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View Chameleon's profile

Cutting board “disaster” – how do I prevent it from happening again?

by Chameleon
posted 12-19-2018 01:33 AM


14 replies so far

View derosa's profile

derosa

1597 posts in 3139 days


#1 posted 12-19-2018 02:21 AM

In my experience router bits don’t do friendly things when grain changes direction, don’t know if its just a lack of technique, other then roundovers I don’t do a lot with mine, but tearout seems par for the course on curves though how the direction of the grain is approached matters a lot. I made the 4 cutting boards in the pic I included in less then 3 hours from rough wood to needing to finish sand by just finding a simpler way of doing it.
Basically there isn’t a need to smooth anything if you cut everything right. I use a variable tooth count blade 5/6 tooth which cuts finer and clears out dust better, make sure the teeth have no offset but are straight inline with the blade, set tension tight so no waviness. The lines will be smooth enough that routing won’t really be needed. I also found that cutting the strips with the same blade and not smoothing/sanding/planing them allowed the tiny ridges to mesh togetherand be even more invisible. Finally once a cut is started don’t stop moving the piece, I’ve noticed pauses cause a less clean spot, pick your line and use a nice steady push to move the blade through the wood in a single motion. I’ve done shows and sold through craft shops and had woodworkers ask how the lines were that tight and clean and even have boards done this way 5 years ago that the glue lines are still tight on. Took a bit to figure the right blade but that’s the only technique I now use.

-- A posse ad esse

View Chameleon's profile

Chameleon

21 posts in 378 days


#2 posted 12-19-2018 06:17 AM

Just noticed that the picture should have been taken with the 1/4” gap (width of routed groove) so the boards would line up correctly—the only gap in the picture is the unintended tearout. Probably obvious, I guess.

View gwilki's profile

gwilki

268 posts in 1777 days


#3 posted 12-19-2018 01:12 PM

To answer your questions first:

No, you should not have reversed directions on the second piece. On a table, you were right to route both pieces going from right to left.

Your router speed was likely OK, too. What diameter of the router bit you are using? Is it a 1/2” shaft or 1/4” shaft?

Now, I have a question or two. If I understand you, you routed a groove in the board less than 1/2” the thickness of the board deep. How thick is the board? I can’t really tell from your pics.

The groove you routed was 1/4” wide and you cut it roughly down the middle on your bandsaw. So, each piece ended up with a “shelf” to be removed that was more than half the depth of the board and just less than 1/8” thick (half the 1/4” minus 1/2 the kerf of your bandsaw blade), correct?

If all of my understandings are right, I suggest that your only misstep was trying to remove all the “shelf” in one pass. In your situation, it would be difficult to do it othewise, since you can’t sneak up on it by lowering the bit. If you have a bigger bearing for your trim bit, you could use it to take some off, then put the flush bearing on to complete the removal. You are trying to remove quite a bit of hardwood in one pass. If your bit is a 1/4” shaft, you are likely getting some flex just to add to your problem. Feed rate is also critical. Go slow! In your situation, you don’t care if you get a bit of burn from going too slow, since that edge will not be seen in your final product.

If you don’t have a bigger bearing, I suggest that, after you cut the piece in two, you remove some of the “shelf” from each piece on your bandsaw. Get it down to 1/16” or so.

-- Grant Wilkinson, Ottawa ON

View LittleShaver's profile

LittleShaver

502 posts in 923 days


#4 posted 12-19-2018 01:29 PM

+1 on derosa’s post. Cut a nice smooth curve with the bandsaw and don’t touch it. Even with my low level skills and cheap old bandsaw this works great. Take a piece of scrap and give it a try.

-- Sawdust Maker

View Robert's profile

Robert

3318 posts in 1784 days


#5 posted 12-19-2018 03:13 PM

Hats off if you can manage that on a bandsaw, guys.

Most huge chunks like that can be avoided if you use the right bit at the right speed and don’t feed too fast.

I don’t think <1 />ve wondered if soaking the grain in cyanoacrylate glue prior to routing will help.

