Bridgeport wiring for VFD

[Richiew]

@6ply is putting me to shame with his mill, so I thought I'd better get on with mine.

Earlier in the week, I removed the knee elevating shaft. It was a struggle but got there in the end. Some oil on the outside of the bearings will be applied when it goes back in. The ram and head also rotated out of the way no bother on the second attempt. I did wash the rusty ring down with WD40 which might have helped.

Time to remove the knee with the engine crane. The mill is on a pallet so the engine crane needs elevating to match. I started with this pallet below. It's rather flimsy, gappy and too low. Fortunately I have loads of dismantled pallet wood to beef it back up.

Two opposing layers of 3/4" boards screwed down later and we are here.

This is as high as I managed to get it today. The crane is at max lift. I can probably get the knee to clear the ways if I can shorten the lifting strap. It's only a couple of inches and I can pad out the area where it is wrapped around to remove some unwanted length. I know straps shouldn't be used like this but it's nowhere near capacity.


I can probably flush out and clean the ways in a satisfactory fashion as it is shown in the picture. The ways seemed fairly clean. I think all the chips and swarf are concentrated near the gib space and I could run some cord up and down there to clean it. It would be nice to properly clean up that horrible rusty patch between the ways, mind.


If I did get the knee clear I'd have very little room to manoeuvre in the cramped space left so it may be unnecessary. If I did remove it fully then the pallet would need turning 90 degrees first so there's more room to withdraw the crane back over.


I've lowered the knee back down and left it resting on the lifting column for now.

 

[Agroshield]

I can probably get the knee to clear the ways if I can shorten the lifting strap.

For use with an engine crane, a 10mm dyneema soft shackle is a good investment. Remove the hook and three chain links and wrap the shackle around the bolt. It gains you some height.

 

[6ply]

I'm sure you'll manage to lift it high enough somehow, but how will you wheel it out of the way with that crane on the pallet? I'd be tempted to host it up towards the rafters and then scoot the mill away on a pallet truck if that's possible?

 

[Agroshield]

I'm sure you'll manage to lift it high enough somehow, but how will you wheel it out of the way with that crane on the pallet?

Once it is off the dovetail, put a piece of sheet metal against the column and let the knee down again until there is no weight on the crane.

 

[Richiew]

If I turn the pallet around there may be enough room on the pallet to pull the crane back some and lay the knee on some boards laid over the crane legs. The pallet is 31" in one direction and 48" in the other. I have plenty of wood to board out some more floor if needed. The floor space is probably the issue. May run out of room first.

I'll have a measure and see what's what. It won't be the end of the world if it doesn't come off. I can clean mostly what's needed when lifted high as shown. I have loads of brake cleaner to dissolve away the rubbish and grime.

 

[Richiew]

I could remove that lifting screw and lay the knee down like Agroshield says.


It's only four bolts. What's another thing to dismantle?

It's good to discuss these things isn't it?

 

[Richiew]

Set up ready for another day, cos I'm not allowed to spend all Christmas day in the garage.
Remembered the wide angle lens this time.

I don't think there's any need to remove the knee post. I'll set the knee down on boards on the crane legs once the crane is pulled back.
It's not complicated, I'm just short of room to manoeuvre.
Merry Xmas.

 

[Richiew]

The knee came off today with no drama. I did this on my own, the previous failed attempts helped as I knew what to expect. Practice runs, so to speak. The ways were very well lubed to prevent any damage, sticking or scraping.

The part of the knee that the strap was wrapped around was padded out with some pieces of wood which gave a greater circumference for the strap to get round. This meant there was less strap remaining to poke out the top and finally gave me the height I needed.

All the filth to remove. You can see a tiny bit of wood showing between the strapping. I had four 3/4" boards in there. The bottom board was drilled to make clearance for the threaded top piece of the column which sticks up a little.

