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I was really hoping to have some progress shots of my les paul to add to this past week's "What's going on in your shop" thread, but as I was routing the control cavities, the bit grabbed the bushing and things went south from there. I imagine that the big grabbed made contact with the bushing's inner diameter, which torqued the baseplate. Whatever happened, the baseplate exploded and I felt lucky to pull the router straight up and out before anything disastrous happened. The replacement bushing, bit, and router baseplate should be here this weekend.

Because the bit is so very close to the inner walls of the bushing, do those of you who've worked with guide bushings have any tips on using them to avoid such issues?

I take it you are using a template that is meant to be used with a flush trim template bit, top bearing, possibly ??/ And as such, not having one of those, used a bit and bushing that are close in size (like 5/16 and 1/4 - mine get chewed up as well, and have to buy new ones every now and then) ???? . I tend not to use these top bearing bits for template work, as unless it a special bit like SM sells, you cant get one with only a 1/2 inch depth of cut .. most are 1 inch or more as std.

If you have to use these, I would recommend only using the tight tolerance combo for the final trim around the edges. Use a bigger guide and the same bit to hog out the centre of the cavity

I mainly use templates I have made for cavities and such, and as a rule of thumb, and because it makes the math easier, only ever use a bit/guide combo where the delta is at least an 1/8 inch, 1/4 is better (say 1/2 inch bit, 5/8 or 3/4 template guide.

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Tony Karol
www.karol-guitars.com
"let my passion .. fulfill yours"

Use the biggest bit you can and take light cuts.

With smaller diameter bits, you are more likely to get chatter which can cause the bit to hit the bushing with disastrous results. similarly, 1/2" shank bits are stiffer than 1/4" shank and less bit sticking out of the collet is better than using an extra long bit.

Also take care to assure that the bit is centered in the bushing. A router with a good base help with this; getting exactly on center is a no-brainer with my Milwaukie, but as far as I can tell it is impossible with by PC laminate trimmer.

I destroyed a bushing on the router table cutting 8/4 purpleheart with a 1/2" straight bit a few years ago. The bit and router baseplate were also damaged and the work piece violently thrown across the shop. I keep the trashed bushing in the case with my other bushings so it will remind me to be careful every time I get a bushing

-jd

Thanks for the responses and tips, guys. It's nice but sobering to know I'm not the only one who's had this experience. It sounds like the solutions are to:

1) Be very intentional about making sure everything is centered
2) Sneak up on the cut

In this case it was a 1/2" straight cutter with an inch exposed. I hogged out most of the material with a forstner bit, but there was still more than a little left. That alone screams out at me now after your posts

The templates are designed for the bushing unfortunately. They're not flush trim templates. I think this is so that you can use the same straight cutter set to different depths for the control cavities, neck pocket, and pickup pockets.

http://www.bartlettwoodworking.com/body/Templates.html

The spiral serrated bits are much less grabby as they work, but at the cost of quality of finish, and the bit, not cheap.
Rob

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Todd, what's the function of the tape?

He is using the tape so that the mortise or pocket being routed will be hair smaller than what he wants to end up with. When he removes the tape he will have the lightest of cuts and will remove any chatter etc. This method will leave a very nicely smooth side to the work piece. It's a way to sneak up on the final size.
I should just let Todd explain it, he writes much better than I do. Sorry James, it's late and I am tired. If this doesn't make sense say so and someone else will explain it better or maybe I will have my wits about me tomorrow.
Link
We need a tired icon.

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Cut to size.....Beat to fit.....Paint to match.

James-I use Tom's templates and do the drill-out stage first. I haven't had the "flex" problems you are suffering. I use a thicker baseplate (3/8" Lexan, counterbored for the PC bushings and a large wave washer-baseplate screws hand-fit for full-length engagement-base from Pat Warner and the "tips" on screws and washer are source "forgotten.").I think I got the washers from MLCS. Keeping everything tight is crucial and I use solid carbide whenever I can for this type routing(I subjectively think they flex less).

I did eat up a bushing on the part that uses that very long cutter, but I was doing my first "practice runs" in ugly African mahogany and was over-confident and pushing the whole set-up. Sounds like you were doing the wire channel for the 3 way switch to large cavity. I hope that was the only incident-.ie.; you were not doing the routing that is completed after the maple is on.

