First attemt to cut driver hole with router.... FAIL!!!

So I just totally botched up my latest little creation. I finally went and got the Sears router jig that Zaph recommends, having cut every previous driver hole with a jigsaw up until now. In the past when I have tried to cut a hole in a baffle that is 1.5" thick, the blade kinda bends without me realizing until after the hole is completely cut, and I have to go around trimming the inside of the hole to make it so the driver can fit, which of course makes for a messy backside of the baffle for hurricane nuts and things to grab onto. I got the router guide and a router bit I assumed (mistake #1) would do the job fine. It was only barely long enough (just over 1.5") to make the cut, but still seemed to cover the thickness of the baffle. To make a long story short, my shop is absolutely THICK with smoke right now. The bit always seemed to be having trouble with the cut, and I had to put alot of pressure on the router to make it move, to the point where I accidentally, without realizing it, slowly extended the dimension of the cut so that when I got around to the beginning of my cut, I was about 1/2" further from center than I started. This is obviously not good, and I am scared to try again without more info. I even experimented and retracted the bit up so only about an inch was into the wood, just to make sure i wasn't forcing a part of the bit that wasn't supposed to be cutting, but it didn't change much at all. Is there some special kind of bit I should be using? Should it be that hard to move it during the cut? Does anybody know of a hole-saw set that goes from 15" down to 3" in 1/4" increments in case I never get this? Any tips from the router-jig-experienced would be GREATLY appreciated.
 
Get the Jasper circle jig - couldn't be easier to use, pretty much foolproof. No adjustments to slip.

I got excellent results on my first attempt using a spiral downcut bit and using multiple passes for deep cuts. I would suggest cutting maybe 1/2 inch of depth per pass. The Jasper jig guarantees repeatable results. Screw the plug that will come out of the hole to the sacrificial board and clamp everything in place so the center point won't move when you complete the hole cut. Do the outermost circle for the driver recess first and then work inwards.

Also hook up a vac system to suck all the dust out. I created a poor man's dust collector system out of a 5 gallon wet/dry vac on sale, a couple of 2" PVC pipe fittings and some smaller diameter vac hose to fit the dust port on the router or the radial arm saw.

And stay out of Woodcraft. That store is worse than having a crack habit.
 
Yeah - don't try and do a 1.5" cut in one pass. Do this in several passes slowly increasing the depth each time.

The only gotcha I've found with the Jasper jig is sometimes the pilot (centre) pin can drop through the hole (with enough vibration or movement) then your router wanders freely. The answer? Use some blu-tak on the reverse side to hold the pin against the MDF or whatever so it doesn't drop through.

Cheers,
David.
 

Geek

Member
2004-09-08 7:17 am
Yup, I learned that way too - ruining a $40 piece of clear pine in the process :bawling:

1/4" per pass is about right. Though I'm far more experienced now, even 3/8" per pass is really pushing it I find (tearout, not smoke the enemy there).

I use a scrollsaw for the big holes, then router the rebates with a homebrew jig that keeps the hole a circle and not some drunken ellipse :D

Glad your bit didn't blow apart and injure you :eek:

Practise makes perfect!

Cheers!



PS: In the hardware store, you'll usually be given the choice of a $10 router bit and a $45 router bit. Get the $45 one... you won't regret it! BIG difference in cut smoothness and performance.
 
With a good bit cutting a hole through a 3/4" board in one pass should be no problem.

Whatever you do using power tools it's probably a bad idea if you have to apply much force with your own hands.

If Zaph recommends the Sears jig over the Jasper jig, he's probably tried both and unless you other guys have tried both maybe you shouldn't be telling him to get the Jasper Jig instead?

I like to use my 1/4" (mounted on a 1/2 shaft) straight bit to cut holes.

If you push hard when you cut you're going to make a lot of heat and prob. dull the bit faster, I've never tried cutting 1 1/2" in one pass, but with a good bit and a good router, I'd had no trouble cutting 3/4" birch plywood sometimes and 1/2" many times. Not sure about hardwoods though, I've used roundover bits on oak that went smooth and easy.

The bits I've got now are either Freud from Amazon.com or "Katana" brand from here: http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/kathome.htm I'm sure the regular carbide bits from MLCS are fine too.

edit: oh, and I like my Hitachi M12V router I got for $150 ( :bigeyes: ) at Amazon.com, unfortuanately, the price seems to have gone up to $280? It's green like the Hulk.
 
To answer some questions, the router is 1/4". I think it's a 2 hp router, although I can't confirm that right now because I am still sitting around in my PJ's with my kid and it's cold out in my shop. The bit was a $16 Freud. I think my answer is gonna be taking multiple passes. I'll just make that the back of the sub, slap another board over that side, and mount the amp there instead. Then I'm sure I will proceed to ruin the other side somehow so I can start from scratch.
 

