While pattern trimming a circle, made of 1″ thick poplar, as the trim bit bites into the end grain I get some tear out and wind up destroying the circle by chipping out the entire side. I’m using a 1/2″ trim bit in a router table with a fence to help reduce the chances of an accident. I bandsaw most of the waste away leaving about an 1/8″ that needs to be trimmed.
How can I prevent the chipping and tear out?
Thanks!
Senor Dorado
Replies
Senor,
How big is your circle? I ask this because I do a lot of circles that are about 3.5-6.0" in diameter and I simply use a hole saw to cut them. I have had great luck of rounding over these pieces on the router table taking light passes at lower speeds (I assume you could go higher but I am a bit cautious here). Once the roundover is done, I sand the top of the circle to 220 grit and the sides to 320 so I can evenly apply stain. I have a photo of a recent circle i've done if you want to see.
Bio
The circles are 4" in diameter and made from 1" thick poplar. Your suggestion of lowering the speed when rounding over brings up a question of what is the proper speed? I'll be using both a 1/8" and a 1/4" round over bit for this project. Both of these bits have 1/4" shanks. Is this a trial and error procedure, or could you give me an idea of the correct setting from 1-5. My router table uses a Bosch 2 hp router which has the versatility of both 1/2" and 1/4" collets. Senor Dorado
Senor D ,
Maybe if you lowered the cutter to just more then a 1/2" make a pass then raise the cutter and do the other half ?
Is the 1/2" trim bit a 1/2" shank ? it should be for a better cut .
does the router have enough power for this job ?
dusty
You'll have to switch to a climb cut (reverse direction) where any of the grain runout is in the wrong direction vs the bit rotation. This can happen even on straight stock if the grain direction angles up toward the edge. On a circle, one side of the grain runout would want a cut in the normal direction, and the other side a climb cut. Cutting closer than 1/8" can help too. I'd aim for 1/16" or closer if your bandsaw doesn't have drift or perpendicularity concerns. The less sticking out past the pattern to get grabbed, the better.
If you build it he will come.
Just to ensure I understand what you mean when you suggest a climb cut in my situation. I am rotating both my pattern disc and 1" thick poplar disc, which are attached together with double sided tape, in a counter clockwise direction on a router table. As the grain direction changes to an end grain perpendicular to the cutter, I now need to reverse my rotation to a clockwise direction in order to avoid tear out and chipping. I'm using a straight fence set up fairly close to the trim bit, that is adjusted to leave about 1/4" clearance for the rotating trim bit. What would be a safe speed to set my 2hp router at? I have 1-5 speed settings on my Bosch router. Is there any else I could do to ensure a safe cut? I understand that less material to trim would be one good suggestion. Senor Dorado
I'm going to defer to the experts and point to Pat Warner's site. He's got a pretty good description of the problem and process.
http://patwarner.com/tearout.html
If you build it he will come.
Thanks for the link, very informative. Senor Dorado
Another option, if you have a belt sander, is to build a jig to mount the sander on its side, turning it into an edge sander. That would be less "automated" than trim routing to a perfect (make once, use many) template, but would eliminate the end-grain concerns. A movable guide-pin supplemental jig on the edge sander table could also ensure a perfect circle on the work piece.
Best answer I have seen.
Go around your blank and mark where the grain chances. I use blue chalk. Makes a world of difference using a climb cut in the right places. Just be careful doing it. If you are taking light cuts it is usually reasonably safe.
Light cuts and take as many as needed to get to the final dimension.
I have to admit though.. I almost always use my router tables. (with jigs if needed). I hardly ever hold the router unless there is no other way to do it.
Use plunger & waste @~1/16 - 1/8/pass; a collar required for this stunt.
Notwithstanding, a depth of cut can always be found, tho often may be quite shallow, that will not tearout end grain.
Routs everyday.
You must use both top and bottom bearing bits. Two opposite quarters are done with one and the other two are done with the other. This way you are always cutting with the grain. To do it otherwise will give some chip out no matter how shallow the cut and it is also prone to catching. A dangerous situation.
If you have a disk sander you can make a circle sanding jig and end your tearout worries forever.
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You can't wait for inspiration. You have to go after it with a club. Jack London
Try a solid carbide spiral upcut bit. You will see a great difference.
Work Safe, Count to 10 when your done for the day !!
Bruce S.
Senor, the answer depends on the size of the disc and it will certainly help if you cut more accurately with the bandsaw. What diameter are you talking about? If it is big enough to use the router free hand then it is simple to climb cut where required, providing the router is heavy and you have a base extension.
The circle diameter is 4". I'm thinking your idea wouldn't work in this situation. Senor Dorado
Senor Dorado, I can not tell from your description if 1/2" is the OD of the cutter with a 1/4" shank or if it is straight 1/2".
Just so you know. A 1/2" shank has 4 times as much metal by volume as the 1/4". That does not mean it is 4 times as stiff. I think it is 8 times. Using a 1/4" shank bit just leaves a lot of flex in the shaft, which causes this problem.
Also, If you move up to a larger cutting circle of the router bit, the cutting geometry changes favorably by getting a smaller sharpness angle.
Sometimes it helps to give a bit more information, like what the final goal is. What will the part be used for. Maybe the router is not the best tool. Although that is not how your question was framed to lead the conversation or suggestions. There are some quick methods for using a lathe for this. But maybe you don't know enough to ask about that method.
So what the hxxx are you making?
Yah Keith, that is the trouble : lack of sufficient info results in much beating about the bush.
For all we know at the moment it may be better to use a different wood species that will not blow out so easily, or if it is only one off and square edged all could be over in 3 minutes via more accurate cutting and some careful sanding on a disc sander....
On the other hand if multiples are required a lathe can be used to turn a cylinder and part them off from it....If they are model wheels or toy wheels then they can be ganged together through the axle hole and turned happily together.
Or if just a few, they can be cleaned up accurately using the table saw, provided the Safety Police are not around....
Who knows?
Philip Marcou
Philip brought up a VERY good point...
it may be better to use a different wood species that will not blow out so easily..
I use Purpleheart, Hickory, Jatabo and Ash most of the time. They all will 'blow out' on a chance of grain direction.
Philip can correct me if I am wrong, but I think any wood that splits easily by hand is very likely to 'fracture' (what I call it) when a bit digs into the grain as it changes direction.
Purpleheart is my worst offender. I love that wood for some reason. It is a real 'fooler' though. The grain will look great as you see it and just below what you see above it changes somehow. I have never been able to tell in advance when this will happen.
Hickory will split beyond repair. I have had the whole length of the stick split on a 1/8 inch deep cut. Hardly ever with straight bits, but profile bits see something very different.
Just my thoughts.
Senor,
Bruce is right - you need one of these:
View Image
Here is the link:
http://eagleamerica.com/product.asp?pn=120-0202
Lee
Are you using a spiral router bit ?
No, its a straight 1/2" trimming bit with a bearing that is also 1/2" in diameter O.D. Senor Dorado
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