Flush Trim Router Bits

Bits and Bits is a long time partner of Jays Custom Creations. They create high quality router bits and offer them with competitive pricing. Check them out at bitsbits.com and use the code JAYBATES to save 10% at checkout.

In the video, I mentioned I’ll be giving away a few of the duplicate bits I have. Leave a router/cnc related comment below, and you’ll be entered. Leave a tip, trick, learning experience, or whatever bit you plan on adding to your arsenal next. I’ll do a quick video and randomly select a winner in a few days.

The following were provided by Bits & Bits. I’ll select three winners. One bit per winner.

  1. Winner #1 will get an Astra coated RFTD5125 1/2″ diameter spiral down cut flush trim bit.
  2. Winner #2 will get an Astra coated 430-CM250FT 1/4″ diameter compression flush trim bit.
  3. Winner #3 will get an Astra coated 430-SRF250FT 1/4″ diameter up cut flush trim bit.

Below are the notes used for the video:

Up vs. Down?

  • Upcut for router table; Using the downcut on the router table with a gnarlier grain wood can push the workpiece up off the table if you’re not expecting it.
    • Caveat – Down for pushing against a template for reduced tearout. 

Bit Diameter?

  • Avoid an “enveloped cut” where the bit is surrounded on three sides by wood, instead of rough cutting close to the line and trimming off 1/16” or so. 
    • If you’re going to envelope the bit, we recommend a single-direction bit instead of the compression, which can get a little jumpy when it’s buried. The single direction is pulling the chips out quickly and not letting them pack into the cut pocket like a compression would.
  • Interior corners may require a smaller diameter bit. 

Router Speed?

  • Router speed is another issue that comes up, especially in the ¼” bits. Most guys install the bit and turn it up to full speed, but chip load applies to all spiral bits, regardless of CNC or router use. Turning the speed up to 27,000RPM + can make the bit erratic as well as cause it to dull quicker because it’s cutting dust and overheating (rubbing vs cutting). 16,000-18,000 is the recommended speed for all spirals.

Router Size?

  • Router size is also important. A solid carbide bit is more brittle than a standard steel shank tool, we have guys sticking a ¼” bit into a 3HP+ router and over-torquing and snapping the bit after it hits a dense pocket of wood or the user moves the router too fast. The thinner ¼” work really well on the smaller trim routers, but a larger router will do much better with a ½” bit.

Worth Considering…

  • The compression isn’t necessarily the ‘ultimate’ bit for trimming. It may produce the most crisp edges but most of the time, you’re going to round over or chamfer the edge anyways, so a little fuzz doesn’t really matter in the long run.
  • Integrated depth stop on the ⅞” bit. You can’t take a massive bite. It just won’t allow it.

218 COMMENTS

  1. The most helpful thing I’ve found is keeping the router bits clean. They cut so much better after a good cleaning particularly after working with soft woods.

  2. I appreciate your easy to understand description of this stuff. Learned about chip load in one of your other videos. Nothing to add to what you’ve said. Part of it is a blatant try for another trim bit for my bit arsenal.

  3. While I am required to use 1/4 inch shank bits from time to time I can’t agree more with how much nicer it is to use 1/2 shank. Just like you said, they just feel much more solid, smooth and safer.

  4. I just bought that large compression bit. It was too good of a black Friday sale to pass up. I appreciate the info in this video. Thanks.

    • Occasionally check the bearing screws are tight. I had one come off while using it. Checked the rest of my bits and found a couple that were loose.’

  5. For me when trying a new bit, or especially technique, I plan on making sawdust and fire wood. Really cool decorative firewood. If something else happens instead, that’s a bonus. It’s all about learning and the journey for me.

  6. I would say that the amount of router bit shank you have extened out of the table or past the base of the router, is crucial to reducing the amount of deflection you might get. Plus the flatness of your router table top will sometimes impact the cut quality. For instance if you have a sag in your router table top, as you enter the cut with any edge profile bit, you will get a deeper cut, in the middle of the workpiece as you span the sag it will even out and when you come to the end of your cut it will cut into the wood deeper. Also for using a router handheld it’s a good idea to take multiple passes with plunge base routers and smaller trim routers. Just like you said really depends on the router.

  7. I recently engineered an insert that falls into the gap of my Bosch jobsite table saw table extension, it accepts a Bosch router underneath to turn the whole thing into a router table. The original fence happens to accept some t-track bolts so I built my own router fence out of it by adding an attachment, this allows me to use top and bottom dust collection.
    All of the router adjustment wrenches and insert plates are attached to the bottom of the drop in unit with magnets so there is never any hunting for tools.