This is the part that locks the knee by pushing the gib tight against the ways. It is ever so slightly proud so gives me confidence that the knee lock can be sorted with some shimming of the gib.

The oil holes on the flats of the ways didn't look too bad but the inner ones on the inside of the vees on both sides were blocked. Makes me glad I've made the effort.

A poke with a small Allen key and and a blow though with the air line and we have daylight again. I must remember to properly clean out those cuts too.

Oil fitting removed. Cleaned out, looking from the side towards the middle.

A wooden trolley and some boards over the crane legs.

Ever so gently down. No bother.

Didn't quite all go to plan. That will teach me not to poke around and try cleaning everything. Rude words may have been uttered.

 

[Richiew]

With the protective spring cover removed we can see an awful lot of wear on the knee screw. It's no surprise. This screw has to move the most mass with the knee, saddle and table. Replacement screws and nuts are available. I'm going to leave as it is. It only has to raise and lower the table. It should be all locked solid when milling so the wear is neither here nor there really. I think.

At least the screw got a clean. Plenty of grease and chips were stuck in top few threads which don't seem to get used judging by the lack of wear.

The screw cover went back together fine, start at the inner end and work your way up. Everything on this Bridgeport has been really easy to work on. They are very simple machines. Well, at least the bottom end has been. The 2J head will probably have something to say about this. I've jinxed myself now, haven't I?

I don't have OCD but this rusty patch was bugging me. I gave it a quick wire brushing and masked it off.

The Ambassador's reception was an expensive do this year so I'm reduced to using the last of my pound shop primer. I guess it will stain something rotten if any oil gets near it. Will have to think about a top coat that doesn't clash or stand out too much. The primer dries pretty quickly.

There's a right old primordial soup going on in the base. It feels like a bed of chips settled in the bottom with a couple of inches of oil and goo. Lovely.

A bit of industrial archaeology pulled out of the base. Some ad hoc filter I think.

I'm running out of rags...

 

[Agroshield]

Replacement screws and nuts are available.

An old trick with a worn lathe leadscrew was to turn it end for end so the unworn part would be used.

I wonder if that would work with a knee screw: it would get most of its wear from raising the knee, so the thread flanks on the other side should be reasonably good.

 

[Richiew]

It's too dark but will have to do. Can always overpaint later, plus it's mostly obscured by the knee.

This is the bearing that sits on top of the knee screw.

Cleaned out some and thick oil applied to see if it might get past the seal. The bearing is "Not great, not terrible.". It doesn't work hard though so it's staying where it is.

Bevel gear teeth cleaned up nicely with an old nail brush. I think the bevel gear has been replaced at some point, otherwise it has done the same work as the knee screw but looks much better.

Little bit of chewing on the teeth but good all the same.

Starts going back together tomorrow.

 

[Richiew]

Halfway back together now. Knee and saddle back on. Knee crank and Y axis screw installed. Every moving part has received a liberal dousing in ISO68 way oil. The knee went back OK. Was glad to have two lifting straps as the original got caught between the screw end and the knee bearing. I could lift it off again, but as the tension was on, the strap could not be moved to one side to clear. I had to set it down again on the column, release the tension, and then rig the other strap to lift and clear the original strap. They have done good service but should really go in the bin now,

Remembered to fit the wiper plate before the saddle.
It's all looking rather clean in there.

I think the Y axis screw is a recent replacement. There's no obvious wear, and there are some shiny electro-pencil markings on the end that don't look 40 years old.
This is the middle of the screw.

It feels like my mill now that I've cleared everyone else's crap from the moving parts.

The next job will be a crafting session, cutting the felt wipers and cutting the shim for the knee gib.
After that, I will have to summon the strength and courage to slide the table back on.

 

[Richiew]

Popped in the garage and found this lurking in plain sight. The other day I absent-mindedly wondered why the gap was so big but told myself the table has to go on yet.

If you're keen eyed you can see it resting on the tail end of the ram in the previous post. It is face on, so not easy to spot. I didn't.


