dowel pins & corresponding drill sizes to get a tight fit....

[HankMcSpank]

Thanks chaps....re changing the glue, my thoughts here are that the problem isn't likely to be the acrylic (the drilled hole will likely be providing a degree of 'keying' for the glue), but more likely the stainless steel dowel....probably little for the glue to grab onto.

RE stressing & cracking over time....this is of little cause for concern, as this is all for a just a cheap winding jig that I've made & I can make another quickly if the acrylic fractures - I'm more miffed that the pins presently have a tendency to work loose than worrying about the acrylic fracturing over time.

Re the increments irving mentions (ie 0.01mm/0.002mm) ....alas I can only source the dowel pins in increments of 0.05mm (& the cost/sourcing options gets out of hand if I start trying to source drills in sizes like 1.58mm!)...I therefore might take a punt & see if I can coax a 1.65mm dowel pin into a 1.6mm hole! (put the pin in the freezer & warm the acrylic in a low heat oven & then see if it fits!)

[GEOFFREY]

Just use an end mill saller than 1.5mm and cut a circle - any dia you want!!! G.

[HankMcSpank]

Just use an end mill saller than 1.5mm and cut a circle - any dia you want!!! G.

Top tip...I have some 1.2mm end mills & will give this idea a try!

[Reg]

A 1/16" drill is a tad smaller than 1.6mm. Using a knurling tool on pins, shafts, axles etc is great for making them grow a bit - almost the proverbial 'putting on' tool. A straight knurl is good in some dry applications whereas a diamond knurl may help hold the glue as a shaft is pushed into a hole.

The usual way to get a hole bang on size is to drill undersize and then ream it.

Reg

[birchy]

Some drills will cut under size, it usually depends on how they are ground. Cheap drill bits are often slightly under. With plastic, if you drill it at a slowish speed and high feed (thus avoiding the drill from spinning in the hole for too long) the plastic will usually "stretch" slightly and produce a hole slightly smaller than the drill bit dia. The other option is to drill something like a 1.5mm hole, heat the pin to around 150C with a paint stripper and push it into the hole. Experiment with offcuts first to get a feel for the best technique!

EDIT:
Seeing as you already have "snug" fitting holes, you could also give the end of the pin a light tap with a small ball pein hammer to make them slightly oval so they fit tighter.