# Cicular Saw Plunge Cuts



## RickKr (Dec 30, 2018)

I'm working on a project where I need to make multiple, short plunge cuts (~40) in 2X lumber, for making oval shaped hand holds in the stringers of a ladder. The cuts will be part of removing waste, to be finished with a straight router pass to size, followed by a 1/2" radius roundover bit. The plunge cuts will be 11" long and as through as I can get them. 

A couple questions:

1) Because I want the cuts as deep as possible, the blade needs to be extended, potentially to its maximum. This requires the saw start the plunge at a fairly steep angle. The way my template is built, there is little "guidance" at the start of the plunge. My question is, should I make some vertical guides to help keep the saw lined up with the guiding side of the template? Such a vertical guide would be at the rear of the saw base plate and might need to be 3-4" high. Or, do I just eye-ball the alignment as the plunge is started? 

2) Should I set the saw to its desired depth (max.) and make the cut full depth in a single pass, or set the saw depth at less, say 1/2 max. and take two passes? I see some potential issues with multiple passes? 

The circular saw is a Skil Model 77 worm drive. I am having the saw blade sharpened before tackling this. 

Thanks,

Rick


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## JOAT (Apr 9, 2010)

You could always drill thru, at each end of the cut, then use a sabre saw.


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## RickKr (Dec 30, 2018)

JOAT said:


> You could always drill thru, at each end of the cut, then use a sabre saw.


I did not mention, but the ends of each handhold will be drilled out to 1 3/8" prior to the saw cuts, using a forstner bit. A portion of the saw cuts (at the top) may break into the drilled out holes. I am planning on finishing the cuts with a crosscut hand saw (which I'm also having sharpened). 

I don't have a sabre saw. I have a reciprocating saw, but am not thrilled with the notion of using it for all these cuts. Too much chance of wandering off the cut line. I probably could use it to finish the cuts. 

Rick


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## Cherryville Chuck (Sep 28, 2010)

I've done lots of those with standard circ saws but never with a worm drive. They are much heavier and therefore might be harder to control as you roll the saw downward. It isn't that hard to stay straight as you rest the saw on the end of the shoe and just lever it down but getting it to line up perfectly with you cut line might require a reposition or two as you start down and find it's off a bit.

You could easily do that job with a pullsaw instead and it would be much safer and more accurate possibly. If you clamp a board down on your line you can use it to guide the saw and it will keep you vertical as well. Once you own a pullsaw your old north american style saw will collect rust hanging on a nail like mine does. 

Here are 2 types, straight handle with two different cutting edges and tooth patterns and pistol grip with one set of teeth.
https://www.amazon.ca/Shark-10-2205...=2025&creative=165953&creativeASIN=B000078ONO

https://www.amazon.ca/Shark-Corpora...=2025&creative=165953&creativeASIN=B00004TBQ0

The double edge is a bit more versatile. The fine teeth really do make a fine cut (suitable for hand cut dovetails) but the coarser teeth on either saw also do a pretty good job. I demonstrated the pistol grip handle one for an uncle by sawing a slice off a 2 x 4 and you could see light through it. He went out and bought one after and those are all he uses now too.


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## Stick486 (Jan 4, 2013)

set the saw on the 2xw/ the blade fully retracted..
loosen the depth lock ...
start the saw...
now plunge while keeping the saw's plate/shoe in full contact w/ the 2x..

better yet...
be safer an get yourself a jigsaw....


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## PhilBa (Sep 25, 2014)

Hmmm, I think I understand what you are trying to do. Essentially you are making through cutouts for a hand for holding the ladder. If I'm wrong then ignore the rest of this.

I have done something similar a number of times but used a router with a template. Forstner bit to hog out the the waste. Here are some pictures when I was making some trays. These were done on a router table but could easily be freehanded. This certainly makes for a clean cut.


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## JOAT (Apr 9, 2010)

Thinking on it, I do not believe I have ever seen a wooden ladder with handholds like you want. Using the rungs for handholds would be easier to use, and I'm sure faster. #1 shows fire department ladders, with no handholds cut in. #2 shows how the San Francisco does for at least part of their wooden ladders, you will note they use spacers, not cut holes, and they are bolted in. I'm not sure if this is to provide cutout handholds, or just a way to strengthen the ladders. I'd go with that if I wanted hand holes.


