What's the best all around size router bit for pu cavities?

Discussion in 'Luthier's Corner' started by Jeremy5000, Nov 8, 2012.


  1. Jeremy5000

    Jeremy5000

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    Hi all.
    Quick question - top bearing obviously for use with a template, depth 5/8ths?
    And the big question whats the best width? 1/4" for making the corners???
    Just getting started so I'll practice - promise ;)

    Oh, I should mention I'm starting off with installing P bass pickups. Guess thats kind of important :rolleyes:
     
  2. Smilodon

    Smilodon Supporting Member

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    Top bearing is a good idea, but when routing the cavities for P pickuos you won't be able to get the corners tight enough. (Finding a 1/4" bit with a top bearing is very difficult. I have never seen one)

    The safest, easiest and cheapest method is probably to do this in two runs. First you make the square holes for the actual pickup using a 1/4" bit and a template collar. (Just remember to compensate the template for the collar and bit diameter) Since the two casings on the P pickups is identical you could make a template with one square that you just re position to make the two holes.

    After you have a square hole you can use a "normal" P pickup template and a top bearing bit to make space to the "ears" of the pickup casing.

    You can't route the ears for the pickup with a template collar. The larger diameter of the collar will make it near impossible to make the tight inner corners between the square part and the ears.


    The proper way of doing it is to use a normal 1:1 template for the pickup and use a pin router, but few people have access to one of those.

    edit: And spend lots of time on the templates. If the templates are perfect the end result becomes so much better. :)
     
  3. suraj

    suraj

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    I too am interested for answers on this..I guess it depends on the pickups itself. I believe pickups that are meant for active electronics are a lot shallower than the hot passive ones. Links to the where people buy such router bits would help :)

    EDIT : For tighter corners and for pickup ears, I guess one can use the appropriate sized drill bit and predrill those out first. And then use a 1/2" or 3/4" top bearing bit ?
     
  4. Smilodon

    Smilodon Supporting Member

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    Stewmac have template bits. You could also make your own if you can find a high speed ball bearing with the correct inner and outer diameter.

    You can drill the corners first and then route the rest, but it's difficult to get the edges to line up perfectly. You'll also have to do some manual chiseling or filing. (The larger bits won't get into the corner properly to cut the wood all the way. If it could there wouldn't be a need to dill in the first place. ;) )
     
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  6. suraj

    suraj

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    I did make a bit like that and found a bearing, but the smallest I could go was for a 16mm diameter bit. And even though the numbers matched, the bit didn't perfectly cut flush to the bearing. Anyway, I think stewmac has the right bits, although a little pricey with shipping and all.
     
  7. Smilodon

    Smilodon Supporting Member

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    You'll never get a 100% match between bearing diameter and bit diameter, but usually it's close enough. 16mm for routing pickup cavities is probably a bit... excessive, I can see that. :smug:

    On my first pickup routing job I made a 1:1 template from aluminium and used a 6mm bit. I just plunge routed to full depth in one go and ran the shank of the bit along the template.

    In retrospect that was utter madness. The friction from the bit actually melted the template. Luckily I had made the template the same size as the pickup. As the template melted the cavity got slightly larger. The end result was near perfect. (The template melted pretty evenly as I kept a constant speed.) Talk about dumb luck...

    Of somebody else is crazy enough to try this, at least use steel for the template, and as much protective gear as you can find... Or... just don't do it! :rollno:
     
  8. MrArose13

    MrArose13 Gold Supporting Member

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    I use a ½” top bearing template bit also and then dremel out the corners with a high speed cutting bit, that is till about 6 months ago… at one of my local woodworking stores (Highland Woodworking) I found a bearing that had a ¼” OD and a 1/8” ID, most dremel router bits have a 1/8” shank, so I put this bearing on my ¼” dremel router bit (the bearing matched the cutter head great) with a 1/8” ID nylon spacer (I’m thinking about trying to get a bronze one) as a stop collar, then the dremel goes in to a router base and a way I go. I only use the dremel to tighten up the corners; it won’t work for the whole job, but I can still use a template till I get down far enough to remove it and use the cavity itself as a guide. :D

    [​IMG]
     
  9. octaedro7

    octaedro7

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    You can use the router's copying guide plus a regular bit, oversizing your template accordingly. This has the benefit of allowing you to use smaller radii bits and also with shorter cutting length, hence being able to match the corners radius and also achieving the proper cavity depth without having to make templates thicker.
    I used the drill method on my current build and it can be quite painful to obtain a flawless template, but it's at least doable.
    I recently bought the shortest and thinnest flush trimming bit in Stewmac, 3/8" diameter. I plan to use it for cavities and recesses.
     
  10. HaMMerHeD

    HaMMerHeD

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    I use a top-bearing 1/2" x 1/2" Amana top-bearing pattern bit.

