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Question... Help me make a good choice on a flush trim bit. I'm not just interested in which bit - I'm interested in why it's a good choice.

I'll share my thinking below so you can confirm, correct, or guide me elsewhere. But first I'll share a little context...
  • I'm a routing newbie, reasonably experienced elsewhere in a shop, about to buy my first bits for use in a Bosch 1617, which will be handheld until I build a table (currently at least four projects down the queue).
  • I'm asking about flush trim bits - just to make the question concrete - but my immediate purchase list also includes others. I'll include specific immediate routing needs at the end of this post in case it's relevant.

How I'm choosing a flush trim bit...
The questions seem to be - what brand, what diameter, what cutting length, number of flutes, what shank size, and straight vs. spiral-up/down/combination...

What brand... is addressed in many other threads on this forum. Here's what I've gleaned from them...
  • Eagle American, Whiteside, Infinity, Sommerfield, CMT, Freud, Amana all seem to be top favored brands with a very slight bias toward those earlier in that list.
  • MLCS seems to be the most recommended brand of the lower tier. Some here favor MLCS for less used bits and others wouldn't use them without full body shrapnel protection.
  • Sommerfield has the edge for matched sets (like tongue and groove) because no height adjustment is required after changing to the second bit. Freud matched sets have fans here but I don't know whether they share that specific advantage. Neither is relevant to my current choices since my immediate purchase needs are not sets.

What diameter...
  • It seems that larger diameter bits are better, as long as the router has the power to swing it... which doesn't appear to be an issue for a Bosch 1617 with a flush trim or any of the other bits I'm considering.
  • Exception: if flush trimming inside corners, a smaller diameter bit may flush trim a tight corner that a larger diameter bit cannot. However, this is not an issue for my current project or for the next four projects in my queue.

What cutting length... I've seen little or no discussion of this question, though it also seems this is an application specific issue. For a flush trim bit there's a minimum required cutting length for whatever material I'm using. Beyond that, I'd pay slightly more for longer cutting length to make it useful in a future project with thicker material. I see no disadvantage to longer cutting length beyond price, as long as the work is supported in a way that doesn't make the extra cutter protruding below the workpiece a major hazard. My current use is flush trimming 1/2" baltic birch, but I'd buy a 1" cutting length over a 1/2" for future versatility.

How many flutes... I understand that more flutes are generally better, yielding a smoother cut and allowing higher feed rates.

Shank size... I'm considering only 1/2" shank for a stronger bit. I might make exceptions and use a 1/4" shank if I needed to flush trim tight inside radius corners (I don't right now) or for cost reasons if I was buying a solid carbide spiral bit (addressed below).

Straight vs Spiral... and spiral up/down/combination...
  • On first look, solid carbide spiral bits seem to have significant advantages if I ignore cost. A second look shows a price difference enough to make me take notice, especially if I stay with a 1/2" shank. Even if my budget allows me to pay $70-100 for what would be $20 in a straight bit, it doesn't mean that I want to.
  • My current projects are shop projects not cabinets. Materials are mostly baltic birch and dimensional lumber. I think straight bits have been successfully used with such materials for decades, so I don't think spiral is needed.
  • If I buy spiral, I'll buy up-cut so the router wants to stay firmly on the work.