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## PhilBa (Sep 25, 2014)

Hmmm, you have a point. I'd be concerned that the holes would weaken the ladder. Here's another approach that could be made to look nice and is a bit more natural vis-a-vis hand/wrist positioning.


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## DesertRatTom (Jul 3, 2012)

What size 2x, 6 or 8? You need an inch and a half for the hand to go through, plus and inch for the hand rail, and you want another 3.5 inches for the main body of the ladder., so that's a total of 6 inches, which would mean starting with a 2x8 and removing about 1.5 inches. That is going to be a pretty heavy ladder. I'd use a 2x4, spacers and work out some sort of hand rail, possibly a 1 inch diameter dowel. I trust you're using kiln dried wood. Will this be used or store outdoors?

I found the attached drawing of a ships ladder, which is metric, but might help you plan. I think that the side rails on firemens ladders aren't so much for holding on to as to keep hoses from falling off. Handrails also make sense if the ladder is at a steep angle.


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## Nickp (Dec 4, 2012)

I have the Mag77 also and use it often to plunge into 2x's...I typically plunge it to start a rip cut in 2x6's to hold it together, then go back and finish the first couple of inches...

For what you are doing I would use the 24T thin kerf demo blade...

Mark your line with a pencil...then do as Stick suggested...put the index mark where it belongs, make sure your depth adjustment is loose, line up your index mark and blade where you want it, hold the toe as you normally would to keep the index mark on the line, lift the saw a bit, pull back on the blade guard so it stays out of the way, turn it on, go for it. If you screwed the direction of the initial cut, do not try to correct it once the blade is in by twisting the saw...it will bind and it will try to counteract the Earth's gravitational pull...

This operation is more an issue of hand/eye coordination than anything else...

Be careful as the deeper you plunge, the slower the feed rate...the M77 is powerful enough but you want to make sure you're not running into any funny grain as you plunge...the weight of the M77 is your friend...don't push it in, let the saw do the work...


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## The Hobbyist (Apr 25, 2015)

I would use a good sharp hole saw and drill multiple holes that overlap. A drill press and some clamps would insure accuracy. Use a hole saw 1/8" smaller than the finished size, and the hand sand the opening "shoe shine" style.


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## DesertRatTom (Jul 3, 2012)

Bracing the saw so it stays put during the plunge is what would concern me most, so I'd lay a couple of 2x4s, one on each side of the workpiece, then a cross piece with a few screws in place across the workpiece to brace the saw against. You could always add some vertical blocks to those outrigger pieces to guide the base of the saw down as you plunge. That is a heavy saw and I could not trust myself to use it for that job safely. If the base is loose, it is still going to stay lined up so a jig with tall sides would be a good choice too. I'd sure want that workpiece clamped down firmly.

Here's a little top view drawing. The jig can slide down the workpiece, or you can make it longer, or clamp it to the edge of something.


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## RickKr (Dec 30, 2018)

Thank you all. Some good ideas. My stringers are 2x8s so it should be sturdy enough, even with the hand holds. And, yes, it will be heavy. It will be transported once and installed with lag screws. No moving this one around. I may assemble it here in my shop, disassemble it enough for transport and reassemble it on site. 

I have completed the jig for aligning and guiding the saw during the plunge and the push forward. I think it is close to what DRTom suggested. I had to modify it from what I designed and built last Fall, based on fitting to the situation and correcting for some errors. I will try Stick's idea of plunging with the shoe flat on the workpiece. The jig will be screwed to the workpiece to avoid any problems with clamping. 

When I took my current blade off for sharpening, I found it is a 40T. I dug out my meager collection of blades and found a new 24T ripping blade, so I'll use that. I think it is not a particularly high quality blade, so I don't know if it will last through this project. The local hardware store had a few Diablo blades, but non 24T. 

