Router Spiral Bits - Up, Down or Combination?

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Forum topic by Calgaryguy posted 09-01-2012 01:32 PM 1832 views 0 times favorited 5 replies Add to Favorites Watch
View Calgaryguy's profile


7 posts in 2339 days

09-01-2012 01:32 PM

Topic tags/keywords: router

I’ve been looking at getting a spiral flush trim bit lately but one thing I’m not sure about is whether to go with a up cut, down cut or combination cut bit. I typically use my flush trim bits in combination with my router table but there is of course the odd occasion where it’s easier to just use the router itself on the piece such as on larger projects. Can anyone give me a little guidance on which one I should be selecting and for which application? I’m assuming one of them is better for use on a router table as opposed to when you’re using just the router.

Also, I’m currently looking at the Whiteside bits, any feed back on them would be appreciated.

5 replies so far

View NiteWalker's profile


2738 posts in 2754 days

#1 posted 09-01-2012 01:43 PM

I use a downshear flush trim bit. Whiteside makes the one I have, but freud and cmt also make them.

-- He who dies with the most tools... dies with the emptiest wallet.

View Wdwerker's profile


333 posts in 2411 days

#2 posted 09-01-2012 01:44 PM

Whiteside just came out with the ultimate spiral trim bits. 7/8 dia cutter bearing over for plunge, bearing under for pattern work, and top and bot bearings for everything. Compression leaves both surfaces clean, shears in from both faces. I think they were $150 to $170 each so not a casual purchase.
I have bought many Whiteside bits and like them all.

-- Fine Custom Woodwork since 1978

View JesseTutt's profile


854 posts in 2288 days

#3 posted 09-01-2012 02:18 PM

Up cut bits pull the shavings out of the cut and towards the router’s Collet.
Down cut bits push the shavings into the cut and away from the router’s collet.

Normally, you would use an Up Cut bit. This cleans out the cut reducing friction and heat. The exception is when you are routing material that has face veneer, or laminate, on it. If you use an Up Cut bit then you will be pulling the veneer away from the wood and that could cause chipping.

I used to buy Whiteside bits from Woodcraft, now I buy my bits from Woodline USA ( They have great customer service and will help selecting the correct bit. If there are any problems I ask for Wayne and he will make it right.

-- Jesse, Saint Louis, Missouri

View Fred Hargis's profile

Fred Hargis

5143 posts in 2671 days

#4 posted 09-01-2012 09:09 PM

I’ve only used upcut flush trim, adn the ones I’ve have now are all Whiteside. I think what Jesse mentioned can happen (the veneer being pulled up) bit I’ve not had that happen first hand. I do get a fuzz on top of the cut that a downcut bit would eliminate; but so does a light sanding. As for Whiteside, my personal opinion is that they are among the best bits on the market today and I’ll typically look at theirs first when i need a new one. That said, they are also very expensive, sometimes the comparable Freud bits can be had for a lot less….and they are also very good bits.

-- Our village hasn't lost it's idiot, he was elected to congress.

View JAGWAH's profile


929 posts in 3261 days

#5 posted 09-01-2012 09:26 PM

Up spiral for routing mortises and any non-through cut. Down spiral for through mortises or cuts fully through stock. As to either with a bearing for flush trim I don’t worry about it, most of mine are down.

I have learned that the more flutes the harder your router has to work. I have light weight routers I only use 1/4” shank with two flutes up or down and my bigger routers that can handle 1/2” shank three flutes up or downs. More flutes mean more cuts per revolution and increased load on the router.

-- ~Just A Guy With A Hammer~

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