    Thanks for teaching me something about BITS! I had no idea.

  8. With router bits I was told to buy a cheap set and replace the ones you use the most with nicer ones. The flush trim bit is not one worth wasting time with cheap ones. Borrowing bits from a friend showed me the difference in a high quality finish.

  9. I just bought my first flush trim router bit a few minutes ago, and this discussion/video helped a lot. I appreciate people helping people!

  10. Thanks Jay. This is the best explanation of the up/down configuration I’ve seen. Also, I now know when to NOT use my compression bit! I had a rather unpleasant experience using the nesting chair templates with Ash wood. The end grain caught the bit and things got ugly quickly. Luckily, only the template and wood were damaged, no body parts.

  11. Thanks for the great information. Would you recommend using the trim router on your chair template with a hand held router?

  12. I’ve only ever had cheap flush trim bits. They’ve gotten the job done, but it’s slow going. Would be great to have something better than the ones I’ve gotten from big box stores.

  13. I purchased a good flush trim bit to use when building your stackable beach chairs. However, I tried to save some money and didn’t get a spiral bit. Big mistake. It’s those little tricky spots that get you. Fortunately, no one was injured, but lesson learned. Next time I’ll be using a spiral bit.

  14. You introduced me to BitsnBits some time ago. I got the 1/2 compression flush trim and absolutely love it. Thanks for the info.

  15. Thanks Jay, always learn something from your videos. Still a novice, still learning my way around. Have no experience with spiral or flush trim bits. A couple things I have learned: dust collection through the fence works mainly for edge cuts; dado cuts generate a ton of dust, which blows out the end of the dado, but it can be captured at the edge of the router table, or through a hole drilled or cut through the table directly downstream of the bit.
    Wishing you and yours a happy holiday.

  16. It may be obvious to many, but a lift for my router was one of the best investments I’ve made into general usability. Now I’m more likely to use the table because bit swaps and setup are easier and faster.

  17. Good stuff. I had not really considered the implications of using up/down bits while using a template. Hope you guys have a Merry Christmas.

  18. Down vs. Up. Easier if you think that the down cut will push chips toward the bearing and Up cut will push chip towards the router. This would apply to bits with bearing at the end. It doesn’t matter if it is handheld or router table.

  19. This was a very helpful video. I’m pretty new to woodworking, and I was really confused about the spiral cut bits. Thank you.

  20. Great info! I have a simple tip, which has saved me time and money. Keep your bits organized and in one place. The only time to leave a bit out, is if you are continuing with an operation, or have a dedicated router with a dedicated bit.

  21. This was a great video with helpful information! I’m not super new to woodworking but I also wouldn’t call myself wildly experienced. I just expand my tools and knowledge bit by bit. (Pun totally intended) :)

  22. My router table still scare the bejeezus out of me. I don’t know if it’s the noise or the ripping of pieces out of my hand. I find the most harrowing is flush trimming around the rounded corner especially in end grain. Definitely use a starting pin to help, double safety blocks. Still not sure about I have it figured out how to do it. I don’t have any solid carbid flush trim yet as they tend to be much more expensive.

  23. I just added a whiteside flush trim bit to my collection. A 1/2″ straight cut bit because the fancy spirals are out of my price range. Im building a router slab flattening nill and am thinking of a way to do other routing jobs with it, one of them is using it as a huge overhead template router with a flush trim bit. Load s template under your slab and use the linear rails to hold the router at the right height and run it around a large piece.

  24. I always find your videos helpful. I have yet to purchase a large spiral flush cut from bits and bits, I’m still using the straight cut. But now I think I might take the plunge.

  25. I picked up some 1/4″ flush bits from bits and bits and I’m hooked!

    I’m now hoping to pick up some larger flush bits and nearly made a move during the black Friday sales but had already spent too much money elsewhere!

  26. Super useful. New garage with dedicated shop space is under construction. I’m looking forward to some shop projects including dust collection and storage improvements on my router table to make it more enjoyable to use.

  27. I recently had an edge blowout while template routing. It was totally my fault. I should have double checked my depth of cut and trimmed the blank more. Every failure is a lesson I guess.

  28. Fairly green still when it comes to the router, so this was great info. I’ve never used a spiral cut bit yet but see they are very popular. I can definitely use a router table, so I’ve been debating a router lift. Routers are one of the most fun tools in the shop!

