Router advice needed

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Lomisz

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I'm was looking at buying a plunge router for a project where I need to cut groves into wood for finger holds which will be up to 55mm deep and probably 20-25mm wide. Ideally I would like the bottom of the groove to have rounded edges so was specifically searching for round nose router bits however I couldn't find any that will cut to this depth or even width. I've seen some that can cut to 30mm depth. I haven't used a router before but I assume that you cannot cut with a router bit deeper than the length of the cutting edge, is that correct? Can anyone point me to some place where I might be able to get such router bit. If such is not available then I will settle for a non rounded end.
 
That’s a huge cut to do on a router with a single cutter pass, but you can cut incrementally. Use a straight cutter to take out most of the material then a box core cutter to finish off and put the root radius on. If you want a single radius to the bottom then you will need a cutter 25mm wide and they are not usually that deep (for non-CNC machine work) it’ll also be tricky to get a smooth finish, but a small flat at the bottom and you have plenty of options.
 
I see what you mean but I'm not sure how one can use the box cutter to finish the bottom of the grooves if the bits are not long enough to reach that far.
 
Just to clarify, you want to cut a 25mm wide, 55mm deep slot in the edge of a board to use as a finger pull? How thick is the board?

As @TheTiddles says, a core box cutter would do it but it’s a big old cut to make, especially for someone who’s never used a router before. Wealden tool have a selection here but the combined length of the shank and cutter won’t get you to the depth you want, because you need a decent amount of the shank in the collet. I’d rethink the design, personally; that’s a very deep finger pull!
 
The Trend T10 router has a plunge depth of 80mm. Most routers are around the 50mm mark. I bought one to do my doors with. Not cheap, but bloody good. As others have said, multiple passes will be required in any cuts as deep as that. If you've never used a router before, watch a few videos on you tube. They are a versatile bit of kit but you need to be careful.
 
You can get ball-nose cutters that long, but this really sounds like one of those times a different approach is needed, for a start, can you really see much of the bottom of a 50mm deep 25mm wide pocket? If no, is a flat bottom a problem?
 
Thanks for the advice. Looks like I will need to settle for flat bottom grooves. The grooves are not in furniture but in a hang board for practicing rock climbing grips. They will vary in depth from 20mm to 50mm in depth. I was thinking of making one clean cut to get the width but it looks like it might not be so easy so what diameter cutting bit will be best to do it in multiple passes?
 
Thanks for the advice. Looks like I will need to settle for flat bottom grooves. The grooves are not in furniture but in a hang board for practicing rock climbing grips. They will vary in depth from 20mm to 50mm in depth. I was thinking of making one clean cut to get the width but it looks like it might not be so easy so what diameter cutting bit will be best to do it in multiple passes?
Use a 12mm spiral bit to rough out the pockets then one of these to finish the edges. As you can see 50mm depth is child’s play for a bit that is 120mm in length, though the advice to take small steps will avoid nasty things happening.
75EBE4CE-15C4-4B59-845D-5D3222BB9823.jpeg

here is one but its actually a 14mm cutter on a 12mm shaft
E6D72CB9-F85C-457F-8CD6-9330A2DAB2F2.jpeg
 
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If the groove/s is/are 20-25mm wide what is the overall thickness of the timber - and the type of timber you are aiming to use?

Something that's come to my mind... You say they are for "hand grips" for practising rock climbing... what comes to my mind is building this up from three pieces of timber - or ply - laminated together giving the U shape to then be able to give you the various depths required. Would seem to be an easier approach - stronger and safer also maybe? Maybe a photo of some existing "grips" would help?
 
The hang boards I have seen use multiple layers of ply usually with screwed on sold bits as well. The holds are often sloping which would mean using an angled sled under the router adding an extra complication. With care and going slowly it is probably possible to do it in solid wood but I think laminations or some carving chisels would be better and safer.
 
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