# Best bit to use for this application...



## frootloops (Jul 12, 2007)

I've been making custom speaker mounts and baffles for automotive applications for a while and was doing it the hard way, with a jig-saw, scroll saw, and multiple sanders. And recently I added to my tool collection a new Porter Cable router and have been using it to cut the mounts out. Not only does it do a better job, it's safer, faster, and a whole lot easier. Three of my favorite things! 

Anyways it does a great job but it makes quite the mess and I have to make multiple passes to get all the way through the 3/4" MDF and I would like to know if there was a better alternative to cut them out with? Right now I am using a 1/2" shank, 1/4" double fluted bit, making at least two passes (plunging about 3/8"-1/2" for the first pass, then 3/8"-1/4" the second pass). Would a spiral bit be a better choice and allow me to plunge all 3/4" of the way through the MDF so I only need to make a single pass?

I'm here to learn as much as possible and thanks in advance.


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## harrysin (Jan 15, 2007)

I presume that you're using a circle cutting jig. Going the full depth in one go would be a no no. I personally would use a 1/2" cutter and do it in two or even three cuts which will keep the cutter cooler and sharper for longer. This type of project is best done on a small bench that you can walk around whilst routing and having a second person holding a vacuum hose close to the the router.


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## Mike (Nov 22, 2004)

Spiral cutters will give you a clean cut with excellent chip removal. I feel you would get a better cut using a larger bit, I would use a 1/2" for this job. The thicker bit will also be stronger/safer. You are still best off making your cut in multiple passes. I always suggest using the 1/4" rule: make cuts removing no more than 1/4" at a time. This is less strain on the bit & router and usually provides the best end results. A good circle cutting jig makes this a cinch.


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## Mike (Nov 22, 2004)

Great minds think alike Harry!


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## bobj3 (Jan 17, 2006)

Hi frootloops

I will agree with Harry and Mike bigger is better MOST of the time but this is one time a 1/4" carb.Spiral bit is the best way to go.... 

My son, who works for Car Toys makes speaker boxes all day long, day in and day out he and I got into it one day talking about bit size for making cut outs for speakers and he said 1/4" is the only bit to use on MDF,,, and I said no the 1/2" one is the right size, and I said OK bud show me,,,,,and he was right, the 1/4" bit was faster ,it removes less of the nasty mdf stock with each pass, that's to say it only needs to remove 1/4" wide in the stock other than the 1/2" bit, he did a 10" hole in 3 turns of the router in some 3/4" thick MDF....and I said you have made a mess how about hooking up a vac.to the router and he said no, the chips help hold the plug in place until the last pass of the router,,,,  just one of the down falls of using MDF, he turned me on to the Jasper jig made for the speaker installer,,,,  If you install many speakers you also may want to have one also.
http://www.soundlabsgroup.com.au/c/Jasper/Jasper+Circle+Jigs.html
I got mind from Amazon alot cheaper than any other place I could find..The #200 is the way to go 2" hole to a 18" hole with one small jig.

I did rework my Jasper jig so I could use the PC type brass guides, this will save the pain of bolting it to the router, just pop in and cut the hole out...

If you look on the left side of this post you will see a View item, it will show the rework I did on the Jasper jig.

I should NOTE*** Car Toys, they use the SHORT Spiral bits the one that's made to cut 1" deep not the long ones that's made to cut 1 1/2" deep the short one will hold up and you will break less bits and they last a bit longer in the MDF stock.......


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## Mike (Nov 22, 2004)

That is interesting information BJ. I must be honest and admit when I answered I went on general principals. The last time I made speaker boxes I used high density particle board and made the cut outs using a RotoZip with a 1/4" saber cutting bit and the circle cutting jig.


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## frootloops (Jul 12, 2007)

Sorry for the late reply guys I've been pretty busy.

*harrysin*, yes I sometimes use a jig (Jasper 200) and sometimes I free hand, all depends on what I am making and what the person wants (speaker rings, teardrop kick panel baffles, boxes, etc.).

*Mike*, I'll definitely look into a spiral bit now, might just make things a bit easier. And I've been doing the 1/4" per pass rule, great results!

*bobj3*, yeah I tried a 1/2" bit and boy that was not fun. It took a lot longer and made a bigger mess (and used up a bit more material).

So it looks like I'll go looking for a spiral bit and see if that helps a bit.

Thanks again guys I really appreciate it!


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