Metric Bridgeport clone dimensions?

[MuzzerParticipant @muzzer]

I have a Taiwanese BP clone which has metric leadscrews etc. There is a variety of fasteners used on it including BSW and metric and I know that many of the key dimensions are common to the original imperial BP design. However, I also know that other parts such as the OD of the leadscrew nuts are definitely non-imperial.

I'm considering making a replacement yoke (this holds the 2 leadscrew nuts and is fastened under the saddle) and I would like to check if the centre distance (between the X and Y leadscrew axes) is the same as the imperial yoke ie 4".

There is a drawing for the Hiwin ballscrew yoke here It's for their ballscrew replacements for std (imperial) BP machines and you can see the critical dimensions such as the axis centre distance, mounting face height etc. Obviously the bore dimensions are specific to their ballscrew OD but it should otherwise be a direct replacement for the original.

Without being able to dismantle my own machine and measure the critical dimensions for various reasons, I'm unable to convince myself I have enough info to draw up my own version of the yoke that will fit my machine.

Can anyone who has one of these or knows them well tell me if the centre distance is the same (101.6mm / 4&quot and presumably the height of the flange (17.2mm) is also unchanged on (most?) metric clones?

Thanks!

[MuzzerParticipant @muzzer]

[John Stevenson 1Participant @johnstevenson1]

My machine is metric but can't help as it's the Warco WM40 which is a clone on steroids and I know for a fact the screws are way bigger than standard in length and diameter so probably the rest is also scaled up, sorry.

[KWILParticipant @kwil]

It might be of interest that the 4 mounting screw centres are imperial.

[MuzzerParticipant @muzzer]

Yes – but of course this is a drawing for an imperial yoke. So my question might be whether the "metric clone" yoke has imperial centres too. It's a feature that could easily be changed without affecting the disposition of the various components. The "metrification" process was obviously fairly ad hoc.

[MuzzerParticipant @muzzer]

Managed to dig out a photo of the yoke and the original split nuts (before I split them).

My problem is that my ballnuts are about 1mm larger diameter than the bores in the yoke. Yes, the obvious question is whether I can simply mount them on the faceplate and bore them out with a boring bar. I really don't fancy making up a replacement yoke, the more I think about it.

I'll need to be able to swing about 135mm radius for one of the bores and about 120mm for the other.

Looks just about possible, assuming that the saddle "ears" don't reduce the swing….

Murray

[Involute CurveParticipant @involutecurve]

Where you at, I could bore it out on the miller.

Shaun

[MuzzerParticipant @muzzer]

Lytham St Annes (= posh name for Blackpool) but this won't be possible for several months, as the machine is at my mother's until we finally move into a proper house. Thanks for the offer Shaun – I'll bear that in mind when the time finally comes if it's clearly not going to fit on the Bantam.

Trying to figure out the remaining tricky bits ahead of getting there – although there aren't many beyond this. But no point modelling and drawing up a yoke if I'm not going to make one now. I think I'll just go for it and if I screw up my only yoke I'll just have to deal with it. That'll teach me.

I'm planning to busy myself by putting the CNC control stuff together in the meantime – servo drives, PSUs, Mesa boards etc to prevent myself going completely doolally here in the armchair.

Murray

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