Y Axis screw needs removing again, unbolt the nut bracket, remove the saddle and fit.

 

[Richiew]

Well, I've jinxed myself and learned a few things along the way.


First of all, I understand the oiling system on the nut yoke/bracket a lot better now. The oil feed nearest the mill column feeds through a hole in one of the nuts and effectively lubricates the x-axis screw. The oil tube on the front feeds through a gap between the two nuts and runs to the oil channel that feeds the lower y-axis screw, albeit a little indirectly. Consequently, when I'm removing one of the lines to feed the y-axis screw directly it's important I reroute the correct one.

I've found out why the knee won't lock or at least one of the reasons why.

On the left of the picture below is a new knee lock plunger. It presses directly onto the gib. The new one measures 0.850" from the base to the top. The one on the right was removed from the mill along with the matching wear spacer. Together they measure 0.753".

To be fair, the new one is oversize. It was trial fitted but couldn't get it flush. Presumably made that way so it can be turned down to fit exacty?

It's probably less trouble to make the old one fit. I should have removed it and checked before blindly ordering the new one. There's a lot of wear on the spacer so the first thing I'll do is flip the spacer around so the wear is on the inside. It might reduce the clearance enough to get it to lock. Can always create more spacers of varying thickness to fit if needs be.

Below shows the knee lock lever with the small cam on the end which has created the wear.

Broke my gib.

The top of the screw notch snapped off as they like to do.
Am really upset with myself. They break surprisingly easy with few turns of the lifting screw when they are jammed. Lesson learned. Lots of people have done this. Got quite off lightly. Took me about an hour of faffing on to get it unjammed. I'd already read all the horror stories beforehand so had a right panic on when it happened. Managed to hammer it out, up from the bottom with a punch and wood block. Was upset with myself as I had the whole bottom end back together with the table back on and everything. Was just trying to sort the knee lock and probably overshimmed the gib. I didn't know the knee lock plunger was worn at the time. The gib wear was hard to measure but seemed worst at the top with a minium at the narrow end of the taper. I shimmed for the wear at the top and I think it was too tight for the small end.


There's some quality Dormer taps on order and some fresh drills. It's getting tapped M5 which is broken tap territory in my books so I don't want to take any chances. The gib needs repairing and fitting in place before I can look at the knee lock plunger.

This is the reverse side of the same gib before the notch broke off. You can also see where the plunger acts on the gib too about halfway down.

 

[Richiew]

Was very apprehensive about messing up the gib further trying to repair it, so I left it a while. It's cast iron and turns out that it drills and taps really nicely, so needn't have worried. I did some practice runs firsts and settled on drilling out to 3mm and then 4.2mm for the M5 thread. I thought this was a good idea as any drill wandering on the first drilling wouldn't matter and it would be a quicker and straighter operation on the second drilling as there's less material to clear. It all seemed to work ok and I can always drill out for an M6 thread if anything goes pear shaped in future.

This lump needs milling into an L shape to drop down into the gap. There's plenty to remove. Might be here a while.

Some split conduit to contain the motor wires. The wires had suffered from abrasion over the years. Not sure whether they were rubbing against each other or against the aperture through the motor case. Regardless, there's less room for movement now with conduit in there too. The wires hadn't rubbed through in forty years so I think they'll manage for the duration of my ownership.

A second earth wire was attached to the spare screw hole on the aluminium case. I have good continuity back to the far end of the earth wire from everywhere over the mill, from the base to the top cover. The paint and filler is a good insulator, mind.

Continued...

 

[Agroshield]

This lump needs milling into an L shape to drop down into the gap.

Is there anything stopping the 'lump' rotating on the securing screw? If it did happen to rotate when in use, would it cause any problem?

 

[Richiew]

Is there anything stopping the 'lump' rotating on the securing screw? If it did happen to rotate when in use, would it cause any problem?

