Argggg - I frustratingly bought the wrong size bits - I got some 1/32" downcuts and am excited to use them, but they are 1/4" shank, and my current collet is 1/8". Is there any hope? Would I be able to get a bigger collet which would fit my machine?
And can someone recommend 1/32" downcut bits that would work?
Photos below:
I got sets of ER11 that had multiples of 1/4". Even the metric set I bought also included 1/4"!
You can get sets of various sized ER11 collets quite easily and cheaply online, Iāve see both metric and Imperial sets offered.
I have several 1/4 shank v-cutters that work just fine using the 7mm collet from my metric set.
This is great news - thank you! 
How does this product look - would it work?
In other news, I broke my new 1/16" downcut bit last night (turns out, the spindle needs to be ON in order to workā¦). Checklists, checklists - whoās got good checklists? I started to write my own, but Iām sure there are some good ones out there.
Looks like the correct part.
I should point out that I paid about the same for a set of 8 metric collets from AliExpress (1mm->8mm) a few years ago.
You may be able to find a proper imperial set, including 1/4, for better value than buying individual collets. It will definitely be handier in the long run since you can then buy bits with different shank sizes, rather than being limited by available collets.
PS:
HeHe; anyone around here who says they have never done this is a liar 
I buy small bits in packs of ten, and factor in a certain level of breakage no matter how careful I am (for PCB cutting I have corn cutters down to 0.6mm)
A certain āzenā is needed, every machine/user/workflow is different so you ned to make your own checklists. I have a āpause before runningā policy where I /never/ quickly start a job. I always set up then make a coffee and have a āopen eyesā look at it all before pressing go.
I also do āair cutsā, eg I set everything up. Then lift the spindle 10mm, and re-set that as Z=0. Then I run the cut (or at least the start of it) in empty air, just to make sure everything is going OK. Then I can go back to X0Y0Z0, lower the head by 10mm, reset the Z zero and run the actual cut.
While most ER collets have a 1mm clamping range, I think that runout is lower near their nominal size. So Iād get 1/4" collets rather than use 7mm clamped down to 6.35mm, if I have a choice. When Iām using ER collets for workholding in the lathe, I choose the smallest size that fits across my metric and imperial sets when Iām trying to hold stock thatās been worked to some particular odd diameter.
The smaller the cutter, the more runout matters. It can make up to a 2x difference in feed (speed at which the bit travels relative to the work) for the same speed (spindle speed in RPM). So collet quality matters more for small bits.
Sometimes a cheap spindle and a cheap collet both have some runout, and you can āclockā them to reduce total runout by cancelling each other a bit.
Like @easytarget I cut a lot of air. Itās a renewable resource and pretty cheap at 1 atmosphere of pressure, as long as you arenāt trying to specify humidity content too precisely! 
1/4" Collet sourced (
Merkatronix Medellin). Back in business, and now I can try out the 1/32" bit I got 
Gracias amigos.