Author Topic: Doug Fir Blowout  (Read 2201 times)

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Offline Naildrivingman

  • Posts: 475
Doug Fir Blowout
« on: August 19, 2017, 05:19 AM »
A coworker of mine is experiencing great difficulty with blowout when machining Doug Fir.  I can assure the forum that he is highly detail oriented and very picky, so I'm leaning towards the fault lying with the material and not the workmanship.

Here's the basics:
1. The boards start as 8' 1x6
2. He rips them to width resulting in face tearout
3. He edge treats them with 1/4 radius resulting in even more tearout

Attempts to correct tearout on rip cut:
1. Tape top and bottom faces prior to rip > no good
2. Plane edge to remove tearout > no good
3. Rout edges with top bearing straight bit and guide > no good

Attempts to correct edge treatment
1. All routing was climb cut
2. 1/4" radius achieved in two passes (1/8 first, then 1/4) > no good

Any and all suggestions appreciated.


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Offline Peter Belisle

  • Posts: 23
Re: Doug Fir Blowout
« Reply #1 on: August 19, 2017, 06:54 AM »
What is the condition of the wood before he cuts?  Ive had fir fray on the edges when it is still green.  it would leave this annoying fringe  edge that was a pain to relieve.

Offline Naildrivingman

  • Posts: 475
Re: Doug Fir Blowout
« Reply #2 on: August 19, 2017, 07:49 AM »
What is the condition of the wood before he cuts?  Ive had fir fray on the edges when it is still green.  it would leave this annoying fringe  edge that was a pain to relieve.
To the best of my knowledge this material is of the highest quality available at a reasonable cost.  The material comes from one of the two largest lumber suppliers in the area.
Dance with who brung ya...

Offline Bob Wolfe

  • Posts: 82
Re: Doug Fir Blowout
« Reply #3 on: August 19, 2017, 09:02 PM »
My guess would be that the wood was poorly kilned resulting in the wood getting brittle.  too fast a dry down or sometimes the wood from the outside of the stack being dried too dry too quick.

Offline Gregor

  • Posts: 928
Re: Doug Fir Blowout
« Reply #4 on: August 19, 2017, 09:17 PM »
Given that the blade and router bit are sharp and work fine on other materials: Most likely the wood.

Ideas to rescue the material:
- do the rip with additional sheets clamped on both sides (to work as splinter guards)
- smaller rounding so the tearout stays within what would be removed material for a 1/4 and sand it to final dimension
- return the material and get some that dosn't have the problem

Surely more work, but in case it's expensive material and the last idea isn't available...

Offline Dovetail65

  • Posts: 4617
    • Rose Farm Floor Medallions and Inlays
Re: Doug Fir Blowout
« Reply #5 on: August 19, 2017, 09:32 PM »
Pictures are needed of the material and the actual bad cuts you are referring to.

Fir leaves a furry edge often, but tear out, not so much.

It can always be the wood, but it can just as well be the blades , bits or  technique. There just isn't near enough information on what the end results looks like the how the cuts are being done to comment on how to make things better.

Grab another species wood and make the same cuts with the same tools, bits and blades, if there is tear out with different wood it may indicate bits, blade technique are the issue.

I use hundreds of different types of wood and not a single time in my life did I have to use tape on the edge to make the cuts with solid wood, ONLY with veneers, ply etc. I have read articles on people doing it and suggesting it. I must be lucky, possibly this is where the expensive blades and 100.00 plus bits make the difference.

I would say slowing down tends to help tear out both with a  saw and router(feed rate). Taking more shallow cuts, adjusting the speed of the router and watching the grain direction of the wood can help stop tear out as well.
« Last Edit: August 20, 2017, 12:09 AM by Dovetail65 »
The one who says it can't be done should avoid interrupting the person doing it.

Offline tjbnwi

  • Posts: 5682
  • Cedar Tucky Indiana
Re: Doug Fir Blowout
« Reply #6 on: August 19, 2017, 10:08 PM »
Does he know how to read grain direction? This sounds like cutting against the grain direction to me.


Offline aloysius

  • Posts: 278
Re: Doug Fir Blowout
« Reply #7 on: August 20, 2017, 01:19 AM »
Pseudotsuga menziesii is a gynosperm, as with many (most?) spp. within the class Conifera will be far more freely splitting than corresponding hardwoods (angiosperms).  One reason is the lack of medullary rays that lock successive seasonal growth wood rings & vessels together, and another their tendency (by no means universal, some softwoods are the slowest growing spp. on earth) to rapidly produce much lower density, fast growth seasonal rings in response to rainfall events and the winter/summer freeze/thaw cycles.

These successive layers of varying density without binding rays allow the individual cell fibers to separate all too easily.  I could suggest that attention be paid to the way the grain lays on the various faces of the plank, but I'm sure your cobber, as an experienced wood machinist, knows this already.  Just as with any other form of planing operation, in just about any timber spp., with a hand plane or machine, results will vary radically dependent on the direction of feed.
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