Sad Bantam

The Colchester Bantam didn't come out of its storage / exposure in best condition after its time under canvas while the garage was being constructed. I had to move the machines during the Winter for various reasons, even though the garage was little more than a concrete pad at the time. Despite being covered by large tarpaulins, I knew they would suffer some surface rusting. I coated some of the surfaces with WD40 etc but it was never going to be pretty.

Both the Bantam and the Bridgeport clone look pretty nasty but I'm reasonably happy that I can recover most of the damage. My preferred technique is to use a vibratory sander with a green pot scrubbing pad - these pads engage with the "hook and loop" base on the machine. I have a cheap and nasty one for this purpose and keep the better machines (Makita etc) for clean work. When lubricated with WD40, the rust comes off fairly quickly and wipes down with industrial tissue. And being fairly benign, the actual base metal is hardly touched by the pot scrubbers. That's the theory anyway. Besides, my machines are hardly in pristine condition.

It's pretty quick and easy to remove the cross slide by simply winding it out to the back and then lifting it off. And the top slide unbolts by removing 2 bolts. This approach makes it much easier to clean off the flat surfaces and clean out loads of swarf and crud at the same time. Most of the other painted(?) surfaces clean up with WD40 and tissue.

This is what the cleaned up machine looks like - somewhat improved: 

I also have a Multifix clone toolpost to fit to the topslide. I bought this from Create Tools in China at a fraction of the price of the Swiss original, yet it seems to be well made and certainly good enough for the likes of me. For the Bantam, the "A" size is the best fit. Naturally it's not supplied as a drop-in replacement for the Dickson system, so some work is required. The bush st the top of the hold-down bolt is soft and can be machined out (drilled) to 16mm to clear the 5/8" stud. I did that on the Blidgeport, using an edge finder and the DRO to locate the centre of the hole accurately. You can see the state of the table in these pictures - I'll sort that out later....

That leaves the location bush at the bottom of the stud. This locates the bore of the toolholder body into the cross slide body. I'll need to reassemble the machine before I can turn down the original bush to the required 20mm OD.

 You can see how the stud assembly is held in a large tee slot in the top slide and located there by the location bush. The large diameter register that pokes out the top fits into the bottom of the Dickson body (the funny castellated thing at top right) but is too big for the new Multifix body (the splined cylindrical thing sitting on the topslide).

 I need to machine a location bush to fit in the 20mm bore of the Multifix body, leaving a sort of top hat shape. Found a suitable piece of steel, clocked it up in the 4-jaw and turned it up, drilled it out and parted it off. Or I would have parted it off if the insert hadn't jammed in the slot. I don't have any coolant and wasn't feeding any WD40 on it, which might not have helped. Used the hacksaw and then faced it off instead. 

It started out nicely enough....

When the parting tool jammed, the work slipped in the 4-jaw. Gives some idea of how hard they can get stuck.

The register ended up almost exactly 20mm, so was an excellent fit in the Multifix body. I find that I can use the micrometer dials on the cross slide and get a very precise and consistent diameter. That's handy, as carbide tooling prefers to take a decent cut, like a couple of mm at once, so if you play your dials right, you can pretty much end up bang on target in one decent final pass.

I finished by chamfering both the bore and the outer edge of the location feature with a boring bar. To avoid having to change the angle of the tool after chamfering the bore, I simply move the tool behind the centre line and turn the spindle in reverse to chamfer the outer edge.

The end result - a tap fit into the top slide and a tight sliding fit into the Multifix body. One of my better efforts, then:

So that's that then. I'll have to set up all my lathe tools in the new holders of course.

The final plan is to replace the topslide with a solid block. That way you lose the ability to do things like chamfering by feeding the tool at an angle, or feeding a threading tool at 29 degrees etc. But on the other hand you gain in rigidity (for operations such as parting off, where insufficient rigidity can result in....the tool jamming). For that approach I will need to make a large-ish block that locates on the central spigot and is held down either by the existing fixings or by some new ones. I don't mind butchering my machines by taping extra holes but there again, the Bantam cross slide is peppered with all manner of holes as standard. These are for things like rear toolposts and the gib adjusters but certainly a few extra won't do any harm. Anyway, that will have to wait for now.....