankshafts etc. It worked pretty well but it does take about a minute per micron - 20 mins for my Y screw. Well worth it when my bearings slid on with a nice tight sliding fit. The journal was about 5µm over size (15.005mm). I don't have the equipment to measure the bearing ID to that accuracy so I can't say how much interference there was in this case.

2) Y ball nut removal.
The Y screw is too long to install from the column side so must be fed through the front of the base casting. Unfortunately this requires that the ball nut is removed and then re-installed once the screw is positioned in the base. I didn't have any of those cardboard tubes you sometimes get with a ball nut, the screws I got came with the nuts pre-installed. I turned a length of steel bar to the diameter of the thread root, minus 0.2mm (0.008" to those using the outdated measurement system). The idea being that you can simply wind the nut off the end of the screw and onto the piece of bar. I got nervous when it came to it and wanted more security, so I turned a small 'pip' on the bar and drilled a small hole in the end of the screw. This way the bar and screw have a location with each other and are less likely to slip apart, with the ensuing explosion of tiny steel balls and swear words. In the end, I actually glued the bar to the screw too, using CA glue. This made it much easier to reinstall the ball nut in the tight confines of the mill base - but I was still sweating at the time! I do NOT want to reload any ball nuts.

Here is a photo of the Y ball screw mounted up to the mill, with the home made ball nut mount bolted securely to the saddle. Love it when things go to plan.



Then I was able to fit the bearing block again - just have to drill and tap some holes to finally fix on the block.



3) X screw test mounting
With my X ball nut mount finished a couple of days back, I test fitted the screw to the mill. This is even tighter than I had hoped. A couple of tenths of a mm need to be removed from what exists of the ball nut flange to clear the table. The cylindrical section of the nut will clear the table by literally the width of a human hair at the closest point!

X screw test install:



I took a photo of the installed Z screw too, realised I hadn't got a picture of that. So far that's been the easiest axis, the opposite of what I expected!



Looking forward to getting a lot more done tomorrow, hopefully.

[digits]

Fantastic pics and fantastic progress LongRat - well done that man!

That X-axis does look rather tight - I really wonder what the hell the official Opti conversion does - I'd love to see some photos of an Opti '30 saddle and table casting...

Looks like you're well on the way to having CNC'ed chips before 2010 - keep up the good work!

[Mongkol]

It's interesting for this project.