So, which flush trim bit? I'm considering the following options from this Eagle America page. Once I narrow to a specific bit, I'll compare that precise bit against other brand choices - at least Whiteside and Freud for their many recommendations on this forum.
  1. #117-0412, 2 flutes, 1/4" diameter, 1" cutting length, 2-7/16" total length, 1/4" shank, single bottom bearing, $28.95
  2. #117-0615, 2 flutes, 3/8" diameter, 1" cutting length, 3-1/8" total length, 1/2" shank, single bottom bearing, $17.95
  3. #117-0825, 2 flutes, 1/2" diameter, 1" cutting length, 3-1/4" total length, 1/2" shank, single bottom bearing, $17.95. (That's also available with downshear for $21.95, but I'm uncertain whether that makes the handheld router less stable as it would with a spiral downcut bit.)
  4. #117-0835, 3 flutes, 1/2" diameter, 1" cutting length, 3-1/4" total length, 1/2" shank, single bottom bearing, $21.95 here
  5. #117-0865, 3 flutes, 1/2" diameter, 1-1/2" cutting length, 3-5/8" total length, 1/2" shank, single bottom bearing, $25.95 (also available with 2 flutes for $19.95, #117-0855; both also available in 2" cutting lengths for about $5 more)
  6. #117-1215, 2 flutes, 3/4" diameter, 1" cutting length, 3" total length, 1/2" shank, single bottom bearing, downshear, $32.95 (yes, still uncertain about downshear; straight version is cheaper; longer cutting lengths available)
  7. #117-1215B, 2 flutes, 3/4" diameter, 1" cutting length, 3" total length, 1/2" shank, top & bottom bearings, downshear, $46.95
  8. #117-1305B, 3 flutes, 3/4" diameter, 2" cutting length, 4" total length, 1/2" shank, top & bottom bearings, $53.95.

If money was no object, I might buy the last one - 3 flutes advantage, 2" cutting length probably exceeds anything I'l ever flush trim, and the versatility of top & bottom bearings. The only anticipated need it can't meet is tight inside radius corners which would suggest the first one - but that's not a need today.

If I ordered this moment, I'd buy #4 - or similar in another brand. It's likely I'll actually buy Freud or Whiteside because I can get Freud locally at a big box store and I can get either fast via Amazon prime. That bit choice is paying a few bucks extra for three flutes (vs #3), and getting 1" cutting length which works fine today. That's missing the opportunity for a longer cutting length for future needs, missing the benefit of top & bottom bearings... and that's ignoring the smoother cut of downshear options because I'm lacking expertise on whether it makes the router squirly.

All input is welcome.

Broader picture promised at top... besides a flush trim bit, here's what I'm buying ASAP for specific uses in current projects...
  • 1/4" straight bit, both for routing 1/4" through slots, and possibly also for routing dados using an exact width dado jig. I may consider a solid carbide spiral up-cut bit for this with a 1/4" shank, or I may stay with a basic straight bit.
  • 3/4" straight bit, for routing 3/4" - 1-1/2" dados using an exact width dado jig.
  • 1/8" roundover bit, for softening edges. My ROS works, but I'll use this bit enough that I'm willing to pay for it. If I was going to consider MLCS anywhere, I might consider it here and get this set for $30 vs paying the same for the single Freud bit needed now..
  • (Optional)I'm considering a rabbet set. I can build what I need without it as the above straight bits are perfectly capable of cutting rabbets with the RA1154 edge guide... though the convenience is tempting.
 

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Which bits... a deep rabbit hole...
dirt or sand.. auger..
rock .. diamond core bit...
 

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Question...

1... Help me make a good choice on a flush trim bit. I'm not just interested in which bit - I'm interested in why it's a good choice.

How I'm choosing a flush trim bit...
The questions seem to be - what brand, what diameter, what cutting length, number of flutes, what shank size, and straight vs. spiral-up/down/combination...

