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UROK
02-07-2013, 06:15 AM
Hey Dino and EZ Guys

Just watched SuperSmart clamp/UG vid. Amazing. Love how Dino tosses the old stuff away! So funny! :)

Got me to thinking about something I saw in a speaker building mag on how to bend a panel (author was making a tractrix horn). I believe bending wood is called 'kerfing'.

The author says, "To bend wood, cut a side of wood grain with slits placed incrementally apart. The depth of the cut should leave the last ply of wood grain in place, typically 1/8" thickness. Most important, when you cut the slits the wood grain should align parallel to the path of the horn, if not, the bending will cause the wood to break instead of bend."

I've attached an image of the horn clamped with threaded rods.

So, what EZ ways of doing repeatable 'kerf' cuts on the EZ1/with EZ system are there or could there be?

havehammerwilltravel
02-07-2013, 10:00 AM
Hope I understand what you're asking for- I've never built speakers or bent plywood-

But you're trying to make repeated and parallel kerfs at a given depth through plywood. Not sure what EZ stuff you've got but the EZ-one would make any method go quick, I'd imagine. Old fashioned "layout" marks with ruler/tape measure aligned with the white edge. Or make/find spacers at the correct width and place them parrallel to your cut line between the panel and clamps/limit stops on the bench. Remove after each cut and slide your panel against the remaining spacers. This would work without the EZ-One as well. Just takes a little more setup and support to recreate a "fence" under the rail that is screwed/clamped in place and allows you to slide your panel under the rail after each cut.
A similar method would work if you have an SRK or SSRK (either makes production routing a lot of fun). And you wouldn't have to move the panel at all. I'm sure there are as many solutions and no doubt better ones than these but maybe this will at least help you eliminate the bad ideas. :D

How crucial is the spacing/uniformity of the kerfs to the performance of the horn? Do they effect (affect?) acoustics?

UROK
02-07-2013, 12:54 PM
I don't think I was specific enough.

Wondering if there's a way to do the kerf cut (depth easily adjustable) then move the panel slightly and do the next cut without measuring everything again.

Dunno if that makes sense, even!

I am thinking of "automatic" stops or something.

Sorry!

Mark Davisson
02-07-2013, 01:17 PM
I think havehammer said it best: "Or make/find spacers at the correct width and place them parrallel to your cut line between the panel and clamps/limit stops on the bench."

If you need your kerfs to be spaced on 1/2-inch centers, find a number of 1/2-inch wide spacers equal to the number of cuts you plan to make, and "stack" them against your stops. Make a cut, remove a spacer, slide your panel, rinse and repeat.

tofu
02-07-2013, 01:37 PM
Are you building a horn or were just interested in kerf slits? If the former, you might have an easier time just stacking sheets of bendable plywood or mdf

Burt
02-07-2013, 01:54 PM
Also there is a plywood called bender board.

I think I would make a simple mark on my squaring stops or fence. Do a cut, slide to the mark and cut again. For each cut align with the mark. If you are off a little it shouldn't matter.

Burt

Dik Harrison
02-07-2013, 02:11 PM
This summer I helped the guys that were pouring a walk for me, by cutting kerfs in several form boards. I marked the first 7-8 inches of the area to be kerfed with marks for each cut. I aligned the first cut with the EAC on my EZ-One , and then cut the first kerf (the blade had already been set to depth). I moved to the next line and so on until the first cut nearly aligned to the edge of the squaring stop that was closest to the track. I adjusted the squaring stop until it was aligned with the first cut, and then slid the board to align the second cut with the stop. I then continued to slide, align, and cut until the area that needed kerfs was done.

I guess you could attack a thin flipper to the squaring stop that would let you more easily align the cuts.

mkdrep
02-07-2013, 02:14 PM
Hey Dino and EZ Guys

Just watched SuperSmart clamp/UG vid. Amazing. Love how Dino tosses the old stuff away! So funny! :)

Got me to thinking about something I saw in a speaker building mag on how to bend a panel (author was making a tractrix horn). I believe bending wood is called 'kerfing'.

The author says, "To bend wood, cut a side of wood grain with slits placed incrementally apart. The depth of the cut should leave the last ply of wood grain in place, typically 1/8" thickness. Most important, when you cut the slits the wood grain should align parallel to the path of the horn, if not, the bending will cause the wood to break instead of bend."

I've attached an image of the horn clamped with threaded rods.

So, what EZ ways of doing repeatable 'kerf' cuts on the EZ1/with EZ system are there or could there be?

Can you past a link to the video you are referring to? Thanks!!

bumpnstump
02-07-2013, 02:23 PM
UROK,
what these guys said. I've done the Burt method on my EZ-1 and it worked great. Depending on the size of piece to be kerfed, and the tightness of the desired radius, next time I will quickly mark the back side of the piece to be kerfed and use the EZ square- goes quicker not having to lift the bridge and shuffle the piece; w/the square, make the cut, shuffle the square to the next line, make the cut, etc. If the piece to be cut is small enough, I usually just use 12" speed square and run the saw along it.
If you've never done kerfing/bending before, you might just run some samples to see how easy it is.
Rick

UROK
02-08-2013, 06:30 AM
Thanks guys!

Happy Chinese new year to you all from Beijing!

I'm most grateful for the replies.

@mkdrep - here's the vid (I watched it again - it is funny!)

http://www.eurekazone.com/emvideo/modal/21/640/392/field_vid_prod_01/youtube/vrrjLYn-6WY

When it comes to horns, curves are better than straight lines. The curve should obviously be accurate and same on both sides (of a tractrix). The need for accurate kerfing is based on how accurately the wood can be bent to the right radius.

Expansion rates / flare rates and horn path length are crucial to determining the frequency range any box can produce.

Straight sides - especially in the rear chamber where the driver is can set up destructive waveform interaction resulting in nulls within the passband (frequency range) of the box esp mid range ones. The author identified this problem and fixed it using curves and asymmetric walls in the rear chamber.

I was trying to imagine a way where you could do the cuts quick without re-measuring or drawing loads of lines.

The SSRK method seems closet to what I had in mind (I think!) hahaha