Thread: Routing irregularity

Grain related tearout. Basically the wood is being pulled out rather than cutting, because the grain of the wood is being cut in its weakest direction, and the angle of attack of the router bit isn't able to provide a clean shearing action for cutting.

Possible solutions:

1) More passes with the router - rather than a roughing cut and a finishing cut, make a roughing cut and two or three finishing passes to sneak up on final size.

2) Climb cut the finishing pass on those areas (climb cutting means making the cutting passes with the direction of the router bit's rotation rather than against) Note that this is one of those techniques that can present considerable risk to both the operator and the piece as the router can grab and either run away by itself, or flick the workpiece into the router holder's body at considerable speed, or worse depending on where your fingers are. You'll find that you'll need to climb cut some areas, but cut the others normally, otherwise all you might do is change the location of where the tearout happens.

3) Does it have to be real wood, or can a relatively grainless substrate like MDF be used?

I'll leave it to the master(s) to confirm but a shear style bit might help.

Just as an example of one (note the angle of the cutting edges): Down Shear Flush Trim Bits : CARBA-TEC

Thx for that i ll translate all of that slowly to make sure i got every single part of the answer ( english is not perfect yet :P )

it is totally fine to use MDF though i guess the strength is similar or so isn't it ?

I have to make 2 others ones next week so i ll let you know how it goes after using the advices

So tried the down climbing ... made it worse. i used a higher speed and it was slightly better but still not amazing ...

Master splinter what do you mean by rough passes and finish passes ?

Not Master Splinter, but I can offer an answer for you anyway.

By suggesting a rough and then final cut, Splinter is suggesting that you initially cut the block about 3mm greater diameter than your finished size, then make another pass to finished diameter. By doing this, the surface finish on the initial cut is largely irrelevant (provided that the surface irregularities do not go through to the finished diameter which should be rare), and you are taking a very shallow cut during the second pass, so there is less chance of ripping chunks out of end grain and spoiling the finish.

If you cannot work with MDF for the job, I suggest that you try to locate some slow growth timber with fine growth rings, rather than rapid growth (coarse growth ring) timber as in the original pictures, as this may be less prone to tearout.

Hope this helps.

Thx so much for all these really helpful replies I ve learnt a lot

Not being able to properly fix the problem I decided to try to cut my blocks with a jigsaw and a circle jig ( simple cavity where the jigsaw is gonna fit and a nail a bit further down the piece of wood for the centre of the block )

Unfortunately once again a new problem ... it seems like the jigsaw ( or the blade ) can't cope with the size of the block ( 14.2cm diametre) and bend a lot making the circle smaller and smaller as i m cutting ... )

was is just a bad idea wanting to make such small circles with a jigsaw ? or is it fixable ?

thx again for your replies

Jon

Small diameter circles in thick material can be problematic with a jigsaw (jigsaws are better with thin stuff), but if it's spiralling inwards, that suggests operator error (the circle cutting jig should prevent such deviation).