Cut 40mm hole in 10mm sheet acrylic

[slarti42uk]

I'm making a plate for my home made router table as the one often recommended didn't fit my router (Ryobi ERT-1150VN). I now want to cut the centre hole for the router bit but I'm not sure of the best method.

The largest cutter I'm using with the table is 37.5mm diameter, 4mm biscuit/slot cutter. So I need a 40mm (ish) hole.

What would be best? hole saw, Forstner bit, spade bit or some kind of router bit.

I don't have a drill press or stand, just a router. I had one idea to cut it roughly to size with a fret saw then use the biscuit/slot cutter to plunge through to clean it up. Would this work or are they only designed to cut edge on?

The acrylic sheet is A4 size and I've drilled the holes to mount it to the router.

Sorry if this is a little rambling.

Cheers
Steve

 

[Paul Chapman]

You could probably do it with your router, but would need to make a small circle cutting jig. I made one like this out of a scrap of MDF and a piece of 6mm brass rod for the centre pin and it works really well http://www.wealdentool.com/acatalog/tips_4.html

Cheers :wink:

Paul

 

[Scrit]

Hi Steve

Acrylics can be very grabby and have a tendency for the chips to melt back, so without a drill stand I'd say clamp the plastic down firmly onto a sacrificial piece of MDF or the like and drill out using a hole saw with a pilot bit. Use a slowish speed (1,000 rpm). Withdraw the cutter from the plastic several times during the cut (to allow it to cool) and clean away the waste. Keep the area cool by spritzing with plain water from a plant spritzer. The edges can be smoothed off using a file and finely abraded using emery paper. The acrylic should come with a protective coat of plastic film on both sides. Leave this in place until you are finished machining and edge polishing as it will protect the surface from scratches.

There are several good articles on acrylic handling over at Ultimate Handyman - the site is owned by someone who works in the plastics industry, so he knows his onions. He's also an occasional member here, too.

Scrit

 

[Lord Nibbo]

Could you not fit the plate to the router and then let the router cut it's own hole? or am I being thick? :lol:

 

[Hitch]

Have a look at the Ultimate Handyman acrylic section, Chez (UHM) is a whizz with the stuff. 8)


http://www.ultimatehandyman.co.uk/forum ... m-f26.html

Or....

http://www.ultimatehandyman.co.uk/ACRYLIC_CENTRE.htm

 

[slarti42uk]

Hi All,

Thanks for the replies.

I think I'm going to have a bash at the small circle cutting jig. I have all the stuff for that already.

I'm a bit worried about buying a hole saw and trying to use it in a hand held drill. Thanks for the link to the acrylic site, very useful.

Lord Nibbo, I was planning to do just as you suggest only I don't have a cutter that diameter to plunge with. I still don't know if the biscuit cutter can cut in that way. As I said I was thinking about using a fret saw to cut the hole then plunge through with the biscuit cutter to clean up. The cutter in question is here

The final question I have is: Would I need a hole for the full diameter of the cutter or just the shank?

 

[Paul Chapman]

I think I'm going to have a bash at the small circle cutting jig.

Just one point about using this type of jig (which you've probably thought of anyway). The piece that you are cutting out contains the pivot point, so it is likely to move as the router cutter breaks through. I find it best to use a piece of double-sided tape between this piece and the sacrificial board to prevent it moving and spoiling the work.

Cheers :wink:

Paul

 

[slarti42uk]

Nope, I hadn't thought of that. Thanks very much, I'll use your suggestion.

Cheers

 

[Scrit]

Would I need a hole for the full diameter of the cutter or just the shank?

That type of cutter is designed for edge or slot cutting, and not plunging, so I'd recommend hogging out as much of the waste from the hole as possible leaving just a millimetre or two to clear away before trying a plunge cut or you may encounter problems (rough cut, workpiece moving, etc). I'd also suggest that you do the plunge cut with the acrylic screwed into position and the router screwed onto to bottom of the plate to ensure the whole plot doesn't move when you plunge. You'll need to secure the plate to the table and the router to the plate in any case, so I can't see that being a problem. Oh yes, and do you have a vertical fine adjuster for your router? That will make for a much more controlled cut and is not a bad idea on router tables of any type

I'm a bit worried about buying a hole saw and trying to use it in a hand held drill.

Hole saws have a pilot drill which leads them through the work, so once the pilot hole is drilled they do will true. The technique is to drill through with the pilot and start the saw part cutting then flip over the piece and finish drilling from the other side. I've routinely drilled kitchen carcasses and the like "freehand" with up to 80mm hole saws without any problems other than the battery running out on the cordless :roll: .

Scrit

 

[j]

The final question I have is: Would I need a hole for the full diameter of the cutter or just the shank?

I don't think you would need to have the hole big enough for the entire cutter to go through.
Firstly, I don't think this kind of cutter is designed to be plunged. And even if it was, is that something you plan on doing on your table with this bit?
Secondly, do people use the plunge on a router while in a table? Maybe if you have one of those plungebar things or similar. I certainly wouldn't do it on mine because I have to wind the height adjuster to set the height and doing that while the router is on is a sure fire way to lose fingers. Whenever I've seen plunging on the router table, the piece is lowered onto the bit. (Admitadly this Norm :norm:, and I know some disagree with his methods).

I'd say, go with the a smaller hole, this will give you more support around the bit when using smaller bits.
What I would do is raise up your router and insert the bit from above the table. Then just remember not to release the plunge lock with that bit in

HTH
J

 

[slarti42uk]

Thanks for the feedback on the hole saws, maybe not a scary as I thought then. I was imagining a lot of vibration and the drill snatching.

Oh yes, and do you have a vertical fine adjuster for your router?

Yes the router came with a threaded rod that locks into the router base.

Firstly, I don't think this kind of cutter is designed to be plunged. And even if it was, is that something you plan on doing on your table with this bit?

I was only planning to plunge this cutter through the perspex to clean up after sawing a rough hole to within a millimetre or so. No I don't plan to plunge it in use on the table.

Then just remember not to release the plunge lock with that bit in Smile

Yes this was the only reason I thought I might need a full sized hole. Or to set the cutter flush or slightly below the table for any reason.

Cheers for all the feed back. I'll report back on the final table

 

[j]

I thought I might need a full sized hole. Or to set the cutter flush or slightly below the table for any reason.

For this, you could always add a sacrificial top to your table.

 

[lemonjeff]

Steve,

How about finding something with a 40mm(ish) dia hole, stick it down with DS tape and use a trimmer or template cutter.

Jeff.

 

[slarti42uk]

Steve,

How about finding something with a 40mm(ish) dia hole, stick it down with DS tape and use a trimmer or template cutter.

Jeff.

Another good plan. However I don't have that type of cutter at the moment. Cheers