Thread: Flush Trimming Bit

I had done this before I got my Jointer/Thicknesser - works great. I don't think there is any diff. in using larger diameter bits. I would go for smaller diameter (1/2") only because you can get longer bits in this range giving you the ability to joint timber of about 50mm thick.

Mat

Do you have a router table? If so, you may get an even better result by using a split fence or a solid fence with shims on the outfeed side. The flush trim bit will work but I seem to find that it takes a bit more effort (concentration ?) when routing with a guide bearing that is a fair way from the base.

I can also recommend a book by Ian Kirby called "THE ACCURATE ROUTER", it has lots simple ideas for getting more from your router, unfortunately he does not include too many ideas about calming down irate neighbours.

Dan

Mat

Dan is on the right track when suggesting that you use a router table (with shimmed outfeed fence). I would just add that you should use a 1/2" x 50mm flush trim bit still (rather than just a straight bit). The roller is extremely helpful when setting up the cutting edge flush with the outfeed fence.

Regards from Perth

Derek

IF you use the fence method then aren't you using the face of the wood that you are jointing (if thats the word) as a reference against the fence?
I assumed that you would need to use a known straight edge as a reference to get a straight cut.

I do have a router table (home made big one with lots of support on in and out sides) I can guarantee that it does not produce the same accurate job as using an aluminium angle guide and a flush cutting bit. I have seen this in action and it works. If the timber is almost straight very little width is lost with this method.

What size angle? (section)

How long?

Is it clamped just on the ends?

Here is the best demonstration and description of jointing on a router table:

http://www.woodshopdemos.com/rtrplnr.htm

Two further points.
(1) Jointing with a straight edge alone may work well - IF the straight edge is indeed straight. The problem with pattern bits is that they do what they are designed to do, that is, conform to shape or irregularity (no matter how small).
(2) You will have much better control of your router-plus-large-bit on a router table than hand held.

Regards from Perth

Derek

I haven't actually set up this system yet. The one I saw in action used an angle approx 40mm x40mm 5mm thick and the angle was screwed to a long board. The board to be jointed was then sitting on top and the whole lot clamped to the bench.

I am planning to use this method for long boards (6ft) approx 1.5 inches thick for a table top.

I looked at the site with the router table demo - thanks for the tip but even on that site when he was talking about the RBI Hawk Jointability which uses the router freehand on top he acknowledges the shortcomings of a jointer for long, thick heavy boards. As I see it the router table method is trying to emulate a jointer.

Mat

You're right when you say that the table method is emulating a jointer. Also, if the edge of the board has a long gentle curve then it is best if either the jointer tables or router fences can support the entire length.

I would be interrested to see the results if/when you give it a go.

Dan

I have read of another way using a Handheld Power Saw. (Note I have not tried this as I have a Jointer).

Butt two of the boards to be joined together. Clamp a straight edge to the straightest board offset by the distance of the Power Saws base to its blade from the Join. Run the Saw along the join with the Saws base running along the straight edge. This will remove a bit of timber from both boards. If a gap is still present, do it again (move the straight edge). I have made a pic which might explain this a bit better.

I would recomend not using angle but rectangular tube at least 25 x 50 x 3.

Angle can deflect badly & twist. at one stage I used 50 x 50 x 3 angle as a ripping guide & found it deflected more than I expected.

If you have a table saw why not joint on that. If you are fussy just lengthen the fence with some extrusion.

Originally posted by mat
As I do not have a jointer I am planning to use a fantastic idea using my Router. The idea is to use an aluminium angle as a guide and a flush trimming bit with a guide bearing that runs along the aluminium angle to provide a perfect edge.
The question - What are the pros and cons of various diameter bits (not the collet size) I assume that a larger diameter bit will run at a higher speed at the cutter surface(any advantage?) and the larger diameter bearing may last longer/run cooler. The larger diameter will push the router out further and have less foot contact with the work piece. I am planning on a cutter with a 38mm cutting depth.

Any thoughts would be appreciated.

Mat the idea of using aluminium angle as a straight edge has merit but only if it dosn't flex and one way is to affix some timber along the length of it with countersunk screws to retain rigidity.

38mm width bits will be running at a fair speed and you need to take this into account as you obviously have reservations about it,I would consider running your router speed at a speed coversant with the bit's manufacturers recommendations which should be in the vicinity of about 18,000rpm on a 1/2" shank bit .

The alternatives that the other guy's have mentioned give you options if you wish not to go down the path you originally wanted more so if you have doubts.

Cheers good luck,stay safe

There are lots of ways to obtain a straight edge. Obviously a jointer. Or a router set up as a jointer (as per the above link).
But as Dan has pointed out, if the timber has a gentle curve, it may take many passes (even with long fences) to get it straight, and this may waste too much wood. Also, you need to maintain a constant pressure against the fences to keep the cut straight.

I don't like (although have never used) Wayne's option of the power saw, as this may leave saw marks which we are trying to avoid.

Then you can use a router with a straight edge. The advantage is you can see exactly where the edge will be, and the cut does not need to be in one continuous movement (you can start and stop, go back if you missed a spot etc). The disadvantage is setup time (clamping) and the (small) risk that the edge might move mid-cut.

Mat's original idea is to use a flush trim bit with bearing to run along an angle iron. This would of couse work, but I don't like the idea of a router bit spinning that close to a metal edge (although in theory it should be fine).

The other option is to use the straight edge as an edge guide for the router base (ie the router base, not the roller bearing, runs along the edge). This is exectly like using a template guide to route dados. The advantage is the bit is away from the metal.

Anyway, all methods will work...
John.

How accurate are flush trimming bits. If I run the bearing along an aluminium guide is there any risk of the bit eating into the aluminium. If so I guess I could use a larger diameter bearing or alternatively I could use a spacer between the guide and workpiece. In this case the carbitool cutter with the double bearing may be of some benefit.