If this is one of the Japanese acers many of them are grafted to a rootstock. This is what Reg Moule the gardening expert at BBC Radio Gloucester has to say:

"These trees are normally budded or grafted on the nursery. You could try taking hardwood cuttings in October. Remove a 15cm (6in) section of the new growth ,as thick as possible.

Remove the softer tip cutting just above a bud, and then cut just below the lowest bud at the bottom of the cutting. Dip the lower end in rooting hormone and insert it into a pot containing a 50-50 mix of multi-purpose compost and horticultural grit or perlite.

Make sure that three quarters of the stem is under the compost and place the cutting in a protected but not hot place, like a cold greenhouse or frame. "

Agree with Moon_growe's advice, but addd that success rate is very low for taking cuttings of Acers. It is easier to sow their seeds in autumn if you want to propagate them.