MJL21193

Disabled Account
2007-03-10 1:20 am
critofur said:
With a good bit cutting a hole through a 3/4" board in one pass should be no problem.



Truly a dangerous thing to do is attempt to cut through 3/4" material in one pass - overheating and the bit "chattering" in the cut are a poor way to do things. When cutting the hole with a router, use multiple passes (takes longer, but saves the expensive bit from getting ruined) and DON'T cut all of the way through. Leave 1/16" so that the centre of the hole doesn't break free and router goes crazy, injury is possible.

I use the router to cut the driver recess (rebate) only and use a jigsaw with a good SHARP blade to cut the hole.
 

Attachments

  • im001275.jpg
    im001275.jpg
    90.1 KB · Views: 965
Definitely don't try to cut the whole pass- 1/4" at a time as others have said. I find steel bits go dull way too fast, and instantly in MDF or other glued up materials. Carbide is the only way to go. If you're burning, you're not cutting fast enough, so reduce the amount of cut until you can move the router effortlessly at a good clip. It should *never* take any huge amount of force to push a router through a cut.
 
a few more thoughts:

Dual flute carbide spiral upcutting bits will go a long way to clearing the dust/chips out of the way and reduce tendency to burn, as will vacuum dust removal.
It's the loose dust remaining in the cut patch that causes a lot of the problem, particularly with MDF which instantly turns to talcum powder sized grains, and except for the newest UF free panels impregnated with that nasty resin glue.

Larger diameter bits will have a higher effective cutting speed which helps things go a little faster (assuming that the motor has enough HP to not bog down), but the Jasper is calibrated for 1/4" bits.


Industrial overhead routers or CNC machining centers can easily route stock as thick as a couple of inches, but they'll have 10-15HP motors on the main router head, controlled feed rates, and a single solid carbide or even diamond coated bit can cost more than most of your hand routers.


As both Conrad and John have noted, cutting more than 1/4" per pass in MDF or BB plywood with a hand held router (even something like a a 3HP Porter Cable) is definitely unwise, if not risky of physical injury. Any industrial first aid attendant can tell you there's more than one way to hurt yourself in the workshop . When ( not if ) that 1/4" bit snaps off and lodges in the material, consider yourself lucky - if it shatters, and pieces escape the confined router base - think IED.



Hey John, IINM that work piece shown in your vice is from the curved baffle beauty you've chronicle before. I can't see in the picture a center pivot hole for a circle jig - care to share your technique?
 

MJL21193

Disabled Account
2007-03-10 1:20 am
chrisb said:

Hey John, IINM that work piece shown in your vice is from the curved baffle beauty you've chronicle before. I can't see in the picture a center pivot hole for a circle jig - care to share your technique?


Hi Chris,
I had to make a template for that and use a follower bit. With that curved baffle, that's the only way (that I know of) to make the driver recess flat.
 

Attachments

  • im001271.jpg
    im001271.jpg
    87.2 KB · Views: 684
MJL21193 said:
Truly a dangerous thing to do is attempt to cut through 3/4" material in one pass - overheating and the bit "chattering" in the cut are a poor way to do things. When cutting the hole with a router, use multiple passes (takes longer, but saves the expensive bit from getting ruined) and DON'T cut all of the way through. Leave 1/16" so that the centre of the hole doesn't break free and router goes crazy, injury is possible.

I use the router to cut the driver recess (rebate) only and use a jigsaw with a good SHARP blade to cut the hole.

Good advice.

Although I also do the trick with leaving the 1/16" (actually closer to 1/4") from cutting all the way through and then I turn the sheet over. I fix the center hole to a 1/8" dowel in my table (only needs to poke out 1/8"), clamp the rest of the sheet and then the center piece of wood doesn't break free.
 
I have to admit, the idea that a roto-zip bit can cut through in one pass is very tasty, especially considering the fact that I have roto-zip bits coming out of my ears. Did you use a special roto-zip bit or just a standard one? I'm pretty sure I tried this all once with my roto-zip and the circle jig you can get for it and had pretty much the same problem, including the force I put on the roto-zip causing the jig to open...
 

ShinOBIWAN

diyAudio Member
2004-02-25 9:13 pm
UK
No hand held router can safely take out 1" in a single pass with a decent diameter bit suited to doing a driver rebate. I do have some very, very slender and fragile bits that could do 1" quite easily if you take it slow, problem with these is they're no where near big enough for cutting a channel and are suited to cutting shapes only.
 
I've cut 15" holes in 1" plywood with a rotozip before. The rotozip worked great, but the stupid cheap circlejig slipped and I ended up with a bit more radius than I started with like Paul, but luckily the hole was big enough that a belt sander could correct without without too much eggshape going on. Next time i will make my own jig with a piece of scrap wood I think.