-- Everything is a prototype thats why its one of a kind!!

View Robert's profile

Robert

3318 posts in 1784 days


#6 posted 12-19-2018 03:15 PM

Router tips that might help: 1) Avoid a straight bladed bit. Best to use a spiral bit. 1/2” shank best. No, they are not cheap. 2) Climb cuts where you think it will tear out (cut as close as possible with bandsaw). Safety factors come into play such as push blocks that don’t slip. 3) Higher bit speed 4) Slower feed rate

-- Everything is a prototype thats why its one of a kind!!

View Chameleon's profile

Chameleon

21 posts in 378 days


#7 posted 12-19-2018 06:13 PM

Gwilke, that was a very helpful response. My “takeaway” is that I tried to remove too much material with one pass. To answer your questions: Board is about 1.25” thick. You’re correct, it was a fairly wide “shelf” to remove. I don’t have a bigger bearing; I thought that flush trim bits were all made to have the diameter of the bit exactly match the diameter of the bearing. Not true? I’ll try to take off some of the shelf with the band saw; I was intentionally staying as close as I could to the middle of the groove to avoid hitting the sides. Bit has a 1/2” shank. rwe2156, thanks—I didn’t know that spiral flush trim bits existed. Just looked them up—expensive, but so is my time (theoretically; I’m retired) and I’d hate to see the same thing happen again.
Question: Why do all the online videos show some of the groove being removed with a router and the rest with a band saw and flush trim bit? One might take a few passes with the router when cutting the groove (perhaps risking what happened to me at an earlier stage of the project!) and make a very deep groove, thus leaving only a thin shelf to remove with the flush trim bit. Or, route the groove all the way through the board. Thanks!

View Chameleon's profile

Chameleon

21 posts in 378 days


#8 posted 12-20-2018 03:21 AM

rwe2156 (or anyone else who can explain this to me), if it’s best to use a spiral bit, do I want an upcut or downcut spiral flush trim bit? I assume that the answer depends on whether I have the “already routed” side of the board on top, with the “shelf that needs to be trimmed” on the router table, or vice-versa (guess that depends on whether the bearing is close to the router or away from the router, “toward the sky” (since I’m working outdoors, it’s not “toward the ceiling”). (In L.A. I can almost always wheel the router table onto my driveway, avoiding dust all over my garage).

View therealSteveN's profile

therealSteveN

2234 posts in 877 days


#9 posted 12-20-2018 05:03 AM

I am in line with what they say here.. The compression bits are the not up, and not down, but kinda both bits, because unless you are on a CNC a lot of the spirals are a bit wiley, and can get squirrely quicker than a flush cutter with smooth sides. You’ve already had squirrely, you want tamer.

For your use, tracing an edge on a piece I like a piloted straight flush cutter, but I like the really much bigger diameter than you might think you need, school of thought. I haven’t gotten any of these yet, but they are talking my language. I do have a few that are 2 blade 1 1/2” diameter that I routinely use to template rout with, provided there are no straight pieces where the bit would trap. For this Infinity bit it has a hybrid edge, it’s a sort of a compression bit, packed as a flush cutter with straight sides.

https://www.youtube.com/watch?time_continue=2&v=Hr29KWj1ELc

I like the short widebody for a router table, running against a pin, and hopefully Santa is bringing me one.. Costy, yes, but they are designed for what you are doing, which is also a routed edge, that isn’t standard fare for most router bits out there, the slow curve. That board design is the rage, and yes I too, have no understanding how a person can bandsaw that curve, and NOT flush it up, never have I heard of a glue line ready BS blade.

But no matter what bit I am using, NO FENCE. I do them off a pin on the router table, or handheld. Handheld direction is a challenge, if you suddenly find yourself making a climb cut freehand, and DON’T know it’s coming, that workpiece will go zippity do dah, faster than a lot of us can recover, and you will scream past a piece of the bit you don’t want to. Handheld you can also do them off a template, still be aware of climb cuts.

