Okay, what's the secret... (1 Viewer)

[Todd Stout]

...to cutting MDF and ending up with clean edges?

A friend of mine and I spent about five and a half hours on Friday cutting up MDF using my dad's Craftsman 10" table saw (with a new Black & Decker 60 tooth carbide tipped blade) for my Adire Kit-281 and Kit-81 speaker kits. The results have me a bit concerned about just how well these parts will fit together.

At first the problem was dealing with the large full sized sheets. The first cut we made was somewhat wavy and not quite 90 degrees towards the end. We then started cutting the larger panels a bit oversized and then running them through the saw again to shave off a little on each side of each panel. This produced much better results but we still ended up with several cuts that resulted in rough curved marks that the blade left behind (I assume from pausing briefly while running the MDF through the saw). I think I'm going to have to do a lot of sanding in order to get the panels to sit flat against each other at the joints.

Just how forgiving are the parts of the Adire Audio 281 and 81 speaker cabinets? Most of the parts ended up at exactly the dimensions they should be but a few were about 1/32" short.

 

[Rory Buszka]

In your situation, I wouldn't be worried. As for me, I use a plywood blade. MDF burns them up but the little teeth make a nice clean edge. Also, don't force the material through the saw very fast. You might not have your fence straight. Make sure to measure the distance between the fence and the blade to both edges of the blade. This is what might be causing the blade to deflect. Also, push the material through in a slow, continuous motion so you don't stop it with the blade in the middle of it.

 

[Dave Poehlman]

I've used wood putty for any... uh... discrepancies in my MDF cuts. :b

 

[Michael Travis]

two really good points, next time use a plywood blade(large amount of small teeth) and as wood putty is a wood workers best friend, trust me, no matter how good you are theres always a little room for wood putty, lol. Also, something I have done in the past is use a jigsaw or saber saw for the cuts. It will take for ever as you will have to go extremely slow but you can actually visually guide it if you have a semi steady hand. But be warned it takes a strong jig saw and it mdf will burn up those blades quick. Mike

 

[Leo Kerr]

Also, for the over-sized sheets, you need good support under the whole sheet so it stays flat on the table-saw without any additional weight, pushing, or leaning by the operator. (That is, if you can't set it on the table and have it stay there by itself, you're gonna be in trouble.)

Saw horses are one solution; the fancy way I've seen is with a set of "arms" that stick out with rollers on them, attached to the table saw itself.

Leo

(Or at work, they'd use the panel saw, similar but better than the ones at the Home Depots, or slap the sucker onto the giant computerized router...)

 

[Dustin B]

I'm not sure what quality the Craftsman saw you have is, but without a decent tablesaw it will be near impossible to get perfect cuts. However, proper setup of any half ways decent saw should allow for relatively clean cuts. Provided the sheet is properly supported as Leo has outlined. Here's a pretty good tablesaw tune up guide:

http://store.thesawshop.com/catalogue/docs/tune-up.pdf

I've seen the guy who wrote that guide make cuts on a good quality contractor saw he setup with his aftermarket fence at a wood show that looked/felt jointer quality to me. No visible teeth marks at all.

A circular saw with a proper guide can be better than a table saw for making the intial cuts on a full sheet. I have and really like the Eurekazone EZ-Smart-Guide.

http://www.eurekazone.org/products/detail/sgs.html

But with a little care a simple saw board can be almost as effective and significantly cheaper.

http://members.aol.com/woodmiser1/sawbd.htm

 

[Todd Stout]

I was wondering what the heck the deal was. I thought it was supposed to be easy to cut MDF with a table saw. We had been carefully measuring things out and sending the MDF through the saw with slow but (somewhat) steady motions but still we ended up with some less-than-desirable looking edges.

I'll take a closer look at how all the parts fit together this weekend. I think they are all close enough to work okay but we shall soon see.

 

[JohnGil]

plenty of elmers wood glue and calk the seams insides the box after the boxes are built. You can also glue and screw but dont use too big of a screw and pre drill or you will get cracks in the mdf. If you do glue and screw use a counter sink and fill the holes with bondo not wood putty.

I agree with Dustin B. A good strait edge and a circular saw works great. More so if your working alone with full sheets.

 

[Mattak]

I use a finish blade when cutting mdf...makes nice sharp edges I also only use my table saw for small pieces or for angle cuts. Otherwise I use my circular saw with a guide exclusively. It just doesn't make sense to me to use a table saw unless you have one with a huge table. I find it much easier to be dead on accurate using the circ. + guide/clamps.

 

[Mattak]

...as far as gluing/screwing, elmers or gorilla glue (or the elmers version of it) work great, and I stick to straight/small shank drywall screws that they sell by the pound. Much better grip and less plitting with them, although they will torque snap if you try to screw them down excessively

 

[Bryan Michael]

for large cuts that you have to free hand and your fence is not able to be used i like the clamp a strait edge like a strait 2x4 or metal stud and use a circle saw. also i will have some pannels pre cut at homedepo on the pannel saw so i dont have to lug the 4x8 sheet of mdfb on my saw and it also keeps my saw blades sharper

 

[Philip_G]

I used a sawboard this weekend and a ridgid cordless circ saw, I got nice clean, square cuts, but think I could be more accurate on a radial arm or table saw. At least on a table saw if I cut 4 boards 15" wide, they might all be 15-1/16, but they're ALL be 15-1/16.

 

[Mattak]

But if you're starting with a 4x8 sheet and your table saw is only 30" wide by 20" deep and you're cutting by yourself...

 

[Joe L.]

I solved that issue by cutting each subsequent board about 1/8th inch larger than the first and then clamping each in turn to the first and trimming the larger board even with a flush trimming bit in my router.

It is really easy to get smooth, accurate, square cuts on multiple boards when building speaker cabinets that way.

Joe L.

 

[RyanCC]

i dont have access to a nice table saw, so i use a circ saw for most of my mdf cuts. it seems i never have too much trouble getting good straight cuts.

 

[Todd Stout]

Well, I think all the parts that we cut are straight enough to be able to use them okay. I'll try the plenty of Elmer's and caulk the seams suggestion when I get ready to put the parts together.

Now for my next trick... figuring out how to make the holes in the front baffles and then rabbeting them. I have access to a router so it shouldn't be too difficult.

I was going to veneer the tops, bottoms, sides, and backs of all of the cabinets and paint the front baffles black but I'm not sure if the cabinets will be straight enough to do that now. I may have to spend some time with Bondo™ and sandpaper making them smooth so I may just end up painting the entire things.

 

[Mattak]

I wouldn't bother with a rabbeting bit, just get a straight cut bit and make a circle jig router base out of a piece of 1/4" wood/plexi. Drill holes in the base for the required radiuses and use a nail in the center to hold it, route the recesses and then go all the way through with the router or use a jigsaw

 

[Todd Stout]

I'm not too familiar with how to use a router. I have seen photos online of how to use a router to do what you are saying but I'm still not sure exactly how the straight cut bits work. I'm sure I'll figure it out soon enough.

I'll probably have to wait until next weekend to continue building my speakers. I just have too much else to do this weekend. Man... I am getting REALLY anxious to hear what these Kit-281s sound like.

 

[Blaine_M]

I did most of the cabinet building for a pair of GR-Research AV-3's and AV-1's. I'm not sure why people are having problems cutting MDF. I used a so so table saw with a rip fence and got cuts straight as an arrow. The stuff is way easy to cut. If anyone wants a photo I can email it to them....