    This one:

    [​IMG]

    Amana # 45487
     
  11. ctmullins

    ctmullins Registered thumper Supporting Member

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    Uh, yeah - regular ol' Bosch top-bearing 1/2" bit for me too. Never had a problem with it. I've done P routes, J routes, MM routes, soapbar routes... Are you guys overthinking it, or am I underthinking it?
     
  12. suraj

    suraj

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    The main problem I can think of with this method is that you would have to use a very small bit. And even if you use forstners to hog out the excess, the small bit would have to go through several shallow passes. Also to surface the bottom of the cavity with such a small bit could be frustrating. Does anyone use the copy collar regularly ??
     
  13. Beauchene Implements

    Beauchene Implements

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    I've made templates out of oak ply, saturated the edge of the template in thin CA glue, sanded to very fine, almost glossy finish, then simply used a 1/4" upcut bit and let the shank ride the template. As long as you don't bear down on the template or stay in once place too long, I've haven't had any problems.

    I have had problems, however, with StewMac's acrylic templates, and a dirty bearing on a pattern bit that didn't quite spin freely... bearing melted through the template. :crying:

    Nowadays I think of my CNC machine as a software-template router.
     
  14. Smilodon

    Smilodon Supporting Member

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    How do you do 1/4" dia, corners, then?


    Hmm. I never thought about that. That's a really good idea since wood doesn't melt like my metal version. :)

    Showoff! :spit:

    :smug:
     
  15. hover

    hover

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    I usually spot tight corners with a 1/4" or 3/8" drill bit, then do the bullwork with the 1/2" top following bearing router bit...then sand the little "nubs" between the two with a flat file or flat stick with sticky-back sandpaper.
     
  16. ctmullins

    ctmullins Registered thumper Supporting Member

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    Um, I don't. ???

    Maybe I got away with this because my P and J routes were a bit oversized?

    I'm going to be doing some EMG 35 and EMG 40 routes soon. Looks like those will require a 1/4" diameter corner. I have a 1/4" Dremel bit, but it's bearingless. Hmmm...
     
  17. Smilodon

    Smilodon Supporting Member

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    Yeah, probably. If you have a couple of mm spacing you'll probably just clear the corners. Doesn't it look odd, though? Or maybe it's my OCD kicking in again? ;)

    EMG35 and 40 casings are very easy to do with a collar and a 1/4" bit. Just make an over sized square template. No need to worry about rounding the corners either, the bit will take care of that. :) I think i spent about 10 minutes making my 40 template.
     
  18. ctmullins

    ctmullins Registered thumper Supporting Member

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    Great tip; thanks!
     
  19. suraj

    suraj

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    Why not use the CNC to route the actual guitar instead of making a template :smug:
     
  20. Jeremy5000

    Jeremy5000

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    Just wondering - what does CNC stand for/is?
    -and-
    I should state the reasoning behind all this as a matter of curiosity if not advice along another line altogether.

    I grew up on P configurations but a few years ago switched to Jazz basses for the sound of them and feel of the thinner neck, but I have developed muscular/skeletal pain in my right hand on the thumb side.
    I can only attribute this to the different feel of resting my thumb on the pickup cover, (J having just a flat surface without that tiny little bit of grip you get with the rounded top of the P pickup cover).
    I confirmed this by religiously not playing any Jazz basses for a week, then I picked up a cheap Squire P on the bay. Been playing that for a week now, going through scales, songs, jammin' out etc., and low and behold my hand is no longer in pain!
    It was even starting to affect other things besides playing like using a wrench or a screwdriver or whatever at work. Whew! glad I found the culprit before I went in for expensive physical therapy.

    At one point I tried adding a screw built up with some very small plastic washers to simulate the P PU cover but it wasn't quite the same. Guess I'm just a P guy, or P right handed guy.
    Now the question is do I route my Jazz basses out for P PUs or replace with P bodies and route J PUs in the brige position?- UGH!
    Think I'm going to have to go to the shop before I start cutting up all my gear.

    Thanks all for your great input. Gotta love the bass tribe.
     
  21. Tdog

    Tdog

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    Let's assume CNC is out of the picture......The simplest way to get the tight corners for P-Bass pups is to make an over-sized template to be used in conjunction with a guide bushing on your router with a 1/8 in spiral router bit.......Hog-out the bulk of the waste on a drill press and gingerly use the 1/8 bit to get your corners and edges clean.

    You'll have to do the calculations to compensate for the size of the bushing you decide to use so that corner radius is correct......1/2 or 5/8 in bushing should do......Be aware....These bushings seldom center perfectly on the router base.

    Making an accurate template using "old school" methods can be time consuming. But, You do want to get it right.

    Cheers!
    Greg
     

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