# Plunging straight bits



## crquack (Oct 10, 2008)

I am about to cut some stopped dadoes, 3/4"x3/4". They will be in pairs, mirror images of each other. I would like to do this on the table so I cannot get away from having to plunge at some point.

I do not have a 3/4" bit. I was looking around and found that some, but not all, companies sell straight bits and also straight *plunge bits*.

The simplest thing would be to order a 3/4" straight plunge bit from MLCS, however, I thought I would look at the issue more throughly. Specifically:

1) Can you plunge with Freud straight bits? Freud is one company that does not make the distinction. They claim you can plunge with their bits, however, examining the bits I was not too sure.

2) Can you plunge with these:

6 pc 1/2" SH 1/4" to 3/4" Straight Router Bit Set on eBay.ca (item 140397520712 end time 13-Apr-10 20:25:06 EDT)

They seem to be quite popular here and I thought somebody might know.

3) is it a good idea to plunge with a 3/4" bit anyway? The wood BTW is pine.


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## jlord (Nov 16, 2009)

Those bits will do the job. An up spiral will do a little better as it pulls the waste up out of the joint as you go. A down spiral will help with any chip out if the joint edge will be seen.


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## jschaben (Jun 21, 2009)

crquack said:


> I am about to cut some stopped dadoes, 3/4"x3/4". They will be in pairs, mirror images of each other. I would like to do this on the table so I cannot get away from having to plunge at some point.
> 
> I do not have a 3/4" bit. I was looking around and found that some, but not all, companies sell straight bits and also straight *plunge bits*.
> 
> ...


Hi - I have to disagree with Jim. Those are not plungers. Scroll down to the larger pics and you can see that there is no cutter across the center of the bottom of the bit. Glad you posted the link though, that's a pretty good price for a set of that many decent straight bits.
Why do you need to do it on the table? I have rarely been able to accomplish a decent plunge on the table. Usually is a little squirrelly where the bit starts to cut. Even with spiral cutters. 
Plunging with a 3/4 bit isn't a problem, depends on how deep you want to go. You should make a couple of passes anyway if you are going deeper than about a 1/4". If you insist on doing it on the table the first few passes shouldn't be much more than scoring passes, about a 1/16" or so, until you get to 1/4". Gives the bit a chance to figure out which way everything is supposed to go.
I think your best bet is with the MLCS bit.
Hope this helps some


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## jlord (Nov 16, 2009)

Ah Yes you are right John I did not look at the bits good enough. I did not even notice you could scroll down for better pictures. I still prefer spiral cutters over the straight bits.


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## bobj3 (Jan 17, 2006)

" is it a good idea to plunge with a 3/4" bit anyway?" = No,
you will cook the bit, it will just spin on the part it can't remove (the center)

3/4" plunge bits

MLCS Plunge Cutting Straight Router Bits

======


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## jschaben (Jun 21, 2009)

jlord said:


> Ah Yes you are right John I did not look at the bits good enough. I did not even notice you could scroll down for better pictures. I still prefer spiral cutters over the straight bits.


Hi James - I guessed that was the case. I like spirals also but once you get over 1/2" you are in CNC territory, at least as far as solid carbide goes. I have found one 3/4" spiral in HSS at Lee Valley. You won't find solid where the shank is smaller than the cutting diameter, probably because the carbide is so brittle. I did manage to score one of these on eBay for $15. Can hardly wait till I gotta replace the bladesh34r:


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## crquack (Oct 10, 2008)

If one abandons the table idea one is in the jig territory using a hand router. Thus I guess no need for a plunging bit, nor, for that matter, a 3/4" bit. I am sure there is a way to stop the dado using a hand router. I just have not thought it through, being in favour of my table and all...Also this is a one-off so I do not want to spend days making a jig for something that will then take 5 minutes to cut. But maybe I am missing the very essence of router work


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## jlord (Nov 16, 2009)

Can you clamp a board as a stop where you want your router to stop the dado? A jig won't take very long to make, it does not need to be elaborate for a one time use but sometimes preferred for a good result.


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## jschaben (Jun 21, 2009)

crquack said:


> If one abandons the table idea one is in the jig territory using a hand router. Thus I guess no need for a plunging bit, nor, for that matter, a 3/4" bit. I am sure there is a way to stop the dado using a hand router. I just have not thought it through, being in favour of my table and all...Also this is a one-off so I do not want to spend days making a jig for something that will then take 5 minutes to cut. But maybe I am missing the very essence of router work


Doesn't need to be elaborate. See attachment. Also don't need a 3/4 bit, just make a pass down one side of the guide and back along the other side. Change depth and do it again
You do need a set of bushings and plunge bit. Works best if the bit is larger than 1/2 the width of the dado. That way the cuts overlap and you don't get the cut mark down the center of the dado.
I just rechecked the pic.. Not easily seen but the distance between the guides would be *width of dado PLUS Bushing diameter MINUS Bit diameter*


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## harrysin (Jan 15, 2007)

Wherever possible I use plunge cutters as shown in the first shot taken from a forthcoming thread and the second shot shows how I use end stops. Why not use a 1/2" cutter then move the fence for the second cut, it's much easier than a 3/4" cutter


