Being new to woodworking, I’m having some difficulty in learning to set the height of bits in my router table. For example, when I use the rounderover bit, it’s trial and error for me to get the bit at the right height. The first several tries generally result in a roundover that leaves a bead or seam on the top surface of the piece. Eventually, I get the bit at a height that just rounds the edge with no further profile.
I’m sure there’s a more precise method. I’d appreciate your thoughts and advice. Thanks.
Replies
I just scoot down and sight across the top of the table. Test the setting on a piece of scrap, adjust if necessary. I almost always do a test cut. Usually, you only have to cut in a few inches to know. You can also use a straight edge on the table top to feel for the edge of the bit, not running, obviously. I use a 12" steel rule for most of my measuring when setting up and just use that as the straight edge.
I typically set up just a whisker shy of being exact, same with setting the fence to the bearing. I don't want to be so close that any discrepancy will result in the corner of the bit cutting in and I don't want to bear hard against the bearing, either. This makes for a smooth cut from start to finish, no snipe and a consistent feel all the way to the end.
For hand held work, I often use the depth setting ring. My routers are PC or Rockwell. Set your bit flush with the base plate, turn the ring to zero, then adjust to the desired depth. Normally, you can't see the depth ring when mounted in a table, setting by eye and running a test is pretty quick. Just don't waste your time trying to be to the .0001", it's woodworking.
setting bits
As Hammer notes, you can use your stock and sight along the edge of the stock to the corner of the bit. Or, you can use the rule of a combination square to make measurements. Just butt the rule against the bottom edge of the head of the square and tighten it down. The width of the square's head allows you to extend the rule into the throat of the bit opening and maintain accuracy in relation to the surface of the table. You still have to get down to view relationships parallel to the surface, though.
Accurate cuts, however, depend on keeping the stock consistently tight against the fence and the top of the table. Often, that means using a finger board on the fence, and/or another on the table, to maintain consistent positioning of the stock through the cut. Push sticks in various sizes and configurations help with all of that, and keep fingers well away from the bit.
I for one have used routers for many, many years.. My first thought was that you want to hog it all off in one pass,, Wrong.. Very wrong!
Take multiple passes a 'bit' at a time......
Confine the bit
Lea,
It makes it a much more accurate business to sight down the table (or to use a steel rule) when the bit exactly fits through the "holes" in the table and fence. Some router table designs make this easy to achieve whilst with others it is not so easy and smaller bits ends up rotating within a lot of empty space. When there is a lot of space from table or fence surfaces to the bit, it is much harder to judge their relative positions.
For example, the Lee Valley router table provides for 3 inch diameter plastic router table insets ("flush cam-locking inserts") to be screw-locked into their router table top. These plastic inserts can be bought in sufficient numbers then drilled out so that every bit you use has its own router table insert with a hole in it just big enough to allow the router bit through. With some router bits, such as a bottom-cutting straight bit, you can cut the hole in the router table insert using the bit itself, resulting in a perfect fit.
Similarly, the LV router table fence allows wooden or mdf "false faces" to be mounted on it, so the bit can be used to cut its own profile by pushing it through the solid false fence as the fence is moved across the bit.
A fully shrouded bit is much easier to set up for height above the table and protrusion from the fence, as it is very easy to eyeball the protrusion without having to take into account wide gaps between the bit and table or fence surfaces.
In addition, safety is greatly increased as there is no space between the bit and the workpiece-supporting surfaces into which the workpiece can be accidentally tipped or rotated.
http://www.leevalley.com/US/wood/page.aspx?cat=1,43053&p=50264
http://www.leevalley.com/US/wood/page.aspx?p=41793&cat=1,43053,43885
You may be able to make a similar arrangement for your own router table, if the table hole can take some form of locking insert which may be drilled; and if your fence can have wood/mdf false fences mounted on it somehow. I think you need a positive lock, though - double-sided sticky tape might risk sudden detachment of any stuck-on fences or table inserts.
Lataxe
Router Table
Sorry, this isn't about router bit height, but about the Veritas router table referenced on Lee Valley. Thanks, Lataxe. I've been looking around for parts to start on a router table and this seems exactly what I've been looking for.
And yes, I know I said I was starting on a router table months ago, but this time I'm really going to do it. I'm really almost ready to start getting everything ready to get started on it.
--jonnieboy
The best bits
Jonnie,
Well, that LV router table "system" is a typical LV item - well designed and made with lots of small innovations to make one's routing activities a pleasure. I've had mine (with most of the doo-dwats) for a decade now and never felt the need for another or any refinements....except for....
They do a "bit jack" which is an arrangement allowing you to use a foot pedal and chain to raise the router into a workpiece as the router is whirring. This is a safer arrangement than lowering (and later raising) the workpiece on/off the spinning bit, for example as one begins/ends a blind dado or groove away from the workpiece edge.
However, I never could get this bit jack to work smoothly; and it was an a'kard thing to adjust for height. It may have been my cack-hand, of course; but I suspect the arrangement requires an ideal router with no drag in it's plunge mechanism. Perhaps it would work well with a Festool? :-)
Otherwise their router table stuff is excellent, especially when used with a router such as the Triton or other having both a fine and coarse height adjustment mechanism, as well as the ability to raise the collet above the table for easy bit changing.
