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Thread: Plunge Cut Jig Question

  1. #1

    Plunge Cut Jig Question

    Hello,

    I am a newbie here but I have learned a lot from the folks on this forum. I am homesteading and building a loft ladder for my workshop and I need to make several plunge cuts with my circular saw. The design uses 2x12 DF stringers with 2x6 DF treads housed at 5/16". I've got quite a few hours into the stringers (dados are done, treads are dry fit) and the cutout for the railings are the last step. I've got a 1 3/8" forstner bit ready to go for the initial holes and then I will plunge cut the tangent/parallel lines in between. I've got quite a few hours into the stringers (I'm pretty pleased with my result) and I'm just nervous about the plunge cut with the circular saw. I don't want it to miss the line and I definitely don't want to have the saw kick back and hurt me or damage the work piece. It's a nice Milwaukee 8 1/4" cordless (top of the line) and I just want a good result. Originally, I had an idea that I could scribe a perpendicular line and tilt the front of the plate onto that line but I had a better idea... I'm not a pro and I don't have a lot of tools so I just want to get this right without overthinking it. I thought maybe I could make a jig to keep the saw right on the line. I have attached a couple drawings of my idea. Does anyone here think this is a bad idea?

    Thanks in advance.Plunge1.jpgPlunge2.jpg

  2. #2
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    Your circular saw blade will not be able to cut all the way into the tangent on your 1-1/2" thick matrial, so you will have to do some work with a hand saw to clean out the waste. Do your plunge cuts about 1/8" inside the tangent line and then plan on using a template and template bushing or template following router bit to clean up the excess material you left behind with the saws. This will give you a cleaner surface inside the openings for less sanding. You will probably want to round over the top and bottom edges anyway.
    Lee Schierer
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  3. #3
    Thanks Lee for that thoughtful response. I made that jig to ensure that my plunge cut is accurate. My question is this: Is the jig that I built going to give me a good result? Is it going to cause kick back? That is the nature of my question.

    Thanks in advance for any thoughts.

  4. #4
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    My personal thoughts on solving the issue would be a little different. Still use a jig, but instead of the way you have it set up, take a piece of 1/2" plywood about 2" larger than the dimensions of your circular saw. Put the saw in the middle and draw out the outline of the bottom plate. Tack straight scrap wood on the outside of your line to give a bounding box effect. Put the saw back in and do a full plunge cut by adjusting the "depth of cut" while the plate is in the jig. You at that point will have a zero tolerance jig that you can clamp on your piece, and as long as you have the saw at 90 degrees to the jig, where you see the line before you put the saw in, will be where you cut.
    As far as kickback, as long as you are firm in holding down (either by clamp, glue, assistant, mental pressure) the jig, and you advance the cut slowly with the saw at full speed, you should be fine.

  5. #5
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    Quote Originally Posted by John Bridgestone View Post
    My question is this: Is the jig that I built going to give me a good result? Is it going to cause kick back? That is the nature of my question.

    Thanks in advance for any thoughts.
    There is always a chance of kick back when making any cut if the saw blade gets pinched. Most circular saws have a built in clutch that will let the blade stop and the motor can still turn. So as you make your plunge cuts. make sure the blades is set as close to 90 degrees to the base as you can get it. Make sure the base leading edge is flat on the material being cut. Control the depth of plug letting the blade do the work. Be smooth in lowering the blade into the wood. Have a firm grip on your saw.

    If after making the first plunge you are uncomfortable for any reason find another way to make your openings such as multiple forstner bit holes and clean up with a chisel or router. Better to work slower than risk an injury or trashing a piece of wood.
    Lee Schierer
    USNA '71
    Go Navy!

    My advice, comments and suggestions are free, but it costs money to run the site. If you found something of value here please give a little something back by becoming a contributor! Please Contribute

  6. #6
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    If you are uncomfortable with a circ saw haw about drilling the 4 corners and using a jig saw? No plunge required.

  7. #7
    Thanks Lee, Doug and Flamone. These are all helpful suggestions. I drilled the holes with the forstner today. Everything is ready for the cutouts. I like the jigsaw idea but I don't have one. I think I'm going to practice on a few scraps tomorrow and see how I feel with the saw. I uploaded a photo of the stringers so folks can see the work I have put into them so far... Hopefully I won't screw them up!

    Stringers1.jpg

  8. #8
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    Maybe time to buy a jig saw?

  9. #9
    Well, I assembled the ladder today. It took a while and I had to make a small clamp adjustment for a slight cup but here's the ladder... Thanks for all the encouragement and I guess my next project will be trying to stain the ladder. It is Fir so hopefully I can get a good result.
    Attached Images Attached Images

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    Slots look good. Amazing how getting the first few under your belt allows for that confidence to grow....

  11. #11
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    I think you have demonstrated a very thoughtful approach to your project and are doing excellent work. However, (there's always a however - right?) my concern is the depth of your stair treads. The "standard" tread varies from 10"-11", with a 7" riser x 11" tread being very common. My concern is when you are carrying lumber, particularly heavy/unbalanced loads up the stairs the 6" tread may not provide adequate footage for your balance leading to a nasty fall.

    Now, the steepness of your loft ladder (unknown to me) may be what dictates your tread depth, as it may be more ladder than stairs (7/11 =32°), thus making the deeper 11" tread unacceptable. Regardless be careful if you are carrying a heavy load!
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