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## jschaben (Jun 21, 2009)

harrysin said:


> Wherever possible I use plunge cutters as show in the first shot taken from a forthcoming thread and the second shot shows how I use end stops. Why not use a 1/2" cutter then move the fence for the second cut, it's much easier than a 3/4" cutter


Hi Harry, I was attempting to propose the same method you are showing in the first shot.
However, in your second shot you have the stops clamped to the fence (as I usually do). Wouldn't clamping the stops to the table make more sense as moving the fence also moves the stops?:sad:


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## crquack (Oct 10, 2008)

> Wherever possible I use plunge cutters as show in the first shot taken from a forthcoming thread and the second shot shows how I use end stops. Why not use a 1/2" cutter then move the fence for the second cut, it's much easier than a 3/4" cutter


I was going to do the second picture thing. What I do not understand where the 40 mm guide comes in. Why use a guide anyway if you are using a table and a fence? Would you not just put a 1/4" spacer between the fence and the workpiece and remove it for the second pass (using a 1/2" cutter for a 3/4" dado)?


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## jschaben (Jun 21, 2009)

crquack said:


> I was going to do the second picture thing. What I do not understand where the 40 mm guide comes in. Why use a guide anyway if you are using a table and a fence? Would you not just put a 1/4" spacer between the fence and the workpiece and remove it for the second pass (using a 1/2" cutter for a 3/4" dado)?


Hi - I thought Harry may have responded by now but I'm abit fuzzy on the time differences.
I think Harry was mainly showing the cutter in his first picture. Notice how there is a cutting edge completely across the bottom of the bit. Normal straight bits don't have that and they just burn their way through if you try plunging with them. Will likely build enough heat it will be the last time you use it anyway. 
Your idea of using a 1/4" spacer on the fence would work. I think it would be kind of a pain as the spacer would need to be replaced and removed for each depth change to bring it all down evenly. 
I guess no one has asked yet, is this dado stopped at both ends or just one? Up until now I have been thinking it was stopped at both ends but that may not neccessarily be true


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## harrysin (Jan 15, 2007)

jschaben said:


> Hi Harry, I was attempting to propose the same method you are showing in the first shot.
> However, in your second shot you have the stops clamped to the fence (as I usually do). Wouldn't clamping the stops to the table make more sense as moving the fence also moves the stops?:sad:


You're quite correct John, however, my table doesn't lend itself to such a thing.


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## harrysin (Jan 15, 2007)

crquack said:


> I was going to do the second picture thing. What I do not understand where the 40 mm guide comes in. Why use a guide anyway if you are using a table and a fence? Would you not just put a 1/4" spacer between the fence and the workpiece and remove it for the second pass (using a 1/2" cutter for a 3/4" dado)?


 John has answered your question, the two shots are totally unrelated. Isn't it about time that we got onto first name terms?


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## crquack (Oct 10, 2008)

> I guess no one has asked yet, is this dado stopped at both ends or just one? Up until now I have been thinking it was stopped at both ends but that may not neccessarily be true


One end only. 6 pairs mirroring each other.



> I think Harry was mainly showing the cutter in his first picture. Notice how there is a cutting edge completely across the bottom of the bit. Normal straight bits don't have that and they just burn their way through if you try plunging with them. Will likely build enough heat it will be the last time you use it anyway.


I get that which is why I was asking specifically about Freud. The company says "plunge", my eyes say "perhaps, perhaps not".



> Your idea of using a 1/4" spacer on the fence would work. I think it would be kind of a pain as the spacer would need to be replaced and removed for each depth change to bring it all down evenly.


Precisely. Hence the ruminations on which 3/4" bit to buy. I do not want to spend what time I have left on this earth cutting 6 measly dadoes. I guess go with MLCS and be done with it...Or build a jig and do it by hand...:shout:


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## jschaben (Jun 21, 2009)

crquack said:


> One end only. 6 pairs mirroring each other.
> 
> 
> 
> ...


Hi - Yeah, they do that. I bought a Amana off Amazon where the picture wasn't that clear. Description said it was a plunge bit... I gripped. It was a pretty good price though and is a good 3/4" straight bit but no plunger. 

Open dado would be OK on a table but I would try to come at it from the open end. I've tried making slots and even with shallow plunges the stock likes to squirrel around on you unless the stock is large enough to get a good grip on. Without getting fingers to close to the cutter. 

I really think you could do all six in under an hour with the method I described a couple of posts ago. All it would take is a couple of 1" wide strips, a bit longer than the dado, of MDF + a 1" square of MDF, a 5/8" bushing and 1/2" bit. Wouldn't even need to be a plunge bit as the dado is open on one end. Come to think of it, if you have a 3/4" straight bit, you could do it in 1 pass with a 1" bushing and 3/4" bit. Set up would be the same.


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## crquack (Oct 10, 2008)

I saw the wisdom of what you suggested and already this morning got me a nice piece of MDF.

The difference between $3 (MDF) and $27 (3/4" bit) makes the bit of extra time worth while.


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