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Discussion Starter · #1 ·
Hello,

I am cutting 1/4 wide/ 3/4 deep mortise using and upspiral bit. I Have cut hundreds of those mortises this way in the same species (ash) but this time I broke 2 bits in like 20 min and damaged my collet in the mean time. Now I'm out of the shop waiting for a new collet from the mail :frown::crying:

What I normally do is a full plunge on both end of the mortise then rout between 3 x 1/4 deep for a total of 3/4 deep. Never had any problem. Now this time I Don't know why but broke 2 bits when plunging full depth at each end. It's like the bit bites in the wood on the last 1/8" or so. Nothing special here same technique like the last hundreds I did but this batch of ash seem different. Table saw was burning it like hell and thickness planer was making tearout sound no matter wich side i feed first.

So I will have to modify my mortise technique. How do you guy do it in very dense & hardwood. I know routing in increment is key but regarding the plunging part, how would you approach it.

My take on this would be to first rout the bulk of the slot using 3 x 1/4 increment staying shy of the ends(Maybe 1/16). when this is done then I will do full plunge at the end leaving more room for the chips to go. It's kinda like the usual method most use but in reverse.

what do you thinks
 

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the wood was either dried at a high temp for faster processing or baked too long accidentally or or high temp w/ longer kiln time because it was to high of an MC when it wen into the kiln...
there's a most excellent chance your wood was tempered/hardened....

was are your external and internal MC's???
 

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what brand of bit are you using???
 

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Discussion Starter · #4 ·
thanks for your answer the bits are freud ones

as for the MC I dont have a way to measure it on hand we are in lockdown. It was air dried by another woodworker who stopped woodworking and sold it to me after it has sat in hia shop for years.

what I can say about its appearance is that this board is very different from the other. It is supposed to be ash but it is heavier, more prone to burn and the open grain structure is very tight.

It is in workpieces coming from this board that the bit broke.

anyways these fellas wil be mortised whether they like it or not.

what do you think of the slightlt different method I proposed in the op
 

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Discussion Starter · #6 ·
yes I know but right now in canada what used to take 3-4 days to arrive now takes about 1.5 month.I have ordered freud router bits from amazon about 3 weeks ago, they are still waiting to be shipped. Used to take about 5 days to arrive. SO even if I order a moisture meter I would be able to respond like in may.

But regardless of MC does the different method would lead to less chance of Breaking :

-Rout the bulk of the mortise using 1/4 pass and staying about 1/16 shy from the ends up to 1/2 deep
-On the final 1/4 I plunge the full 3/4 on the ends wich will have lots of roomfor the chips to go then rout the final 1/4 (total 3/4 deep)
 

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since it was air dried...
that leaves...
it isn't Ash...
and I'm WTB it's still hardened, sunlight will do that ....
you could be hitting wild grain.. (a knot)

is this the bit you are using???
https://www.freudtools.com/explore/router-cnc/straight-spiral/compression
have you considered a double flute straight bit???
https://www.freudtools.com/explore/router-cnc/straight-spiral/double-flute-straight

chatter is a bit breaker...
you said you tore up your collet...
how in world did you do that???
one way was not having your bit fully encompassed by the collet, only partially..
is there run out in your router's shaft???

BTW..
do we still keep calling you N/A for a 1st name???...
 

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Discussion Starter · #8 ·
haha you can call me Pascal

The bit is an upspiral fullcarbide one. The collet did not tore but the 2nd bit broke in the collet so it left a mark inside the collet. Other bits became very had to slip into the collet so I feared this would be a receipe for disaster.
 

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well Pascal...
ditch the N/A and put you in it's place...

feed rate is too fast for the wood...
smart thinking on the collet...
 

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I've always found that removing as much of the waste as is practical results in easier routing and about 1/3 as much wear on the bit. If you're grooving then make a pass or two on the table saw first. In this case I would drill as many holes as possible with a 3/16" bit. Drilling is fast and easy and drill bits are cheap. If you set up accurately on a drill press with a fence to keep you inside the mortise lines then you could go with a 1/4" and then all you have to rout is the points between circles. Even if you are off a tiny bit with the drilling that's not a bad thing because it gives the air in the mortise a way to escape if the fit is otherwise very tight.
 

