Bridgeport Manual to CNC conversion...

[Muzzer]

I was talking of this but now I look again it's the size of a bus. https://ebay.co.uk/itm/DAH-LIH-MCV-1....c100005.m1851

The second one looks like a classical Bridgeport based machine but a proper CNC system from new. Might be OK but has only 5" quill movement and no enclosure(!).

Quite a few nice looking VMCs on Craigslist around the £5-6k. Didn't know Craigslist had become so established over here. It's the default marketplace over in Canada / US - must keep an eye on it now I'm back in UK.....

[Muzzer]

That Tyrax looks pretty nice but as a non-runner the price seems a bit high. Perhaps you should offer half of that and see if they bite. They obviously don't think it's worth fixing it themselves...

The Centroid controller should be OK to work with. The issues are likely to be with the spindle and drive (at least). Could be a risk hence don't offer too much. Who's going to pay £3k for it?

[Chaz]

That Tyrax looks pretty nice but as a non-runner the price seems a bit high. Perhaps you should offer half of that and see if they bite. They obviously don't think it's worth fixing it themselves...

The Centroid controller should be OK to work with. The issues are likely to be with the spindle and drive (at least). Could be a risk hence don't offer too much. Who's going to pay £3k for it?

It does seem high however the machine looks fairly new. There are 2 bids on it already (lets assume they are real) ..... suppose Id pay £3K for it if the spindle wasnt too difficult (expensive) to fix or replace. Even putting on a smaller spindle if possible will work.

[Chaz]

Might not be the same machine but they are large.

Anyone want to co rent some workshop space in West London?

https://www.aptint.com/en/used-secon...0-z-560mm_3157

[Davek0974]

I was looking at those machines too ;) theres some good stuff on there at present.

The worst part with a BP conversion is the Z axis/quill drive - it has to be canted out in front of the quill and all the force must go through a single bolt into the quill - that bolt was never made to take anything more than a quill-stop :)

As the screw is driving the quill from one side there is a lot of axial twist moment on the screw which is not good, they work but i don't know how long for.

At the end of the day with a BP you take a machine worth maybe £3k, spend £8k on it and its worth maybe £3k - there is no return value here.

[Muzzer]

I was looking at those machines too ;) theres some good stuff on there at present.

The worst part with a BP conversion is the Z axis/quill drive - it has to be canted out in front of the quill and all the force must go through a single bolt into the quill - that bolt was never made to take anything more than a quill-stop :)

As the screw is driving the quill from one side there is a lot of axial twist moment on the screw which is not good.....

That's why I fitted a 1604 ballscrew on mine where the old quill stop / feed trip rod went. That reduces the overhang by a factor of 2 or so. Also makes for a more compact installation. Having said that, there are many professional installations that seem to last, as long as the bolt doesn't work loose.

There's an Ozzie guy who did the same thing as me although his is sort of upside down compared to mine. Worked out nicely. This vid shows the way he did it:

https://youtube.com/watch?v=RsUnoXgF...Nr5wQ&index=21

https://youtube.com/watch?v=4CXcWXZj...Nr5wQ&index=19

When you change your leadscrews over to ballscrews on a BP you get to realise how much spring there is in the yoke (in the saddle, holds the leadscrew nuts) and bearing brackets, even if you were to eliminate the backlash. Puts all the bollocks willy waving about "holding tenths" into perspective. In comparison, my Shiz is rock solid.

[Davek0974]

Yeah seen those vids, its a nice tight job he did there. I modified my quill connector so that there is more meat below the screw - this takes the down thrust and eases the strain on the bolt a lot.

Tenths LOL, I love those discussions :) Having said that, i am really pleased how accurate my old girl is, plenty for my needs. Lately i had need to asses my probing accuracy, its only a basic probe with the three-point contact setup but i get repeatability of around +/-0.03mm which i think is pretty good for a conversion.

All good fun :)

[Colin Barron]

I was looking at those machines too ;) theres some good stuff on there at present.

The worst part with a BP conversion is the Z axis/quill drive - it has to be canted out in front of the quill and all the force must go through a single bolt into the quill - that bolt was never made to take anything more than a quill-stop :)

As the screw is driving the quill from one side there is a lot of axial twist moment on the screw which is not good, they work but i don't know how long for.

At the end of the day with a BP you take a machine worth maybe £3k, spend £8k on it and its worth maybe £3k - there is no return value here.

The return is you have an accurate machine which weighs 875Kg, has a small foot print, low current, spares are cheap second hand because so many were manufactured, many conversions have been done on Bridgeports and ballscrew drawings are available, if it breaks you can fix it.

[Davek0974]

Of course, there is a value but you will never make money on a conversion.

Sadly the very flexibility of a Bridgeport is the downfall of a conversion - recently lost a fair bit of stock and time following a simple tool breakage, it was not working well, the homing position was off, just wrong, it took a while to discover that the small tool breakage had nodded and tilted the head by a few degrees in both axes!

It was only a small tool but must have bucked the head as it snapped, a fixed head machine with a table as big as the BP would be lovely but the height goes up due to having all the Z travel in the head not the knee and just won't fit :)

Lesson learnt - re-tram the head every time something happens!

Yes parts are plentiful, power is usable, rpm could do with being higher - currently running 1:1 3Hp motor at 4000rpm, I think she would take 5000 but the motor would not be happy so needs raising to maybe 1:1.5 ratio or so but then bottom end suffers and rigid tapping may not be possible, I was going to fit a servo drive up there but could not figure a suitable size unit that would give speed and torque needed.

Its a lovely machine though, helps even more as i spent so long using her in manual mode as well, get to know the sounds and feel of it so you can spot a CNC tool-path thats a bit over the top ;)

[Chaz]

Any reason not to go for this?

https://www.ebay.co.uk/itm/Bridgepor....c100005.m1851

Seller indicates its 2150mm to highest point. The newer interacts are too tall.

Thanks