2... Eagle American, Whiteside, Infinity, Sommerfield, CMT, Freud, Amana all seem to be top favored brands with a very slight bias toward those earlier in that list.
3... MLCS seems to be the most recommended brand of the lower tier. Some here favor MLCS for less used bits and others wouldn't use them without full body shrapnel protection.
4... It seems that larger diameter bits are better, as long as the router has the power to swing it...
5... Exception: if flush trimming inside corners, a smaller diameter bit may flush trim a tight corner that a larger diameter bit cannot.
6.. What cutting length...
7... How many flutes... I understand that more flutes are generally better, yielding a smoother cut and allowing higher feed rates.
8... Shank size... I'm considering only 1/2" shank for a stronger bit. I might make exceptions and use a 1/4" shank if I needed to flush trim tight inside radius corners
9... Straight vs Spiral... and spiral up/down/combination...
10. On first look, solid carbide spiral bits seem to have significant advantages if I ignore cost. A second look shows a price difference enough to make me take notice, especially if I stay with a 1/2" shank. Even if my budget allows me to pay $70-100 for what would be $20 in a straight bit, it doesn't mean that I want to.
11. My current projects are shop projects not cabinets. Materials are mostly Baltic birch and dimensional lumber. I think straight bits have been successfully used with such materials for decades, so I don't think spiral is needed.
12. If I buy spiral, I'll buy up-cut so the router wants to stay firmly on the work.
13. So, which flush trim bit? I'm considering the following options from this Eagle America 14. I'm uncertain whether that makes the handheld router less stable as it would with a spiral downcut bit.)
14. I'm considering a rabbet set. I can build what I need without it as the above straight bits are perfectly capable of cutting rabbets with the RA1154 edge guide... though the convenience is tempting.
1... I was a commercial operation... My choice ended up being Freud because they were the best value.. cost of bit vs LF of material cut... they made for a decent return to the bottom line..
2... as long as the bits are USA, Italian, Swiss, Austrian, German or Israel made you'll do fine..
some these mfrs import bits from the far east and put their name on them... Amana/China are some really sad bits... expensive junk too...
3... the shrapnel issue was me.. got hit w/ a flute in the left ear... now that was expensive.. their balance could be a lot better.. out of balance bits are prone to failure, give mediocre cuts at best and are hard on the router's bearings...
4... correct...
5... correct...
6... little more than you need to do the job...
over length bits aren't worth it over all scheme of things since you are only using a section of the bit... what you end up w/ is a partially worn out bit that you can't use in it's entirety..
also.. if you use just the end of the bit against thinner material the bit won't like the lateral forces at all and you are setting yourself up for a dangerous situation if the body of the bit separates from the shank because of the the lateral stresses..... I did what you are thinking... VOE...
7... correct... the more the merrier.. wait till you experience a Freud Quadracut...
8... good bet... bit body strength is a major item here...
9... this is where I migrated to.. very nice economical trade off... quality cuts too... the bit shears the wood fibers instead of tearing the..
Freud Tools - Search Results for helix
10. up-cut bits tend to pull into the work and generally leave a fuzzy top edge.. down-cut bits tend to push away and leave clean top edges... up/down bits are are the fix for the pull/push thing and top fuzzy edges..
11. correct.. make sure they can plunge cut...
12. not an issue.. unless you try to hog w/ it...
13. at those prices those are imported bits... I've learned a long time ago the are not worth the money...
FWIW... I tend not to think strictly w/ my wallet.. but go for value. less danger, less down time, better CS, better production and etc...
14. good choice.. better accuracy and control...
one thing you'll learn is to cut away as much material w/ your table, band or jig saw before you rout and save the drops.. valuable pieces of material... 1,001 uses for them...

15.. what do you do... type 200 plus WPM???

NOTE:

discoveries of on/of Asian bits...
  1. out of balance..
  2. 2 piece bits..
  3. poor brazing..
  4. shanks out of tolerance..
  5. bits out of tolerance..
  6. dull
  7. short usage life..
  8. soft carbide..
  9. poor CS.. (you bought it.. you own it.. now go away..)
  10. tapered straight bits..
  11. bent...
  12. do not handle heat well...
 
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I'd say a good part of it depends on what you want the bit for. With me, for what I do 99.9% of the time, I use a flush trim bit, 1/4" shank, 1" cut, no HSS (unless that is all that is available, until I can get better), used in my router table. The brand I use is, whatever is available at the local hardware, or Lowes, when my last bit dies. I don't use 1/2" shank bits because none of my routers are 1/2". Works for me.
 

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@stick, re 15: I've been thinking about this far too long. Over processing.


Sent from my iPad using Tapatalk
take the humor and run w/ it...
you did that typing on your phone...
YOWZER!!!
sure beats my 5~WPM...
I edited my original response...
 