So 2 of my rules of routing. Pins can look scary, but they are really the best way to control the work, and not have the work, just bang into the spinning bit. If the piece is BIG, you can hold the end not at the cutter, and you will be removed from the bit by your workpiece. Being in control on the opposing side, you not only have a distance, but you gain leverage, and leverage is control over the pin.

If it’s a short piece, do NOT hold onto it, if the piece does do that zippity thing, your hands are right there. Instead use some type of work holder. Climb cuts happen in hand held, or router table use whenever you go against the grain. On your curvy edge you likely went against the grain a few times, but were thinking straight line, well sorta.

You can buy something like this.

You can make something like this. Note the nice cover over the bit, you can make a safety bar to mount anything you want to a router table, not just a fence. Just make sure it’s secure.

Best bet yet is you may already have a great work holding clamp laying around. Hardly anyone uses them for clamps anymore. Mine were from a time before dirt.

Always do a practice run through, with power off, look at what you are about to do, wonder what could go wrong???? It won’t be long before you’ll wonder how you ever made a mistake. Wood mistakes, while a PIA, are actually just a little extra time. Other mistakes can be serious injury, so always use that best tool, yer brain.

Best safety practice, is if you look at something, and it just sux, every way you look at it, you see pain, and trouble. Ask a question here.

-- Think safe, be safe

View gwilki's profile

gwilki

268 posts in 1777 days


#10 posted 12-20-2018 04:31 PM

chameleon: You’re right in thinking that for a bit to be “flush trim”, the bearing must be the same size as the diameter of the cutters. But, you can buy bearing kits that include several sizes of bearings so that you can do offset trimming. The kits are not pricey and they let you nibble away to arrive at the true flush trim.

-- Grant Wilkinson, Ottawa ON

View sras's profile

sras

5019 posts in 3432 days


#11 posted 12-20-2018 04:54 PM

Good advice here. One thing I can add is I often will make shallow passes (bearing is not in contact with the reference surface). I use light pressure and maybe take 2 or 3 passes until the bearing is finally in contact.

-- Steve - Impatience is Expensive

View Chameleon's profile

Chameleon

21 posts in 378 days


#12 posted 12-21-2018 06:49 PM

Progress! Routed a 1/4” groove, cut the board in half on the band saw, “flush trimmed” both sides successfully. Did this with a Freud straight flush trim bit—I bought a spiral flush trim bit ($$) but when I practiced with it on a 2×4, it kept “catching” and I couldn’t control it well; undoubtedly just my inexperience with this bit. What seemed to help: Faster router speed, slower feed, removing as much of the shelf as I felt comfortable with on the band saw (still left a lot of shelf), doing the cut in several stages, only having the bearing against the already-routed part of the board on the last two passes. Lousy photo attached; shows board thickness (about 1-1/4”; blue blocks on left). Edge is very smooth despite horizontal line near the top. Long way to go with this board. Thanks for all the help.

View Chameleon's profile

Chameleon

21 posts in 378 days


#13 posted 12-21-2018 06:53 PM

Addendum: Groove I routed was much deeper than line at the top, and the already-routed surface was the “reference face” for the flush trim bit. Don’t know what caused this line, but since it’s smooth it doesn’t really matter. No one addressed this one: Why not route the entire thickness of the board, avoiding the band saw and flush trim?

View Chameleon's profile

Chameleon

21 posts in 378 days


#14 posted 12-30-2018 09:05 PM

Thanks to all! Finally got the “curves thing” right. Board is not quite finished (and not “oiled”) but here’s what it looks like now. Either didn’t use enough glue or didn’t tighten the clamps enough (probably the former) on the final (4th) glue-up, but I think I’ll be able to fill in the gaps (far left side of board in picture) with a little glue and sawdust (or, just cut this off). Main board is maple and cherry. One inlay is padauk, one is walnut and maple, one is walnut and yellowheart. Best of all: After listening to me complain that my SawStop jobsite saw had trouble with thick hardwoods, my wife bought me a 3 hp SawStop cabinet saw with industrial mobile base! Happy holidays, Howard (I breed chameleons, hence my username)

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