General Woodworking Question(s)

[Gusta]

I'm wondering how you guys go about ensuring that internal bracing pieces of MDF end up flush with the side panels (with the intention of fully contacting front baffle and rear panels later)?

I'm predicting that I will not be able to cut the pieces accurately enough to achieve this (but haven't tried yet). Is it relatively easy to trim oversized pieces with a router? Or, is that the wrong way to go about it?

Thanks.

[cobblepots]

I tried 2 solutions and both worked pretty well for me:

first one, set up the fence on your tablesaw to cut the sides and top, then do so. If your sides are identical in length as the braces, cut the braces at the same time without moving the fence. This will give you identical lengths. This can be repeated for the other dimension of the brace by doing the top and brace without changing the fence.

If your sides are not the same (ie, one piece of wood thiner) take a piece of wood and place it between the fence and your work piece. The wood should be positioned so that it's thickness is between the workpiece and fence. Push both through with the tablesaw guide.

If you don't have a tablesaw, cut the braces about 1/16-1/8" larger depending on the overall size and your confidence in your measurements. Glue them in and Use a belt sander to make smooth after dry.

Hope this helps!

[Gusta]

I should have mentioned I don't have a table saw, nor a belt sander, but I may have to invest in one or both. I do have an orbital sander, but I'm not sure if that will do. Thanks for the tips.

[cobblepots]

An orbital sander will be a nightmare for trying to make edges the same length. You'll be spending hours and have no real way of making sure it's perfect.

If you have a circular saw and don't want to make an investment in a table saw or belt sander, try searching for a DIY rip fence. I've seen a few around at some point in time but can't remember where. Basically, they are made of 1/8" ply and allow you to make a portable ripfence that you can clamp on a 4X8 sheet of ply. If you cut the sides and braces in one pass, this will give you exact sizes. However, I would highly recomend a tablesaw. It's a great investment and will make your speaker build a million times easier.

[jliedeka]

I wouldn't necessarily recommend this but my table saw is a POS. I've been cutting my boards about 1/8 to 3/16 over sized with a saber saw and then trimming them to size with a flush cutting bit. When I have a piece of a certain size as good as I can make it, I use it as a template for identically sized pieces. You have to climb cut a corner that way but it's been working for me.

Jim

[dlneubec]

If your sides are not the same (ie, one piece of wood thiner) take a piece of wood and place it between the fence and your work piece. The wood should be positioned so that it's thickness is between the workpiece and fence. Push both through with the tablesaw guide.

I agree with most of your post, but I have concern about this statement. You are asking for trouble pushing two pieces of wood, in diffrent orientations, through a table saw, especially tight agains the rip fence. It is so easy to have a piece bind and kick back or worse. ;zx

The approach I would suggest is to clamp the short spacer piece at the back end of the rip fence, well short of the blade. Use it to position the piece you wish to cut one width shorter along your mitre guide, but make sure that work piece is not touching the spacer piece when it nears the blade. That way no binding can take place and you can keep all your vital parts. :banana: :banana: :banana:

[cobblepots]

I agree with most of your post, but I have concern about this statement. You are asking for trouble pushing two pieces of wood, in diffrent orientations, through a table saw, especially tight agains the rip fence. It is so easy to have a piece bind and kick back or worse. ;zx

The approach I would suggest is to clamp the short spacer piece at the back end of the rip fence, well short of the blade. Use it to position the piece you wish to cut one width shorter along your mitre guide, but make sure that work piece is not touching the spacer piece when it nears the blade. That way no binding can take place and you can keep all your vital parts. :banana: :banana: :banana:

Good point... Guess I've been lucky up until this point. However, if the fence is 10" or so away from the blade, you should be ok. The shim will not come anywhere near the blade. However, you could clamp the piece to the fence...

[Gusta]

cobblepots,

I assume you're talking about a hand-held belt sander? Can you achieve good accuracy by eye? Or, is there a specific method? I ask because I assume the belt sander would be the cheapest route, but I just noticed they're looking pretty pricey.

I've carefully cut all the side pieces already using a homemade jig and circular saw.

[stink]

Gusta, what about ladder bracing? I have done it both ways and only difference I can see is that ladder bracing doesnt look as nice.

I was only able to get accurate 1-piece braces after adding a sled to my tablesaw (and lots of technique/practice!). It requires accurate rips and crosscuts...

cobblepots: listen to dlneubec. Thats the proper method. What I think you were saying is VERY dangerous. Table saws can be VERY dangerous... something like 30K ER visits in US alone every year (used to be - maybe higher now).