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I use both 1/4" shank and 1/2" shank bits. All of my routers now have 1/2" collets, so I use them more than the small shank. Also the selection of 1/2" shank bits is greater for different profiles than the 1/4" shank.

A lot of my favorite profiles are only made for 1/2" shank.
Herb
 

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Hey Ashly, I now buy Whiteside bits because of their quality but I am sure Freud bits are just as good or better. I also try to buy all 1/2" shank bits for safety reasons. I do have a trim router that I do have to have 1/4" shank bits for. For a flush trim bits I like the solid carbide ones. They sure make a smooth cut. I would buy Freud bits if I could find a good place to buy them without having to pay sales tax. Ours is 9 3/4% where I live.

Here is where I buy WS bits. No tax and no shipping.


https://www.hartvilletool.com/category/router-bits
 

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Hey Ashly, I now buy Whiteside bits because of their quality but I am sure Freud bits are just as good or better.
no issues w/ WS bits...
better than Freud out of the box...
good items..
but.......
the Freuds are way better in the mileage category...
I think this because WS have a fuzz softer carbide than Freud...
softer carbide can be made sharper than harder carbide w/o extra process...
 
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no issues w/ WS bits...
better than Freud out of the box...
good items..
but.......
the Freuds are way better in the mileage category...
I think this because WS have a fuzz softer carbide than Freud...
softer carbide can be made sharper than harder carbide w/o extra process...
How do you know that fuzzy softer carbide?
Herb
 

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Discussion Starter #12
Ok, I'm narrowing options to Whiteside, Freud, Eagle America, and CMT... very likely Freud due to local availability.

For my 1/4" slot cutting and dados, I'll buy a solid carbide spiral upcut with 1/4" shank and 1" cutting length from Whiteside, Freud, CMT, or Eagle America (106-0412)... all around around $20.

For my 1/8" round over, I'll buy 1/2" shank bits from Whiteside, Freud, or Eagle America (165-0525)... for $20-28.

For my 3/4" to 1-1/2" dados cut with an exact width dado jig...
...and for my flush trimming...
I'm tempted to try a single bit - the Eagle America 102-1205B 4-In-1 Dado Clean-Out Bit (dado, planer, hinge boring, and pattern cutter), 3/4” diameter, 1/4” cutting length, 2” total length, 1/2” shank, $24.95.

That seems an amazingly good price for what I need, especially considering the 3/8" cutting length version (116-1205B) goes for $45.95. My only disadvantage with the shorter cutting length on the cheaper bit is needing multiple passes when flush trimming... and that's not an issue on the dados as I wouldn't be cutting more than 1/4" at a pass anyway. I'm certain I'll eventually buy a flush trim bit with a longer cutting edge, but this seems a reasonable way to get the project queue moving since I'll have less than 25 linear feet to flush trim.

Am I crazy?
No, ignore that question. I already know the answer.
Better question - anything you'd change in my direction?
 

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You're way overthinking this . . . . This won't be the last router bit, or even the last trim router bit you buy. Stay away from cheap junk. Anything else, you'll find a use for someday. Someday, you'll have a project that doesn't require the purchase of yet another router bit. I've been doing this 30 years, and only occasionally find such a project. Build your collection and enjoy the ride.
 

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Hi Ashley, what a great string! I don't use spiral bits much, and I often use a down spiral bit because it leaves a cleaner edge. A mortising bit is a real asset, and for that I use the half inch mortising bit from Freud. It works well for cutting dados. Mine is a Freud mortising bit. It also works for recesses for hinges and door hardware. I do use and like my small Colt router for such mortising tasks.

The pictures show the features and differences. The long, red bit is a trim bit. Notice all the cutting edge is on the sides. The yellow and red "pudgy" bits are mortising bits. Notice that there is a fairly wide area of carbide that gives you a flat bottom dado or groove. The bearings are what you run on the edge of your template. The yellow is a 3/4 bit, the smaller one is a half inch bit. You can see the profile the mortising bits cut.
 

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