Mortiser Bits


Chip Sawdust

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Just bought a PM mortiser, and it’s a great machine. I was too cheap to spring for the $180 PM bit set, however. I went to Lee Valley instead and bought their mid-range set for around $65. While I was waiting for those to show up, the machine arrived! Well, one can’t have a new machine sitting there and no bits to try it out so I went to a local power tool shop and bought a 3/8” Shop Fox bit (they had PM bits but one was $50+ and the SF was $16). 

Now, I don’t expect as much from a $16 but as a $50 bit, but I took the Shop Fox bit home and followed the tune-up advice in a video on FWW. It require a lot of filing internally as well as honing. It worked and I was happy.

in come the Lee Valley bits. First impression, the machining was a lot better than the SF bit. The chisel and bore were both much cleaner looking and I had no need to do anything internally to the LV bits, any of the four. 

A point for the SF bit is it required installation of the larger chisel holder. In the world of machines, I think bigger is beefier and better. So yay! Even though the stress on this past is mostly vertical compression, I like the bigger diameter of the chisel mount. 

But overall I have to give the nod to the LV chisels for overall smoothness of machining and design. Some may prefer the flute design of the SF but they both seem to work. 

The Shop Fox bit is on the left in the picture below, and in fact all the following pictures. I invite opinions and comments to educate me on these things as this is my first mortiser and I know there are things I don’t know.

 

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I would polish the sides of the chisels on waterstones, but that's just me.

I like for the bits to seat all the way home in the chuck.  If they don't the bit can be pushed up into the chisel, which is not something you want to happen.

After using Delta sets for so long, I had a job come up that required a Lot of mortises, so I sprang for the Japanese Star M bits, which are the ones LV sells as their Premium sets.  There is a difference in these, and the lower grade, but for just making a piece of furniture once in a while, the high end sets might not be worth the extra dollars.  The Star M's are all I'll buy from now on though.

The Star M bits come with long drill bits that have to be cut to length.  I cut mine with a Dremel wheel.  After enjoying having the first set exactly the right length, and no worrying about using a dime for setup, I super glued a bunch of small washers, from Ace Hardware, on the ends of my other sets' bits that didn't come with long bits to start with.  That way, I can just stick the set in, tighten everything, and know it's good to go.

After some amount of use, even if the chisel never hits the bit, the chisel will develop burrs up in those curved openings.  I keep an X-fine diamond paddle with the mortisers, and keep the burrs flattened off the sides of the chisel while they're still in the machine.  If they start to develop burrs, they get REALLY difficult to pull back out of the wood.  After touching up the sides of the chisel, don't touch it to see if it's sharp.  It is, and will shave skin a lot easier than wood.

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That’s good info Tom, and I did touch up all those bits on a 3000 grit Waterstone. It may just be me, but they’re a little tough to hold exactly square the entire process through, so I end up putting little gouges in my Waterstones. I’m better off, probably, sticking with my 1200 grit Arkansas. 

Even after honing, you can see the coarseness of the machining on the Shop Fox. 

All these bits cut well, which is the bottom line, and yes I’ve proven that offering them up to the machine with my fingertips rather than a block of wood results in blood leakage :) 

 

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Thanks for the post Chip. I am planning to purchase a mortiser with my refund check. I have been looking at the LV mortise chisels that you bought as well. Im glad they are a good item, and Ill be sure to pick them up.

 

Question to you guys, 

what do you use to touch up the inner cone (I dont know how else to refer to it) of the chisel after you hone the outer surfaces? 

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I used to use the little tool that Delta sold for the job, but it never did anything impressive.  I always thought it was some sort of stock countersink tool for machinists. 

Some time later I bought the diamond cone sharpener sold by Lee Valley.  It does a good job, but they rarely ever need that.  Hitting the outside flat with the x-fine diamond paddle is used much more often than the cone on the inside.  I don't remember ever having to hit the inside of the chisel while in the middle of a long run, but might hit the outside flats a couple of times if it gets harder to push down, or pull up.

For a hobbyist, if you set the bit up, like I was talking about earlier, so it's not possible for it to ever get pushed up into the chisel, you very well could never need to hit the inside of the chisel.

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On 2/26/2019 at 2:13 PM, RichardA said:

You can buy a round cone shaped stone from almost anyone for honing the inside of a mortise chisel.

The PM mortiser comes with a cone sharpener on the machine, but I haven’t used it yet. It looks ok. I have a set of cones from the square chisel set I bought for cutting G&G ebony plug holes. There’s a coarse and fine one in that set. Also from LV iirc.

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  • 4 weeks later...

Thanks for the post Chip and for very useful information. I like to get knowledge from an experienced person. You did a good bit analysis now I'm starting to understand the difference. I also read reviews about sets of bits https://drilling-it.com/best-countersink-bit-sets-reviews/ and I liked IRWIN tools 1877793 metal countersink bit I think it will be universal. What do you think, I need recommendation. Thank you.

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On 2/26/2019 at 10:42 AM, woodbutcher said:

Thanks for the post Chip. I am planning to purchase a mortiser with my refund check. I have been looking at the LV mortise chisels that you bought as well. Im glad they are a good item, and Ill be sure to pick them up.

 

Question to you guys, 

what do you use to touch up the inner cone (I dont know how else to refer to it) of the chisel after you hone the outer surfaces? 

I use the Rockler set that goes on sale now and again.

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