Cutting half laps with a dado blade?

[Upscale]

I'm looking for tips on cutting half laps with a dado blade on my table saw. The saw lives in a friend's garage and I haven't installed the rails and fence because I don't need them for the outdoor projects I've building.

My problem is sneaking up on the cut lines for these half laps since I can't see them because they're turned down when doing the cutting. Careful as I am sneaking up on the turned down cut lines, occasionally, I've cut too much off which is a pain. Anybody got any tips for cutting these without going to the effort of installing the rails and fence to use with a start off reference block against the fence?

Thanks

[Morris Dovey]

Perhaps it would be easier if you put the marks on the /edge/ (that goes into the sawblade first)...

[Peter Huebner]

Well I do those on the radial arm saw, but all the same ... when I can't see exactly where I might be going because the original mark is facing away from me, I get my 6" engineer's square out and a marking knife and I scribe all 'round so I CAN see where the blade enters the wood relative to the mark - then adjust as necessary. Knife is much more accurate than pen, especially for this job, somewhat prevents splintering and I find my ageing eyes can pick a knife mark out more easily than the Rotring.

That little square is one of the tools I'd most hate to give up.

-P.

[Larry C]

I have also put down a couple of strips masking tape in front of the blade on my table saw. Then I take a straight edge and place it along side the saw blade and score a line with a knife. Then I peal away one side of the tape and I now have a reference of where the side of the blade is. You could also draw a pencil mark.

I think I did a terrible job of explaining but I hope you get the idea.

Larry C

[Upscale]

I *do* put reference marks on the sides and bottom of the wood. Problem is sitting in the wheelchair, I can't feed the wood and lean over it at the same time to see where the leading edge is going into the blade. However, it did occur to me to cut do the cut from the back of the table saw, pulling the wood towards me into the blade, something I'd be able to see from the get go.

I can't envision a specific safety issue doing it that way, but then that's exactly when those safety issues jump up and bite you in the ass.

[dadiOH]

Step #1 is to mark your board on the leading edge.

Step #2 is to have some way of aligning the edge mark with the blade edge.

In my case, I used a knife to scribe lines from each side of the blade onto the cast iron table and throat plate, sprayed paint onto same, wiped off excess paint leaving it in the scribed lines. I still prefer to use my radial saw for cutting out half laps.

[Upscale]

I do understand what you explained. I was negligent in my original explanation by not explaining that I use a wheelchair and can't easily feed the wood and lean over it and at the same time watch the leading edge of the wood feed into the blade. Perhaps the solution is what I suggested to Morris which is an unconventional solution, but not in the realm of impossible.

[Morris Dovey]

I forgot that you worked from a wheelchair - sorry.

Sometimes I do this kind of cutting with a sled on my TS. The sled has only ever been used with one blade, and so the slot in the bottom and rear fence are "zero clearance". I can envision pulling the sled back until it tips - then fitting it with stop blocks or clamping the work in place using the zero-clearance slot as a reference...

I think there's too much room in that picture for the blade to grab the workpiece and throw it in your face.

[John Grossbohlin]

I'd clamp a straight board to the table top, parallel to the miter slots/blade, to act as a fence. This to control the length of the lap as would your regular fence. You could use an adjustable square with the head in a miter slot and the end of the blade against the "fence" to position the temporary fence.

John

[Puckdropper]

"Upscale" wrote in news:95395$4a756ad9$cef88bc5$ [e-mail]:

I sometimes make one cut at the line (where I want it) and then cut the rest out. You could even cut the line with a hand saw or router. The advantage to this is you gain a kerf's width of fudge room.

Another thing I did was mark the outsides of the blade on the little orange insert my saw has for doing this kind of stuff. That way, I've got a reference to work with before the saw blade enters the work. It's not always accurate with a wabble dado, though.

Puckdropper

[Larry C]

How about if you use the method of making a first cut at your line with a saw of choice. That way you would have a reference point on the back of the board. Then take the method of extending a line from the edge of the blade to the front of the table saw. That way you would have the fudge factor of a saw blade and a reference point at the back of the stock to line up to the edge of the blade. Both would at the back of the stock.

Larry C

[Leon]

Attach an adjustable stop to your miter gauge and sneak up on the cut.