*******
One attribute of the sheet steel LV router table top is that it is made with a very slight crown around the bit opening, so the weight of the attached router pulls the table flat rather than introducing a sag in the middle.
It did occur to me that the OP's problem in avoiding the ledge-effect when using a roundover or cove bit might be due to table sag. If there is such sag, a longish piece will be cut lower at both ends than in the middle, as the middle of the workpiece is raised above the saggy spot in the table when the two ends of the workpiece bridge the router table edges.
So, if the bit height is set to cut the ends correctly (maximum roundover or cove without a ledge) it will not cut the centre section of the workpiece correctly (not fully rounded or coved). If the bit is set to cut the middle section of the workpiece correctly, it will cut ledges on the ends of the workpiece, since the bit will have to be raised too much in order to "reach up to" the middle of the workpiece.
Lataxe, rambling on.
table sag
I put an anti-gravity plate on the bottom (top, actually) of the router motor to eliminate table or plate sag. ;-)
You do raise a good point though - the need to use a precision straight edge to check the plate and table for sag. Making assumptions in that regard often lead to disappointment.
Height adjustment
I've found that trial and error is the best way to set about every tool in the shop. Get it close by eye or tape measure then make a test cut. Make small adjustments until it's right. With practice, it takes very little time to get it right.
For the router table, one of the best things I ever did was to use a plunge router with a height adjustment knob. The height adjuster replaces the one that comes with the router and allows you to easily make minor changes in bit height by turning a knob. They look like the ones here- http://www.thefind.com/hardware/info-router-height-adjuster
dmd
scrap is good
For me it depends. If it's a repeatable cut that I'm going to make a lot of and have to change setups in between, I keep a piece as a set up block and just slide it in and lower or raise the bit till it fits. I used this method for things like my glass panel bit set and my rail & stile set. Its fast and easy. It only works though if your stock is the same thickness as your set up block.
For my second method I mill a scrap set up piece of a secondary wood with the good stuff so it's the same thickness. I like to use poplar for two reasons. It's easy on the bit and its cheap. I've always got some around and its better to screw up a piece of scrap poplar than a good piece of cherry.
An example of this would be some raised panels I just did for two wine cabinets I'm making. I wanted a test run to be sure I had it down right. I milled some poplar along with the bookmatched cherry and glued it up like the cherry and did my test run with this panel. Worked great and I knew I had my technique down when I put the good stuff through. I could not aford a mess up. When it was done I threw the poplar pane in the scrap bucket to be used in the future for a spacer block or something. I'm pretty good at not wasting anything.
lea
Seems to me that no matter how precisely I set up the bit height before using, the torque of the motor turning on is enough to move the bit slightly up, down or sideways to throw it off. So multiple passes is necessary whenever possible.
bit migration
The bit should stay put once tightened in the collet. If they tend to move in or out of the (sufficiently tightened) collet, I think that's an inidcation of a problem - worn or dirty collet, or worn or dirty shanks on the bits. Cleaning the collet and the shanks with naptha and an old toothbrush might help. There might also be some play in the router shaft causing run-out, but that's a different problem with a different solution. Taking too-aggressive of a cut will exacerbate any residue issue, though, so taking multiple passes is still a good idea.
The bit should stay put once tightened in the collet.. I agree!
Old router user here. Mostly I use a router table. I avoid hand routing if at all possible.
Most of my routers are 1 1/2 hp and one 'BIG' router.. I forget the hp on that big one. I use it only for my Leigh jigs.. Yes, I like my Leigh jigs! (Not an advertisement for them?) All of my routers have 1/4 and 1/2 inch collets and chucks.
With all of my routers.. I NEVER tighten the collet with brute force. I tighten it to a moderate tightness (whatever that is?). The collet should be tight, but I avoid over tightening. (Old US Army Artillary self propelled gun mechanic here... 8 inch to the tiny 155's ;>) ) I know what really tight means....
Impossible to describe with words, but I tighten untill the whench stops with firm pressure. I then push just a bit harder so that I see the collet move a 'bit more' and leave it at that.
I have never had a a bit move! I do clean my bit shafts and use my air compressor to blow out any sawdust in my routers when I feel a need to do it.
I'd say, if your bit moves.. You have serious problems somewhere.
My 'BIG' router is a Bosh.. I like that router alot but I really have to work at removing the bit from the collet and chuck. My 'little' Porter Cable chucks are really nice! Bosh sucks at bit removal! Maybe some patent by PC for the easy to remove 'bits from the collets and chucks'? Or Bosh just does not care?
And a thought about your bit movement:
Are you using a plunge router? I have never found a plunge router that will move the bit 'true center' while moving the bit.
I even looked at the Festool OF 2200 Plunge Router ($800.00 USA) at my local Rockler.. I took a dial indicator to the store and the bit moves while plunging. About the same (a bit less) as my Bosh. I did NOT run the Festool.. I just 'looked' at what I saw at the time. I am NOT knocking the Festool! I only expected 'true' pilot shafts for $800.00 USA.
And then again.. I probably have used some $800.00 hammers that were sold the US military!
As for setting a bit:
Not that I am correct in my methods. I always cut in multiple passes. I NEVER take one pass at any cut. I set my 'bit in use' to cut shallow and work from there. I do not have to worry about production objectives,,,,
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