Got the test piece bored for the end clearance holes. It is 1 3/8" dia. and my finish size wants to be 1 1/2", which will be done with the router/jig. It all looks good, setting the saw on it and checking alignment of the blade relative to my drawn outline. It is set up to leave 1/8" clearance between the saw blade and the finish dimension. 

It was really tempting to give it a go tonight, after finishing the jig. But I am exhausted. I shoveled a bunch of snow for my daughter today and I am beat. So decided it would be prudent to wait until tomorrow morning, when I am fresh. Time to kick back and take it easy for a few hours, maybe have some ice cream.

Rick


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## Herb Stoops (Aug 28, 2012)

Make sure you hold the nose of the saw down good and hard during the plunge or it will grab and walk back on you fast.
Just saying,
Herb


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## DesertRatTom (Jul 3, 2012)

Lookin good! Good idea to rest first. I spent the afternoon trenching to redo my backyard watering system. Just about did me in after doing about 80ft. Comes a point where your concentration lags and you goof it up.


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## tooler2 (Aug 11, 2012)

Plunging the circular saw is just a question of practice to become confident, don't forget to try a scrap piece first. That being said a router would do the entire job perfectly with a similar jig, start with a drilled through hole if you do not have a plunge router. Depending on router you would probably want to cut 1/2'' deep with each pass.
Rob


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## Bushwhacker (Jun 16, 2009)

Stick486 said:


> set the saw on the 2xw/ the blade fully retracted..
> loosen the depth lock ...
> start the saw...
> now plunge while keeping the saw's plate/shoe in full contact w/ the 2x..
> ...


My first thought was a jig saw.


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## PhilBa (Sep 25, 2014)

tooler2 said:


> Plunging the circular saw is just a question of practice to become confident, don't forget to try a scrap piece first. That being said a router would do the entire job perfectly with a similar jig, start with a drilled through hole if you do not have a plunge router. Depending on router you would probably want to cut 1/2'' deep with each pass.
> Rob


Yes yes yes. Using a C-saw on this scares the crapoutame. I'd hog out the waste with a forstner and if the router bit isn't long enough, clean from the other side with a flush trim bit.


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## Stick486 (Jan 4, 2013)

Bushwhacker said:


> My first thought was a jig saw.


sure would be easier less goof proof...
here's your chance to test drive a Progressor saw blade...


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## DaninVan (Jan 1, 2012)

I'm with Stick, and the others that proposed a better system of hand grips (rails etc.). This cutout concept doesn't seem ergonomically desirable, in fact, rather user unfriendly.
Also a perfect justification for buying a jig saw.


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## RickKr (Dec 30, 2018)

Hmmm. Quite a bit of sentiment pointing in other directions. 

Trial with the C-saw (on test stock). The jig worked great. Even better once I realigned it to match the slot centerline. The underside fence was off a bit; couple new screw holes to solve. 

Plunging as Stick suggested worked reasonably well. The top handle gives some good stability. Does have to be taken slowly and methodically. 

It only took a few pulls on the Dozuki saw in each corner to free the waste. Now it is a matter of finding out how well the router jig works. The open space on the left will be filled with a guide fence screwed to the bottom side. The jig will be used to route deep enough for bearing guided 1/2" dia. straight bits to complete it.

Rick


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## tooler2 (Aug 11, 2012)

You do not need a bearing on the router bit, the base of the router follows the jig that is made with the off set in mind. you size the jig for say a 1/2'' bit, cut out the blank with a 3/8'' bit then swap to a 1/2'' for a finish cut.
Rob


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## RickKr (Dec 30, 2018)

tooler2 said:


> You do not need a bearing on the router bit, the base of the router follows the jig that is made with the off set in mind. you size the jig for say a 1/2'' bit, cut out the blank with a 3/8'' bit then swap to a 1/2'' for a finish cut.
> Rob


True enough. The jig offset has been sized for a 1/2" bit. I could do the full depth relying on the jig only. That was my original plan and is still an option. I may try both to see what seems to work better. 

Rick


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## Lemuzz (Jul 25, 2008)

Yes after 35 years in the fire service I believe I am qualified to say: When ascending or descending a ladder grip the rungs for safety and control


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## DaninVan (Jan 1, 2012)

Excellent point, Lemuzz!


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