Can I safely cut a rabbet?

[spf45]

Well, the last time I admitted on this forum that I had a lot to learn, I ended up learning quite a bit. I thought I would post my latest mistake. I broke a bit in my 1/4” router. I was trying to cut a rabbet in 3/4” plywood. Instead of taking 1/8” of depth at a time, I thought I could take 1/8” of WIDTH each time and set the bit at the full depth. By doing this, I figured that I would be using more of the bit (instead of just the area at the tip), I was not taking out any more wood than if I simply modified the depth, and that I would avoid problems associated with changing the depth on an inexpensive router. I hate those little "steps" left on the wood at each cut depth. Anyway, I thought it was a nice theory.


I think my plan ignored some key laws of physics, and I put too much side pressure on a 1/4” router bit. It snapped. Luckily, the tip did not go through me or anything else—this time.

I will eventually get a 1/2” router. I realize that a 1/2” router would be better but it will still not make me immune from stupid mistakes. I think I can mitigate the risk to some degree with my current router by varying the depth.

In my past use of the router, I have always taken off just a little bit of depth at a time and I never had a problem. In fact, this time I noticed that I almost had to “force” the router--not really, but you know what I mean. Using force is always a bad deal with cutting tools and I should have known then.

This event led me to consider using other tools for the 4 foot rabbets and the upcoming 2 foot dadoes. I have never really wanted to use the table saw for such things, as I don't want to take off the table saw splitter assembly. Ever since my junior high shop teacher explained why there was a dent in the wall a trillion feet from the table saw, I take kickback very seriously. (That was years ago and it the impression is still there .)

Any great advice?

[LCHIEN]

I too, broke a 1/4" spiral upcut bit in the exact way you describe.

Well, cutting dados in a TS is much less likely to kick back than cutting jobs where you have small cutoffs. Rather than fear it you should understand it.

Usually the cutoffs are what kicks back, with a dado there are no cutoffs.

If it were straight dados or rabbets, 1/4", I would not hesitate to use my TS to make those in two passes were I too lazy to change the bit (and probably would not unless I were making several).

Esp. if they were 2-4 feet long, mucho faster than with a router.
With my microadjuster I could make it a perfect 1/4" wide, two cuts, full depth.

[LarryG]

I will eventually get a 1/2” router. I realize that a 1/2” router would be better but it will still not make me immune from stupid mistakes. I think I can mitigate the risk to some degree with my current router by varying the depth.

Not trying to cut too deep is important regardless of the bit's shank size.

I'm unclear on the diameter of the cutter itself. I understand the shank size was 1/4", but was the cutterhead also 1/4"? I ask this because if it was, that's a situation in which a 1/2" shank really wouldn't have made any difference. A 1/4" cutter with a 1/2" shank may have a lot more mass buried within the collet, but the weak point where the bit necks down to 1/4" is no different than the same 1/4" diameter cutter with a 1/4" shank. Point being ... yes, you should upgrade to a router with a 1/2" collet, because that's far better overall for larger-diameter cutters, but for this particular incident your current 1/4" shank router wasn't a liability.

As regards your main question, I agree with Loring's central point that respect and understanding of the process of cutting dados on a table saw should make your fears mostly groundless. Do it wrong and/or carelessly and sure, you're asking for it. Take all the proper precautions and the odds of having a problem are minimal, probably in the fluke category.

[spf45]

Not trying to cut too deep is important regardless of the bit's shank size.

I'm unclear on the diameter of the cutter itself. I understand the shank size was 1/4", but was the cutterhead also 1/4"? I ask this because if it was, that's a situation in which a 1/2" shank really wouldn't have made any difference. A 1/4" cutter with a 1/2" shank may have a lot more mass buried within the collet, but the weak point where the bit necks down to 1/4" is no different than the same 1/4" diameter cutter with a 1/4" shank. Point being ... yes, you should upgrade to a router with a 1/2" collet, because that's far better overall for larger-diameter cutters, but for this particular incident your current 1/4" shank router wasn't a liability.

As regards your main question, I agree with Loring's central point that respect and understanding of the process of cutting dados on a table saw should make your fears mostly groundless. Do it wrong and/or carelessly and sure, you're asking for it. Take all the proper precautions and the odds of having a problem are minimal, probably in the fluke category.

Yes, I was using a 1/4" cutter and I realize the 1/2" shank would not have saved the day. I guess I was just mentioning that I was aware that of the the benefits of the 1/2" router. I guess on a rabbet, I could use a 1/2" shank and a 1/2" cutter. The dadoes would depend on the width of the cut, but in my case, they would work.

I am going to consider using the saw for the rabbets. I think there are some semantics involved when it comes to fear vs. respect on the table saw--or any other tool. If I was "afraid" of the saw, I wouldn't use it at all. At the same time, I make "darned" sure I keep the odds in my favor at every step. Before that plug goes into the socket I have systematically checked everything and executed a little walkthrough of the cut. Every time. So far, I still have all my fingers.

Having read posts from you guys over time, I have a lot respect for your feedback. Thanks for sharing with me.

