Router table tear out

[transatlantic]

Why am I getting this tear out on the entry cut?

The exit cut is very clean, as to be expected by having a backing board.




Exit cut

 

[Peter Sefton]

It's because the back of the cutter is back cutting, if you position a sacrificial board in front of the cut it should stop the breakout. It may also be worth taking a relief cut first.

 

[clogs]

if you use a backer /sacrif board it has to be held tight against the work peice....
make sure the bit it is very sharp, old used bits doing that kinda work will cause you this lind of prob....

 

[transatlantic]

It's because the back of the cutter is back cutting, if you position a sacrificial board in front of the cut it should stop the breakout. It may also be worth taking a relief cut first.

So I need a piece infront and behind?

 

[Peter Sefton]

So I need a piece infront and behind?

Yes, but as said by by clogs, make sure everything is held and use sharp cutters.

 

[monster]

You only need a piece in front because you are cutting with the full width of the cutter - so as you start your cut you in effect have a point where the cutter enters the timber which is where you have zero tear out and then a point where the cutter exits the timber which is where you are seeing the tear out on the other side of the slot.

 

[transatlantic]

I'm a little confused. How come I don't get this issue when I'm using a handheld router as per the right side of the image below? I've always expected it on the exit cut, but not had it on the entry cut.

The bit is Wealden and very new.

 

[Spectric]

What router profile, are you doing a single cut or several passes as I have never had this problem and want to know more, plus I use a lot of Wealdons cutters.

 

[mikej460]

Sorry if this sounds patronising but you are feeding from the right going left? If so try shallower cuts and you should never cut more than the diameter of the cutter.

...and then I looked at your pics and clearly you are!

 

[transatlantic]

What router profile, are you doing a single cut or several passes as I have never had this problem and want to know more, plus I use a lot of Wealdons cutters.

It's a two flute straight bit, about 1/4". I did cut it in a single pass, but it was only 3mm.

Sorry if this sounds patronising but you are feeding from the right going left? If so try shallower cuts and you should never cut more than the diameter of the cutter.

...and then I looked at your pics and clearly you are!

 

[mikej460]

looking g at the size of the hole around your cutter and the width of the wood I'd think about it moving on entry? can you fit a plate or try clamping the piece to your mitre gauge? I'd also consider making a simple sled with a toggle clamp to hold the piece solid.

 

[transatlantic]

looking g at the size of the hole around your cutter and the width of the wood I'd think about it moving on entry? can you fit a plate or try clamping the piece to your mitre gauge? I'd also consider making a simple sled with a toggle clamp to hold the piece solid.

I'm using the backer piece to hold it square. It's not moving as the groove is fine. The only issue is the bad entry tearout.

 

[mikej460]

does it do it on scrap softwood (same width)?

 

[Ollie78]

I am suggesting the bit is blunt, causing a jolt as it makes contact with the timber. Also if you are feeding it too fast it can do this.
Spiral cutters are good as they reduce this sort of thing.

Ollie

 

[transatlantic]

does it do it on scrap softwood (same width)?

I'll try to test that after work

I am suggesting the bit is blunt, causing a jolt as it makes contact with the timber. Also if you are feeding it too fast it can do this.
Spiral cutters are good as they reduce this sort of thing.

Ollie

It's certainly not blunt.

 

[TheTiddles]

A sacrificial piece in front will help, as would a faster rotation, slower feed and shallower cut

 

[transatlantic]

so, bit of an update on this.

- Testing the same cut on some pine appeared to result in less tearout, but still not what I'd call a clean cut
- Slower feed rate made no difference
- Increasing the speed made no difference (it was already close to max speed anyway)
- Adding a sacrificial piece in front solved the issue, but trying to move all three pieces and keep the middle piece held down prooved inpractical, at least for me. So I think a coping sled would be needed with that approach.

Switching to a 4 flute spiral bit produces a perfectly clean entry without having to use a sacrificial piece in front of the cut, so I guess I'll just use that.

Out of interest, what coping sleds are people using? this one seems fairly neat?

 

[MikeK]

I use the Woodpeckers coping sled, but the first sled in the YouTube link you provided looks good. My only comment about the YouTube version is the inability to adjust the polycarbonate shield that rides along the fence. This is a minor issue, and would not stop me from building the sled if I didn't want to buy one.

 

[Spectric]

I use this one made by Infinity and it is solid, works well and no issues Professional Coping Sled - Infinity Tools

 

[transatlantic]

I use the Woodpeckers coping sled, but the first sled in the YouTube link you provided looks good. My only comment about the YouTube version is the inability to adjust the polycarbonate shield that rides along the fence. This is a minor issue, and would not stop me from building the sled if I didn't want to buy one.

Do you mean adjust for square or adjust for depth?

If it's the former, I think I could just have the holes in the poly be larger than the bolt, giving a small amount of wiggle room for squaring it up.