Bridgeport power table feeds, AKA more masochism, AKA The Next Big Thing

 The old Bridgeport power table feeds came in several different models.  Mine is the first one they came out with, which is the Model 6F, generation A.  First, right, okay.  Wanna bet the serial number is dumb too? 😂

So this beast consists of...

1. The motor/control assembly:

elegant, wot? >_<

 Note the shaft passes through (as it does with all power feeds) for the handle and dial.  This will come up later.

 This unit contains the oil-filled gearbox on top - note sight glass - and below that, the electrical box with a speed control knob and a fast-traverse switch.  The motor is at an angle behind it.  Why at an angle?  Who knows?  Perhaps to make it less obvious and so make the whole box less bulky looking... maybe.  Maybe it was just convenient.

  The direction lever passes through the gearbox (where it engages or disengages the motor) and enters the electrical box on the bottom via an o-ring, where it actuates forward or reverse motor directions.

 The motor is of the "field-wound DC" type, which just means it's a normal commutator-and-brushes DC motor, except the field is provided by a separate winding, not permanent magnets.  Any DC motor drive will have a field output, usually adjustable as some percentage of the line voltage.  So there's an extra pair of wires going to the motor drive box.

 The limit switches are also wired back to the motor drive, which means that fat cable between the two units has a lot of wires in it.

 The reason any restoration job is so dire is that Bridgeport, in their infinite wisdom, put the gearbox above the electrical housing containing the switches and speed knob... the gearbox full of oil... the gearbox full of oil with 1970s (Buna-N? Neoprene?) O-rings and seals.  So of course oil leaks into the electrical box of the motor assembly, slowly destroying wire insulation (because why would you use oil-proof insulation in an oily environment), the potentiometer, and most likely the pushbutton and limit switches too.  Well, at least I have the PB switch on hand.  Oi.  I mean oil.  I'll likely need to order microswitches (there can be only one brand - Cherry - are they even in business any more?) and the pot.  There is sufficient extra cable I should be able to just cut off the dried and cracked wires, and cut it all back to where the wires are flexible.  I hope.

2.  The motor drive (electronic PCB) is located in a separate box, mounted to the column:

could they locate the power switch
in a more inconvenient place?!?

The electronics are from 1972.  That's too old for the aluminum electrolytics in it, for starters.  It's possible other things are wrong too.  The stud-mount SCRs and rectifiers are obsolete as hell.  OBTW, it plugs into 120, doesn't pull much current.

 None of that matters because, ta-da! this kind of motor control is still needed today, so suitable drop-in motor drives are available (I like Minarik, not sure if still in business) for $50 - $100 new, cheaper used.

 Instead of external limit switches, it has a moveable rod mounted on the table, with adjustable stops on it, which in turn pick up a whatchamacallit (named Fred) on the saddle when the limit is reached.  That fixture also provides for physical stops mounted in the front t-slot.

in lieu of any guidance from
Bridgeport, I'm calling that
thing 'Fred'

 One end of the rod is attached to the direction-selecting handle on the power feed. When the rod is moved by Fred, it pushes the handle toward center-off.  The actual switches are inside the electrical box.  That shaft through the gearbox into the electrical box always ends up leaking oil (after thirty years or so) through its o-ring seal, because all they had in 1972 for oil seals was neoprene or Buna-N (AFAIK, plz correct me if I am wrong).  Both exhibit aging (AFAIK).  Viton does not.

The other end of the rod used to hang out into free space, which bugged me until I fabricated a little support for it, which is mounted into the front t-slot.

 "Why not just replace the funky old Bridgeport power feed with a modern Servo or Chinesium Servo clone?"

 That was my first question to my benefactor, from whom I purchased the mill at a steal.  Despite being a professional machinist and tool & die maker, he hadn't gotten it done in a lot of years so I figured Something Was Up.  He patiently explained that Bridgeport, in their infinite wisdom* - again - had made the end of the lead screw shaft differently, depending on if it was with or without a factory power feed. 

 All of the aftermarket power feeds are designed to "drop in" (with some fiddly work with shims) on tables that never had a power feed.  So none of the aftermarket units will fit the shaft of a Bridgie that did have a factory feed on it.

 My benefactor had already started on an adapter to help with this.  I have it, and it still needs a spot of work including some broaching for a key.

 However, I looked at the whole situation, including the fact that the drive itself was Tango Uniform, and decided the shortest path would be to rebuild the factory unit; rebuild it mechanically, replacing o-rings and/or gaskets, and of course replacing the actual motor drive electronics as well.