[Tom Hintz]

Using a small diameter bit requires taking even less of a cut in terms of depth as the shaft and the diameter of the bit itself can't handle side loads, as you discovered.
Using the table saw for dados is very safe as long as basic procedures are followed. As has been mentioned, kickbacks usually happen with small pieces, often the cut offs. I suppose it cold happen with a dado cutter but as long as you pay attention to what you are doing and keep the saw aligned, all will be fine.
I have a story on cutting dados at the link below that might have a tip or two in it for you.

http://www.newwoodworker.com/hottodado.html

[chauvan]

Howdy! I'm brand new to the forum, table saws and rabbet cuts. I am a work in progress.

This weekend I was practicing making a rabbet cut on my new BT3100 for a day bed I'm building. The rabbet is 3/4" by 1 1/2" into a 2X6 yellow pine. I had no fear doing it along the wider face, setting the blade at 3/4" and using a feather board along the side. Went very smoothly; though I think it will save motor wear if I make several passes, though it didn't seem to bog down going the full depth.

That said, when I stood the board on it's end, trying to make the 1 1/2" cut (in a single pass), I was way more nervous that the board would try to fling itself back.

Would taking this cut in increments, just like with the router, make this a smoother operation?

Thanks!

[LCHIEN]

Howdy! I'm brand new to the forum, table saws and rabbet cuts. I am a work in progress.

This weekend I was practicing making a rabbet cut on my new BT3100 for a day bed I'm building. The rabbet is 3/4" by 1 1/2" into a 2X6 yellow pine. I had no fear doing it along the wider face, setting the blade at 3/4" and using a feather board along the side. Went very smoothly; though I think it will save motor wear if I make several passes, though it didn't seem to bog down going the full depth.

That said, when I stood the board on it's end, trying to make the 1 1/2" cut (in a single pass), I was way more nervous that the board would try to fling itself back.

Would taking this cut in increments, just like with the router, make this a smoother operation?

Thanks!

As an aside, you should have started a new thread rather than attaching to a month-old discussion.

As for your question, I think saw blade cuts can easily be 3/4" or in your case 1-1/2" with no problem. Overall you'll get best results if you can make them in one pass.

If I understand right you are making a 3/4 x 1.5" rabbet down the length of a 2x6 board, using two saw blade cuts.

I would sure do it in one cut. I'd strongly consider using a auxiliary tall fence to help support the 6" height when running that cut. You have to use T-nuts in the face of the rip fence to hold the taller fence in place.

Personally I'd make the cut with the 2x6 on edge first
then make the cut with the 2x6 flat next. For reasons of stability.

[Tom Miller]

Another couple suggestions:

When you make the second cut of the rabbet, don't let the offcut be hidden under the workpiece, between the blade and fence. Set up the cut such that the offcut is on the other side of the blade. Otherwise you could lose control of it.

Secondly, here's where a cut-down riving knife really comes in handy. It doesn't get in the way of a pocket cut (i.e. where the blade is buried in the workpiece), and it can really save your bacon especially with this type of wood (SYP) that is more likely to be hiding internal stresses than other hardwoods.

Regards,
Tom

[vaking]

Ditto on Tom's suggestion for a cut-down riving knife. And it answers the original concern from SPF45 about need to remove the splitter assembly. For this type of cut you need to remove the blade guard but not the splitter. If it is a Ryobi original assembly you have to remove the whole thing. But with shark guard you remove only the guard leaving the splitter in place. A lot safer. Please also note that Lee sells shark splitter separately and very inexpensively (about $20 shipped). Shark splitter is a part of shark guard, there might even be a chance you can buy splitter now and add the rest of the shark later (that was my route, I was lucky to buy a shark without splitter here at the forum).
Also, besides straight router bits and table saws rabbets can be made on a router with specialized rabbeting bit or on a jointer.

[cabinetman]

I would first like to address doing your rabbets and dadoes with a router. If you are using a basically underpowered router (like a trim router), under load you will have to push too much. Likewise if your bit is dull you will have the same problem. Those two conditions will slow down the cutting speed and efficiency. I try to use a large enough router, with a sharp carbide tipped bit, and, a one-pass is very smooth. HSS bits will not give the same results as a carbide tipped bit over a period of time.

As for doing dadoes on the table saw, the blade is pushing up on the stock and the quality of the pass is determined by holding down the stock while pushing it through. I prefer to do those machine procedures with a router. It's much easier to control a router than moving stock.



"I'M NEVER WRONG - BUT I'M NOT ALWAYS RIGHT"

[gary]

My current project (Adjustable Height Assembly table workbench) uses many rabbets to make the tongue and dado joints. I cut them with my BT and a SD206 dado blade. The hollow legs and cabinet carcass are built this way. The torsion box bench top is not shown here.

I have a tall piece of MDF attached to the fence and the dado blade is partially buried in the fence. I have a feather board attached to put down pressure right above the blade. I always make 2 passes (same fence position and blade height) because I find the dado blade will still push the piece up in places due to the forces involved. The second cut removes a small amount of material in the high spots.