# Best bit for pattern cutting?



## NewMontanaWorkshop (Sep 10, 2004)

I'm using some templates to route various items using Cherry, Ash, Oak and Walnut. In the process I'm getting occasional bad tearouts.

Right now I am using a standard straight 1/4" pattern cutting bit with the bearing on top.

Would a spiral pattern bit reduce the amount of tearout?

Thanks.


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## delroy33 (Sep 10, 2004)

Yes it would but keep in mind that grain structure in some wood it can still happen.

watch the depth of cut,feed and grain direction.

There will be better more accurate information from other.


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## Bob N (Oct 12, 2004)

Stan,

Is there a way you can secure or clamp a piece of 1/8 inch scrap over the area you are routing and route thru it to the good stock? This would eliminate most of the problem on the wood you want to keep.


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## reible (Sep 10, 2004)

Stan,

I don't ever recall seeing top bearing spiral bits..... have you spotted some somewhere? 

It seems that the normal top bearing bits have straight cutters..... if you could find some with a shear angle they would cut better. I have a bottom bearing bit with the shear and it works well. Sorry I have no spiral bits for pattern cutting so I can not compare but in general spiral bits do cut very clean.

Ed


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## NewMontanaWorkshop (Sep 10, 2004)

reible said:


> Stan,
> 
> I don't ever recall seeing top bearing spiral bits..... have you spotted some somewhere?


 Something like this (actually called a Flush Trim Spiral Bit -- now that I have looked one up  ).
http://www.woodworkersworld.net/flush_trim_bits.shtml#sc
The flush trim spiral bit is towards the bottom of the page.


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## Woodnut65 (Oct 11, 2004)

Hi Stan: The smaller the diameter of the pattern bit the more tear out you get. If the diameter is 3/8" you can only remore less than three 16ths. I bought a set of rabiting bits from Infinity. The set comes with a bit that is about 1 & 1/8th ", and a set of bearings for different rabits, plus a bit to make it a trimmer. That is the bearings mount to the bottom of the bit. I had band sawed out some things to reproduce and used the big bit. It resulted in no tearout. If you can get a spiral pattern bit that would also be a way to go. I have not seen a spiral bit with the bearing mounted to the top of the bit. Good luck with it.. Woodnut65


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## kp91 (Sep 10, 2004)

spiral bits with template guides work well, especially if you sneak up on your final dimension by using different guide diameters.

Also, if you are experiencing tear out trimming the outside edge to final dimension, sometimes it works if you "break-up" the long grain by making several smaller cuts along the long grain side. This way, if the bit catches, it can only pull a small chunk out instead of a large sliver.

Of course, the old rule still applies, the more special the piece of wood you are working on, the more likely an Ooops is to occur.......


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## template tom (Sep 18, 2004)

Snowshoe said:


> I'm using some templates to route various items using Cherry, Ash, Oak and Walnut. In the process I'm getting occasional bad tearouts.
> 
> Right now I am using a standard straight 1/4" pattern cutting bit with the bearing on top.
> 
> ...


I am only assuming you are routing thick material say greater than 25mm (1" thick) My suggestion is to change your tactics and use the router in the plunge mode with the aid of template guides and cut the material in four stages (depths) this will certainly reduce your problem
Tom


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## reible (Sep 10, 2004)

Snowshoe said:


> I'm using some templates to route various items using Cherry, Ash, Oak and Walnut. In the process I'm getting occasional bad tearouts.
> 
> Right now I am using a standard straight 1/4" pattern cutting bit with the bearing on top.
> 
> ...


 I was just looking at the June flyer from Lee Valley and on page three they have a double-bearing flush trimming/template bit.... 

I guess I missed the point of these bits....... what I failed to see was if you are trimming to a pattern that is on top of the workpiece and then get in to a place where the are going against the grain you simply flip the part over and adjust the bit height to use the other bearing and you can cut with the grain again...... Now I have to put an order in for one of these....

part # 16j09.90 or 16j04.90 if you have to look online.

Ed


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