Precision Chainsaw plunge cutting - jigs, guides, etc... for mortise and tenons

[sleddin]

I want to make mortises and tenons on round logs flattened only at the joints using my chainsaw.  My rail system for flattening logs works okay for tenons, but not ideally, and I can't find much of anything on the web about a jig or guide system that could somewhat precisely guide the bar for plunge cutting.  I guess I'm trying to make a poor person's chain mortiser.  My narrow kerf, low profile bar and chain bore fairly well, but my freehand cuts look more like a wood chainsaw massacre than accurate joinery.  I realize this may improve with lots of practice, but I also like the increased safety of a guided system.

I'm too poor or at least cheap to buy a chain mortiser.  I don't think a boring machine is a good option for me only due to the mostly round and swept surface of my logs.  Hitting resistance while boring deep holes with my right angle Milwaukee makes me curse God for my pathetic lack of upper body strength, and my hand brace and auger bits are a boring exercise in futility, leaving me staring longingly at the heavy artillery – my Stihl...  Can anybody share their techniques, jigs, tips and experiences mortising or precision plunge cutting with a chainsaw?

Aikenback, you posted the following in part back in 2012, can you elaborate on your tenon and slot mortising jigs?

"...I have jigs I use with it for tenonning (unlimited tenon length, uniform offset from reference, and uniformly cut tenons on multiple pieces), and I use it on another jig as a slot mortiser. .."

Thank you kindly in advance,
Shannon

[VictorH]

Sleddin, I can't help you any with your questions but I would like to welcome you to the forestry forum.

VictorH

[beenthere]

Welcome to the Forestry Forum.

How about some pics of what you describe, and some that you think are passable or acceptable.

That would help when offering some advice of what to do and what not to do.

[Thehardway]

I want to cut my hair using a 21" 5hp lawnmower, however, I am having trouble doing the trim work around the ears. It makes me a little nervous about getting scalped. Does anyone have a template for touching up around the ears with a lawnmower without getting nicked?  Perhaps someone makes a blade guard for this purpose?  I hate to buy a set of clippers as I can only use them for trimming hair and I only cut my hair about twice a year. Scissors and a comb are just too slow and hard to do the back myself.


Sorry, I couldn't resist the temptation... had to yank your chainsaw a bit.  Welcome to the forum.


I tried a similar home brew project a few years back and it is still in pieces and parts in various boxes scattered about. It never got finished. I was going to start by mounting a Remington electric chainsaw on a plate with two slides connected to an adjustable angle vise.  Picture a plunge router (chainsaw) with an adjustable angle vise for the base.  I figured the electric saw was a little easier on the ears, no exhaust in the shop, a little safer, and a whole lot cheaper not to mention it already had the smaller kerf chain.  I had all the parts just never got it put together as the chisel, hammer and auger bits in the Milwaukee were sharp and handy enough.  The old way took longer than I would have liked.   To be honest I am glad I never finished the chain morticer as I found the chisel and mallet method very rewarding and therapeutic.  It takes a lot longer to make a mistake using chisel and mallet than chainsaw.  You usually catch the mistake  before you ruin a timber or log completely.

I still think my idea would work and could be done afford-ably.  Electric chainsaws are pretty easy to come by.  A jig could easily be welded up using some plate steel and some threaded rod with couplers for horizontal adjustment and some smooth rod for vertical plunge guide.  I had some roller bearing guides I salvaged from somewhere.   Good luck and if you ever get it together send us some pics.  I bet you could even rent it out, this about the 5oth post of guys wishing for a cheap chain morticer. 

[sleddin]

I did see the numerous posts on chainsaw mortising and while there weren't many detailed responses, at least a few people on this board have made references to the fact that they use a chainsaw to mortise and more so for cutting tenons, so I thought I'd give it a shot anyway.

I know, I probably should just stick to the old ways, but sometimes I'll work really hard just to be lazy.  I appreciate you sharing your experience and advice, and I may well end up with a drawer full of glides, bar attachments and broken dreams in a few weeks.  The Milwaukee has yet to pull my arms off, though it has tried a time or two. 
Thanks for all the welcomes and for bustin' my chops a bit.  I've seen some pretty nice log chainsaw work on the web, so I know some pros out there can trim around the ears with a lawnmower even if I can't, and am unwilling to dip into my martini budget to buy the clippers. 

