Routing questions and a routing observation to report.

[boneyguy]

So I've fired up my table that I've finished building. There's a couple details to work out but it's basically good to go so I began flush trimming my semi-hollow body project.

I'm very new to routing. To date I've only done some hand held routing of cavities on guitar bodies.

So here's something I learned immediately. It's important to rough cut as close as possible to the line you've drawn from your template. Because the jigsaw that I used tends to cut on a bit of an angle the top of the cut is nice and close to the line but the bottom of the cut is at least an 1/8" farther out from the top of the cut.

Then when I went to trim with my top bearing bit the bottom of the cut actually hits the shaft of the router bit.

(The top piece of wood in the photo below is the middle part of a 3 piece sandwich that I've designed for the body. I cut it from a template I made and then did the final shaping by hand.)


I realize I could be using a taller bit and that would eliminate that problem but it may create another whereby I'm biting into a large section of wood which would increase the chances of tear out. Yes?
I guess I also could be using a larger diameter bit and that might be the way to go. Yes?

So what I had to do was make a pass with the bit up high and then lower the bit and make a lower pass and then repeat. It worked pretty well but seems like alot of extra moves to me.

A couple more questions.

1.) My router is variable speed. What are the guidelines for selecting RPM? I imagine it's largely based on the type of wood your using but there's probably more to it than that.


2.) I noticed that in Preeb's '56 Tele build he was using an upward spiral bit rather than a flush trim bit. Do they both do the same job and is one better suited than the other to the kind of trimming I'm doing at the moment? It seems to me that the spiral bit has several advantages. Most obviously it seems really unlikely to cause tear out. So why do I see most people on this forum using flush trim bits instead of the spiral bits then?

Thanks in advance for any suggestions and help.

[guitarbuilder]

Get a 1" long flush trimmer bit. Spirals are not as common and tend to be more costly. Whiteside, Freud, and CMT are your higher end bits. They are sharper, have a better grade of carbide, and last a lot longer. These style bits are your workhorses and you shouldn't skimp on a lower quality one in my opinion. Freud used to make a 3 wing flush trim bit. It produces 50% more cuts per revolution. I love mine.
Marty

[Jack Wells]

First of all, you're using the wrong kind of bit. You should be using a pattern bit with the bearing on the shaft.

......

If the bit is small diameter ....... like 1/2 in. use your maximum speed.

[guitarbuilder]

First of all, you're using the wrong kind of bit. You should be using a pattern bit with the bearing on the shaft.

Not if the pattern is on the top of the blank??? Or am I looking at the picture wrong? Are you telling him to flip over the piece in the pic?

You really need both type of bits to do the job correctly in my opinion. I'd use the shaft mounted one with the pattern on the bottom and the laminate trimmer one to remove the uncut wood after removing the pattern off the blank.

[Jack Wells]

True ............... he's using that bit correctly but he'd be better off with a pattern bit with the template on the bottom.

He wouldn't have the problem of his body blank contacting the shaft of his bit.

[Colt W. Knight]

Hello BoneyGuy. You will learn a lot just working through router problems.
If you are going to be building guitars you are going to have to get one of each of these.

[guitarbuilder]

exactly...and there is no one right way to do any of this... there are many different options available to you.

[Jack Wells]

I rout a 1 3/4 in. body using only a 1 in. long bit pattern bit but I understand how you could use both types of bits.

[Colt W. Knight]

Do you just take off your template, and leave some extra shank Jack?

[Mystic6]

My first suggestion is one of the best router books. The Router Handbook by Patrick Spielman. When I first got interested in woodworking, it was from watching Norm Abrams use a router. I bought this book and it launched me. I didn't even purchase a table saw until 5 years later.

I agree with the suggestion above for longer bits.

Here is a decent article on router speeds.

[Jack Wells]

I use a router table. When the bearing gets above the template I remove the template. The total length of my bit is 2 1/2 in. If I put a little less than 3/4 in. of the shaft into the router collet, I can completely rout the body before the collet reaches the table surface.

[Colt W. Knight]

My router starts to chatter if I leave too much shank out.

[Nick JD]

Originally Posted by Colt W. Knight

My router starts to chatter if I leave too much shank out.

At full revs?

[Colt W. Knight]

Originally Posted by Nick JD

At full revs?

If you mean revolutions/speed, than yes. It's not too awful bad, but its enough to leave a rough finish on the wood.

[boneyguy]

Okay. So far I'm following the advice your all giving me and it all makes sense. But what about my question in my OP regarding an upward spiral bit? Can someone address that. I'm dying to know.

This is the pic from Preeb's '56 build thread showing an upward spiral bit with a bearing that he's used to trim the body.

[Colt W. Knight]

Those two inch spiral bits are nice IF...
You have minimal material outside the line.
You have a powerful enough router to use a bit of that size.
You can afford one of the bits.
Remember, I router isn't a saw, so it shouldn't be substituted for one. If you are continually removing a lot of material with your router, you are going to dull your bit quickly and increase the chance your bit is going to grab the end grain and make splinters, shoot your work piece across the room, or hurt yourself.
Most of those larger bits have 1/2" shank, and are really intended for shaper/moulding machines. However, some routers are heavy duty enough to use a large bit like that, and come equiped with interchangeable 1/2" and 1/4" coilettes.

[Jimmy_D]

If you were using a helical bit it would be a down shear - pulling the work down to the table - an upshear would be pretty hard to use, but both are available.

[jkingma]

Originally Posted by boneyguy

(The top piece of wood in the photo below is the middle part of a 3 piece sandwich that I've designed for the body. I cut it from a template I made and then did the final shaping by hand.)

The biggest problem I see in this picture is that the bearing is bigger than the cutter. Using this type of bit, your body will end up being a bit bigger than the pattern you are using.

[Jack Wells]

The biggest problem I see in this picture is that the bearing is bigger than the cutter.

Maybe .......maybe not. Could be the angle at which the picture was taken doesn't show the full diameter of the cutter.

[jkingma]

Originally Posted by jwells393

Maybe .......maybe not. Could be the angle at which the picture was taken doesn't show the full diameter of the cutter.

In retrospect and having taken another look, I think you are right Jack.