Drill Press

I’ve wanted a drill press for a very long time, and I finally decided I could justify one, if only to myself. This is a modeler’s drill press, technically a jeweler’s drill press, designed for drilling a variety of materials including wood, plastic, brass and light aluminum and steel. The only thing it isn’t is a mill, but those cost at least three times as much. It may be possible to use it to mill the light metal used in locomotive frames, although that will likely shorten the motor or motor bearing life. I need to do some more research before I use it for that.

Buying a drill press turned out to be complicated in ways I hadn’t considered. I’ve used drills for years, but those were hand drills, almost entirely used on wood. My few attempts to drill metal had usually gone poorly, one reason I wanted a drill press (it’s important to immobilize drill and material with metal, due to the higher forces involved). But I hadn’t known that there were different drills made specifically for metal, or that clamping equipment in place was as complicated, and badly documented, as it turned out to be.

If you want to know more than you ever knew about drills, read this Beginner’s Guide to Drills. It’s quite useful.

Some good advice from that:

- go slow if you can.

- use a few drops of cutting oil when drilling metal to extend bit life.

- round drills (vs hex) are easier to center precisely; hex are only needed for very high torque use

- In metal, normal (spade tip) bits should have the hole position punched (indented) to prevent the drill from wandering, special split-tipped (pilot) bits are available that eliminate the need for that.

The Drill Press

After a bit of research, I ended up buying the MicroMark Variable Speed Mini Hobby Drill Press (part number 82959). This is the better of the two models they sell, with a PWM motor control giving high torque variable speed from zero to maximum. Just as with trains, PWM provides better low-speed torque than a simple rheostat or potentiometer voltage control, as is found in the common “foot pedal” speed controls.

The chuck is sized for 1/4” drill shanks, but can obviously be used with much smaller drills. MicroLux claims the smallest size is 1/64”, which is 0.0156”, or just a hair smaller than a #78 or metric 0.40 mm drill bit. I’d hoped to find some larger bits with small shanks to I could drill larger holes in plastic for lighting and similar purposes, but all of the reduced-shaft bits I’ve found so far are for 3/8” shafts.

Note: if I ever need/want to use smaller bits, there are “precision pin chucks” available that fit into the chuck and hold small bits just like a pin vise. One of these would allow me to use #79 and #80 bits.

Like most inexpensive power tools, this is made in China to a standard design, and you can find similar models (sometimes without the electronic speed control or with other features) under other brand names. And, despite everything MicroMark says, this is a metric tool in every way except the markings on the depth gauge. Metric screws, metric bolts, metric clamping channels (I’ll get to those). Which isn’t a problem, but it would be nice if the documented this more clearly (to be fair, the parts list in the manual clearly lists all the screws and bolts as metric).

For reference: the channel is a metric xx mm T-Slot (interior width xx mm), which takes xx mm T-Nuts.

Most other small drills are limited to three speeds, with changes achieved by moving a belt between pulleys (which is a complex setup process you don’t want to have to keep doing mid-job). Even my drill actually has two sets of pulleys, providing ranges up to either 3,600 RPM or 5,000 RPM. The lower range provides more torque at low speeds used for styrene and other soft materials, the higher range allows for higher maximum speeds, but provides lower torque at low speeds. Unless I’m doing something abnormal, I expect to leave it set on the low range. The benefit of variable speed is that I can more precisely adjust speed to material. For example, plastic will melt rather than be cut, at even normal “slow” drill speeds.

[drill photo here]

The drill comes without drills or other accessories, so there are a bunch of things needing to be bought with one. This can easily double the cost (or more), one reason I’d held off for so long in buying one.

Some minimal assembly was required, but for the drill this went smoothly (accessories were another issue).

The drill’s base is a machined cast-iron platform, quite solid and heavy. While this will likely hold the drill in place all by itself, there are two recessed mounting holes just in front of the vertical post that can be used for bolts to hold it firmly on a workbench. I bought/built a small table for the drill, and used two bolts to attach it.

The base also has a small ruler inset into it, and two channels in the shape of inverted T’s used for clamping. These actually became something of a problem, as I’ll describe when I get to attaching the X/Y table, but the short of it is that the drill comes with a set of square nuts and bolts (metric M5) used for clamping things like vises, but these won’t fit the X/Y table MicroMark sells, despite being described as “hardware to attach X-Y table” in the manual. The table comes with usable, but less than ideal, hardware of it’s own.

