chain mortisers and chainsaw plunge cuts

[NCEric]

I was thinking recently that a chain mortiser might be useful tool and then I looked at the prices.  It seems like it's more or less just an electric chainsaw with a jig to control the angle of the cut.  What makes them so expensive?  What more is there to a chain mortiser beyond a chainsaw with a jig to control the angle of the cut?  Does anyone ever use a chainsaw to make freehand plunge cuts as an intermediate labor-saving step between using all traditional hand tools and a chain mortiser?  Does anyone ever make a custom jig to control the angle of cut with a chainsaw?  If you wanted to make mortises in large timbers but didn't think a chain mortiser was in the budget, would any kind of chainsaw (with or without associated jigs) be a tool you'd consider using?  Do chainsaws ever have a place for making mortises?  I have a couple regular gas chainsaws, but I've thought about buying a small electric chainsaw with a 12" bar to use especially for mortises.  What do you all think of that idea?  Are there any other power tool options to consider?

[rusticretreater]

A chain mortiser is much more than a chain saw.  The chain is much heavier and tailored to make a square cut.  Because it also cuts much wider than a chainsaw kerf, its motor is high torque.  And to handle that high torque requires a sturdy base.

You could certainly make something to guide a chainsaw and probably many have.  You will still need to clean it all up with a framing slick and maybe a corner cutter too.  But it would be a big time saver. 

A freehand cut could do as a starter if you can control it.  The chain is designed to pull it into a cut so you are fighting the forces.  Many folks start with drilling a series of holes instead to quickly remove material.

[Dan_Shade]

This may be an option:

Building ORCA - Episode 10: Installing the Stern Post - YouTube

@ 4:12,

At 4:12, he starts the process he uses to cut a mortise with a chainsaw.

[Planeiron]

I wouldn't recommend a chainsaw plunge cut for safety reasons. The suggestion of several drill holes is time tested and works well. If speed is a factor then just invest in a chain mortiser and resell when you're finished. You'll be able to resell easily and won't lose out much at all. I've done this myself and looked at it like a long term extremely good value rental.

[dogbo2013]

I went through the same thought process and before deciding to invest in a chain mortiser. Although I still think they are a little overpriced, you cannot replicate what they do. You would be frustrated trying to use a chainsaw and the end product would be disappointing. If you have the resources to purchase one, I would do it. Once you're done using it, sell it. They maintain their value.

[Dave Shepard]

HoleHawg with the right sized bit will work circles around a homemade chainsaw based mortiser.