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Reply by JeffP

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Posted on Dewalt 734 undercut

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JeffP

573 posts in 1998 days


#1 posted 10-04-2015 12:32 PM

I think to really solve this you would need to figure out which one of two possible “reasons” is causing this on your machine.

Seems it is one of these two:
1) front rollers not in perfect agreement with back rollers
2) back rollers plus outfeed table not adequate to keep board level after leaving front rollers

Clearly, all of the common answers focus on #2 above. If that is the right reason, then to the previous posts, you can add the idea of putting a much longer and very flat board underneath your work-piece. This would (hopefully) act as a “built in outfeed table” to keep the work-piece perfectly level well past the cutter head.

If even that doesn’t improve the situation, then have a look at #1. If you’re sure that the board is not changing angle after it leaves the back rollers…then it pretty much proves that the cutter head is changing position slightly once it is no longer supported by the front roller.

I haven’t ever take a planer apart, but thinking through the process suggests that perfection would only be achieved if the front roller and back roller were offset by the same amount as the depth of cut. The front roller rides on the “un-cut” board as it comes in, and the back roller rides on the “cut” board after it goes past the cutter.

Unless the rear roller is slightly deeper than the front, there would be a natural unloading of the springs and soft roller material and any play in the height adjustment mechanism. Not surprising then, that a 30 thou. shift in the height of the cutter could come from that.

BTW, all possible disclaimers apply here…this is just an engineer doing arm-chair figuring, not deep experience with a planer. FWIW, my 735, which has only a few hours of use so far does not exhibit this issue at all…and I didn’t even bother to put the cheesey in and outfeed tables on the machine. If there is an adjustment for tension on either the front or rear roller, maybe yours needs some tweaking after it has become an “experienced” machine?

Also, the common practice of feeding another workpiece or sacrificial piece right behind your workpiece would tend to remove the issues caused by #1.

-- Last week I finally got my $*i# together. Unfortunately, it was in my shop, so I will probably never find it again.


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