Using a high fence

[Ed62]

Trying something new, I wanted to make a kerf running 2 1/2" high, parallel to the face. After making a 5" high fence to straddle the fence on a BT3K, everything looked good after making sure it was at 90 degrees to the table and parallel to the blade.

The finished size of the piece was to be 3" X7", and the kerf was to run
2 1/2" deep, leaving 1/2" of stock left uncut (not sure if I made that clear). Anyhow, I used a piece about 7" X 12" to be cut to size later so I would have plenty to hold onto while making the cut.

With the blade raised 2 1/2", it was cause for concern without the blade guard available. After thinking about a safe solution, and considering that tipping the top of the board even 1/32" I was flirting with a possible kickback because the bottom could move even further toward the spinning blade (not good!).

My solution was to move to the right side of the saw, with the fence between me and the blade. This would effectively function as a blade guard if something went wrong. A featherboard was used on the bottom of the board to keep it against the fence. But my concern was what might happen after the board cleared the featherboard. So I stopped the saw before clearing the featherboard, and I still had enough to cut to size. It worked, but there's gotta be a better mousetrap! Any words of wisdom? Thanks. Simply trying to learn a new technique.

Ed

[LCHIEN]

to me the trick to this would be how to push the workpiece and not put anything in a bind.

As you said, partial thru cut, = no blade guard. I do use the Sharkguard riving knife which still provides the splitter (does not go higher than the blade) and thus stays on for partial thru cuts like this. You can make a cut down splitter by using the existing splitter as a pattern and taking 1" off the top. There's more discussion else where.

A feather board as you suggest placed to keep the workpiece against the rip fence in front of the blade is very good.

Your high rip fence attachment and rip fence must not move laterally at the top. I don't like the straddle fences so much, it seem to me like they can move. I bolt my high fence to the rip fence using t-nuts and the slot in the face along with countersunk holes for the bolt heads.

I would now use a homemade push shoe or a commercial push shoe - a thing that's 3/4" wide, has a handle, rests on top of the workpiece and has a catch lip at the trailing edge to help push the workpiece thru. I'd rest that on top of the workpiece and push down (mostly) and forward (enough to move the piece into the blade) and bear slight pressure towards the fence (just enough to keep it tight to the fence but not make the fence lean any). The pressure towards the fence should be pretty small because there's no force really pushing it away, esp. once the cut is started it should want to stay there, and the bottom is already tight to the fence from your featherboard.

It's a matter of practice and feel, you want to keep all three pressures firm and constant.

[Jeffrey Schronce]

I agree that it is mostly a matter of technique. Also, IMHO most kick back is created by freehanding, using a fence and miter causing bind or lack of splitter on wood that tends to move after being cut. You are avoiding the first two issues. The third issue is really a big one for kickback. What is happening is that even though you are removing the kerf width of the blade, the wood, as it exits the other side of the blade becomes less stable due to its being cut down, often into small thin strips. The material you are working with should cut reduce that exposure since you are working with a thick piece AND you are leaving a few inchs of height in uncut wood which keeps the cut portion from pinching the blade.
I think you just need to be aware of the potential, but understand and be assured that you are doing the cut the right way. I think you have low kick back potential here.

[Ed62]

Hi Loring,

Thanks for the reply. The fence I made has a leveling screw on each end, and all-thread ran through t-nuts to secure the whole thing to the original fence from the non-cutting side. It seems pretty stable, but that's not to say it *can't* tilt.

I have shop made push blocks, which I didn't use because I felt it would be easier to put something in a bind if using them. But your post made me think it wouldn't be hard to make a push block that would ride on top of the shop made fence to push the workpiece. I could also add a small cleat to hold the workpiece against the fence without exerting much pressure at all.

Everything I'm doing now is pretty much experimental, and shop made devices are likely to be improved on. Thanks again for "food for thought".

Ed

[LarryG]

I think I"m correctly envisioning your workpiece and the cut, but have two questions:

1. How thick was the workpiece?

2. Where was the kerf located laterally; i.e. where was it within that thickness? Centered, offset toward the blade, or offset toward the fence?

[Ed62]

Thanks for the reply Jeffrey. I'm aware of the dangers and most causes of kickbacks. I was working with one of my sons when he got a kickback while using a circular saw. This caused him to lose one finger, and 1/3 of the next one. It was not a fun time.

Ed

[Ed62]

I think I"m correctly envisioning your workpiece and the cut, but have two questions:

1. How thick was the workpiece?

2. Where was the kerf located laterally; i.e. where was it within that thickness? Centered, offset toward the blade, or offset toward the fence?

The workpiece was 3/4" thick, and the kerf was located closer to the blade, being 3/8" from the edge. Now you've got me wondering what's going on in your mind. Anxiously waiting your thoughts.

Ed

[Tom Miller]

This is exactly the type of cut (pocket cut) that sent me to the ER a few years back. As with most accidents, it was the result of several circumstances. But, I think if I had been using a cut-down riving knife, the other circumstances would not have been sufficient to cause an injury.

To make such a cut now, in addition to religiously using a cut-down riving knife, I would use a lateral featherboard, a fence-mounted featherboard (pushing down), and a push stick.