 The new board being smaller than the old board, it will fit neatly inside the stock enclosure - In fact, that's where it's been stashed for years, so it wouldn't get lost or broken knocking around the shop.  I have written destructions from someone else who did this, including illustrations, wiring diagram (!!) and the like.  The case I will sandblast, paint an approximation of Bridgeport's gray, and once baked, re-sand the raised letters like new. 

(pro tip: good quality industrial paint, oil resistant and
rust-preventing, such as Rustoleum's "industrial" line,
takes one hell of a long time to fully harden enough
to be sanded.  It will feel hard and dry to the touch,
but will prove gummy when you try to sand it. Either
bake under heat lamps or bake in direct sun on a warm day.)

~≈{👁}≈~

 Okay, so I'm still working on the outriggers for the hoisting cart, and those are mostly waiting for money and steel, as usual.  But once that's in the bag, this is The Next Big Project.  I might actually have to write down an order of battle for this one instead of just winging it with most of the stuff kept in my head. That trick only works on really good days, now. >_>

________________________________________________________
* get used to that phrase, you'll be reading it a lot in this blog.
I love my mill, I wouldn't part with it, and I'm impossibly grateful
to the friend who made it possible... but man, Bridgeport made
some odd design decisions.

peening for the fjords

Oh dear, he's off polishing his crank again.

  I observe that there a lot of dings and dents in the (mill knee lift) crank handle that I want to polish.
It's in front, the machine is from 197, the handle is mild steel, it's constantly right under the mill vise, so that's  to be expected.

 I have decided to diminish some of the worst dings by peening.  For those just joining the class, dings and dents raise the material around them, cuz for there to be a hole, the material has to go somewhere, after all.  If we carefully smack the material around and over the raised bits, starting at a short distance from the hole and moving inward, we can damn near erase the hole's existence (almost, not quite) faster than a denounced general could be removed from a Russian propaganda photograph.

(before peen)

 Really, it goes rather quickly, only light taps are required (just a lot of them), but in this one case, this bloody handle is covered in dents, and I am not going to do them all because arthritis, patience, and madness. 😱

  Nevertheless, doing the most egregious divots will markedly improve its final appearance, once I get around to the cleaning and polishing stage.  "Cleaning" in this case means using a very coarse grade of polishing compound first, which actually cuts, and will further smooth the edges of the divots.  Then I go straight to the finest grade I have, skipping the ones in between, for final polishing.

(after peen)

 This is the last handle and dial on the mill.  The dial graduations and surfaces need to be righteous on this one, because it is the only (thousandths) dial I actually use and my failing, cataract-laden eyes need to be able to read it.  The other axes are covered by the DRO which of course can be read from across the room.

 Hey I wonder if older machinist/hobbyists could get a DRO covered as supportive medical equipment? 😂

 

(see? perfectly normal)

  Also, for some reason, this handle (saddle or X axis) is not like the other two (table or Y axis) handles.  This handle mounts perfectly normally, with a keyed shaft, a key, and a nut. Simple.  What you would expect.

 

 

 

  What I didn't expect were the table handles. The table handles mount over the shaft with a thin bronze bearing between, a floating pin transfers torque from the handle to the shaft via a hub.  This adds more slop than was already there, but the dial remains locked to the screw which is what matters.  Then the handle is retained with a spring, which is fully compressed (?!?) and retained in turn by a beveled washer and a nut.  Odd.

 All I can think is that the pin is very soft and sacrificial, because this thing came with a factory table power feed, and if the handle hits something while turning, you'd prefer not to tear up the gears inside the power feed.  Trust me, you don't want to open an old Bridgeport table feed unless you absolutely have to.†

 My guess is that those are meant to be shear pins.  Except they are a quarter-inch thick and a file test suggests it's mild steel not leadalloy or pure aluminum or brass or anything else soft, so I don't figure they're gonna shear no matter what happens.  Maybe someone got tired of the right thing shearing off all the time because the operator kept leaving their stool near one end of the table...
You know, I should probably replace them before I forget.

 If I ever restore my table feed, I think I'll use soft (pure) aluminum or maybe as soft a brass as I can find.  Actually brass, because I'd have to buy a length of aluminum and I only need two little pieces 3/4 in long.  Art stores sell pure-aluminum wire for armatures / maquettes, but I don't think they sell it that thick.