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Hey,Pascal; welcome, if I haven't previously done so!
Re; the 'name' point that Stick mentioned. N/A and United States are the default entries under your screen name (upper left corner of your comments). Stick is suggesting in his unique style, that you actually enter the correct info into your 'Bio' so that it appears on your comments.
LEFT Click on your own screen name to see what I mean.
-left click on Public profile
-left click on the edit function
 

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since it was air dried...
that leaves...
it isn't Ash...
and I'm WTB it's still hardened, sunlight will do that ....
you could be hitting wild grain.. (a knot)

is this the bit you are using???
https://www.freudtools.com/explore/router-cnc/straight-spiral/compression
have you considered a double flute straight bit???
https://www.freudtools.com/explore/router-cnc/straight-spiral/double-flute-straight

chatter is a bit breaker...
you said you tore up your collet...
how in world did you do that???
one way was not having your bit fully encompassed by the collet, only partially..
is there run out in your router's shaft???

BTW..
do we still keep calling you N/A for a 1st name???...
Just an aside, but I've had some Post Oak that was air dried (no sunlight issues) that routed with difficulty. Very tenacious wood that will tear into skinny strips rather than just cut clean. Have actually clogged the vacuum port at times. I just go slow and shallow to avoid sidewall tears, etc. Might be my direction of grain too. Knots are no-go, ever.
 

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I've found that ash has a tendency to be difficult to cut in that it tends to be springy when the blade cuts into it. I call this "Grabby", and it tends to pull on the cutter harder than other woods. When cutting mortises, I make overlapping plunge cuts the full length of the mortise, then go back and remove the rest in increasing depths and several passes. Be very careful when you reach the end of the mortise, as it will grab the full length of the bit.
You might consider using a hardened steel bit for these passes, as the steel won't break as easily as carbide, but it doesn't hold it's sharp cutting edges as well, so you may need to stone the edge to resharpen it occasionally, or if you have a steel bit with carbide edges, even if straight blade, it would be better for this cleaning out work. I prefer carbide cutting edges, but steel shanks survive much better than solid carbide.

Charley
 

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Pascal, You have received good advice from other posters. I would like to add a couple other thoughts. You don't say where you are in Canada, but you might want to consider shopping at Lee Valley. (Moderators, I have no connection with this company so I hope I haven't committed a faux pas by mentioning it.) Their prices may be a little higher, but their selection & service are great. Right now, if you don't live where you can access one of their stores, they have free shipping. The length of time you are having to wait For Amazon orders would seem to indicate they are depending on cross border shipping. L.V. is all Canadian.
Back to your routing issues. Solid carbide bits in the small sizes tend to be overly long, which allows for a lot of side loading while routing. This combined with solid carbides brittleness means you have to be careful you don't force the cut to avoid breaking the bit, especially in hard or difficult woods. Just because you are using an up cut bit it doesn't always mean the chips will clear, resulting in a loaded up bit. A loaded up bit has no more room for shavings between the flutes so you push a little harder to keep it cutting. You get the picture? Be sensitive to how much pressure it takes to keep the bit cutting. It may be that the 1/4" deep first pass will be will be too much depth for subsequent passes. And, if you see the previous pass is not clear of shavings, clean it out before starting the next. Existing chips will contribute to loading in the next pass.
 

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I generally try to cut no more than 1/8 to 3/16ths at a time. On very hard material, I think 1/4 is a lot to hog out at once. Also, are you letting the bit do the work or are you forcing it?
 

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I've always found that removing as much of the waste as is practical results in easier routing and about 1/3 as much wear on the bit. If you're grooving then make a pass or two on the table saw first. In this case I would drill as many holes as possible with a 3/16" bit. Drilling is fast and easy and drill bits are cheap. If you set up accurately on a drill press with a fence to keep you inside the mortise lines then you could go with a 1/4" and then all you have to rout is the points between circles. Even if you are off a tiny bit with the drilling that's not a bad thing because it gives the air in the mortise a way to escape if the fit is otherwise very tight.
Drill bits.... that's interesting. Maybe forstner bits.
 

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Drill bits.... that's interesting. Maybe forstner bits.
Or Lee Valley's brad point bits. https://www.leevalley.com/en-us/sho...s/42247-hss-lipped-imperial-brad-point-drills They cut the cleanest, most accurate holes of any bit I've tried. So do their Forstner bits. I have a set of the lipped brad points to 1/2". A little pricey but worth it. A standard 135* split point can wander in odd grain but the brad point is far less likely to because of the way it cuts.
 
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