Router chip/tear out causes???

[DaveO]

What causes it? Is it techinque, dull or type of cutter, species of wood, or router speed/feed rate???

Here's my senerio: 1/2" bearing guided round-over on Purpleheart with a 1/4" shank Skil bit, that I have had for a while. DW 618 router in table, speed set at 3-4 range.

I was making multiple passes anticipating problems. The first light pass took out a hunk :crybaby2: Luckly the next two passes almost smoothed out the divot. What was I doing wrong? Or am I just doomed for working with Purpleheart???

Dave

 

[SteveColes]

Where was the tearout, at the end, which end. which way was the grain running comapred to router bit rotation.

 

[Monty]

Is it techinque, dull or type of cutter, species of wood, or router speed/feed rate???

Yes.


Happy to help. :lol:

 

[rickc]

Have you tried some sacrifical stock at your starting and ending point? (Assuming you are working with straight stock). Maybe even try doing some slight camfering first then proceeding to the round over. A small hand plane or even your router might do the trick. Could serve to remove just enough stock so that first / last bite isn't so aggressive.

 

[DaveO]

Rick, in this case the damage was in the middle of the pieced.The router basically grabbed a giant splinter and tore it out. My first pass barely took off the edge because I anticipated this might happen, and the piece was almost finished so I wasn't gonna take any chances. I believe that I did all I could to prevent the problem, but it happened anyways....what did I miss?

Dave

 

[Joe Scharle]

Had it happen many times with purpleheart, router bits & tablesaw.

 

[SteveColes]

Rick, in this case the damage was in the middle of the pieced.The router basically grabbed a giant splinter and tore it out. My first pass barely took off the edge because I anticipated this might happen, and the piece was almost finished so I wasn't gonna take any chances. I believe that I did all I could to prevent the problem, but it happened anyways....what did I miss?

Dave

Dave, I had that happen with cheap oak from HD. The only way I found to stop it was a climb cut for the first cut.

 

[rickc]

Rick, in this case the damage was in the middle of the pieced.The router basically grabbed a giant splinter and tore it out. My first pass barely took off the edge because I anticipated this might happen, and the piece was almost finished so I wasn't gonna take any chances. I believe that I did all I could to prevent the problem, but it happened anyways....what did I miss?

Dave

Ouch! That's a tough one. I wonder if a hand plane would react the same way? Bill Anderson (from TWA) has quite a collection of planes and it seems as if he had some that would do a round over. He drops in here occassionally, but you might want to check with him about a possible alternative technique. (His contact information is in the club newsletter.)

Hearing that it came from the middle - it sounds as if you are fighting a characteristic of the wood. Maybe hand tools will be the way to go. Other than that approach you may want to consider getting a new, high quality, top end router bit. Just seems that a new sharp bit would cut better and perhaps not "grab" the stock.

 

[Sweetgum]

Could it potentially be related to growth stress in the wood?

 

[DaveO]

I have a feeling that most of issue lies in the Purpleheart itself. I know it is prone to chip out. But I thought I took every precaution that I know of to prevent it and still got some.

Steve, a climb cut is something I didn't think about. I think that would have helped, prolly scare the poop out of me, but at least not hunks out of the wood.

I also think that it is time for a new round over bit, too bad that isn't one offered in the WC $5 bit collect....I like to keep color coordinated :roll:

Dave

 

[junquecol]

Tear out with a router bit is a MAJOR PITA. It comes from the fact that bits are so small in diameter. Cutter is always cuting perpendicular to edge. Same thing occurs when making doors on router table, while shaper (larger diameter bit) seldom does it. Can you cut a rabbet on edge and glue in replacemant and then route roundover? Last Christmas, I built two highchairs from birch- NEVER AGAIN. Same problem. On tray tried climb cutting and bit grabed tray destroying on edge. This was last operation on finnished tray:BangHead:

 

[Howard Acheson]

Rick, in this case the damage was in the middle of the pieced.The router basically grabbed a giant splinter and tore it out. My first pass barely took off the edge because I anticipated this might happen, and the piece was almost finished so I wasn't gonna take any chances. I believe that I did all I could to prevent the problem, but it happened anyways....what did I miss?

Dave

Sounds like you are routing into the "uphill" slant of the grain. Just like when you are using a handplane, you have to "read" the grain direction so that the cutter cuts "downhill". Same thing with jointers and planers.

Frequently, it means that you need to use a technique called "backcutting". This means moving the router or the item being routed in the opposite direction from normal (with the direction of cut instead of against it). When moving the router this way, there is some danger and you need to be sure the item is tightly clamped down, take small cuts, hold onto the router tightly and move slowly. When backcutting on a router table, there is real danger. The piece being routed is going to want to catch the wood and fling it out of your hand. Take very small bites and only do it with hold downs and really hold on.

If you want to avoid the dangers of backcutting, your only option is the take very small bites and hope for the best.

 

[DavidF]

Use as large dia bit as possible and/or change to a spiral or shear action bit. I have just purchased a 1/2 shear cut bit from MLCS also in anticipation of problems with the cherry. About $11.00

 

[jglord]

Hey - we do have both a 3/16" and 3/8" radius round-over in the $5 bits - all with 1/2" shank and they'd count as power tool accessories.