Best way to cut 4" woofer hole?

[jwmbro]

I'm building some Zaph speakers right now, and I'm kinda indecisive how to make the woofer hole. I guess my options are

a) buy a 4" hole-saw bit for my drill
b) buy a router jig from ebay
c) use a jigsaw with a circle-jig (would also require purchase)

I don't think c is that good, but I'm not sure whether to go for a or b... what are your ideas?

Also, the woofer needs a chamfer around the back, but I don't have an actual chamfer bit (the kind with a wheel at the tip), but I do have a countersink bit, so I was thinking maybe use a jig and the countersink bit to make a v shaped groove where the woofer hole goes, and then route the inside part out, leaving only the outer chamfer. What do you think about that, would it work, or am I better off investing in a proper chamfer bit, and first making the hole, and then chamfering?

[gareth]

I think that a 4" hole-saw would work better when used with a pillar drill as sometimes the hole can be a little 'un-clean' when hand-held.
The jig-saw blade may, depending on the depth of wood, curve inwards at the bottom of the cut, leaving you with a bit of work to do cleaning it up, unless you take your time and get a feel for the machine.
For me the best option would be the router used with either a shop-bought or a home-made jig, and I would invest in the proper round over bit. They are not that expensive ( €10-15) when you weigh it off against the quality of finish.

Gareth

[jwmbro]

As for the pillar drill, I'm pretty sure I have a pillar to mount the hand drill in available for my use, so that should at least enable that... I'll take a look around ebay for some router bits, if I find a set with a roundover and a chamfer in it, I'll get it, because I definitely need a roundover. Just might be able to do without the chamfer.

[ocool_15]

I think a hole cutter jig for a router and chamfer bit will give you the best finish. If you use a jigsaw set to 45deg you can get close for less cost.

[Geek]

Hi,

A 4" hole saw in a hand drill can end up just as ugly as a jigsaw made hole, unless you're patient. Scrollsaw would be better than a jigsaw.

If you have a drill press, that's the ticket. But is dangerous unless you know the tricks and a bit of experience.

And do spend the extra $ for the bimetal blades... they are worth it

So, I'll just leave that as my

Cheers!

[JLC7]

I'd go for the router jig, at least then you can make clean holes of various sizes instead of just 4".

I've used a drill press to make holes and they came out ok. The difficulty is finding/having the right sized hole saw and even then, you're going to have to use a router anyway to make the rabbets for the driver flanges.

[cyberspyder]

Coming from a guy that has just finished cutting the holes on his baffle for his set of ZMB4, I used a 'knuckle buster'/circle cutter':


(done on a test piece)

Then I used a roundover to slightly notch the front of the baffles so that it'll stay flush with the step on the frame of the woofers, roundover because it gives more room for the sealant you're using, so that it provides a better seal (I used silicone caulk). The back was cut with a chamfer bit.

Also, you probably may have problems cutting the tweeter hole. The Forstner bit I have (1 3/8") is a tad too small. I had to drum sand the hole with a drill press (not recommended for drill presses used for drilling as it throws the accuracy off and messes up the bearings, as it wasn't designed to be subjected to side to side force; I used a POS drill press we had especially for that purpose) to widen the hole. I marked my 36mm line with a compass prior to drilling out the hole so I can have a reference line.

Brendan

[Tristanc1]

I'd say router, diy circle jigs are simple to construct(not to mention a good use for excess wood) and they'll work for a variety of holes. Also works a lot better for flushmounting drivers. If you already have a router it's a no-brainer IMHO.

You'd need one hell of a drill to make a 4" hole saw work through MDF, and once your done I suspect that'll be near the end of the line for that particular hole saw. At least it was for me anyways, I used to use a 3" hole saw to do the final cut out for tweeters, and I usually got 1 maybe two pairs of speakers out if it before the teeth would become basically unusable, not to mention the ridiculous amount of smoke it created. Goes well with a drill press though, but from your post it sounds like you only have a handheld drill?

[JLC7]

I had 6" holes cut out using a hole saw for my woofers. The key to not getting a whole bunch of smoke is to stop and let the MDF dust out of the cutting groove every so often as you go down. If you don't, it clogs the teeth up, nothing cuts, and eventually it burns.

It also doesn't hurt to flip the piece over and continue the hole from the backside instead of trying to go all the way from one side. Gives the MDF dust somewhere to go.

[mightydub]

Definitely get a circle jig. I bought a Jasper jig, yes I know I could make a DIY jig, but the Jasper was not terribly expensive, is simple, easy to use, accurate, and delivers repeatable results. It was very easy to do a beautiful job on the first try first routing out the recess to flush mount the drivers, then cut the hole.

After you use it for the first time you'll wonder how you ever got along without it, and the cost probably won't be much different than a hole saw plus the center drill adapter. Plus the hole saw is fixed diameter, the Jasper jig gets you any size you want in 1/16th increments.

I have all of the various tools mentioned so far - jig saw, hole saws in various sizes, and an adjustable circle cutter as shown by cyberspyder. (yes, I have a tool problem, I admit it.) The adjustable circle cutter requires a drill press. For smaller holes (less than a few inches) I'll use a hole saw if I have the right size, if I don't have the right size or the hole is over 2", it's the Jasper jig on the router every time.

One more caution on the hole saw, you need to firmly clamp the piece you are drilling to a sacrificial backing board otherwise the back side can splinter/break instead of cutting cleanly through. Flipping the piece over and drilling from the reverse side can also solve the problem.

PS cyberspyder, I'm looking forward to seeing the pics of your completed project.