  29. Your advice on bits over the past few years has been so helpful to both my quality of work and my safety, also my wallet, so thanks again for the great video!

  30. Just purchased a router lift and will be making a permanent router stand and was wondering what bits I would need, be it up or down. Thanks for the info.

  31. Thanks for the info, I’ve been looking to buy a flush trim bit and have been so confused. This helps a lot and I now know what I’m going to buy. Keep your videos coming!

  32. Jay, thanks for the info as always. I also picked up that monster template but. Can’t wait to see how it feels. Don’t you just hate double tools, be happy to help you out there!

  33. Thanks for sharing this info. Would love to see more videos on router bits. Showing when and when not to use a certain bit. ie. down cut/ up cut, compression

    • your perspective on flush trim bits is some of the best advice i’ve ever seen, most people discuss the up downs compressions bla bla it always seems like a sales pitch. I fell in the trap of buying the most expensive compression bit and i’ve only used it a few times as i quickly realized its not that jack of all trades bit i thought it was.. if only you had made this sooner i would have known haha. thanks jay

  34. Your video was very comprehensive. I hadn’t thought about the possibility of jumping on the router table with narly woods probably because I’ve mostly worked with softer wood and only using a hand held. Thanks for the insight as I improve my woodworking.

  35. informative video thanks for the explanation of the differences between the bits, merry christmas to you and your family!!!

  36. My number 1 tip is don’t move the cnc with the router turned off and below the surface of the workpiece or the bit will snap. Ask me how I know.🤦‍♂️

  37. Do you have any advice on using a flush trim bit on endgrain? I just bought a compression bit from bits and bits and had a lot of blow out on the endgrain of my quartersawn white oak.

  38. I love your videos. This is super helpful and explained what was going on with a project I did years ago. I was making slats for a crib and it jumped up several times and gouged my template. This makes a lot of sense now. Also, I always just thought that spirals just dulled faster. I have apparently just been a grip it and rip it woodworker with my router, lol

    Thanks for the videos

  39. Helpful video, thank you. I’ve been eyeing spiral bits for a while but haven’t felt confident about the relative strengths and weaknesses of the various kinds.

  40. Really helpful info I haven’t heard anywhere else. I have a few Bits & Bits router bits and love them. They are way better than any of my other bits.

  41. Great info on router bits Jay. I always like hearing peoples take on routers and router use. Always somthing to learn.
    Whiteside bits are great.

  42. Been following you for years and I greatly appreciate the knowledge you share with this amazing community of Woodworkers. God Bless you and your family 🙏🏼❤️✝️❤️🙏🏼

  43. Such solid info. Thanks for taking the time to write out the notes and providing them below the video. Been subbed many years. You’ve been such a wealth of knowledge, and I have to say incredibly motivating. Not just in woodworking and creativity, but also in work ethic and self-care in the realm of fitness and what it can do for anyone. Really appreciate the powerlifting content and would love to see more on the second channel.

  44. Great video. Does not matter how many times I use a router I always have to stop and think about the right direction — don’t know why it messes with my mind so much!

  45. I haven’t had particularly a good experience with spiral bits in the past. I’ve had a few kick backs happen while flush trimming leg blanks and ended up destroying the piece and end up with a bent 1/2” solid carbide spiral flush trim bit. Now I am nervous about using them in general. Not sure if the router with a slight runout was the issue or trying to flush trim 2” stock but it’s not something I want to repeat again.

  46. Best tip: You WILL get what you pay for! A $60 bit will cut better, cleaner, and longer than a $15 bit. And it won’t break as easily either. :)

  47. I only have straight flush cut bits, and they do pretty well for me. With your comments about not using them except for mortising, I’m wondering if I’m missing something. I guess I hope I win one of the bits and can personally compare.

  48. I need to print this and keep it handy for reference. Great information. I keep looking at up and down cut bits and couldn’t pull the trigger on buying due to my lack of knowledge on the precise use for each. Thank you

  49. Thanks for the video Jay! I’ve appreciated the bitsbits discount a few times now!
    Don’t cheap out on whatever blade or bit is doing the cutting, even if you’re using cheaper tools! Had my eye on a good quality flush trim bit for awhile now, but I think it’ll be a bowl/tray bit next for me!

  50. I definutely need to expand beyond the Ryobi assorted pack of bits I have. Seems like some more sophisticated flush trim bits and maybe a surfacing bit for end grain cutting boards would be good.

