Power feed for a DW mk 1 mill

[Robin teslarParticipant @robinteslar]

I recently acquired a treasured Dore Westbury mk 1 universal Mill. I felt that I would like to fit some power feed to the table as per Mk 2. Not much information available. Can anyone shed a light on the reduction ratio needed. DW recommends a 2800 rpm 50W motor for their kit and hints at a double worm reduction gearbox. It has a 3 step pulley shown on the motor as well

Any suggestions pls

Also I am considering stepper motor approach as I would like to digitise my mill, which seems a popular thing to do

Looking at Ebay, not much product info on show so I am a bit bewildered

I suppose I could knock up a gear train given time, but I don't want to be one of those machinists that spends all his time making gadgets for his machine. I want to do some real work – if you get my meaning

Any pointers or links much appreciated

Cheers

Robin

[Robin teslarParticipant @robinteslar]

Any suggestions

[Ian S CParticipant @iansc]

Robin, a cheap non digital drive can be made using a windscreen wiper motor, with the worm wheel shaft extended to take a sprocket, and a bit of bike chain to another sprocket on the milling machine. These motors will take 18 volts quite safely. Thats what I use on my Rexon mill / drill, only took a couple of hours to knock it together, I was going to tidy it up, but that was about twenty years ago, so it's still pretty rough, but it works. Ian S C

[john fletcher 1Participant @johnfletcher1]

Better to use a window up/down motor/gearbox which are are slow speed and are designed to work in reverse,some wiper motors are not reversable. I made up a gear box using ex photo copier gears and made a dog clutch. In one of the earlier copies of MEW was a really useful low voltage motor speed control circuit. So, that gives me forward/reverse, speed control and fast traverse. Like Robin mine has been working 20 plus years. Robin if your mill is an RDM 350 I have several 1970's Model Engineering articles which list a series of mods to improve the machine. 5 years ago I fitted a pre owned inverter and 3 phase motor plus a fly wheel which has made things smooth. Finally, Robin have you ever had the column to pieces/out.Ted

[john fletcher 1Participant @johnfletcher1]

Sorry fellows I got the names mixed up.Ted

[AndyfParticipant @andyf]

Robin,

The reference to a double worm reduction drive probably stems from the articles in MEW issues 14, 15 and 16. Those dealt with a power feed for the Westbury miller, which was redesigned and improved into the DW Mk 1, but having read the articles in the digital archive a week ago, I think the design would go on a DW with only minor modifications.

I too have a Mk 1, but that design looked a bit complicated, with its two worms, universal joints and telescoping drive shaft. I'm very slowly concocting a power feed on somewhat simpler lines. The basic idea is to put a cheap £9 Chinese 12V gearmotor (looks very like those supplied in the UK by MFAComo) with a 120 or 148:1 (I forget which) ratio in a housing of aluminum square tube. The tube will be attached to the rear sloping side of the tray-like feedscrew bracket using a good quality door hinge. A plate will be fixed to the front of the motor and tube, and will extend far enough to carry a stud with a Mod 1 32T idler gear, in permanent mesh with a 48T on the motor output shaft. I have trued up the 1" diameter boss on the handwheel, and bored out a 60T gear to fit on it. The general idea is that the whole motor/32T idler assembly can be swung on the hinge to bring the idler in and out of mesh with the gear on the handwheel as required for power or manual feed. The motor will be under PWM speed control, with an electro-mechanical control system, including autostops like Mike's shown here , which allows for slow travel in either direction for cutting and a quick traverse back at the flick of a switch, without altering the speed control. The control box will be attached to the LH end of the table; there isn't room for it at the handwheel end.

The gears came from Technobots, but have had to be reduced both in thickness and in length of boss to get things to fit between the dial and the handwheel. Indeed, the idler has no boss at all.

Andy Franks

[Robin teslarParticipant @robinteslar]

Hi Andy

Do you mean this one

technobotsonline.com/re-385-metal-gearbox-148-1.html

Am I right the stall torque is 62kg-cms? Surely that would twist the shaft off? Mybe it needs a break away clutch to limit damage?

technobotsonline.com/panel-mounted-bi-directional-variable-speed-regulator.html

Is this the regulator?

It all looks very neat

So you get slow and fast traverse by a switch applying full voltage (and reverse), bypassing the speed control knob so you don't change the cutting speed – is that right?