I am lucky enough to have a master woodworker friend. He made me read Kelly Mehler's book before I even turned on my first table saw! I think its a must read for any body using a table saw: http://www.amazon.com/Table-Saw-Book...0602657&sr=8-1

Good luck and be safe

[dlneubec]

Good point... Guess I've been lucky up until this point. However, if the fence is 10" or so away from the blade, you should be ok. The shim will not come anywhere near the blade. However, you could clamp the piece to the fence...

You have two different issues here when pushing two pieces along the rip fence, one being cut. If you are doing it with narrow pieces and you get both hands close to the blade there is more risk of having your fingers or hands pulled into the blade, if the piece or pieces bind, or even accidentally moving one into the blade yourself in a momentary laps of concentration. :Z

Kickback is always a concern and the further the rip fence is from the blade and the narrower the piece is you are pushing through (the short side of the board being along the rip fence) the more likely you will get binding and kickback.

Table saws are great tools, I use mine more than about any other tool when building speakers, but extreme caution is the best approach. Clamping the spacer piece is a must, IMO, and it must be clamped so that the work piece is completely clear of it before the work piece reaches the blade.

[cobblepots]

I am aware of kickback, I've spent a lot of time in the machine shop and have seen a few "bad" things happen. The narrowness of the pieces I'm refering to would be 10X10" or along those lines, hardly narrow. However, your advice is well taken, thanks.

[topp]

Without a table saw I would think that jliedeka idea of using one of the pieces as a template then using a router would be the best and safest idea. So if I understand your brace, it goes front to back, so it would need to be the same length as the side panels. Therefore, cut it about 1/8" to long, then line it up with the side panels then use a flush trim bit to get them the same length. Also, to help cutting with the circular saw try making a saw board, http://wayneofthewoods.com/circular-...ing-guide.html.

[royceb]

Hey Gusta,

If you have a circular saw, I would recommend you look at this product - http://eurekazone.com/ . I just got one for Christmas. I could never cut a straight line at the exact length with a saw until I started using this. Go with the EZ Smart Guide and the Cabinet Maker add-on. At $400 total, it is expensive but much safer (and cheaper) than a table saw. In fact, my wife bought this for me because she didn't want a table saw in the house since we have small children. I can't wait to start building a new set of speakers with the system.

[yardbird]

I would suggest building the box first (without baffle). Then you can place the brace against the speaker then mark it. This is typically more accurate than trying to measure. You might consider clamping a straight edge to the peice of wood you are cutting. have fun!

[Gusta]

I think I'm going to try the router method first since I have all the tools needed. Thanks for the suggestions.

[collo]

If you rebate the shelf brace into the box sides by 5mm, any slack will be taken up by the glue. Stronger too....

[JonP]

Lots of good suggestions...

I've used a "cut slightly long, and shave down by moving the saw fence slightly" as well as the "sand an awful lot" methods... :B Going slow is good, nothing like finding you suddenly have a too short brace and have to make another one!

Attaching a piece of sandpaper to a long scrap of MDF for a "wood file", or even cutting a sanding belt and attaching on a flat board, can help you sand and keep the edges perpendicular.

Another suggestion I've heard and use... 2 part Epoxy is better than wood glue for filling gaps or uneven joints like these... Easier to dab around the edges if needed, for extra strength.

Uh, happy New Year!

[Gusta]

If you rebate the shelf brace into the box sides by 5mm, any slack will be taken up by the glue. Stronger too....

Sorry for the noobness, but I take it you would have to add the glue in there after the sides and/or baffles are glued on? If so, what is the widest gap you can get away with?

[Gusta]

Another question about using the router method. I've never used a router but recently bought a Dewalt 625 and quite a few Whiteside bits (I have five lower quality ones as well from another manufacturer).

Can the flush trim bit be used perpendicular to the cutting surface (in other words, the mdf to be cut underneath the router)? If not, what other type of bit could be used? It seems this would give the most accurate result, but I'm not sure. For example, I'm assuming that two pieces of wood could set on/clamped to the baffle side of the speaker, where the braces are currently exposed, leaving a gap for the router bit? Then the router could be run through the gap, shaving the brace even with the side panels (if the router was set up properly).

I'm not sure if this is the proper/best way to do this, or even if it's too dangerous.

Thanks.

[collo]

I glue the box top, sides and back first. There is a slot to accept the shelf bracing. The brace is then slid into position (and glued) and then the front panel (which is also slotted) is glued on.

With a 5mm rebate depth, you should aim for a brace that only has 1 or 2mm play sideways.

There are some more tips on shelf bracing in this Speaker Building Walk-thru


You probably have router bits similar to these...

The flush-trim is on the right hand end of the picture. The bearing prevents you from plunging this into the surface at 90 degrees.
The bit on the left hand end of the picture (or a fatter version) is the one you want.