As for the request for pictures, I don't really have any of my failed attempts, and my standards of work require only the walls to remain standing, and hopefully straight, but here are a couple of examples from the web of what I'm hoping to do with some dimensional tie beams through posts, hence mortises through round logs. 


  

 
Japanese Wedged Tie Beams


http://www.timelesstimberworks.com/horsebarn.html

[beenthere]

Some very respectable looking joinery in those pics. I can see where you would not want to mess up with a lousy chainsaw cut.  A real good jig certainly would be a plus and hopefully some good ideas will come along.

Short of the tool already mentioned, I don't know what that would be.
A step by step primer of how and when these mortises progress would be interesting to see, if you can make some pics while working those timbers.

The right angle elect drill may be easier if you go in steps from small diam. bit up to the large if continuing by hand.

The objective to work on round timbers (a bit similar to the "dream cabin" thread by boss Jeff) may mean getting into some larger drill press equipment with a carriage to securely hold the log or cant in a true squared position for accurate right angle drilling or boring.

[shelbycharger400]

Pick up a jet chisel mortiser or equivalent for the hole.  Cheaply is $150 , A fixture and a router with a two flute bit.  I've free hand a bed set it works but a fixture will be way easier.     

[Satamax]

Sledin, two holes in the bar, two threaded rods with spacers (washers) nuts and a piece of metal that is longer than your bar by 6 or 8 inches. Fit that piece of metal parallel to your bar, spaced accordingly. That keeps your spacing between the side of the wood and the inside of the mortice or tenon. Carefull tho. It's dangerous.

[Dave VH]

I now have a reason to buy an electric chainsaw!  I have been lookin for an excuse.  I am also a bit cheap in that I don't want to shell out to buy a true chain mortiser.  An electric chainsaw makes perfect sense.  I will get started on my jig right away.  Thanks for the great idea, I can't believe that I've never thought about it before.

Dave

[Jim_Rogers]

I don't think a boring machine is a good option for me only due to the mostly round and swept surface of my logs. 

Using a boring machine to bore holes in round logs can be a challenge for sure. But there are methods or "jigs" that can be used to allow you to do so.

We did this:



 

Which is we created a flat table to sit the boring machine on beside and over the log. And this worked to hold the boring machine and it's operator while the holes were being drilled.

To rough out flat spots you can use a chain saw to remove the bulk of the wood. Then you could use an adze to shape the log more. Then maybe a draw knife and or a slick to flatten the spot smooth.

There are many tools you can use, without re-inventing the wheel that could/can do the job you want to do.

Good luck with your project.

Jim Rogers

[sleddin]

Thanks for all the suggestions.  Jim, I thought about trying something similar to what you did to keep various tools level while hugging the top of a round piece, like a circular saw or router guide, but I didn't even think of it for the boring machine.  Thanks so much for the picture.  Satamax, do you have any pictures of the setup you describe?

I know, I should sell a kidney to buy a chain mortiser or just shut my pie hole, but I think the forum rules require one's first posting to be a really stupid one--oh wait, I misread that...  Were I tackling larger projects, I'd be more likely to invest in the tools the pros use, but this is for a tiny greenhouse and if it passes the chicken inspection, then a coop for them as well. 

Besides, making tenons and mortises with a chainsaw is mentioned on this forum and many others, sans the required details or images, especially amongst the log building crowd. Many say that they freehand it, which I prefer not to.  Some posts on other sites refer to plunging the bar into a box mounted on the surface of the work-piece (usually flat) with some kind of spacer blocks mounted to the bar to guide it tightly through the box-- I may even try that one incorporating elements of Jim's setup.  Since I already own a chainsaw, it made sense to me to sniff out the good leads until I found details from someone who does this or until I determined that dozens of posters on the web are completely all full of it—quite possible ... 

Well, if I do ever get anything to work, I'll post the details for any others like me.  Otherwise, I'll post my failures with grace and humility, and we'll all have a good laugh at my foolishness.  Then, I'll email Jim to see if I can buy one of his restored boring machines along with the exact two blocks in the picture that he uses to keep it flat over a log.  Jim, do you take credit? –just kidding.

Cheers all and please, keep those suggestions or jabs coming.
Shannon

[beenthere]

but this is for a tiny greenhouse and if it passes the chicken inspection, then a coop for them as well. 

Scratch the chainsaw idea, and just use a handheld drill with a spade bit to make some holes at the corners of the mortise, then a chisel to work out the sides and ends.
Better precision that way too, and little investment.

