Router bit questions

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This topic contains 13 replies, has 5 voices, and was last updated by  Michael Mittleman 2 weeks, 5 days ago.

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  • #2523

    Bill Leonhardt
    Participant

    Hi Folks,

    I have read where people have used up-cut spiral router bits and down-cut spiral router bits and some of the descriptions have left me feeling that I would have chosen the opposite one from what they did for the application described. So, I am inviting comments about which bit you would use for what application. Right off, I think it is important to state whether you are cutting an open edge or an internal slot. Also, whether it is a “hand held” operation or one with a router table.

    Please…..let’s hear from you experienced woodworkers.

    Bill

  • #2524

    Daryl Rosenblatt
    Participant

    When hand holding a router, I prefer the downcut, since it holds the router in place better. But I take very light cuts since it won’t clear the chips as well. When using it in a router table I prefer the upcut, since it will clear the chips down, onto the table. I usually use some kind of hold down, so the piece stays flat on the table anyway. Probably not the textbook answer, but it works for me.

    Those are for internal cuts. I don’t think I use spiral bits on edges much, if at all.

  • #2525

    Michael Mittleman
    Participant

    Hey Bill –

    I use up-cut spiral bits and end mills almost exclusively since they have met my needs which include groves, dadoes, rabbets and stock flattening. The groves, dadoes and rabbets have been largely performed using a router table. The results have been excellent; cuts have been crisp and smooth on edges and bottoms. Board flattening tasks have been performed exclusively with hand-held routers.

    On occasion while kayak building I have had one or two of the strips change position after gluing and apparently misaligned clamping. To save the work, the offending area can be “thinned” of flattened by making a few passes with a router and an end mill (1/2″ or larger). New strip(s) overlay the target area and are glued/epoxied in place. Later, sanding fairs the work area.

    Down-cut spiral bits are really problematic with joinery work since the debris from the cuts tends to collect in the joint and obfuscate the layout lines.

    Hope this helps,

    Mike

  • #2526

    Joe Bottigliere
    Participant

    Bill,
    When it comes to their operations, spiral bits can be viewed as screw threads – left handed or right handed. They pull/push the bit or the work in the corresponding direction. It is said that down-cut spirals can pull the bit out of the chuck. I say, take light cuts and tighten your collet nut better. Likewise, they tend to “pull” the wood chips down (or up) towards the tip of the bit. This is helpful where the show face of the board is adjacent to the router plate. Think of trimming plywood edge and you want the top veneer kept pristine. Another example would be a through mortise where you want the chips to fly out the bottom. However, before you break through that work piece, you will be creating a lot of chips in your mortise first. This could cause a lot of turbulence during the cut. Here, an up-cut spiral is more beneficial. These will tend to pull the chips towards the base of the router (regardless of hand held or table mounted) clearing the mortise thereby reducing interference and providing a better cut. Despite it’s tendency to pull up the fibers, I have never had a problem cutting a mortise in this manner. My first cut is typically a very shallow scoring cut. (Or, you could scribe your mortise outline.) I don’t worry too much about layout lines, though. Machine work typically relies on jigs and set-ups.
    Several bit manufacturers make dual-cut bits so you can straddle a sheet of plywood with the bit and reduce chipping on both faces. I guess it works. It’s still in the catalogs. And for the record, I don’t own a down-cut bit only up-cut.

  • #2527

    Charlie James
    Participant

    Wow, good question, lot’s of answers! I tend to use the upcut bits. It cleans the hole out as I’m plunging and it’s important that I see what I’m doing. I tend to use the bits more for inlays but use them for mortises for the same reason. I don’t have a problem with a rough edge on inlays since I mark my cuts with a knife first. When using an upcut or downcut or any bit for that matter, it’s important to take small bites…The big difference is price, spiral bits are a lot more money. They seem last a bit longer but can be burnt by to much pressure just like a carbide bit. I don’t feel my router pushing or pulling when using either bit I can feel it when I start to push the bit too hard. When making mortises the shoulder of the tenon hides any roughness from the bit so I don’t concern myself with that.

  • #2529

    Michael Mittleman
    Participant

    Bill,

    Please forgive the typo in my earlier post. Therein grove = groove. Also, “…’thinned’ of flattened” should read, “‘thinned’ or flattened…” Sorry for the confusion…

    Mike

  • #2530

    Bill Leonhardt
    Participant

    Thank you Daryl, Mike, Joe and Charlie for your very detailed and wise responses. Good information all around. I have seen an up-cut leave a fuzzy edge when shallow cutting for an inlay, but, as Charlie says, it’s best to score the outline first with a knife to preserve the crisp edge. The most important thing for me to take away is that up-cut means “toward the router” and down-cut means “away from the router”. I can determine the best bit if I remember that.

    Bill

  • #2531

    Daryl Rosenblatt
    Participant

    I’ve seen all sorts of demos on inlay (I tend to like doing them by hand), but the best powered one was by Steve Latta (who has forgotten more about inlay than I will ever know). He uses a Dremel with one of his milling bits (I bought a ton of them, good for when I do use power). Here is the link:

    http://www.drilltechnology.com/sapfm.html

    Interesting since he’s the one who designed the Lie Nielsen inlay tools, so it’s OK to do either. When he uses his Dremel. he made a template that was 1/8″ smaller, and used the bit as an edge guide as he ran the cutter. I don’t know if they are upcut, downcut, side cut, or light saber cut, but they do a good job. Based on what he said, when it’s straight lines or arcs, he will do them by hand, but when compound curves, the Dremel comes out.

  • #2532

    Joe Bottigliere
    Participant

    I’ve heard of his Dremel bits but never saw the price. Is that for one bit? These seem rather fragile despite the 1/32 depth you may limit it to. Am I missing something?

  • #2534

    Bill Leonhardt
    Participant

    Joe, When Daryl and I took the inlay class with Mother-of-Pearl inlay material, we used the Dremel bits with the 1/32″ cutter. They seemed reasonably robust.

  • #2535

    Daryl Rosenblatt
    Participant

    The Latta bits hold up for a long time. They were also about 1/3 the price when I bought a bunch of them about 10 years ago. Steve made a point of saying that you don’t take all the wood out, even for inlay, in one pass. I usually use them in 3 passes or even 4 if the wood is dense.

  • #2536

    Charlie James
    Participant

    I mostly do my inlays/banding by hand especially with curved work since you’re really only scratching the surface. I make my cutter from old chisels or any scrap steel with body to it. I just make a quick jig first, sometimes I even do a jig first! I will use an upcut when removing wood for a fan inlay because it’s faster and the depth is easily controlled.

  • #2537

    Daryl Rosenblatt
    Participant

    I’m a much bigger fan of inlay by hand than by power. It’s a much more controlled cut. But if it’s an irregular shape, I would make a template for a Dremel. However, from a design perspective, most irregular curves that look “right” are almost always compound curves from regular arcs. When I made my bed headboard, to get the camelback top, I used a compass with over a 7 foot radius connected to my router. It’s a series of several really large arcs. And with an arc, an inlay cut is easy to control by hand, except in woods like curly maple. Then the grain runs in so many places and ways, a rotary cut with a bit is better, just take 1/64″ cuts. Yes, that shallow. 4 passes and you have a perfect cut. Also, if possible, always cut “downhill” on a curve.

    Any other ways?

  • #2538

    Michael Mittleman
    Participant

    This discussion thread seems ripe for a presentation. Daryl, Charlie or others… how about it? I think many of the LIW members would be interested.

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