 And if anyone reading this knows what's up with those fully-compressed springs, please comment or email me.

_______________________________________________
† I absolutely have to, to resurrect mine from the dead,
but that is going to be another big project requiring a
long series of long posts.  Which I'm starting to get
obsessed with, which means I'll probably start it soon.

 At least I have have the replacement (Minarik) DC
motor drive on hand, but the restoration is nevertheless
heinous.  The original Bridgeport power feed is a bad
/ strange / baffling design.

drat. (what I am up against - and so are you)

 I am not giving you $18 for this hot garbage.  I wouldn't give you $10.  WTH.

your tool paths are shit, brah

 Imagine being so proud of your terrible workmanship that you put your name on the photo so nobody can steal your photo.  spoilers: Nobody was gonna steal your photo, dude.  And this seems to be most of what's available cheap.  Now I'm looking at sellers with much higher prices. 

 If I had a broaching kit I could maybe make my own although I really think it is or needs to be heat-treated a little, and I haven't got an oven. ¯\_(ツ)_/¯

(the cracked one works fine but I want to replace it)

I am NOT 'polishing cannonballs'! I'm naawwt!

  When things slow down in the shop, usually because of money, I always end up finding something to do out there, usually in the morning with my coffee and news on the radio, so even if I only put in an hour every morning, I still feel as though I am "working in the shop".

 Lately, it has been polishing all the crank handles and their dials:

It is nice that one wrench fits almost everything on the mill

  So long as the handles are reasonably smooth so they won't abrade your skin in use, polishing these parts serves no utilitarian purpose.  But against the permanently-filthy table, sadle, and knee, they stand out, and IMNSHO* make it look nicer.  This is just for aesthetics.

 I cleaned the column and turret/ram, and the head, about as much as they can be cleaned, and they do look much better.  But there is no point in cleaning the table, saddle, or knee, because they are constantly bathed in cutting fluids.

Polishing the parts isn't too hard since I own a buffer with a bunch of wheels and different media.

 I did not use the buffer on the actual engraved dial surfaces, because I feared rounding the edges of the engraved numbers and lines.  For those surfaces, I laboriously hand-cleaned them with 0000 steel wool, carefully avoiding the already-too-smooth knurl on one edge, and that resulted in a very reasonable surface and shine, with no visible damage to the engraving.

 I don't actually use the dials on the table since I have a DRO, but I do need and use the dial on the knee lift.

 One very curious thing I discovered was what seemed an overly-complex mounting of the cranks to their shafts, with some springs, no key but a pin engaging a flange with a notch in it... and none of it is shown in the two old Bridgeport manuals I have been able to get my hands on.  The crank is apparently intended to "float" on a bronze bearing on the shaft, even after it's installed and the nut tightened (fully compressing the spring so WTF)  This is either weird shop mods, or I don't have the right manual for that year. (1972)

__________________________________________
* and after all, mine is the only one that counts

the three best mods I made to my drill press

1.  I put it next to the workbench, with plenty of room to swing the table (or head) around.  Not only can one lay long stock on the bench and drill it with the press, there is a vise on the bench...

2.  I bolted it down.  It ought to be nearly rigid and not wiggle, but there is inadequate material and tall webs in the base casting, which flexes some.  I have pondered how much "fun" it would be to fix this problem for many years, and I have done nothing because it looks like an immense PITA.  It's not broke...

3.  I swapped out the set screws which hold the head in place on the column for shop-made T-handle bolts, enabling casual moving of the head around.  But the head is heavy on the spindle side, so don't try this until you have done #2.

man that pink handle is fugly

 I've probably mentioned this before, but I just used it again this AM and was reminded how darn handy it is, so I was compelled to bring it up again.  Of course you can be forgiven for abusing this new feature as  I do, by keeping the head swung out of the way most of the time and using the table as yet another work surface... 😂

 Also, that pink handle has to go, eventually.  To avoid interference with the T-handle, I might install a somewhat longer shaft with a nice phenolic ball handle.

oh just FYI on the creeper wheels

 I added some thoughts about 3D printing some new wheels for the creeper's failing casters:
https://railgap.blogspot.com/2026/02/more-breakage-less-give-damn.html

more breakage, less give-a-damn

  I have a cheapo (Harbor Freight, from before I declared a moratorium on them) mechanics creeper.
It has only been used a few times since I'm not a mechanic, just someone who can't afford mechanics.
I figured the fabric cover would fail first and when it did, I would think about reuipholstering the pads or not.

