Mortising question

[Papa Jim]

I'm building a mission style recliner out of cherry. In my eagerness to try out the Powermatic 701 that I got at auction, the sides will consist of eleven vertical 1' X 3/4" pieces one inch apart. That's 44 1" x 3/4" holes to dig.  The machine didn't come with any bits but a fellow woodworker gave me the set he got with a Delta drill press a number of years ago, although they have no identifying marks on them.  I followed the instructions on how to sharpen them and they worked fine on soft wood, BUT when I tried the 3/4 bit on the cherry all it did was burn a circle in it.  No amount of adjusting the lead distance of the auger made any difference. Since then I have been looking to buy a new 3/4" bit. In trying to decide how much to spend I ran across one article that said that smaller bits were much easier to use and you could make a bigger mortise hole simply by making multiple plunges with a small bit. Instead of two plunges with a 3/4" I could do 4 with a 1/2" bit.  Is that right, or do I just need a better 3/4" bit? I could really use some help her from you guys that have experience with a mortising machine and bits.

Papa Jim

[Stwood_]

Even a good, expensive 3/4 bit is tough to chew.
I would drop back to a 1/2 bit.

Practice with some scrap first.

[shoottmx]

Hog out most of the waste with a 5/8" forstner bit on your DP. Finish up with the 3/4" mortise bit in the 701.

g

[retrdwoodwkr]

I'm building a mission style recliner out of cherry. In my eagerness to try out the Powermatic 701 that I got at auction, the sides will consist of eleven vertical 1' X 3/4" pieces one inch apart. That's 44 1" x 3/4" holes to dig.  The machine didn't come with any bits but a fellow woodworker gave me the set he got with a Delta drill press a number of years ago, although they have no identifying marks on them.  I followed the instructions on how to sharpen them and they worked fine on soft wood, BUT when I tried the 3/4 bit on the cherry all it did was burn a circle in it.  No amount of adjusting the lead distance of the auger made any difference. Since then I have been looking to buy a new 3/4" bit. In trying to decide how much to spend I ran across one article that said that smaller bits were much easier to use and you could make a bigger mortise hole simply by making multiple plunges with a small bit. Instead of two plunges with a 3/4" I could do 4 with a 1/2" bit.  Is that right, or do I just need a better 3/4" bit? I could really use some help her from you guys that have experience with a mortising machine and bits.

Papa Jim

I have done a bunch of A & C small tables where the cross member tenons are centered in the table leg.  I do one pass with a either a 1/4 or 3/8 bit then rotate 180 the leg to insure the mortise is centered.  This allows me to use a smaller bit while centering the mortice.  Also if you have a piece that is not centered, make sure you mark it before cutting your mortice.  VERY CLEARLY MARKED.  Plus the other good suggestions from the previous posts.  Especially the comment about scrap trials if you have not done many mortices before.  Good luck!

[Papa Jim]

Even a good, expensive 3/4 bit is tough to chew.
I would drop back to a 1/2 bit.

Practice with some scrap first.

It occured to me after I posted this that I might be engaging in overkill by trying to bury the individual posts. How about just putting a 1/2" wide tenon on each end? Strong enough?

[Redman]

All of the above. I have done 1" cross shaped through mortises in cherry with a 1/2" mortising bit successfully. With a relatively inexpensive Craftsman mortising chisel set on an inexpensive Craftsman drill press at that.

[Papa Jim]

Hog out most of the waste with a 5/8" forstner bit on your DP. Finish up with the 3/4" mortise bit in the 701.

g

Thanks! I will try this too. I plan to practice a lot before I attempt the final cut.

[Papa Jim]

I have done a bunch of A & C small tables where the cross member tenons are centered in the table leg.  I do one pass with a either a 1/4 or 3/8 bit then rotate 180 the leg to insure the mortise is centered.  This allows me to use a smaller bit while centering the mortice.  Also if you have a piece that is not centered, make sure you mark it before cutting your mortice.  VERY CLEARLY MARKED.  Plus the other good suggestions from the previous posts.  Especially the comment about scrap trials if you have not done many mortices before.  Good luck!

Makes perfect sense. I failed to mention that the cross members are also mortised into the legs and this trick would work perfect on the longer mortises. My confidence is building.

Papa Jim

[jteneyck]

A much easier way to go about it is to plow a 3/4" (or 1/2") wide dado where you want the mortises.  Then when you install the slats glue 1" spacers between them.  I usually make those spacers just slightly higher than the dado which avoids having to get them perfectly flush and also gives a nice shadow line.   Here's a picture to show you what I'm talking about; it's for balcony balusters but is the same process.  



John

[Stwood_]

It occured to me after I posted this that I might be engaging in overkill by trying to bury the individual posts. How about just putting a 1/2" wide tenon on each end? Strong enough?

1/2" is a strong tenon in that application.