Bridgeport Manual to CNC conversion...

[Muzzer]

I dunno about komatias but I got mine from AliExpress, machined to my own drawings for a nominal cost, like $5 per ballscrew - that saved a lot of messing about and they did a good job. The std ballnut diameter is slightly bigger than the std leadscrew nut, so I machined my yoke out on the (Bantam) lathe. Unless your machine is in almost new condition, you may struggle to justify expensive ballscrews, as there will be slop and backlash even once the gibs are adjusted. The ballscrews account for only a part of the total.

Using an MPG means I don't need the X & Y handwheels, which (in my case) added a lot of unhelpful moment of inertia to the servos so I removed them and have a better servo response. I still have the original DRO I fitted years ago but this simply tells me how worn the machine is. If you can achieve backlash below 20-30um (0.001"), I'd say you are doing well. However, the actual accuracy will be worse when you are machining as opposed to cutting air, as there will be additional forces at play - but the willy wavers tend not to get into measuring that, as it spoils the fun.

[V8kid]

I dunno about komatias but I got mine from AliExpress, machined to my own drawings for a nominal cost, like $5 per ballscrew - that saved a lot of messing about and they did a good job. The std ballnut diameter is slightly bigger than the std leadscrew nut, so I machined my yoke out on the (Bantam) lathe. Unless your machine is in almost new condition, you may struggle to justify expensive ballscrews, as there will be slop and backlash even once the gibs are adjusted. The ballscrews account for only a part of the total.

Using an MPG means I don't need the X & Y handwheels, which (in my case) added a lot of unhelpful moment of inertia to the servos so I removed them and have a better servo response. I still have the original DRO I fitted years ago but this simply tells me how worn the machine is. If you can achieve backlash below 20-30um (0.001"), I'd say you are doing well. However, the actual accuracy will be worse when you are machining as opposed to cutting air, as there will be additional forces at play - but the willy wavers tend not to get into measuring that, as it spoils the fun.

Thanks for the info I have already converted my Series 1 to CNC using the standard acme screws and also removed the handles 'cos I was getting fed up with getting the occasional thump. By the way I'm with you on appropriate accuracy for outlay I paid £130 for my Bridgeport as it literally had fallen off a lorry and the head casting was cracked. Another £150 in used spares got me going and I've spent another £700 on the CNC conversion. So value.

One thing that puzzles me is the wall thickness on the standard Bridgeport yolk. I can see there is enough meat to machine out from 32mm to 40 mm but there does not appear to be enough wall thickness for the securing bolts without breaking through the wall. How did you manage?

I guess I could buy a 2505 ballnut and dismantle the X axis to see better but I'm pushed for time as we are moving house in the spring so any info would be highly appreciated.

Cheers
David

[Muzzer]

Not sure where you get the 32mm figure from. The yoke bores are designed to take bronze cylindrical leadscrew nuts, as opposed to being directly threaded. On my Series 1 BP clone, the original X&Y leadscrews were 1-1/4" ie ~32mm OD. The actual leadscrew nuts themselves were pretty much 39mm OD and the DFU2505 ballnuts are 40mm OD, so I only had to bore the yoke bores out about 1mm on their diameters.

As for fixing, there's really no need to use all 6 holes. I only fitted two M6 screws and there was enough meat for me to drill and tap the holes. If you look at the tensile load that would cause an M6 bolt to fail, you'll see that this wouldn't be the first link in the chain to break.

Here's a bit about the actual boring: https://mightyshiz.blogspot.com/2018...or-larger.html

And fitting the thing back on the machine. Note that the Y axis ballnut may foul something (I forget - possibly the knee lift?), which required some angle grinder action on mine.
https://mightyshiz.blogspot.com/2018...allscrews.html

Murray

[V8kid]

Not sure where you get the 32mm figure from. The yoke bores are designed to take bronze cylindrical leadscrew nuts, as opposed to being directly threaded. On my Series 1 BP clone, the original X&Y leadscrews were 1-1/4" ie ~32mm OD. The actual leadscrew nuts themselves were pretty much 39mm OD and the DFU2505 ballnuts are 40mm OD, so I only had to bore the yoke bores out about 1mm on their diameters.

As for fixing, there's really no need to use all 6 holes. I only fitted two M6 screws and there was enough meat for me to drill and tap the holes. If you look at the tensile load that would cause an M6 bolt to fail, you'll see that this wouldn't be the first link in the chain to break.

Here's a bit about the actual boring: https://mightyshiz.blogspot.com/2018...or-larger.html

And fitting the thing back on the machine. Note that the Y axis ballnut may foul something (I forget - possibly the knee lift?), which required some angle grinder action on mine.
https://mightyshiz.blogspot.com/2018...allscrews.html

Murray

Excellent thanks Murray I appreciate the work you put into documenting that. I'll spec the end machining myself as my drive arrangements are a little different to yours and whilst I'm waiting on China Post will bore out yoke.

Yup 32mm was a mistake on my part.

Never used a faceplate before fortunately one came with my Triumph lathe so it promises to be good fun.

Cheers
David