[Brian_Weekley]

Personally, I'd go for the boring machine.  However, if you have a radial arm saw, you might be able to rig something up to use this...

Available for a fraction of a makita chain mortiser.  Made by Platte River.

[jander3]

Talking large round logs.  Big mortises.   Freehand works fine.  Use a chisel score the line pretty deep and cut her out.  Finish it off with chisel.  Take a pile of crap logs and practice. 

Make sure you can safely operate a saw and you are comfortable with plunge cutting.

i use a 35 cc saw with 16" bar.

Roughing out the tenons is not too hard either.


Tenons below were laid out with four lines on round logs.  Roughed out with a chainsaw (cut to about 1/8" of the layout line) and finished with slick.



  

  

  

Another approach for smaller mortises.  Cut a flat spot in the log.  This mortise was hogged out with one Jim's boring machines.



 

[Satamax]

Satamax, do you have any pictures of the setup you describe?

Nope Shannon.

It looks a bit like an alaskan MK3But way less complicated. It's just a piece of metal parallel to the bar. Held by threaded rods and spacers (washers)  Sometimes left long to be used touching the side of the beam or the tree before the chain touches. Or same lengh as the bar for tenons, where they do a first cut with another chainsaw, put the parallel guide piece of metal in the kerf, and chainsaw the second cut which stays parallel. Mind you, it's crude, takes time to tune, not extremely safe etc.

[scrout]

http://www.youtube.com/watch?v=YX7bUf_oJJQ

Same device Brian had mentioned above, pretty slick.

[Jim_Rogers]

I just posted a story you can download that shows how to make a jig for cutting with an electric chain saw.
Here: https://forestryforum.com/board/index.php/topic,70971.180.html

See if you think this may help you.

Jim Rogers

[MattJ]

I know this is about a month late but I have the platte river mortiser referenced in the picture above and can vouch that it works pretty well.  The sides of the mortise aren't furniture grade but if you want that just stay an extra 1/8" inside the lines and finish with a chisel.  On my old craftsman radial arm saw (recall saw, $75 on craigslist) I can knock out a 2"x4" mortise in less than a minute.  Really nice control with a 200lb radial arm saw attached to it.  It also handles knots really well.  The only issue is after each mortise you need to sweep away the mounds of sawdust it piles on the saw.

Matt

[Black Creek]

I'm doing some digging and want to wake up this thread....    has anyone come up with this yet?..... https://ruralfencing.com/products/mortice-safe-chainsaw-attachment?variant=40387265804  (seems pricey for what it is tho) and mount that onto one of these....  https://www.ebay.com/itm/11-5-Steel-Electric-Chainsaw-Sharp-Chain-Saw-Blade-Stand-for-Angle-Grinder-ST/392911434749?hash=item5b7b58b3fd:g:tRIAAOSw4Q1f-Em9    wondering if a few homemade guards and parts may make something a little more manageable than a full size electric chainsaw.    Thin blade on them too

[Black Creek]

Just sketched this up to visualize the whole thing

 

[Black Creek]

Cheap harbor freight grinder and ebay attachment

 

 

[Jim_Rogers]

Put a chain on it and test it out in a sample piece of timber.

Jim Rogers

[Black Creek]

The drive sprocket it came with is too small.   Just ordered the correct size so who knows how long it'll take to show up from China.   There is no oiler but there is an oil port.   I guess I was just looking for some feedback on my drawing before starting to build it

[Don P]

You're probably going to let the magic blue smoke out of that grinder in short order, that isn't enough power for a plunge. A chain has poor cutting depth bite control around the nose. Go slow. Your cross shaft that the angle grinder mounts on probably needs to be square tube to keep it from rotating as it tries to kick around in response to the the rotation direction. Maybe nesting square tubes with a welded on nut and lock bolt so you can track back and forth in that direction.

I have a Prazi beam saw attachment on a worm drive saw that probably has the power but is slow rpm's and you would need to figure out how to drop the saw vertically for it to plunge like that.

[Black Creek]

The angle grinder is [I have typed a profane word that is automatically changed by the forum censored words program I should know better] but I'll burn it up during the build and put something better on there.    The wood clamp plan needs to be addressed to make it adjustable for beam size and multiple plunges.     I'm thinking cannibalize 2 clamps per side using just the sliding adjustment screw section on 2 clamp bars and weld a small C channel to the clamp to hold on to the 2nd bar.   the uprights can be sandwiched between the 2 clamp bars.    I feel like it can work