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Correct end mill bit size for routing mortise

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Forum topic by Graeme posted 07-31-2012 05:38 PM 1087 views 0 times favorited 10 replies Add to Favorites Watch
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Graeme

27 posts in 861 days


07-31-2012 05:38 PM

I am still a rookie when it comes to these things and I was wondering if someone had a quick answer. I want to mortise a piece using a jig that has a 1/2” top. The mortise is 7/8” deep giving a total depth with jig of 1 3/8”. The mortise is 5/16” wide so I know a 5/16” bit would be ideal, but how long should the overall bit be? 2”? Longer? Also is it ok to use a bit with a cutting length that is shorter than the total depth? Say 3/4”?


10 replies so far

View Loren's profile

Loren

7734 posts in 2337 days


#1 posted 07-31-2012 05:52 PM

Do you have a machine with a 5/16” collet you are going
to use to do this?

Mills which are turned down from, for example 1/2”
(great for routers) for woodworking have a limited
cutting depth because after 1.25” or so the cutting
flutes end and the mill flares out to fit the collet.

Also, the smaller upcut and downcut cutters tend
to be more fragile and for that reason the cutting
length is not comparable to the larger 1/2” ones

-- http://lawoodworking.com

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Graeme

27 posts in 861 days


#2 posted 07-31-2012 06:18 PM

Sorry. Wrong size. I meant 1/4”.

This is the one I was looking at:

Carbide Bit

What I was wondering is would a bit like this work for a 7/8” deep mortise? It’s overall length is 2 1/2”, but it has a cutting length of 3/4”. Not quite 7/8”. It could reach the overall depth of 1 3/8” with the extra jig depth. But is that an appropriate way to do it? Or should I look for a bit that has a 1” cutting length?

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Loren

7734 posts in 2337 days


#3 posted 07-31-2012 06:27 PM

You can do it. Don’t plunge the ends of the mortises
all at once. Plunge the ends to 1/2 depth and then the
chips can escape. Then route the length of the mortise
to 1/2 depth. Then plunge the ends to full depth and
route the rest.

See, when the flutes run out there’s nowhere for the
chips to go and the wood burns in there.

-- http://lawoodworking.com

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Graeme

27 posts in 861 days


#4 posted 07-31-2012 06:35 PM

I see. So maybe sucking them up as I go would remedy that for the shorter cutting length. I do have a 1” upcut on the way, but I want a couple of cheaper backups to practice or replace if something breaks.

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Loren

7734 posts in 2337 days


#5 posted 07-31-2012 07:37 PM

To elaborate, you can plunge and drill with a mill, but when you
cut sideways you have to take modest cuts or else the mill can break.

-- http://lawoodworking.com

View Hoosier25's profile

Hoosier25

18 posts in 815 days


#6 posted 07-31-2012 07:40 PM

With spiral-up bits in a plunge router, I’ve found use them as a “drill” to full depth, with 1/16” web between each plunge, vaccumm out dust, then use sweeping cut to clear, works best for me when making mortises.

Give it a try.

-- Roger

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Graeme

27 posts in 861 days


#7 posted 07-31-2012 07:43 PM

So Rick of the 2 you go with 2 flutes?

I was looking at both:

2 flute
4 flute

I can see why the 4 would resist more it is less expensive though.

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Graeme

27 posts in 861 days


#8 posted 07-31-2012 07:50 PM

I have an upcut coming and I want to compare it to the end mill to see which one works for me. At any rate I will take it slow. My favorite little Dewalt router is only 1.25 hp anyways so it can’t handle big chews.. I know I should upgrade to a larger plunge, but I like the little guy. Maybe if I break some bits it will make me upgrade…

View NiteWalker's profile

NiteWalker

2710 posts in 1265 days


#9 posted 07-31-2012 08:40 PM

Definitely go for two flutes.
I use a two flute 1/4” spiral upcut for all my loose tenon joinery. Works great.

-- He who dies with the most tools... dies with the emptiest wallet.

View Graeme's profile

Graeme

27 posts in 861 days


#10 posted 08-01-2012 02:41 PM

Rick I wound up going to ebay because of free shipping. Getting things to Alaska is a bit of a challenge and shipping can be outrageous.

I know about complication, just trying to learn. Thanks.

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