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Help, Router Bites Into Wood!


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Hi,

I've made a template with which I can reproduce my own design solid body. I used to saw with a jigsaw and sand until I dropped, but now I stick my template onto the body blank, use a bandsaw to cut fairly close to the template and then finish the contour with a template router bit (with bearing running against the template). I machine as parrallel to the grain of the wood as I can, always 'down hill'. As I was told, long ago.

But at two places, the bit diggs out chunks of wood, instead of leaving a smooth surface. Picture a strat body in your mind, if you will:

1) at the lower half of the inner corner of the upper horn, it left ugly bitemarks.

2) Starting at 6 o'clock on the rear curve, say below the knobs, I move up towards 9 o'clock. About in the middle, it goes wrong. On the other side of this rear curve, say from 12 o'clock down to 9, it's perfect and smooth.

Some facts:

The bit is new and sharp, not spiral.

The wood is American Elder, not quarter sawn but the other one (my English runs out, here).

What am I doing wrong? I've never had this with quarter sawn mahogany, which I used on previous projects. Will using a spiral bit make a difference? Please advise, all input is welcome.

Cheers,

Hugo

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id much rather draw the outline on the wwod and do that part on the bandsaw and sanders, but;

if you go to the stewmac site and look under binding techniques, look at the pattern they use for preventing tear-out; its basically going the opposite way on all the areas your fightin with.

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just be careful, as by doing it like that, you are running the risk of the bit catching and running away from you, or snapping. I wouldnt try to take more than 1/8" off at a time by going 'backwards'. If you have more than that to remove, just 'shave' it down a few times by running the router along the area, but without cutting the full depth.

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You should use a spiral downcut bit versus a straight bit.

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3/8" is just a convention. You can't get a 1/4" bearing bit because the smallest router collet is 1/4." 3/8" diameter is the smallest bearing bit that I've found. Also, a lot of cavities, for pickups and what not have 3/8" radii in their corners. I use a 3/8" bearing bit and a forstener drill bit for my cavities and a 1" or 1.5" bearing bit to rout out body/neck profiles. There are exceptions, but that's generally my rule of thumb.

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Certain areas of a git body need to have a reverse cut, in other words guide your router in the opposite direction that you would normally use. If I can learn to load up a simple pic from my computer, I have a diagram for you! :D

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Just use a 1/4" bit with a router base bushing thingy. You just have to adjust your templates to make up the extra width of the follower thing.

GBS-1.jpg

I have yet to find a 1/4 " bit that will take any kind of load unless you want to make 1/4" increments.Even aftrer that if you try and rout past 3/4 inch the bit will chatter and break.If routing a body I would use the biggest bit available.3/4" or larger.Cavities are different and should only be finished with a router after being roughed out with a forstner bit

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Phil, I wasn't really looking for a way to route smaller cavities as much as I was for small spiral bits with bearings, but thanks for the suggestion. If my choice is between a carbide bit with a bearing and a spiral bit with a bushing, I'd prefer the former. However, I do love the way spiral bits cut and would jump on one if I found it in 3/8" dia with a bearing. Spend enough time in a machine shop and our traditional carbide tipped bits seem archaic compared to solid carbide spiral end mills.

Edited by thegarehanman
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your question sound like when your routing the end grain.

if this is what your asking I can tell you that end grain is much harder to rout.

I would say try and take less off at one time when routing end grain.

what I do in this case is sand or cut more and rout less when working with this kind of grain.

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Todd, the problem with the design of that spiral flute bearing bit is that it limits your routing capabilities. With that bit, you can only route all the way through the material. With a bit that has the bearing on the end where the bit's shank is, you have the option of routing to a certain depth, rather than fully through.

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Sorry, missed that.

Since you really only care about the cut being perfect on the top surface, you could under route with or strait bit and then use the downcut spiral bit to get the surface edge perfect. Or you could have a 1/2" shaft spiral bit ground down to let you mount the bearing on top if it were that critical.

I'll just make shallow careful passes with a sharp strait bit until someone makes a top bearing spiral bit for under $50.

Todd

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It sounds like you are hitting end grain. First off if that is the case, then take shallower cuts and use a climb cut. This is the opposite direction than recommended but they are very usefull when done correctly. They can be dangerous though. I would recommend reading up on it on some of the woodworking websites if you are not used to doing it ( they can become tricky at times). Now if the wood is of highly figured grain. This makes it even more difficult. I would suggest getting close with a rabbet bit using an oversize bearing, then using a spiral cut with either a collar or bearing and climb cutting again. Another tip is to slow the speed down and also your feed rate when encoutering endgrain sometimes this helps ( most will say to speed it up) Just my .02 cents

Mike

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