BUX Magnetic Base, Rockwell drill - repair

[FliesLikeABrick]

I've had an eBay auto-search for BUX magnetic drill bases for a long time, 2-3 years. I've always liked how the casting is shaped, and it seemed like the kind of tool that I might have on hand with no particular project in mind... but it would be invaluable the day that I need it and can reach for it.

One day my autosearch e-mailed me some new results, including one from nearby for $159 including free shipping. It was in need of repairs, but appeared largely intact - including a Rockwell drill/power unit.

I jumped on the opportunity, and upon it being delivered I realized what a bargain I got - indeed a complete unit, and this must have cost $75-100 for them to ship based on weight and bulk.

Here are the pictures that were on the eBay listing:





Dirty, intact -- except for the power cord and the connector from the drill to the base.

Upon receiving it, I took it apart into its major units and gave it the rest of the triage...

• The wiring was all terrible, scary in fact. The switches were cracked and damaged, the fuse holder was cracked and the wires were barely twisted on instead of any positive affixation, the indicator neon was also cracked with exposed power
• The plug that the drill uses to attach to the base for control was missing its plug. Based on the female portion in the base, it was a non-NEMA layout. This is good, explained below. However, it means I would need to track down the proprietary non-NEMA male plug to match, or replace both portions
• The support peg/stud in the back was bent. It had an extra jam nut on it because the original one was seized on the distorted threadform.
• I applied power to the eletromagnet and rectifier. It appeared to work, and held a piece of scrap cast iron I had nearby. This was probably the single most-important test, since almost everything else could be repaired or a replacement made
• The power inlet cord was completely missing
• The number of wires going to the drill indicated it was designed to be reversible, but the switch that was being used to control the power was only wired to one lead - presumably "forward"
• Extremely dirty, and any parts that were ferrous were rusty (such as the handles)

Now time to strip it down to the bare casting for cleaning and inspection of all the remaining parts.

The base casting has only a handful of important machined surfaces, all of which appeared to be in decent condition

• The bore for the spindle that drives the pinion against the rack on the back of the slide
• The flat sliding surfaces for the slide to bear against
• The bottom, where the electromagnet is fastened on
• Lots of tapped holes (for the slide retainer as well as grub screws on the side that adjust the preload on the bearing shims), all of which appear to be undamaged

The slide has a total of 4 bearing surfaces. Two that face forward, and two that face outward. All 4 have copper or brass shims that also act as bearing surfaces. These were pretty greasy and gummy, but not damaged beyond use.

The way the up/down feed mechanism works is similar to a normal drill press -- a pinion gear on a hand-fed spindle; which drives the quill up and down. Except in this case it isn't a quill, it is a sliding motor mount for the drill power unit itself to be moved toward and away from the work.



Did I mention this thing was incredibly grimy and dirty?



Here is the laundry basket of small parts, ready for the ultrasonic cleaner. There are two bronze bushings in here for the pinion shaft, which were completely fouled with grease. I was pretty sure these were oilite, but they were so gummed up that they needed to go in the ultrasonic cleaner to have a chance at being loaded with oil again.





While those were cooking, I took to the casting in the parts washer. About 2 hours spent with picks, scrapers, blue scotch brite pads, etc. It came out very clean:



This is a repair, not a restoration... but I couldn't resist the urge to bring the BUX lettering back to life.

I had a red spraypaint close enough to the original shade, so I sprayed it on some paper and dabbed it onto the raised lettering. This gave a nice "stamped" look where it just touched the high points, instead of me having to decide - with a brush - where to draw the boundary of each letter.



I did spend some time at the vise to straighten out the support peg/stud, so that the original jam nut could be freed and reused. I used some pieces of aluminum and steel off-cuts to brace the part and focus the bending forces in the right areas, which made quick work of it.





One of the last pieces I wanted to tune-up aesthetically was the electromagnet. It was covered in rust, oil, chips, and general grime. I hit it with a wire wheel to knock down the outermost and offensive debris, then took a carbide scraper to the machined flat surface on top





I masked the top off, used the "tap with a hammer" trick to cut the tape to the edge of the machined surface. A quick 2 coats of black paint as well as a clear coat - and that was good enough




Ready for reassembly.

