Boxford 260 VMC rebuild

[mike-f]

Hello All,

This is a bit of an introduction and hopefully some of the information and pictures may help others faced with a Boxford CNC mill rebuild or update. First an introduction, I am a UK based design engineer based in the UK, I have owed a couple of other Boxford cnc's including a 250 CNC lathe and a a 190 VMC mill. At the time of purchasing the 260 I was using the 190 which is partially converted to Mach3 (manual spindle control). As a matter of course I have an permanent eBay search for any Boxford cnc parts or machines in the hope of picking up cheap tool holders, I was especially looking for an original machine vice. So it was found a 260VMC in very poor condition but complete with a vice and four tool holders. With biding very low it seemed a bargain for £225!

Of course collecting it was a challenge as it would only just fit in my car!











If you are considering purchasing one of these mills be warned they are pretty heavy at around 200 - 250Kg, I was lucky in that the machine was located on a farm and the seller had a forklift to get it into the boot of my car. even then it was pretty hard to get it in. Even harder to get it out at the other end.

My original plan was to strip it for parts like the vice and tool holders and sell the rest. But under the rust and muck it looked like it might make a nice machine.
First the bad bits:-
Rust everywhere, the cabinet was peelings and rusty so was everything else.
Electronics, 1980s drives and spindle. Spindle drive and electronics had obviously blown up at some point!
Other bits I did not know about until striped, Like spindle bearings shot, and very wonky Easy change chuck!

Good bits
Larger table and travel than my 190vmc
Larger ball screws 12mm vs 8mm in the 190
It has a happy ending!

The plan was to spend a few months striping and cleaning, followed by installing updated controls and spindle drive. As it happened it took a year and I ended up doing far more work than I planned!

More to follow.

[mike-f]

The first thing to do was strip down and see what needed doing. The bed ways and head come off pretty easy and most of the rust was on the surface only, The ball screws seemed OK but felt very gritty, so needed striping and cleaning at the least. The milling head is removed by removing the stepper motor and ball screw attachment bracket, the hole lot then lifts off. The actual milling head on the 260 can be rotated to turn the machine into a horizontal machine, with the head being pivoted. Once the slides had been removed the slideways looked pretty good with the original scraping still looking good. The base of the Y axis is bolted and glued to the cabinet and requires quite a bit of force to remove once the bolts are removed. The column is held to the Y axis with M8 screws from the underside, forming a very substantial and heavy assembly! Pictures below.

Attachment 32601
Attachment 32600
Above Z axis drive belt and pulleys
Attachment 32602
Above the Y axis removed showing the ball screw and nut

Attachment 32603
Above the spindle pivot for, which retains the head to the Z axis for rotation to horizontal position.


Above the spindle removed from the head, the bearings are are just deep grove ball races so these will be upgraded to angular contact bearing of the same size.


The vertical column and y axis base removed from the cabinet


Above the stripped out cabinet, waiting for a decision on what to do to it!

[mike-f]

So pretty much after checking all the parts I decided to rebuild the 260, I was originally going to scrap the cabinet as it was rusty inside and out, and also made machine pretty large for my cramped workshop. But in the end I kept it and do think it was the right decision. The plan was to replace all the electronics, replace the spindle motor with a 1Kw AC servo motor, make a new control panel with jog wheel, feed rate and spindle overrides. The controller chosen was a the very capable UCCNC UC400ETH. I had also decided to replace the spindle bearings with 7009 angular contact bearing instead of the deep groove ball races.


It took a few days to totally strip the machine, the main base is held in place with M8 cap screws one of which is hidden behind a cover that run up the edge of the column. With the bolts removed it is possible with large amount of persuasion to break the bond of the glue that seal and holds the base firmly attached to the cabinet.

With all the parts removed I made a start on the spindle upgrade this was to be straight forward and was to start off! after cleaning and removing the spindle first thing was to set up the spindle housing to drill and tap holes for a spindle nose cover, this is needed as the angular contact bearings do not have dust/ oil seals. so the plan was to use "NILOS" sealing rings and an spindle nose cover to protect the Nilos ring and act as an extra protection from swarf, I also decided to fit a Z axis wiper while the machine was apart and the Boxford is only fitted with bed wipers on the Y axis. Pictures below I hope will be useful to someone!

Attachment 32617
Above cross section of the spindle showing the Nilos ring (yellow) and spindle nose cover

Attachment 32618Attachment 32618
Above Z axis wiper, which was 3D printed in nylon.

Attachment 32619

Attachment 32620
Above test fit of a 3d printed spindle cover.

Attachment 32621
Above: completed spindle cover fitted

Attachment 32622
Above: I also added some oil grooves to the Z axis as it only had a 3mm hole at one end on each side.

Below are pictures of the Cabinet parts, clean up and painting.

Attachment 32623

Attachment 32624

Attachment 32625

Attachment 32626

Attachment 32624

Attachment 32627

Attachment 32628

Attachment 32629