Flush Trimming Router Bit

[Ed Gibbons]

I’m using a router table to flush trim edges on a template. What would be the best and safest bit to use. I read some info about compression bits.

[Mel Fulks]

I’ve never used a compression bit, but have read they work well . My method is to use sand paper to remove any rough corners . Then use
a two flute or single flute carbide bit . Single flute is faster. The slight rounding of the corners is much like cutting off a loose thread on a shirt
to keep it from unraveling.

[Thomas McCurnin]

Before I can answer this question, I would need to know if the template is on top of the workpiece or on the bottom.

[Justin Rapp]

A spiral flush trim bit is definitely supposed to make a cleaner cut. I have yet to buy one (because I have not figured out which brand to go with honestly). However there are upcut, down cut and compression. When you up cut, the bottom of the work piece should be clean and you might experience some tear out at the top. This is vice versa for the down cut. However compression is pulling both the top and the bottom edge material to the board helping to prevent any tear out on the top or bottom. With that said, if you are riding your template on top and using an up-cut bit, the template should act as a zero clearance edge and should help prevent tear out.

From a safety standpoint, It seems that spiral has less chance of catching and triggering a kick, so it 'should' be safer. I suspect the jury is still out on that discussion.

From a cost standpoint, spiral bits are more pricey and Whiteside's compression is nearing the $200 mark for 1 bit. I been thinking of grabbing a few bits from SpeTools (spetools.com) but have been seeing some bad reviews with some breaking apart on the first few cuts. That is my holdback - it doesn't sound so safe.

[Mel Fulks]

Justin ,those bits are quite expensive and I’m not sure that they can be sharpened. Try my method .

[George Bokros]

From a cost standpoint, spiral bits are more pricey and Whiteside's compression is nearing the $200 mark for 1 bit.

Not all true. Here is one https://www.amazon.com/Whiteside-Router-Bits-RFT2100-Diameter/dp/B000HPYOJ6/ref=pd_lpo_2?pd_rd_w=ok0le&content-id=amzn1.sym.116f529c-aa4d-4763-b2b6-4d614ec7dc00&pf_rd_p=116f529c-aa4d-4763-b2b6-4d614ec7dc00&pf_rd_r=KJGN5KK2Y2A0NBSYGD99&pd_rd_wg=jL9ES&pd_rd_r=91964568-5188-4815-8156-42fc5a3ea63c&pd_rd_i=B000HPYOJ6&psc=1 This bit works well, I have one.

[Jim Becker]

Jay Bates just did an excellent video on the 'Tube about this very topic. In reality, there is no "one" flush trim tool that's best all around. What you need to do impacts what cutter configuration is best for "that" job. Factors include material thickness, radius of any curves required, top or bottom (or both) bearing configuration and up/down/compression which is also influences by material thickness and template location.

[Patrick Varley]

Agree that it's task-specific.

That being said, I've found myself using the Infinity Mega Flush Trim most frequently. Offers a compression design (though not a carbide spiral) and combo too/bottom bearing.

https://www.infinitytools.com/mega-flush-trim-router-bits

[Justin Rapp]

Not all true. Here is one https://www.amazon.com/Whiteside-Router-Bits-RFT2100-Diameter/dp/B000HPYOJ6/ref=pd_lpo_2?pd_rd_w=ok0le&content-id=amzn1.sym.116f529c-aa4d-4763-b2b6-4d614ec7dc00&pf_rd_p=116f529c-aa4d-4763-b2b6-4d614ec7dc00&pf_rd_r=KJGN5KK2Y2A0NBSYGD99&pd_rd_wg=jL9ES&pd_rd_r=91964568-5188-4815-8156-42fc5a3ea63c&pd_rd_i=B000HPYOJ6&psc=1 This bit works well, I have one.

George,

This bit you sent is an up cut bit, and also a 1/4" shank, and yes, it's about $45. The OP was specifically asking about the compression bits. Anyway, I hope the info below looking for an upgrade to my flute flush trim bits helps folks save some time.

- The compression 1/4" bit is a little bit more money then the up-cut bit you have, running about $56. whiteside part # UDFT2100
- The compression 1/2" bit is $132 - whiteside part # UDFT5152.
- The ultimate compression bit, which I hear is amazing is between 182 and 195 depending on if you get a single or double bearing model.
- Here is the link to Whiteside's spiral flush trim bits. I figure those who want will look up the price on their favorite store.
- https://www.whitesiderouterbits.com/collections/flush-trim-spirals
- Amana and some other brands like SpeTool, and Yonico (maybe good or junk, I dunno) have their various copies as well.
- I also saw infinity tools and CMT has a pretty neat compression bit but it's not a spiral, but an angled flute bit.
- https://www.infinitytools.com/mega-flush-trim-router-bits?gclid=Cj0KCQiAkMGcBhCSARIsAIW6d0DzRhCqSSoZSVr Jc9JAxZQCfO4xBFkDCy-q2wEbRA5Pg3IZSlrV52saAqh2EALw_wcB

[Jeff Bartley]

I bought the Yonico compression bit last year for a specific job and didn’t regret it for a second, I can’t remember exactly what I paid for it.

Regardless of the bit you use Mel’s suggestion sounds great, I’ll definitely be trying that next time I pattern-route!

Also, I should add that I’ve used that Yonico bit a good bit this last year and performance has not diminished. Whenever this bit does dull to the point of needing replacement I honestly don’t know which I’d get. Now that I’ve seen the benefit of a compression bit I might spring for the Whiteside.

[Alan Schwabacher]

Take a look at Izzy Swan's latest youtube video. He talks about flush trim and pattern bits, and is of the opinion that spiral bits are not needed a lot of the time.

[Tom Bain]

Agree that it's task-specific.

That being said, I've found myself using the Infinity Mega Flush Trim most frequently. Offers a compression design (though not a carbide spiral) and combo too/bottom bearing.

https://www.infinitytools.com/mega-flush-trim-router-bits


Another vote for the Infinity bits, they are the nicest flush trim/templating bits I’ve used. I try to use the largest diameter bit that will work for the radius of curves in the template. The theory being that reduces the shearing angle of the cutter and hopefully the chance of tear-out.