  51. Very new to the router game having used a little harbor freight trim router for just about everything until recently when I purchased a CNC and router table to really up my game, but with that little trim router and my limited experience my biggest router advice is to take things slow. More often than not trying to rush or take deep passes with the router just cause more headache and waste more time. Slow shallow cuts for safety and more time saved overall!

  52. Jay. Great video as always, and very timely for me. I have a project that requires a lot of 3/8 slots cut into the interior of 1/4″ MDF. I’m using a template to get the slots in the correct position. I have drilled 5/16″ holes and used my bitsbits spiral upcut template bit in my router table to remove the rest of the material, but its an envelope cut and I don’t really want to continue this method. Can you recommend a better process to remove most of the material without the envelope cut?

  53. Super informative! I really appreciate your videos and how relatable you are! I recently built my first router table. It’s not perfect (gonna have to figure out how to get it a little flatter) but overall it turned out great! My next step is to build the fence for it as well as the drawers for bit/tool storage. I honestly never considered deflection with the 1/4” bits. Looks like I’m going to have to start investing in 1/2” bits. Thanks again for the info!

  54. Thanks jay for the video been I haven’t tried any of the bit bits astra coated bits yet but was planning on getting a few to try out maybe I’ll get lucky and win one of these

  55. That was incredibly helpful Jay! Question: I have a Porter Cable 690 fixed speed router. What do you recommend I add that will convert it into a variable speed router?

  56. Last month a bought a very nice compression flush trim bit from Fraiser Tools. But still I am very curious about the special astra coating and what the difference will be. Currently my eyes are on a 1/4 flush trim bit

  57. Thanks for the great tips! I was always under the impression to start with a higher speed and slow the router down to the best speed! I’ll try the other way and start slow and work up the the best speed! Thanks Jay!

  58. Thanks for the info. I’ve been woodworking for about a year now so I still consider myself a rookie. I’m always thankful for information like this as I continue the learning process, which never ends. I will check out their website for router bits. Thanks

  59. Thanks, Jay; I appreciate the information presented in this video. I watched the video on Youtube. This is the type of information one needs to commit to memory so you will have it in your brain to pull from.
    Thanks for sharing. Felix!

  60. I recently purchased a flush trim bit from the big box store and was not impressed with the amount of tear out. I’m going to cry once and try a compression bit that has more quality. Thanks for the info in your video.

  61. Thanks for the info. I have several routers from trim to 3hp plunge, but find myself using my 50yo Craftsman the most. Familiarity I guess.

  62. Jay, thanks for the video a lot of useful information packed in there. Quick question do you have any experience with the Shaper Origin?

  63. Can’t wait to get rid of my standalone router table and use the wing extension of my table saw for that purpose instead.

  64. Thanks for the detailed, high level explanation, Jay. I typically struggle to know when to use an upcut vs. downcut bit for flush trimming. This video should help and be a good reference. Cold and snowy up here in Michigan. Hope it is comfortable down in Mississippi this time of year for you!

  65. Thanks Jay. I liked your explanations. Very clear and gave me some new insight into speed and how to use the upcut and down cut bits.

  66. Jay, great video and article! As coincidences happen, I just bought a couple of those bits from Bits & Bits myself for my little CNC. I haven’t tried them out yet but I’m looking forward to it.

  67. Love your content Jay. I get your newsletter and I’ve been watching your videos for many years since way back in the early days. You certainly have come along way! I notice the care that you put into your annunciation such as in every time you say the word “the“ so I thought I might point out that you use the word “especially“ several times in this video and each time included an X in the word. EXSPECIALLY
    I do it also if I’m not being conscious of it. I miss the next several words after that each time.
    Keep up the great work!

  68. One of the greatly overlooked aspects to using a router, particularly in a router table is the collet runout. If you are doing high precision routing, then you should consider the collets made by Think & Tinker Limited. I have NO affiliation with them whatsoever, but I can tell you from first-hand experience, their collets are outstanding. It is much easier to get the correct “grab” of the bit without overtightening. One of my most terrifying experiences was with a spiral bit climbing up out of the collet blindly. I am happy to say that I use push blocks pretty extensively and that prevented a bad injury.

    As always, Jay’s information is super helpful and well organized. It is a pleasure to follow him.

  69. Excellent information on using the router. I haven’t had much experience using my router yet so I like learning all I can from videos and articles. My next bit might be a spiral bit or something else depending on any sales happening at the time.