For the Les Paul procedures I have a separate set of nothing but Whiteside bits and bought the CNC style for clean plunge and side cutting. Before my back and knees got so bad( can't do stairs until surgery coming up), I was working on jigging up the whole deal for my Duplicarver(Marlin) to see if I could get similar results using the guide pins to serve the same role as bushings in relation to cutter size and 1:1. Because there is a bit of arc in the engagement between router and wood, the drilling will still be necessary, especially on the deep cuts. My Marlin is quite tight tolerance-wise-the gain I perceive is more overall mass and better control. I also did some successful test cutting using my Over-arm Pin Router

I am so far behind on building because of waiting for BC/BS to approve "out of home area" surgery and a couple week stay in Minneapolis for post-surgery physical therapy. I can't get away with scooting down on my butt very often and the knees have added to the problem of coming back up. I have 4 maple tops and 4 Honduras(C.Amer.)bodies waiting and a mock-up of a neck pattern for the Marlin-I'm a bit frustrated, but given the illnesses of others, I'm lucky-nothing is killing me yet.When I'm back at speed, I am going to video the two processes including the top-carve from a master.mt

Hi Mike. I was routing the pickup selector switch on the back. Luckily there wasn't any damage to the work piece. I'm not sure how, but it popped, the base shattered, and I managed to pull it straight up and out before the cutter could contact anything to destroy or throw. I looked up the Pat Warner base. It looks nice!

Todd, Link, thanks! That makes so much sense. I'm feeling somewhat comfortable with giving it another go now.

While I don't know if this is the problem I suspect the using an upcut bit is the culprit, packing material between the bit and the close fitting bushing will deflect the bit into the bushing .
Try using a downcut bit.

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Keith MacKenzie
Location: Florida
"To err is human to really screw up you need tools"

I'm up and somewhat recovered. We bought a house and I am pulling double duty. Worked at least 14 hours yesterday.
Anyway, James one more thing. When I hog out stuff with the Forstner I will do a quick chisel job to connect dots so to speak. Those little protrusions of wood from the series of forstner holes can be very grabby and unpleasent. They can chunk off in fairly larges pieces and jam between the sides of the pocket and the bit and potentially cause at the least a rough cut and possibly what you experienced. So quick clean up with a chisel is time well spent.
Link

_________________
Cut to size.....Beat to fit.....Paint to match.

Thanks, This is a great tip !

-jd

The call-out for the switch cavity is a 1.5" long, .50 diameter bit with a .625 bushing; this leaves .062 clearance which is not that unusual. So, I'm betting on base or bushing movement, or not centered in the first place. On top of that an "Upcut" would really compound. I have a completed body/top glued up for use with the Marlin. It is a beautiful "Burst" replica spec body, but it is a comparator, so to speak, and is only shellac sealed. I ought to finish it but it was done by a genuine master of vintage spec LP's- a very versatile acoustic and electric luthier. He has taught many of us as he goes along. He does NOT retail them out; he respects those aspects held in legitimate copyright by Gibson(they were so arrogant and lazy that the only LP aspects they could get locked in were the "open book" headstock crest and specific pearl logo placement, size and font. Fender sat on their rights the same way and only control their logo and the Tele and Strat headstock shape.

About once a month on "My Les Paul" someone asks the "Is it illegal for me to build an exact replica just for myself?" Then the debate is on. I pulled as much of the Federal Courts of Appeals caselaw as I could but I have to resurrect it from my dead laptop. Of course, the ultimate issue is that one actually has no, shall we say, "hands-on" control over what heirs may do and the guitar could still end up in commerce.


For myself, I have worked up the "Highway 61 Guitars, LLC"[tm] Special. It is a two pickup, LP Jr. shaped solid body with top binding, back binding and fretboard binding and the LP control layout.
Three way "wheel switch" is inlet and just peeking out of the bottom of the pickguard.Much of it can be done with Bartlett templates-it's kind of a dressed up studio with a long-tenon neck-nice but not very original. The wine mahogany with grained ivoroid binding looks good.mt

It worked! Everything went so smoothly that I had to check a few times just to make sure it was cutting

Thanks

I hate template guides. They can be tricky to use. I have chewed up a few and damaged some projects using them. They can vibrate loose. I found that using teflon plumbers tape wrapped around the bushing threads can prevent this.

James-glad it went well-I was cheering for you. The wave-loc washer I was talking about is sold by MLCS-it is cheap and really works to keep the threaded bushing and collar together. Keep on routing your way to LP success! mike