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Spiral upcut bit

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ScaredyCat

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I've just picked up a spiral upcut bit from Wealden but appear to be having an issue. I'm not sure if it's just me or not.

My understanding is that a upcut bit would remove waste from the hole being made and that it could be used in a hand help router rather than needing to be in a table. I'm having quite a lot of bother with the bit, even when only partially exposed, causing the router to bounce around like a mad thing. No router bit I've ever used before has done this so I'm wondering if I need to treat it differently.

Any ideas?
 

Sideways

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Could they have supplied you a downcut bit by mistake ? Downward shearing cut is meant to be good for leaving a clean edge on a laminated top surface but would tend to push a handheld router up off the work.
 

Trevanion

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Never used a spiral cutter, but I can imagine they could pull you around a bit because of the constant shear cutting which will want to pull the router into the workpiece. A bit like a drill bit I suppose.
 

sunnybob

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Maybe I'm reading the first post wrong, but i thought he was complaining that the bit was dragging around the hole. the video explains that a downcut bit is the closest to a drill and cuts deep and clean with clean edges. the upcut bit removes waste from the hole, but does no cut clean edges in a hand held router.
 

custard

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It might help to think about the actual application and what you're trying to achieve.

If you're cutting a mortice, or anything that's fairly deep, then the number one priority is to remove the waste. If you don't get the waste out of a deep cut the router bit will be surrounded by packed in sawdust which will act as a heat insulator. Consequently the bit will overheat in the blink of an eye and quickly go blunt. The solution is an upcut spiral bit. The edge of the cut may not be as clean as it possibly could be, but all the waste will get transported out of the cut the instant it is created.

Alternatively imagine you're cutting a shallow groove for an inlay line. Your top priority is an ultra clean cut, any chips along the edge of the inlay line will look horrible. However, the cut will only be one or two mill deep, so you're not really bothered about clearing out waste. Here the choice is equally obvious, a downcut spiral bit and a brisk feed rate to avoid scorching.

These are two extreme choices, but think about which of these your project is nearest to and decide accordingly.
 

HappyHacker

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May or not be related: I use a downcut spiral in a jig and if I don't slow the router down to its slowest the finish is rubbish.
 
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