  70. Really good info ! Makes me more knowledgeable to choose the right bit for the right job. Cleaning those bits after use makes them more efficient for the next job they’ll do. Thanks

  71. Great video on these type of bits, and great explanation on the compression bit. I think it would be good on something like MDF where you’re doing sign work and want the top and bottom crisp when applying to the back of the sign itself, as in raised lettering etc.

  72. Jay, I own a trim router but want up my game with a full sized router, preferably with a plunge base.
    Any recommendations or a video on setting one up and when to use trim versus full size for a newbie would be great.

  73. Really enjoy the videos. I’ve learned a lot in a relatively short time! I’ll be honest, I’ve had more than one hair rasing/butt puckering incidents with my routers. Not fun, but very good learning experiences nonetheless!

  74. Very informative video, I don’t know if I’ll ever keep up and down right in my head, I have to twist the bit in my fingers to know if I have the right one!

  75. Thanks for sharing your indepth knowledge on the router bits, as a relatively new woodworker this will be extremely helpful when choosing the next bits to buy/use.

  76. Jay, thanks for the video. I have a 1/2 inch compression trim bit from bits & bits. When I use in on your nesting chair template, it seems to want to grab whenever i reach the inside curves for the notches for the slates. It’s not like there is a lot of material to remove either. I trim it pretty close. On the seat pattern, when routing the notch closest to the end of the pattern, I have had it grab and rip out a chunk of the piece I am routing…which is always great. I have only made one set of these and they were white oak. Side note, I didn’t realize that white oak smelled so good when working with it.

  77. Damn Jay Bates how am I supposed to leave a comment when you got so many comments!

    Couldn’t find the form!

    Insert joke bout trimming down…lol jk, love to see it! Actually got a white side with multiple bearing sizes that works well., and upcut spiral is prolly the next buy though.

  78. The best tip I have is to make sure you have a hold on what you are routing. I had a split-second accident where the wood was pulled through the router table and my finger into the bit. It was a hard lesson to learn, and I got lucky with only a minor injury. It could have been much worse.

  79. Thanks for this video, Jay. Very informative! I thought I had a good grasp of router bit philosophy, but I definitely learned a few things!

  80. The router is the one tool I always talk myself out of using. I need to do a router table but never find the time. Maybe some nice bits would help drive me to use it more often ;-). Thanks for the content! Love the videos!

  81. Hi Jay. I recently bought a couple of Compression bits from Bits&Bits. Their Products are excellent. That said I really did not know what I was doing until I saw this video. This is easily one of the most informative router videos I have seen thanks to your collaboration with the folks at Bits&Bits. Better even than the offerings of Stumpy the Pius!! It is worth watching several times. Many thanks.

  82. Love the videos Jay. I am just getting into woodworking and actually looking at purchasing a plunge router to go with my makita track saw. Would love your advice!

  83. Great video presentation. I never thought about it being too fast on the smaller diameter bits! I’ll definitely try slowing my router speed down. Thank you both Jay and Bits and Bits for sharing your knowledge! Not really a glamorous topic, but definitely a necessary one for anyone using a router. Thanks again from a very novice ‘woodworker’!

  84. Thanks for making this video! I’m kind of new to working with routers and the information you gave really helped! I was really struggling with trying to decide which bits to purchase, but now I have a better understanding.

  85. Great Video. My favorite part was about a down cut bit on a router table could push the work piece off the table. Never thought of that.

  86. This was another top-notch video! Thanks for always being informative, Jay! It’s funny, I was just explaining stuff like this over the phone to my friend who asked about router bits and I said, “it’s easier to show you some videos than try to explain it over the phone.” Then, sure enough, your video popped up in my subscription feed! Haha! So, I’m definitely sending this video to my friend for them to check out! Thanks for all the great content over the years, man! You’re one of the best to ever do it!

  87. Very useful information-the biggest thing for me has been trying to get 1/2″ shank whenever possible (even for 1/4 or 1/8 endmills.

  88. I wish we had a Bits and Bits in Canada. We don’t get much in the way of router bit options here. I was planning on adding a compression bit to my arsenal, but now you have me second guessing that.

  89. Thanks for the video Jay – very helpful particularly the discussion on up vs. down and using the orientation to determine it! Thanks again!

  90. Great video! I’m a relatively new woodworker and I fried a 1/4 flush trim bit earlier today. It turns out that I needed a much wider bit for the project. Now I know what to buy! Thanks Jay.

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