Cheers for the tips

Robin

[AndyfParticipant @andyf]

Hi Robin,

My motor is similar to that, but bought on Ebay, direct from China.It's a bit like this one , though with a much longer motor. The specs at Technobots are hard to find, but it may be that the one you refer to is 25mm diameter (27mm across the plastic shroud which covers the gears) and with a 4mm output shaft. Mine is 35 mm and 37mm with a 6mm shaft, and (like the one I linked to), the shroud is metal held on with screws, rather than a push-on plastic thing, and has six M3 holes on the end of my shroud, so the motor can be fixed end-on to a metal plate, whereas the MFAcomo ones come with a useless thin, bendy 1mm thick bracket (I know, because I bought one from Maplin). Being able to fix to the shroud means the motor is restrained by being attached at its torquey end.

I can't comment on torque, but Mike finds his to be perfectly adequate. Something like crashing the spindle into a badly positioned clamp would probably make the motor tear itself apart. If there was room for one, a breakaway clutch wouldn't be a bad idea. A wooden key fixing the 60T gear to the handwheel might be easier to implement.

For speed control, I will be using a Velleman PWM kit, built some time ago. Mike used a Maplin ready-built one. The Technobots one has an on-board reverse, but that would be pointless in the circuit shown on Mike's page. There, SW1 sets the cut direction, either to the left or to the right.. SW2 (which is centre-off) sets the cut in motion, with the motor's speed regulated by the controller. When the table opens the limit switch at the end of the cut, the motor stops (very quickly, because its terminals are shorted by the relay). With the limit switch open, the motor cannot restart in the cut direction; it will only start in the return direction, when SW2 is switched over. When that is done, the motor runs at max speed under full 12V power, taking the table back until it opens the other limit switch, stopping it ready for the next cut. Again, it won't restart until SW2 is flicked over for the next cut. To stop the table part-way, either switch can be flicked to its midway centre-off position.

Once the speed for the cut has been set, the speed control knob can be left alone throughout. I reckon that my feedscrew will do about 60rpm on the return, so the table will go about 1" in ten seconds. That's only half as fast winding quickly by hand, but boredom shouldn't set in except on very long cuts.

Hope this explanation helps a bit. Sorry it's so complicated, but you can imagine the headscratching which went into designing the basics of the circuit in the first place.

Andy

[Gone AwayParticipant @goneaway]

I built a power feed for the x-axis of my WM14/16 sized mill using the common home-brew cnc driving arrangement ….. mounting plate, standoffs and size-23 stepper driving the leadscrew via a 2:1 step down using a toothed belt.

I got a cheap stepper driver from China (eBay) to drive the motor and fed it pulses from a regular 555 timer circuit with a pot to vary frequency (speed).

I've since changed to to a "real" power-feed from Grizzly designed for these machines but my home-brew worked well enough while I used it.

[Robin teslarParticipant @robinteslar]

Hi All

This is great stuff, much appreciated, will follow links. Actually while I was looking at PWM motor controllers, I noticed it said "suitable for mini drills etc", then I had another Meldrew moment, ive got all these defucnt nicad drill drivers where the battery has died (and its cheaper to buy a new drill than a new battery pack), So these use 14.4vdc and have speed control in the trigger, lots of torque, variable speed, readymade chuck

Got to try this out on otherwise junk kit

too good to be true?

Robin

[AndyfParticipant @andyf]

Nothing wrong with the drill/driver idea, Robin; I've seen recipes for power feeds on the net which use 'em. They have torque clutches, too, but those are often such an integral part of the housing that you can't really use them. The speed might be too fast, though, in the sense that on minimum speed there could be insufficient torque, so a bit of gearing down may be needed.

Thought needs to be given to clearance around the power feed. Assuming you put a motor behind the feedscrew bracket, it must be held out far enough that is doesn't bump into the X-axis base, about an inch of which is exposed when the table is as far to the left as it will go. Similarly, the "tightened up" position of the column clamp levers may need adjusting with different sized washers, to the motor doesn't hit their knobs. At the other end of the table, where my control box will be, 2" of the X-axis base is exposed when the table is fully to the right, so anything bolted direct to the end of the table will need to be pretty shallow, and allow axis to the T-slot at that end.

Andy

[Gone AwayParticipant @goneaway]

One of the American mags … HSM or MW …. had an article some years ago on using a power drill innards as a power feed.

I do effectively the same to wind my head (of the mill that is) to the top of the column. 18V power drill fitted with a hex socket and used on the retaining nut for the winding wheel. Fast and effortless (just keep your fingers clear of the handle). You can set the drill clutch as a fail-safe too.

[AndyfParticipant @andyf]

Apologies for the typos in my last post. Kipper the cat was tramping on the keyboard and obscuring the screen.