[Kevin]

I would say from your position in the wheelchair most of the usual ways of getting a stop block reference are going to be a PITA. What happens is you end up sneaking up on your final stop block position, and as happened too many times to count just when you've got it almost perfect and you're dialing in that last adjustment the bugger slides or the clamp slips off and you have to start all over. And this is when you can actually see what you're doing, much less trying to do it from a seated position. This is where having the stop block attached to a good fence that always locks down perfectly and has a measurement scale to use as a reference becomes very handy. If you move the fence too much you still know where it was supposed to be.

But failing that, you could just clamp a block of wood to the table farther away from the final setting and use shims to get it less than the final setting. Take out shims until you get where you need to be. I'm assuming that the half lap is not in the middle of a long board that extends beyond the table. The other way is to attach an extended fence to the miter gage, but then you won't be able to see the stop block so I think clamping to the table will work better.

In the future, if you don't already have one, I would definitely build yourself a good sled with some hold down clamps so all you have to worry about is pushing the sled through the cut. While you're at it make two so you can use one for dado cuts.

-Kevin

[Upscale]

As you (and Kevin have noted) an adjustable stop would solve the problem. All along I've been using the stock mitre that came with the saw over thirty years ago.

I've made up my mind to buy a decent mitre gauge with a larger fence and adjustable stops built into it. I was thinking I could use one even before this problem started. I've seen a number of reviews on them so I'll go through them and select something suitable.

[Luigi Zanasi]

Screw on a scrap length of wood to your mitre gauge, one that goes beyond the blade. Lift the blade higher than the wood and cut it off. You now have a reference for your cut lines at the exact position the blade is. Bring the blade down to the height you want for the half laps, line up your mark with the wood attached to the mitre gauge & Bob's your uncle.

HTH

Luigi

[Lew Hodgett]

That was standard issue on a couple of old T/S I had.

The miter gauge had a couple of holes thuru which you could insert a

3/8" dia. rod (I would use a 36" length), then tighten in place with thumb screws.

A 2nd rod, about 12" long, had a hook and could be clamped beside the long rod.

Make a story board as a means of setting the length.

If you screw up the setting, make a new story board.

"Upscale" wrote>

A couple of good sleds as has been suggested (T/S blade and dado) along with a piece of plywood screwed to a standard miter gauge face is a lot less expensive and IMHO, a whole lot more useful.

Lew

[Leon]

I have been using the "Dubby" for about 10 years and am very happy with it. Actually I have both the right and left side Dubby. One Dubby will cost you about the same price as a better grade after market miter gauge. I also have a Kreg miter gauge with stop that I use mostly for squaring stock and cutting short pieces to length. The Dubby has a pretty large capicity but is also easy to use for small pieces.

[Upscale]

The "Dubby" type of attachment I'll consider when the time comes to upgrade from a contractor's saw to a cabinet saw. Along the same lines the Exalibur and Jessem add-ons are interesting. ~ Stuff for future consideration.

I'm going to go to Lee Valley and have a look at a Kreg and Accu-mitre. Considering that the Accu-mitre is more than twice the cost of the Kreg, it's unlikely I'll buy it, but I'll examine both and see how I like them.

[Leon]

I bought my Kreg just as Kreg had bought the rights to manufacture the gauge. Just to let you know, I considered 3 brands, Incra, Kreg, and the Osborne. The Osborne was the most disappointing as when adjusted to one of the 45 degree settings vs. the opposite setting the fence wobbled. The adjustment support flexed "VERY" easily. I could see how inconsistent miters would be common. I tried 3 of these jigs and they all had the problem. The Incra jigs all IMHO took up too much real-estate behind the fence which limited the width of the stock being cut. The Kreg was not with out its problems however Kreg was very helpful in resolving the problem, as opposed to Osborne. Basically the Kreg uses indexing pins that either fit too tightly or too loosely. Kreg ended up sending me a replacement that they pulled off the line and tested before shipping. Osborne simply denied a problem.

One thing that I do appreciate with the Kreg, it is 99% aluminum so it is light weight and easy to handle.

Swingman has an Accu-miter and IIRC he is pretty pleased with his.

[David Nebenzahl]

On 8/2/2009 4:59 AM Upscale spake thus:

Maybe a stupid idea, but is there any chance you could rig up a mirror so you can see in front of the piece being cut?