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26th November 2023, 11:35 AM #1SENIOR MEMBER
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Is a spiral upcut bit a better choice?
I am routing out stair stringers using a template.
up until now they have all been done using straight cutter bits in mdf using 5mm deep passes.
I have a set to do in Tas oak and was wondering if a spiral up cut bit
would be a better option.
Cheers Jim.
.95DEA394-47FB-4E07-AE09-67841247C5B0.jpegC24160D8-31C7-4898-8D6D-FF3ABAEA7910.jpg95A78899-8C8D-48D7-9B15-1D62C7BA0ABF.jpeg
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26th November 2023 11:35 AM # ADSGoogle Adsense Advertisement
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26th November 2023, 12:50 PM #2GOLD MEMBER
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Downcut will leave a very clean virtually splinter free finish on the top surface.
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27th November 2023, 12:01 AM #3
The basics are:
A spiral upcut actively lifts the shavings out of the cut, but in doing so also tends to raise splinters on the upper surface of the timber. Primarily used where shaving clearance is essential, or for through cuts where the router is operating from the back side of the material and the presentation side needs to be absolutely clear of defects.
A standard straight flute bit does nothing to actively dispose of shavings, and might leave some splintering on the upper surface, caused by pushing fibres away from the cutting edges of the bit instead of slicing through them. That's a function of how sharp the flutes of the bit are, bit RPM and feedrate, the actual material in use, and the direction of cut relative to the grain.
A spiral downcut actively pushes the surface fibres down into the body of the material, which backs up the fibres during the cut, resulting in minimal surface damage. However it also tends to drive the shavings down into the groove and can compact them fairly solidly in instances where the bit is making a groove one bit diameter wide. However compaction should be less of an issue in your instance as the area being rebated is significantly wider than the bit, requiring one pass to create the outline of the rebate, then multiple passes to clear the field, which will break up most of the initial compaction and avoid creating further compacted shavings.I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.
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27th November 2023, 08:10 AM #4SENIOR MEMBER
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Thanks Malb
that’s very clearly explained.
Cheers Jim
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27th November 2023, 04:51 PM #5GOLD MEMBER
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To give you an idea of the difference, Jim, have a look at the attached pics.
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27th November 2023, 07:47 PM #6
never mind. mis read post.
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