I can get a dab of braze in the broken off corner to help prevent rotation. Once it is clamped down though there's nothing to make it rotate. It sits in the Vee of the column ways. Wouldn't want it to move and rub I suppose. I could chamfer the lump where it meets the gib and put some braze in there too.

I've seen examples of people using two screws but I wasn't comfortable with the limited room for drilling and tapping.

 

[Richiew]

I'd been warned before buying that the quill spring wasn't working and I'd bought a replacement in anticipation. The spring cover was removed today. The spring was missing and the pin that the spring sits against was sheared off.

I did some more research and weighed up the cost/benefit analysis for fixing the thing against breaking it more like I've done already. The quill pinion was fairly simple to remove in theory and I'd already bought the spring so I thought I'd have a go.

This is the other side. Cover and clutch have been removed. The pinion has been punched out. It came out very easily. There was a very awkward circlip that wouldn't shift. The two holes on the clip were tiny and I couldn't get the circlip pliers on it. It gave way without breaking so it can still be reused on reassembly. It shows in later pictures.

There's the circlip. The holes can barely be seen. The pinion gear and surrounding area was covered in grease and this spare woodruff key was found in the gunge. I think it was the original one from the shaft. I expect it was "lost" and replaced as no-one looked through the grease to find it. There's a lot of wear on one side but it doesn't matter. The other end sits in the brass bearing and that side is fine. The worn side accommodates the spring and I presume a broken or loose spring was rubbing on it for a long time.

This is what's left of the spring retension pin. I had looked it up online and they are a push fit so I thought it was worth trying to drill it out/pull it out somehow.

Success for once. Was overdue for some good fortune.
It was punched then initially drilled 3mm. The 4mm drill pulled it clean out while drilling. The pin is 3/16" Looks like I'll be making one on the lathe.

This what it's supposed to look like.

This is the spring waiting for it once fixed.

 

[Richiew]

Managed a little repair today.

I lost my first attempt at a pin trying to shorten it with flap disc. It slipped out of the vice, propelled at great speed, never to be seen again.

The second pin was turned up much quicker. EN1A steel. I kept overshooting the diameter trying to make the first one.

Just waiting a for a slotted spring case to arrive in the post then it all goes back together. One of these below.

The Chinese spring I have seems a little too large in diameter to fit in my original spring case. The retaining screw is also missing. The slotted case looks easier to put together. I could have cut the original case but didn't want to butcher it in case it doesn't work out.

Looking to wire up the VFD over the weekend and get the gib repair sorted.

 

[Richiew]

An few updates.

The VFD got wired up last week. I didn't want to test run the motor until the quill was back together.

I milled and ground the gib repair piece to shape. My idea was to make is slightly smaller in every dimension so that it doesn't rub on the ways. It's only there to allow the screw to jack the gib out. The piece was milled to shape and once I thought I'd got there I used a flap disc to smooth the sharp corners and put in a chamfer for a dab of braze or two.


To the Marlow mill.

Starting to get there.

Smoothed off and chamfered.

I left it a few days then put my brave pants on and brazed it. Totally overdid the brazing. It only needed a couple of dabs to assist in stopping it from rotating but I had my welding head on and filled all the gaps. A mistake I wouldn't repeat in future. I think I have got away with it. The gib is still flat. The screw is there to hold the two pieces together. I doubt the braze has much mechanical strength in tension.

The knee and table can start going back together now. I couldn't face building it back up with that worn screw, so on payday I splashed out for a new screw and nut.



A lot of money, but it won't wear out in my lifetime with the work I'll put it through, so I'm taking the long view.

Bridgeport are no more, and I'm not sure who makes the parts now. The new nut is not counter sunk for the allen screws. so longer bolts are required. Also a lubrication screw hole is missing. The old one was blocked and full of chips, possibly contributing to the wear. Either way it wasn't being maintained correctly.

Continued...