Abrasive "sticks" needed...

[vx220]

Literally no idea where to put this, so I'll leave it here and trust in the mods to direct towards people who know...

I need a tapered abrasive stick, kind of like a fully round file, but with emery/wet and dry/sandpaper instead?

The idea is I have some holes to enlarge in some plastic parts, and the hole will need to be a fairly tight push fit on the new part that will be going in (a tweeter)

Normally I'd get a holesaw of the right size, but as there is a hole already there, I have no centre to line up to. What I have done previously is to enlarge the holes using a round, tapered whetstone, a little at a time until the holes were the right size, but I need to go almost up to 2" diameter, so the whetstone I have is too small

A file won't work, as it cuts in the fore-aft plane. It needs to be tapered along its length so I can push it in from behind, give it a twist and then check the fit.

Any ideas gratefully received! Thank you

[Codswallop]

Would a step drill bit do the job? Just insert and it'll be centred, then drill to the right size.

[haggishunter]

Dremmel?

[vx220]

Either of them would definitely do, just it's quite soft plastic, so I don't want anything too aggressive for my clumsy oafish hands to go too far!

Got me wondering about dremel bits, I could use it by hand?

[Krikkit]

I would definitely use a step cutter as above - anything which can't be centred that way has potential to make a real mess.

[steveo3002]

fashion a stick to what you need then glue on some wet n dry

[vx220]

steveo3002 said:

fashion a stick to what you need then glue on some wet n dry

It may come to this! Thanks for all replies

[saaby93]

Do we need a forum for tools?

[Easternlight]

Try "Permagrit" they're brilliant, I've used them for years in R.C. modeling and never worn one out, Not cheap mind.

http://www.permagrit.com/index.php?cPath=68

[Ray Luxury-Yacht]

Codswallop said:

Would a step drill bit do the job? Just insert and it'll be centred, then drill to the right size.

I'd advise caution with one of these. I have one, and whilst I have used it on many occasions with great success, with delicate plastic you have to be VERY careful, because it has a tendency to 'draw' itself into the hole unless you're right on the ball.

One false move and zzzzzzzip! You have a massive hole with the step drill bit hanging the other side of the hole in it's entirity, quietly laughing at you

[66mpg]

Ray Luxury-Yacht said:

Codswallop said:

Would a step drill bit do the job? Just insert and it'll be centred, then drill to the right size.

I'd advise caution with one of these. I have one, and whilst I have used it on many occasions with great success, with delicate plastic you have to be VERY careful, because it has a tendency to 'draw' itself into the hole unless you're right on the ball.

One false move and zzzzzzzip! You have a massive hole with the step drill bit hanging the other side of the hole in it's entirity, quietly laughing at you

Try using it on a drill with a depth stop.

[InitialDave]

What about a plastic funnel, with some wet and dry or similar wrapped around the cone? Get the hole almost big enough, then use that for fine finishing.

[the_stoat]

Just wrap tape round the step drill where you want it to stop.

[vx220]

saaby93 said:

Do we need a forum for tools?

Mate, that's a bit harsh! I'm not a... oh, I see what you mean

[vx220]

Funnily enough, when I use to cut out the searches for my RC cars I used wet and dry wrapped around something to smooth them out, so I may just be able to wrap the wet and dry around the tapered whetstone I already have.

Thanks for all the ideas, anymore gratefully received

[4Q]

Google conecut, it's like the stepper drill above but without the steps, just go gently and you'll be fine unless the plastic is really flimsy. I use them on plastic (and steel) regularly.

Edited to add, if you buy a stepper drill avoid the erbauer spiral one from screwfix as its very aggressive when using. Better with a straight fluted one.

Edited by 4Q on Sunday 16th October 08:04

[Simpo Two]

You need a reamer:

[samdale]

[woodypup59]

Clamp the job to a piece of plywood and use an ordinary hole saw (the pilot drill goes in the wood).

[hairyben]

samdale said:

Never seen one of those, some arbours have long enough threads to stack two holesaws on

OP also google file drill, may be of help.