I have a very simple router table setup that I’ve been using for years, basically a recessed rectangle in the deck to the right of my table saw where I can drop in a 1/4″ piece of corian that I’ve attached my router base to. I use my biesmeyer fence as a router fence. It’s always served me quite well.
I just bought a 3/8″ upward cutting spiral router bit to use for cutting a series of mortises. It cuts a nice clean hole on the plunge down, but as soon as I advance the board to cut the length of the mortise, I get the most terrible chatter, no matter how slowly I advance. (Just to be sure, I have tried advancing the wood in the wrong direction, to confirm that I am advancing in the right direction.)
I’ve used spiral bits in the past without any trouble, or so I think. Is there something I might be overlooking?
Replies
You should fill in more details --- e.g. what type of router, have you had this chattering problem with any other bits, etc.
Is the bit properly seated in the collet? Have you tried the bit in another router?
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"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
Some possibles.
1) Spiral is left handed.
2) Work is mishapen (not square with crook?).
3) Fence is mishapen, not square or straight.
4) You are doing a suicide blind mortice, always with adversity on the RT.
5) Insufficient shank in the collet, 3/4" min.
Routers & Safety
>>1) Spiral is left handed.
looking down the length of the bit from the shank to the point the spiral turns clockwise. if plunging down a hole, it would pull the chips out. I believe this is called an "upward cut".>>4) You are doing a suicide blind mortice, always with adversity on the RT.
could you please elaborate? what is a suicide blind mortice. why the adversity on the RT? does "RT" mean "right"?>>5) Insufficient shank in the collet, 3/4" min.
i think I put it in down to the bottom. i will check for sure.I am running a 1.5 hp PC router. This is a very long bit. As a consequence, the router is backed nearly all the way out of the base. I am going to revisit this!Thanks for the input!
RT often means router table.
Your bit should not be bottomed out in the collet, raise it up about 1/16.
Is your insert truly flush with the table?
Since the house is on fire let us warm ourselves. ~Italian Proverb
You might suspect the collet. If it's dirty or even worn out (they do wear out) then you can get bit wobble. Wobble equals chatter during use (and could equal a flung bit as the collet is further pounded out). Test this with a straight bit and a similar piece of wood - if no screaming chatter, then the collet gets a walk, and the new bit becomes the suspect of choice. Manufacturing defects are not unheard of.
Don't bottom the bit out in the collet. Most bits have a fillet at the shoulder and this causes the bit to slip out since the collet is tightened onto the fillet. The chatter could be from bushing wear if the router is old. RT probably means 'Router Table'.If the router is backed out too far, you may want to make a spacer that attaches to the base- maybe 1/2" thick.
"I cut this piece four times and it's still too short."
No time to address your points now but one.
You are at serious risk with any thing less than 1.5" of motor barrel in that casting. All 4 pins barrel pins must be engaged in the twin helixes.
I suspect that is where the vibration is coming from, use a shorter cutter.
And maybe a straight, not a spiral bit.
See No.12 Faq
Are you plunging the full depth of the cut or taking shallow passes? Does the chatter happen with shallow passes, say 1/4" at a time?
That cutter is an 'upcut' spiral bit. Methinks your insert is being agitated by the bit's tendency to draw up the work which imparts vibration in the insert. I've attached screws to hold the insert down
to the table. Drill and tap and countersink four holes whilst the insert is in place. Steinmetz
That makes the most sense to me. I'm going to give it a shot. I did some tests. The 1/2 spiral bit I have did the same thing. The standard cutting bits I have did not, but they don't cut deep enough and create too much heat. I actually popped a clump of burning sawdust out of the hole during one test today.Anyway, I ended up cutting the holes on the drill press and finishing with a chisel.
You mentioned that it is an upward spiral. You need a downward spiral. The upward spiral is lifting the piece off the table, that is what is causing the chatter. Try a downward.
Best,
John
I think it's the opposite since the router is upside down in the table, the up spiral is pulling the work towards the routerand trying to lift the insert out of the table.
Since the house is on fire let us warm ourselves. ~Italian Proverb
Dear Dgreen,
You know, I think that you are right. I stand corrected! I retract my earlier statement!Best,John
An upward spiral is referenced to the router being out of a table, handheld. With the router upright on the workpiece, if the rotation causes the fibers to be lifted out of the wood, it's an upcut bit. If they're being pushed into the wood, it shears the fibers more cleanly but causes the router to lift if an agressive cut is taken."Up-cut Bits provide faster cutting while they pull chips up and out of the work or towards the router. They are excellent bits to use when cutting material in a table mounted router. They hold the work piece to the router. Ideal for mortise and tenon, grooving, slotting or routing deep blind holes.Down-cut Bits cut slower and push chips away from the router to eliminate top surface splintering. Use for pattern cutting or when going completely through the board as it allows clear vision of the cutting line. Ideal for fine finish work such as veneers, laminates, inlays and repairs because they prevent upper edge tear outs. Use Down-cuts for trimming and sizing."Taken from the Eagle America website.
"I cut this piece four times and it's still too short."
Hello
There is a lot of good info. about possible reasons you have chatter.
But as I see it if there is no problems on the plunge cut, Why not make a series of plunge cuts useing a plung router instead of useing a table ? and then remove the waste material, As I see it you may be bitting off to much at a time for the router to handle. If you handle your mortising more like you would with a chisel, perhaps everything would work out better?
Good luck and let us know how it turns out.
Edited 8/26/2006 1:46 pm ET by Curtis
From what you have said, I suspect your problem is caused by the long length of bit extending from the collet. To keep this at a minimum when cutting deep mortises, do not try to make it all in one cut. Make several shallow cuts and don't crowd the tool. Trying to take a heavy cut with a long bit causes flexing and thus the loud screeching sound. This is especially true when using 1/4 inch bits. You might also try ising a 1/2 inch diameter bit.
The last time this sort of thing happened to me, I was trying to cut dovetails on a jig and, no matter what I would do, they just didn't fit properly. I discovered that the collet had come lose from the motor shaft and was wobbling. After tightening it up again, no more problem with chatter.
Mike Hennessy
Pittsburgh, PA
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