Attachment limit reached -- continues in reply below...

 

[FliesLikeABrick]

I reinstalled the metal retainer plates to the front of the casting, with the various brass/copper bearing shim. The zinc-plated hex screws were not my first choice, but they are what I had on hand in the right diameter, length, and thread pitch. I did later on order more appropriate flat-head screws which I stripped the zinc from, so they would have the right patina for this tool.

These steel plates are what create the channel that the slide moves up and down in. The shims are held in place by some subtle features in the machining of the base, and the order of assembly (such that they do not move out of the top or bottom of the casting).



I did not get pictures of this... but the two bushings were indeed sintered oilite material. I heated them up with a heat gun until water stopped boiling out, then dropped them into a jar of oil.

Once they cooled, I pulled them out and put them on a piece of rubber, to form a seal at the bottom side. I then filled each with oil from the top, and pushed my thumb or palm over them to create pressure and force oil into the pores. I did this until I saw oil coming out the outside of the bushings, meaning I had full penetration through the material. This is the first time I had ever done this, and it was pretty satisfying to see it work.

The larger of the two bushings was not quite a press fit into the housing. I put a few punch marks in the inside of the casting bore to give it some purchase to avoid i spinning over time.

Neither bushing seemed to have excessive wear that resulted in play on the pinion shaft.


The pinion shaft has the hub machined into the end, and slides right in. Nothing special here.



A big nylock nut retains it from the other side


I screwed the handles in, and ordered 3 new ball ends for them from McMaster. At least one or two were broken/chipped, and one might have been missing altogether.



Now time to turn attention to the drill unit itself

I did not want to go overkill on this, but did want to split the case to check that it had reasonable lubrication and do some light cleaning of the brushes and commutator if they were fouled (which they were, somewhat)



The brushes had pretty significant wear, and it was impossible to find replacements. I did find someone that could make custom brushes with a minimum quantity and expense that I am not interested in... but maybe I will order then and put the spares on ebay if they work. Might as well help out someone else who can keep this unit in service but would be forced to scrap it for lack of brushes.

(I contacted Delta/Rockwell and they could not help with locating brushes or documentation)




I put the motor unit back together, and mounted it on the slide using the same brackets it came with, I saw no reason to change it.


To wire the unit back up, I ordered some new 14/5 cable. There are 5 conductors that come down from the motor unit to allow for reversible control - enough connection points from the field windings and brushes to allow the relationship between them to be swapped; as well as a ground. While there are locking NEMA connectors with 5 conductors (such as NEMA L21 series with 3phase+neutral+ground), it would be dangerous to use those on this application. If someone tried to plug the drill directly into a 3 phase power connection with that connector, it would immediately short-circuit at least 2 phases together and blow a connection in the back of the drill, if it didn't trip the breaker fast enough.

I really wanted to make this reversible, since it originally had this capability. A few approaches I considered:

• Don't, just skip this and keep a basic single-pole single-throw switch like they had
• Mount a junction box and double-pole double-throw switch on the back of the motor itself. I had seen this in the way some other models were assembled. Use one switch in the base to control power to the drill; and the switch on the back of the drill to change direction when the power is off
• Mount a DPDT switch in the base. This runs the risk of swapping directions while the drill is still spinning, spiking current and potentially leading to damage of the drill or bit/tap/implement

Noodling on all of that, I liked the 3rd option best, and found the Eaton 7992K10 "Hesitation" switch. If you try to move from one direction to the other in a single motion, a cam inside engages and prevents it. You must relieve pressure in the middle position before moving to the opposite position - almost eliminating the chance of an accidental hard direction switch. This is the normal style of toggle switch on the outside, uses the same mounting hole diameter, and seemed like a slam dunk. I bought one new-old-stock for $30 and didn't look back.

Before assembly I also ordered a new neon power indicator to replace the cracked one, and an inline fuse holder to protect the rectifier and electromagnet wiring.