 I got it out the other day to get under the shop bathroom sink to attack a fitting with a torch, the alternative being the cold tile/cement floor.  Fine.

 But the cheap PVC tires on the casters are starting to crack: 

 

More copies of the exact same wheel are readily available, but a set of six new real creeper casters with PU tires, with the right mounting stud, is north of $40.  I had a Craftsman creeper before this one.  I ran over it with a car because I'm a genius.  >_<

Apologies I haven't anything more interesting to show lately, I've been kinda stalled in the shop, just puttering around.  And the sink still needs fixing, blast it.  Feeling kinda old lately, sorry.

PS, from later: I'm thinking about printing wheels from something groovy like TPU.  I don't have any PU filament right now, but I might get some.  There is still some work to do to get the printer and my limited slicer skills to play well together, and the Rπ really needs a wired network connection, which I am also working on.  I have half a dozen network switches lying around, and I can't find any of the power supply wall-warts for them.  It's like that.  But the printer is printing again, and everything from here on is just gravy and optimization.  And the upgraded heater / hotend / heat break means I can now print the hotter filaments.  I think the hot end needs new fans, which is one upgrade I have not yet touched.  Le Sigh.  Thankfully they are cheap, and I understand airflow better than most of the duct designers (for these fans I mean) on ThingiVerse, but I'll put something together, and I doubt it will cost me more than $20 and possibly some filament.

not "wear and tear", this one was abuse

 To keep busy while broke and unable to push projects, I've been polishing the handles and their cranks, and parts of their dials, on the knee mill.

 In the process, I found this: 

well, shit - also, why are there vise marks?!?

 This is the clutch for the knee elevating crank handle.  I can get a new clutch with a new handle for $16 shipped off ebay or Aliexpress, although the metal on those cranks looks as thin as a prayer. 

 My handle is a little sloppy, but not in need of replacement and a new clutch will help tighten up that interface anyway. So, not the end of the world. But when I first looked at it, I couldn't figure out how it got cracked. It goes inside a close-fitting part and over a close-fitting pin, so it's very well supported, there's no way for a side-load to appear on it.

 Then I looked in the end with a bright light...

 Some ham-handed buffoon didn't line it up with the key and when it wouldn't go in, he forced it.  Probably used a hammer.

😭 O_O I don't... I, I, I can't even.  WHY?? 😱

 This is abuse of a very fine and expensive tool.  The crack made it a bit of a spring fit inside the bearing housing it goes into, but I was able to get it out with skinny 60 year old brute strength and no tools, wooden wedges, etc so I've got that going for me, which is nice.

 Obviously I can't let this go.  Hopefully I can find a replacement that is cheap and also machined from billet, not some HIP / powdered metal BS*.  Mostly what I'm finding so far is handles with the clutch are cheaper than buying a clutch alone.  WTH.  Of course.

New plan: buy the package, sell the handle, now the part I need is "free" minus my time.  »sigh«

_______________________________________________________________
powdered metallurgy from Europe or America I'll buy.
powderered metallurgy from China I will not buy, due to past experience.
But what if they machine it a bit after? Can you tell? I don't know if I can. :(

"There is hardly anything in the world that some man cannot make a little
worse and sell a little cheaper, and the people who consider price only are
this man’s lawful prey." -- J. A. Richards

the secret of steel

 Is no longer at my neighborhood Ace Hardware.  The store is a train-wreck, always, and they haven't restocked the steel rack in a couple of years, real talk.  I could go to other stores, but I was getting a good discount at the old one.  I can't afford full retail prices.  All good things must come to an end. 

 I need just a couple of sizes of flat strap, 3ft - 4ft long, before I can get started on the outriggers for the hoist cart, but I will probably end up with 8 ft or so, from McMaster, we'll see.  For the weight, McMaster's prices are not terrible, last I checked.  The scrap yard is cheaper, but I am still having a lot of pain and I don't feel up to the trip out there.  Heck, I've bought small pieces of steel off of eBay when I found the right price and free shipping.

 We'll see, but I'm done shopping at my old store. My old manager seems to think it's okay to treat me like shit compared to total stranger customers, just because he knows who I am.  Familiarity breeds contempt, apparently.  He knew he couldn't handle the big city, he said he should have moved back to Small Town, MN, but he didn't, and 'the big city' broke him.  Can you imagine how he'd have faired in NYC??

welding nuts inside long tubing

Jer Schmidt has a good dodge for this problem: