Wrong router bit?

[Rennie Heuer]

I have many finger joints to do for the G&G speaker cabinets I am building. They are 11/16” deep in 9/16” mahogany. I wanted a bit that was a length that would allow me to cut them in a single pass so I looked around to find a 1/2” diameter pattern bit that had a cutting length of 3/4”. Surprisingly, many of the places I would normally shop were sold out.

I found a CMT bit for a reasonable price in the size I needed on amazon prime and purchased that. CMT not usually my first choice, but I had trouble finding a Freud or Whiteside that was in stock.

The first thing I noticed was that the bit was sending out a lot of dust and almost no shavings when cutting. Then came the smoke. I was getting a lot of burning. I’m beginning to think that I have a dull bit, a low quality bit, or that I have chosen the wrong type of bit for the task. I’ve cut hundreds of finger joints using this jig in many species of wood and never had this problem before.

So, bad bit, or bad me?

 

[Carol Reed]

Contact the manufacturer. CMT had been a quality bit -but not that one.

 

[Jim DeLaney]

Try using a 4 flute (metal working) end mill. They're a spiral bit, and they cut very well. MSC is a good source. Tn coated HSS mills last a long time.

 

[Rennie Heuer]

Try using a 4 flute (metal working) end mill. They're a spiral bit, and they cut very well. MSC is a good source. Tn coated HSS mills last a long time.

Interesting. Hadn’t thought about those. I would have to reengineer my jig a bit to use these because there is no guide bearing. I would have to rig it to work with a guide bushing.

 

[larry merlau]

another vote for bad bit, cmt were good.. and i second jims vote but along that line whiteside make a spiral bit to do your cut as well.

 

[Rennie Heuer]

another vote for bad bit, cmt were good..

I’m returning it for a refund. Dummy me, I dug through my bit drawer and found that I had a Freud in the right size. So, the orange bit goes back with a note complaining of the burning and smoking right out of the box.

 

[Charles Hans]

Rennie, Have you tried here? https://www.holbren.com/ultimate-flush-trim-pattern-router-bits

 

[Leo Voisine]

I would steer you away from a 4 flute spiral bit designed for metal cutting.

If you wanted something like that, then I would suggest a 2 flute bit, or even a single flute bit. Reason is - the gullet in a 4 flute bit is really not large enough to evacuate the larger chip from cutting wood. Also, the right hand spiral tends to pull up at the top surface and possibly chip the top corner of the cut.

 

[Rennie Heuer]

Rennie, Have you tried here? https://www.holbren.com/ultimate-flush-trim-pattern-router-bits

I saw these. Drooled a little on my keyboard. Then continued shopping for something 1/5 the price. ;o)

 

[Rennie Heuer]

I would steer you away from a 4 flute spiral bit designed for metal cutting.

If you wanted something like that, then I would suggest a 2 flute bit, or even a single flute bit. Reason is - the gullet in a 4 flute bit is really not large enough to evacuate the larger chip from cutting wood. Also, the right hand spiral tends to pull up at the top surface and possibly chip the top corner of the cut.

Makes sense, but the prohibitive price renders it a moot point. Such things just are not in my budget.

 

[Carol Reed]

Rennie, I don't find end mills to be prohibitively priced from a machinist tool vendor rather than a woodworking tool vendor. I have a local vendor I get my spiral bits from. Tons less expensive that spiral woodworking bits. Two flute right hand twist is the terminology.

 

[Rennie Heuer]

Rennie, I don't find end mills to be prohibitively priced from a machinist tool vendor rather than a woodworking tool vendor. I have a local vendor I get my spiral bits from. Tons less expensive that spiral woodworking bits. Two flute right hand twist is the terminology.

Thanks Carol! This is something I want to explore. Never used an end mill before - at least not one made for metal.

 

[Rennie Heuer]

In the column entitled "I do my best thinking when I'm not thinking"...

Lying awake in bed last night, dreading today's shop time because of all the routing I needed to do on those finger joints, I hit upon an idea. The reason I dreaded the work was because of the tremendous amount of router dust each of these cuts generates. So much so that I actually find it necessary to sweep up after each cutting. What it does for the air quality in the shop goes without saying.

Then it hit me - - I had my "Elementary my dear Watson" moment. Why not bandsaw out 99% of the waste? This takes a great load off the bit, generates a lot less dust, and will be a lot faster in the end. Wow. If I actually had a brain I'd be unstoppable!!

 

[Jim DeLaney]

I would steer you away from a 4 flute spiral bit ...the gullet in a 4 flute bit is really not large enough to evacuate the larger chip from cutting wood. Also, the right hand spiral tends to pull up at the top surface and possibly chip the top corner of the cut.

Disagree. Yes, the gullet is a little bit smaller, but there are twice as many cuts per revolution, so the chips are smaller, too. Also, the more (and smaller) cuts make for a much smoother surface.

As for chipping out the upper corner, any up cut spiral bit might do that - particularly if you're trying to hog out a lot of material at once - but I've never found that to be problem so long as I took reasonably sized cuts at a reasonable cutting rate.

All that said, two flute mills work quite well, too.