Power feed for a benchtop mill

There are lots of vendors supplying their variations of mills based on standard components produced, and usually assembled, in China. These are excellent value machines, and the few I have used I have found to be quite capable.

The power feed solutions available for the X-axis are all pretty much the same. It looks to me like a power feed design, from many decades ago, has been replicated and then very basic solutions used to adapt the fitting of that design to other mills.

The original product looks like it was designed for a large floor standing Boxford knee mill. This is not ideal for a benchtop mill and none of the attachment methods that I have seen are quite right for my requirements. Therefore, I have designed my own bracket. 

My mounting bracket

I have a Warco WM18 mill but my design, or a slight variation of it, probably applies to similar mills marketed by Chester in the UK and Precision Matthews in the US among other vendors.

The finished result

Position

The main requirement I was trying to solve with my solution was to mount the power feed so that it does not foul the bench or the chip tray of the mill, while also not requiring too much bench real-estate.

Photo from an eBay advert

The fitment for benchtop mills provided by all the versions that I could find use a horizontal bracket held by a rather disappointing looking pair of bolts clamping that to the mill table. The motor is in line with the table so the power feed sticks out a long way, usually to the left of the mill table. I did not have enough space for that arrangement.

I briefly thought about designing and building a solution from scratch, using a stepper motor. I decided that the design of this had some complications to ensure that the handwheels still worked, so for the time being an off the shelf motor with the clutch and controls built-in was going to be a quicker to implement solution. I therefore concentrated on a better method to mount a readily available power feed.

For inspiration, I looked at the way a few others had mounted the feed and concluded that I would prefer to replace the left handwheel and have the power feed motor at right angles to the table and the controls horizontal facing upwards.

Having part of the housing and the controls above the surface of the table may get in the way at some point, but my guess is that if I have something that big on the table, raising it up to avoid the motor is unlikely to be the most difficult part of holding that work.

Typical advert on eBay

Having made that decision, I bought the standard kit intended to hang from the right handwheel of a Boxford mill.

Mounting

My design fits to the left hand end with the bronze gear between the motor and the table. This is the opposite of where it would fit on a Boxford mill.

3D printed mock-up

I designed and 3D printed a couple of possible brackets to bolt on in place of the original end bracket. The result was a bit too large to mill out from a block of aluminium so I opted to weld together some 15mm thick steel plate.

This mounts using the original M6 threaded holes and the holes for the 6mm dowel pins.

My mill has a DRO scale mounted on the left hand side. I adjusted the bracket to maximise the movement of the table, but my design does reduce the table travel by about 50mm. I could probably gain a further 15mm if I moved the DRO scale, but for the moment, I don't need that travel.

Gears

The main bronze gear is supplied bored for a 16mm shaft. The newer WM18 mills, such as mine, have a 17mm shaft with a 5mm key.

I found it fairly easy to mount that gear in the lathe and enlarge the bore. I also pressed in a 5mm keyway.

At a later time during prototyping I cut 15mm off the length of the gear.

I also cross drilled a 5mm hole and threaded for an M6 grub screw.

I bought and used some 17mm ID shims to help position the gear, but these are probably redundant with the grub screw.

Bracket

As mentioned, the larger bracket is made from 15mm and a small length of 6mm mild steel plate. The end mounting plate which the motor housing is bolted to, is made form 6mm steel plate.

Inevitably, the design evolved slightly as the prototype progressed. 

I originally had a bearing in the design, but I have eventually opted for a ball oiler instead. That is in keeping with the rest of the mill. I also had to mill a clearance slot for a stepped radius on the bronze gear, that was just a fraction larger than I had initially allowed for.

On the largest section I drilled the mounting holes on the mill, before assembly. Also before assembly, I faced one side on the lathe and bored out the hole for the shaft.

My welding leaves a bit to be desired, but it's more than strong enough and I've been able to clean up most of it.

As welding inevitably pulls the assembly out of alignment, I've used the mill to get to the final dimensions.

Alignment

The last job was making sure that the motor axis aligned correctly with the shaft.

I made a bush to fit with a 17mm ID for the shaft and a 24mm OD to fit the motor mount spindle.

Sketch of the bush

With the bush in place on the shaft and the end plate attached to the motor mount, I held the motor in place on the shaft and square to the bracket while carefully transfer punching the mounting holes.

Ready To Go

With the holes drilled and tapped and everything assembled it was time to test.

It worked well, first time.

I've cleaned it up and painted it yellow to match Warco's colour scheme.

I've also 3D printed the cosmetic covers to match.

I'm pleased with the end result.

End Stops

The track fitting on the rear of the sprung stops that came with the kit were too wide to fit the track on the mill table. A simple job to mill those down to fit. Luckily a standard M6 nut would fit in the groove, so I have not had to make threaded inserts for the track yet, but I probably will at some point.

The bracket for the cut out switches, did not align with any holes in the mill table and the existing holes made adapting the existing bracket difficult. Therefore I made a new bracket.

I thought about all sorts of complicated designs for threaded adapters to try to use the existing holes in the table but in the end it was much easier and tidier to drill and tap some M6 holes in the front of the table. That made the bracket a simple T-shaped bent bit of steel.

I also added a threaded hold to secure a P-clip to keep the cable clear of the slide.

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Plans

For anyone interested in making their own, here are the drawings:

Hardware:

I used cap head machine screws to match the mill.

4x M6x25mm - to mount the bracket to the table.

2x 6mm dia., x18mm stainless steel dowel pins - to align the bracket with the table.

4x M6x20mm - to mount the motor housing to the end plate.

4x M6x12mm - to mount the end plate to the bracket.

2x M6x10mm - to mount the front and end cosmetic covers.

2x M6x45mm and nuts - to mount the rear cosmetic cover.

2x 5mm dia., x10mm roll pins - to align the motor housing.

Download:

PDF drawings and 3D print parts (zip)

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Update on the mill and lathe

Having used the mill a bit more, I have made a couple of adjustments and completed some bits I had planned for the lathe.

Guards

On both the mill and the lathe I've added some simple clear guards to replace the cumbersome factory supplied ones.

These are magnetic, so I can easily move them about to suit where I'm working. To me, it nearly always feels like guards that come with machines have been designed by someone who has never worked at a machine that is even close to the one the guards are fitted to.

Obviously I don't want chips heading towards my face, but I wear glasses or a face shield, so the guard is not the primary protection in that area. I find that more hot chips hit my hands, which are by necessity closer to the machine and largely unprotected. Most commonly, this is while using the handwheels. My solutions sort that out.

R8 Spindle

Since I've had the WM18 mill, I have been disappointed with the poor engagement of the keyway in my R8 tools. Never having used this before, I did not know what to expect, but I decided it should be better. The collet chuck would engage but not very positively, the Jacobs chuck arbour would fit at any angle!

Over the weekend, I decided to take some time to check that there was not a fault. It did not take me very long to find the issue.

I now know that the key is a simple grub screw and it was nearly all the way out the wrong side! I added a little medium strength thread lock and put it back in, to a depth that felt right. It now works as I imagined it should.

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