If you make the cut in several passes, be sure that the lateral featherboard is positioned high enough so as not to push the previous kerf closed. Not so much an issue of danger, as it is a sloppy cut.

Regards,
Tom
[Added later: Oops, I didn't realize until reading Larry's post below that the piece being cut is 7" tall as it's riding on it's side. That all but rules out the fence-mounted featherboard and push stick option.]

[LarryG]

Now you've got me wondering what's going on in your mind.

Just the usual nothingness, mostly.

I asked about the width because as Loring says, pushing the workpiece without putting anything into a bind is the key. The narrower the workpiece, the less bearing area it has on the table, and the more likely it is to tilt sideways and bind. Three-quarter material is pretty thin so your instincts to use a high fence were correct.

I asked where the kerf was located laterally mostly for informational purposes, to help me better visualize the situation. I'm not sure that made a whole lot of difference, if any, in this case.

I wouldn't have used push sticks, either, since the 7" x 12" face size gave you plenty of room to hang onto the workpiece directly. There are times when push sticks are the only way to be safe BUT they complicate the situation by introducing a second element that must also be controlled; that is, your "grip" on the workpiece itself is now indirect, via the push stick. So I tend to avoid push sticks except when my fingers would come within about 3" of the blade.

Overall, I agree with Jeffrey that you had a pretty low potential for excitement here, given the precautions you took.

A couple of for-what-they're-worth comments in closing. First, I always feel safest when it feels like I have a "firm but relaxed" hold on the workpiece and it is sliding through the blade fairly effortlessly. When I tense up and use a death grip on the piece, that's when I most feel like something might easily go very wrong. Second -- and I'm aware that a lot of folks don't agree with me on this -- I am emphatically NOT in the "never stand behind the blade" camp. I stand wherever I need to stand in order to exercise the most control. Sure, I'll stand off to the side whenever I can (and being a lefty, I'm often standing right where you were, on the right side of the fence). But not if it compromises control. If moving off to the side puts me in an awkward position where my ability to hang onto the workpiece and guide it accurately is diminished, I'll move over and stand right behind the blade.

[Ed62]

Thank you Larry. It's got to be rough being a southpaw when the world is made the other way.

Now I have another question that might be answered by "personal preference". Since my fence was 5" high, and the cut was 2 1/2" deep, if I handheld the workpiece, my fingers would probably be 1" or so above the blade if I were "squeezing" (holding) the workpiece to the fence while feeding. I was not comfortable with that, so I actually held the workpiece with my fingers slightly above the fence. This was cause for concern because I wasn't sure I could hold the workpiece without getting it "tilted" in the process. Now I think if I have need to make more cuts like this, I'll either use a higher fence that will allow me to "squeeze" the workpiece to the fence while feeding, or I'll make a push block with 2 cleits, 1 for pushing, and the other for holding the workpiece to the top of the fence. Either way would allow for more stability during the cut. Other thoughts on this?

Ed

[LarryG]

Being left-handed ain't so hard; but then I've had a lifetime of practice. I've found it to actually be advantageous since living in a right-handed world has caused me to learn to use my right hand maybe a little more adroitly than the average right-hander is able to use his left. For example when I was a kid playing sandlot baseball, all the gloves were for righties so I learned to throw and bat right handed (I can switch-hit, after a fashion, but if I throw a ball with my left hand, that may be the last time anyone will ever see it). OTOH if I tried to eat right-handed, I'd stab myself in the face with my fork.

I actually held the workpiece with my fingers slightly above the fence. This was cause for concern because I wasn't sure I could hold the workpiece without getting it "tilted" in the process. Now I think if I have need to make more cuts like this, I'll either use a higher fence that will allow me to "squeeze" the workpiece to the fence while feeding

Ah, that do make a difference. With your fingers above the fence, the top of the fence became a pivot point that could have led to some control problems, so yes, a higher fence next time around would be an excellent idea.

Another way to do it, probably the way I would have done it, would be to stack up three or four pieces roughly the same size as the workpiece, clamp them together with the actual workpiece nearest the fence, and shove the whole works through the blade. Four 3/4" pieces stacked together would give you 3" of bearing width on the table, making it highly unlikely the clamped-up stack would tilt. With this setup, you really wouldn't even need a high fence.

[niki]

I went to the garage and made some prototype of a jig from scraps, no dimensions, only the idea.

I took a few pictures otherwise you would end up making a table with my explanation.

I strongly recommend using a riving knife or kind of low splitter.

niki

[Ed62]

Both excellent ideas. Thanks guys.

Ed

[footprintsinconc]

niki's jig

hi,

i followed your pictures and was confused about the last picture, as the blade is not visible in any of the pictures. is the piece being cut: the white board with holes in last picture?

[niki]

Hi Omar

On the last picture I added another white piece (with the holes) in front (right), this is the piece that is going to be cut.
The back (left) piece is sacrificial and acts as a pusher while the 2x4 acts as guiding board (or second fence) that you push.
When the work piece is out of the blade, the sacrificial piece is inside the blade, that’s the reason that I said “when the board that you are cutting is out of the blade, stop the saw, wait for the blade to stop and pull the jig (the sacrificial piece) out.

That’s the safest way that I can think of re-sawing on TS that is not designed for this job, the Band saw will be a better choice (but I don’t have BS).

niki