Will it fit your mini grinder?

Probably,or not, I made it for my mini grinder to transform it in a micro router. I still have to design the lower part that touches the part I will be routing in, upgrades on the way as I design them, print them and test them.

The body diameter is 56mm , and the collar diameter is 38mm, total space over the handles is 250mm to give you batter grip.  It might fit slightly larger diameters, it certainly fits smaller diameters if you buffer the gap around with thick some ruber or plastic ribon before tightening the bolts.

How to fit it to any mini grinder tool like a Dremel?

By trial and error, I recomend you buy the cehap PLA first and see ho it fits, if you find a way to fit it and PLA is not your thing, tha you may jumpon some more strong polymers.

The revolution in design is made not at 180 degees per half handle, but at 175 degrees for the half handle, so that there will always be a small gap between collars to improve grip, when bolts are tightened, I do not expect the two halves to touch at the collars, but to have good grip around the tool. however at the extreme ends, at the handles, is better if the oval shaped peices have no gap on the touch line, for your skin safety.

For the price you have one  pair of minirouter handles.   You need to buy the M5 nuts and bolts.

Word of advice from experience, PLA will fail in time due to proximity of hot elements like minirouteer in full exploit that can reach 50 C anytime.

If you intend to run yourrouter on the hot side do not go for PLA, rather nylon, or PPS or similar, if you intend to go really hot I reccomend you go PEI or PEKK.