…held out far enough that it doesn't bump…

…so the motor doesn't hit their knobs…

…allow access to the T-slot… (that can't be blamed on the cat)

Andy

[Gone AwayParticipant @goneaway]

Oh, and …. however you end up doing it, don't forget the thing that Andy referred briefly to way up there. You will need to operate the table manually and you will not want a heavy drag on it while you do so. So you need to be able to disengage the drive somehow – either a swing-away or clutch or even a drive belt that you can easily slip off.

In my case, with the stepper/toothed-belt drive, the drag was (just about) tolerable as-is but I did have to fit a switch to open the circuit to the motor windings to prevent circulating currents from braking the motor. Even then, for extended periods of manual operation I would slip the drive belt off.

[Sub MandrelParticipant @submandrel]

I have a small 3V rechargeable electric screwdriver. Far to punyu for real use, but plenty of torque to turn the handle on my mill. I might see if it would work as auto feed.

Neil

[Ian S CParticipant @iansc]

With my lash up, wiper motor drive(old Lucas), when I want manual opperation, The bike chain is very slack, and just lifts off the sprocket. Well worth a try with the battery drill, mount a sprocket on a short shaft in the chuck, make up some sort of bracket on the table, and a sprocket on the lead screw, proberbly 20 or so teeth on the mill, and maybe 10 on the drive is a good start.

My power supply came from an old Xerox copier, and the transformer weighs about 10kg, or more. I wound an extra winding to give me about 18 volts, also to isolate things a bit, the transformer is of the autotransformer type. Ian S C

[BrianParticipant @brian]

Robin, the subject has been addressed by David Haythornthwaite in MEW 118 and 119 and I think well worth a read. Bit of work involved but I will be doing the same for my DW.

[Sub MandrelParticipant @submandrel]

Thanks for the thoughts Ian, but I had a pootle around under the table last night

The X2 has a slot in the leadscrew at the en opposite the handle, ready made for adding a drive, and the end plate on the table just lifts off when the two screws are loosened (makes it easy to clean).

The obvious route is mounting a the gearbox on an alternative plate using the existing mounting screws, with an extended shaft to mate with the leadscrew. Naturally this woudl avoid any need to interfere with the existing handle arrangement.

My main issue might be I like the X-gibs a bit stiff, as I have a predilection for climb milling and using the Y axis to feed while X only applies the cut.

Neil

[Gone AwayParticipant @goneaway]

One thing that people might want to consider with any power feed is what happens if you run into trouble.

Say you jam the cutter and perhaps blow the fuse/cutout for the mill. The power feed is happily carrying on as though nothing has happened. This can cause serious damage – at the very least screwing up the tramming of the mill-head.

I've done this on my setup (commercial power-feed) and I must admit I haven't come up with a satisfactory solution. What really is needed is a circuit breaker that operates from the mill current alone but cuts power not only to the mill but also a second circuit. Come to think of it, it could probably be done with a relay. I wonder if there's anything commercially available.

The reverse problem – the power feed jams/stops while the cutter still runs is not really a problem except perhaps in respect of surface finish and then only on a final cut.

[Ian S CParticipant @iansc]

Sid, I'v thought of fitting micro switches for the feed motor.

I forgot to mention that my Rexon mill has a T slot along the front of the table the the table stops fit in, and the right hand end of this is where the drive unit is mounted, two bolts in a long T nut. Ian S C

[Gone AwayParticipant @goneaway]

Ian, if I read you correctly those would be limit-switches that prevent the table exceeding a certain amount of travel. (Mine is actually running without at the moment since I've used the front table slot to mount the DRO scale …. yeah, yeah – I know )

They won't though, cover the situation where you've just run the cutter into a clamp, the cutter has stalled, the fuse has blown but the power feed is still running ….. nicely twisting the head around on its axis.

[Ian HewsonParticipant @ianhewson99641]

Hi

Using the small Chinese moters, you don't get enough torque to cause damage if you run the cutter up against an obstacle, they just stall.

The Maplins control board seems to stand the abuse also.

No prizes for guessing how I know.

Ian

[Gone AwayParticipant @goneaway]

I don't know what motors you are referring to there, Ian. Car window/seat motors were discussed as well as portable drill motors and I'm pretty sure they would give enough torque to run you into trouble, especially with additional gearing.

In any event, if the motor stalls easily even using gearing my guess is that you'd find the feed under-powered for anything more than very light cuts.

(Does anone else find this editor missing characters when typing?)

[Robin teslarParticipant @robinteslar]

Back to basics and an early belt driven model had power feed and if you ran the travel into a stop, then the drive had a shear pin and you had to go to the foreman for a smack round the ear and a new shear pin. Lovely but seriously cruel old boy who hated stupid boys

[Sub MandrelParticipant @submandrel]

(Does anone else find this editor missing characters when typing?)

So it ISN'T my imagination!

Neil

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