The lid of the press has to be removed to move the belt. It comes with hex nuts, but according to this site these can be replaced with knobs with a M5x0.8 - 50 mm shaft, so I’ll eventually do that.

The Work Table

I wanted a dedicated workspace for this, and I had a little room in my shop area where I could fit it in, so I bought a Sears tool stand for it from a local store. I’d link to it, but the online description doesn’t seem to be the same item. Mine was similar to their model 22305 (and was labeled as such), but had a rectangular top. Perhaps they’ve changed suppliers, and I got an old one.

The stand comes with bolts and leg sections, but you have to assemble them (32 bolts!) and you have to provide your own top. My usual practice when assembling bolts is to use a pair of locking pliers on the nut, and a deep socket on the bolt head, attached to my electric screwdriver. When I went to do this, I discovered that the bolts were metric (I ended up buying a socket set, although all I really needed was an M6 socket). Even after the top was attached (eight more bolts I had to supply) it still felt a bit unsteady, so I ended up hand-tightening the 32 leg bolts since I could apply more force than my electric screwdriver could. With the drill on it, the table is now quite stable, but still has more “give” to it than I’d like.

The tabletop was a piece of 3/4” (19mm) plywood cut from a 2x2 panel to 24” x 18” (61 x 46 cm). When I went to get this cut at the local home supply store, I discovered that their saw wasn’t designed to cut a 6” strip off the end of a sheet. I’d swear I’d done this before, and eventually talked the clerk into doing it, but the wood was clearly not supported properly at one end. That’s something I’ll need to remember for future projects. I did get a clean cut though.

Back home, I painted the top with two coats of my usual gray primer to seal it against oils or other liquids that may get on it while drilling (I still have a gallon of the primer left, even though it’s been discontinued for two years now). After drying I carefully counter-sunk the top of the bolt holes (using a Forstner bit) so they went about halfway through the wood, and the bolt-heads would be flush with the top and not interfere if I wanted to clamp wood to the edge of the table for sawing. Then I bolted on the table-top, and attached the drill to it.

I’m quite happy with the results, even if I did lose several evenings of hobby time to the bench assembly and store trips.

The X/Y Table

An X/Y table is a small worktop, cut with T-channels (see below) for clamping parts to it, which can be moved very precisely by the use of two knobs with graduated markings. These are useful both for drilling holes in a row (or making rivet punches in a grid) and for simply placing holes specific distances from each other.

The table has channels cut in the top. These are xx mm wide slots with a narrower xx mm top slot.

One important tool for setting up an X/Y table: a small metal square. Use this to align the table to the edge of the drill press vise before clamping, and to verify that it didn’t move after clamping. This may not be essential, since the work is attached only to the X/Y table and it’s the motion of that that needs to be precise. But squaring it up seems to me to be a good way of avoiding problems.

After setting up the drill I attached the X/Y table to it. I was going to use the hardware supplied with the drill press for clamping, until I discovered that the holes in the base of the X/Y table were too small for the M5 bolts. I could drill them out larger, and I probably will, eventually, but that seemed like a more precise task than I wanted to try for my first attempt at drilling aluminum, so I set that plan aside for later.

Instead I tried to use the hardware that came with the X/Y table itself. This uses four phillips-head screws (which turned out to be metric M4x70 although that’s not documented anywhere). The screws go through unthreaded holes in the X/Y table base and connect to square nuts that fit into the T-channel in the drill press base. Screw them down, and the nuts press against the top of the channel (and the channel width keeps the nuts from turning) and clamp the table in place. Except, they do this very badly and a great deal of force needs to be applied, and doing so risks stripping out the screws.

The first problem here is that the square nuts are really too small for the channel in the drill press base. They work, but only just barely. They’re really sized for the smaller channels in the X/Y table. I can live with them for now, but I’ll likely want something better eventually. The second problem is more serious: the phillips-head screws are the wrong choice for this kind of attachment, and these are somewhat shallow phillips-head screws at that. Stripping the heads is nearly inevitable. Those had to go, immediately.

So, my next trip to the hardware store was to acquire four hex-head bolts (M4x70, 16 mm) to replace the screws. I had to do this twice, because I measured the length wrong the first time. Those were easily installed, and clamped the table nicely, which removes any risk of stripping the screw heads. Why they couldn’t simply supply the correct hardware is anyone’s guess. They do for the drill attachment clamps.

