Tap Threading Newbie Question

I see. Well, luckily the 1/2" 12TPI did the job nicely.

Hi Peter

The 12TPI 1/2" and 17mm flat blade worked very nicely and the Dremel fits snug and secure in the 10mm perspex.

I see what everyone meant about water though - I did a trial run on a offcut and it doesn't half melt the plastic, although I was able to clear the hole easily with a stanley knife.

Thanks

The tapping into the perspex went very smoothly and the Dremel screws into the hole without being too tight but is nevertheless secure. I'll see how the durability goes and try some hardwood or vulcanised rubber if it fails.

My main problem is cutting the perspex. I am using a scroll saw and tried to cut a v-shaped chunk out of it but it melts the plastic and causes it to fuse back together just enough so the cutout wont detach from the main piece. My attempts to extracate it caused the whole thing to crack, but then I got frustrated and used a chisel! I can't use water in this application as it'll go into the scroll saw unit.

Any power tool (saw, mill, drill,) will melt Perspex unless you can reduce the speed drastically or cool the cutting zone. Cutting by hand is the simplest solution, but even then care must be taken not to overheat the plastic. Add to that the problem of stress cracking and it would be advisable to seek a more forgiving material. You only make things difficult for yourself by persevering with Perspex.

Cliff Coggin.

I eventually made the effort to go and check my mains powered Dremel and found that the collar is 3/4" x 12 TPI. I guess there must be variations.

Henry

Cut it with a tenon saw, a panel saw or a hacksaw - using water...

Even though they are now owned by Bosch, they started off as an American company, so 3/4"x12tpi is not an unreasonable thread.

A large hacksaw made light work of it thanks