Router straight bit w/bearing on top

[wsm66]

Hi all,

I'm mostly a lurker, and I do a small amount of WW mostly for home improvement projects. Recently I had the need to rout out a straight channel in my deck to inset a brace to assist in holding up a post.

So I set out to find a straigt bit with a bearing on top (rather than on the bottom, like a rabbiting bit) so I could follow a jig I had created. I could not find such a bit. Am I looking for something that doesn't exist? It seems like a very usfull bit.

I ended up using a guide clampped down to the deck instead, but I am curious about whether the bit I want exists.

Thanks,

[ChrisD]

Scott,
Welcome to the best forum on the planet! It's called a pattern bit, and you can find it at Rockler, Mike's Tools, and a lot of other places:

http://www.rockler.com/ecom7/product...=pattern%20bit

http://www.mikestools.com/cmt/cmt_ro...n_bits_812.asp

[Ken Massingale]

You want a pattern bit:
http://www.mlcswoodworking.com/shops.../bt_patrn.html
Ken

[WoodPirate]

I guess I need to get one of those, as well. I trace the outline of my pattern piece onto the stock and rough cut a little proud of the line with a jigsaw. Then I clamp the piece on top of the pattern and chase it with the bit that has the bearing on the bottom.

It's been working so far, but a pattern bit would make more sense.

[LarryG]

A tip for those shopping for pattern bits, or for that matter any bit with a guide bearing: if there's a category of router bit for which it pays to spend more on a name-brand bit, this is it. I have some cheap, generic bearing-guided bits, and some CMTs and Whitesides, and there's just no comparison. With the cheap bits it's common for the cutting flutes to not be perfectly aligned with the bearing, which means your flush cut isn't, or your round-over has a little ledge on it that has to be planed or sanded off.

Besides being more accurate, these bits will end up being among the most used in your collection, so it also pays to spend more and get the better, longer-lasting carbide used on name-brand bits, too.

[ChrisD]

quote:Originally posted by LarryG

A tip for those shopping for pattern bits, or for that matter any bit with a guide bearing: if there's a category of router bit for which it pays to spend more on a name-brand bit, this is it. I have some cheap, generic bearing-guided bits, and some CMTs and Whitesides, and there's just no comparison. With the cheap bits it's common for the cutting flutes to not be perfectly aligned with the bearing, which means your flush cut isn't, or your round-over has a little ledge on it that has to be planed or sanded off.

Besides being more accurate, these bits will end up being among the most used in your collection, so it also pays to spend more and get the better, longer-lasting carbide used on name-brand bits, too.

I second that! I have a 1.25" CMT pattern bit. The alignment of the bearing surface to the cutting edge is perfect.

[monte]

Another thing you need to do is check to make sure that the screw or nut that holds the bearing in place is tight each time you use it. DAMHIKT

[wsm66]

Yup - That's what I was looking for allright. As near as I could determine, Borg, Lowes, and the like do not seem to carry these. I'm tempted to just get a set of bearings to go with the straight bits I already have, but I can see where drop-dead accuracy is important. I'll decide the next time I need one.

Thanks to all for your help

[LCHIEN]

quote:Originally posted by wsm66

Yup - That's what I was looking for allright. As near as I could determine, Borg, Lowes, and the like do not seem to carry these. I'm tempted to just get a set of bearings to go with the straight bits I already have, but I can see where drop-dead accuracy is important. I'll decide the next time I need one.

Thanks to all for your help

I don't think there's an easy way to add a top bearing to a straight bit...

--P.S. OK Ken, I stand corrected![)]

[kwgeorge]

Actually there is Loring;

http://www.woodcraft.com/family.aspx...&FamilyID=5145

Several bearing kits are available that come with a locking collar to allow the adding of a top bearing.

[ejs1097]

quote:Originally posted by wsm66

Yup - That's what I was looking for allright. As near as I could determine, Borg, Lowes, and the like do not seem to carry these. I'm tempted to just get a set of bearings to go with the straight bits I already have, but I can see where drop-dead accuracy is important. I'll decide the next time I need one.

Thanks to all for your help

Is the channel you want to rout straight? Sounds like you wouldn't neccessarily use a pattern bit that much and they can be pretty pricey. If your channel is straight can you clamp a straight edge offset by the distance from the outside edge of your straight bit to the outside edge on the router base and run the router along the straight edge?

[LarryG]

I agree with Eric. If you're making straight cuts, you don't HAVE to have a pattern bit because there are other ways to guide the router. Bearing-guided bits are really only absolutely necessary when you're working with curves or other irregular shapes (although they are fast and convenient, to be sure).

Steve: there's really nothing wrong with what you've been doing. The main application for a top-bearing bit is when you have a jig that mounts atop the workpiece and you need the bearing to follow the edge of the jig. For flush-trimming a workpiece to match a pattern, I really can't think of any advantage to having the bearing on top; for that application, one works as well as the other.

[ChrisD]

quote:Originally posted by LarryG

Steve: there's really nothing wrong with what you've been doing. The main application for a top-bearing bit is when you have a jig that mounts atop the workpiece and you need the bearing to follow the edge of the jig. For flush-trimming a workpiece to match a pattern, I really can't think of any advantage to having the bearing on top; for that application, one works as well as the other.

Actually, Larry, there can be advantage to having both bits. As you rout a curve using a top-bearing pattern bit, you can easily go from routing with the grain to routing against it, causing tearout. Sometimes even climb cuts won’t help. So the only solution is to flip the board over, with the template now under the work piece, and rout with a bottom-bearing bit.

[LarryG]

quote:Originally posted by ChrisD

As you rout a curve using a top-bearing pattern bit, you can easily go from routing with the grain to routing against it, causing tearout. Sometimes even climb cuts won’t help. So the only solution is to flip the board over, with the template now under the work piece, and rout with a bottom-bearing bit.

No, no, NO, that's not the way you do it. You should try the method I use, which involves bulling ahead until you ruin the workpiece and have to make another one and start all over.

Seriously, that's a very good tip. I'm not sure I ever would have thought of that (although I can't say I've yet run into a situation requiring it ... but in time I'm sure I will.)

[ejs1097]

quote:So the only solution is to flip the board over, with the template now under the work piece, and rout with a bottom-bearing bit.

that's what I do. I make fullsize hardboard templates for projects I think'll make more then once. Depending on the size of the template, I'll clamp it with spring clamps (quilt rack) or use carpet tape (adarondak(sp) chairs) and flip it over. It's hard to see sometimes. Carpet tape and a flush trip bit mounted in a router table works well too.

sorry for the tangents WSM