I also did a lot of googling here, and learned quite a bit about clamping for drill presses (and other tools).

Clamping with Machine Tools

This is apparently one of those “it’s so obvious nobody documents it” kinds of things. I expect you learn it the first time someone shows you how to use a machine tool, and it’s so foundational you never think of it again. But the only time I ever used a drill press was in junior high woodshop (very long ago) and we used C-clamps, if we clamped the wood at all (you can get away with not clamping with wood, something that’s not possible with metal, and not a good idea with plastic).

First, the reason to clamp the workpiece in place is so that force imparted to it won’t cause it to turn. Seems obvious, but if you’re used to drilling wood you’re probably also used to “clamping” things with a hand (or foot), since other types of clamp can mark the wood. The forces involved with metal are much higher (it’s more resistant to being drilled) and the edges are thinner and sharper. Hand-clamping metal is a good way to visit the emergency room, or even lose fingers. I’d figured this out before I even turned on the drill, mostly through some bad experiences in the past drilling metal with a hand-drill (thankfully no emergency room visits were involved in my case).

I even bought a drill-press vise. This is a flat-bottom vise with slots through which bolts can be fed to attach it to the base plate of the drill press, letting you place it pretty much anywhere you want, quickly clamp it in place with a hex wrench, and then mount the material to be drilled in the vise. But it turns out that the attachment bolts are more sophisticated than I first thought.

While you can clamp using an ordinary square nut, this isn’t ideal. There is actually specialty hardware made for this purpose. It’s not cheap, individual nuts sell for more than US$3, but it will do a much better job. It’s not strictly needed for the lightweight work a jeweler’s drill press should be used for, but I expect I’ll eventually order some of this hardware. Although the nuts are specialty items, they’re usually used with an ordinary hex-socket bolt, so you can tighten them down precisely using a hex wrench.

The magic to it is what’s called a T-nut or T-slot nut (not to be confused with the similar T-nut used with 80/20 channel; same idea, not quite the same dimensions). This nut fits almost exactly into the channel, has a longer rectangular shape to allow more pressure against the top of the channel, and isn’t threaded all the way through. That last part seems odd, but it’s to keep you from damaging the channel (and distorting its shape) by running a too-long bolt through the nut and into the base of the channel, forcing the nut up and ripping the slot apart. Ick. Let’s not do that.

Note: Although the slot is often called a “channel” in online pages, the formal name appears to be T-Slot (to go along with T-Nut).

The T-slot is an old idea (patented in 1887)

You use T-nuts with different length hex-head bolts and washers, and need to pick the correct length for what you’re clamping. They also make special bolts with T-channel heads, so the bolt part sticks up, and you use a normal nut/washer on that. This is useful for deeper items, and provides more variabily of length with fewer parts.

T-slots also come in a variety of sizes, both metric and English (a.k.a., Imperial but we don’t call it that here). The nuts are characterized by slot width (in mm or 16ths of an inch) and threading, although length (along the channel) may also be specified). In some cases the same nut is listed with both metric and English units, so you can probably substitute one for the other, if for some reason you prefer using English-threaded bolts on your metric-channel base.

However, rather confusingly, slots are characterized by the width of the visible slot, not the wider part into which the nut fits. Typical channel widths per one UK website are: 3/8”, 7/16”, 15/16”, 7.6mm, 9.5mm, 12mm, and 13.7mm, but I’ve seen larger ones listed also.

The nuts are sized slightly larger (because they’re sized for the wide part of the slot, go figure). So a 3/8” channel (which is 6/16ths) takes a 9/16” nut. Similarly a 7.6mm slot takes a 14 mm nut.

Now that I know what to look for, MicroMark actually sells a clamping kit for their milling machines with t-nuts for 12mm channels (which is what the drill press has). Harbor Freight sells what appears to be the exact same clamping kit, at the same (normal) price, so I may see about picking one up discounted there.

They don’t have anything similar for the X/Y table. They do sell a step-clamp set, but it uses square nuts, perhaps because the softer aluminum can’t stand up to the forces a t-nut could apply.

There are also specialty clamps sold for use with t-channel systems. Some of these look interesting, and I may end up with some later. Interestingly, the generic term for this is “milling machine furniture”, or just “furniture”.