Unfortunately I did not get pictures of the one machining part of this project -- the aluminum cord grip I used for the back of the motor. They originally abused a NM cable clamp which did not fit the cable correctly, and their cable was damaged.

This aluminum cord grip was in a box of fittings I got at an auction, but was too long to fit nicely in the confined space within the rear of the motor by the brushes. I took it to the lathe and faced the end down to a shorter length. I also used a boring bar to open up the ID, because the 14/5 cable was a very snug fit.









Works great! I made one test hole with it, and later used it to mount a different vise on my welding table.


A couple tasks to circle back to in the future:

• I would like to identify how the chuck mounts to the drill output, so that I might put other chucks on it for smaller bits (this holds a minimum of 1/4 or 5/16) or for weldon shank annular cutters
• Perhaps ordering the brushes and listing on ebay as described above

Here is a previous, similar writeup that I did on the same project. Mostly the same, a couple different pictures and steps written up since these were written from scratch at two different times

https://imgur.com/a/k5FpxLW

Thanks for reading

 

[brino]

The brushes had pretty significant wear, and it was impossible to find replacements. I did find someone that could make custom brushes with a minimum quantity and expense that I am not interested in... but maybe I will order then and put the spares on ebay if they work. Might as well help out someone else who can keep this unit in service but would be forced to scrap it for lack of brushes.

(I contacted Delta/Rockwell and they could not help with locating brushes or documentation)

Admirable attitude to help others.

Years ago when I needed some specific sized motor brushes that I could not find I bought a mixed-lot pile of motor brushes on ebay.
I successfully sanded down oversized ones to make what I needed.
I thought I had posted a picture here somewhere of that lot of brushes, but cannot find it now.....

If you post the size/shape of brushes you need maybe there's something in that pile that will work.
You are welcome to any that would work for you.... no charge!

Brian

EDIT: update I found a link to one picture of "spare" brushes I have:
https://www.hobby-machinist.com/thr...e-and-carbon-brush-sourcing.45762/post-389980

 

[FliesLikeABrick]

If you post the size/shape of brushes you need maybe there's something in that pile that will work.

Thanks. Here are the specs, dug up from the quote requests I sent around. I don't have a picture of my brushes handy, but can pull one and get a picture or confirm measurements if you think you have something that might work

Brush cross-section is 5/16 x 1/2 The brush length is probably 1 to 1.5 inches. This is a spring+braided copper design, with a end cap that has ears. The spring is .400 diameter, approximately 1.5" long spring length. The end cap is approximately .588 diameter, with .486 across the ears.

 

[ConValSam]

It may not be a restoration in your mind, but I'd call it a semi-restoration. Leaving the patina, but fixing all the scary bits makes for a result fit to display; if I may suggest, find a prominent shelf to "store" it.

 

[FliesLikeABrick]

It may not be a restoration in your mind, but I'd call it a semi-restoration. Leaving the patina, but fixing all the scary bits makes for a result fit to display; if I may suggest, find a prominent shelf to "store" it.

Hah. It has its "special place" on the floor behind my main drill press by the door -- about as prominently as I want to place it, given its 78 lbs heft.

 

[brino]

@FliesLikeABrick

Very sorry for the delay.

I have finally checked my bin of motor brushes.
Picture below......
The biggest ones (in the orange holders) are 5/16" x 7/16" and about 1.5" long.

.....so NOT the 5/16" x 1/2" you were looking for.
Just let me know if you think you can make them work.

Brian

 

[FliesLikeABrick]

@FliesLikeABrick


I have finally checked my bin of motor brushes.
Picture below......
The biggest ones (in the orange holders) are 5/16" x 7/16" and about 1.5" long.

.....so NOT the 5/16" x 1/2" you were looking for.
Just let me know if you think you can make them work.

Brian

Thanks for getting back to me. I will try to purchase the ones I had specced out, but if that doesn't work I may have you mail me those largest ones to machine down and try to make fit. The thing that makes me hesitant to try that first is that I think the holder style is too different and may be difficult to adapt via whichever means.