Routing against the grain?

[bcp]

I am building a harp with three laminations on the curved pillar and neck (11mmpurpleheart, 15mm tas oak, 11mm purpleheart).

The centre piece is routed to shape, and I've now glued on the outer laminations of purple heart and was using a flush trim bit to match the shape. I still had about 5-8mm overhang so was trying to take it slowly. As soon as I went against the grain it shattered some of the wood - thankfully all exterior. Ok, I was experimenting because I have gotten away with it twice before with rock maple and honduras mahogany.

So what do I do? I intended to flush trim, and then use a curved bit with ballbearing (correct name?) to round the edges. But because of the curve on this piece, half of the grain will always face into the router bit.

I have now planed and spokeshaved the timber almost flush. But I'm not game to attempt a pass or to use the rounding bit until I understand more.319751

[bcp]

Of course my first lesson is that I should have routed the individual pieces against my template before gluing (because I can turn them upside down), and then could have used hidden pins to align the pieces when gluing.

But it still doesn't help me with the problem of whether I can use the rounding over bit against the grain.

[specialist]

It's not exactly recommended, but I have in the past done a climb cut to negate the affects of going against the grain. I would do the same for the round over, only doing light cuts, so you can control the router. I find that when doing this a big heavy router is easier to control if you have one.

There will be people that will disagree totally with this advise, but sometimes I find that it is the only way.:shrug:

Rob

[elanjacobs]

:whs:
5-8mm is a pretty big cut, even going with the grain. Cutting into the grain won't be an issue as long as your bit is SHARP (either freshly sharpened or new) and you don't have more than 2mm to cut. When using profile bits, use several passes to gradually get to the desired depth.

[bcp]

Ok, had a good look at the bit - realise my son has been using it lately. It's quite blunt. Where do I go to get it sharpened? What does it cost? I'm not really game to sharpen something that has so much horsepower behind it.

[elanjacobs]

Any saw sharpening service should be able to do it. If they want to charge more than $15 you're getting screwed.

[soundman]

acouple of things with tear out and chipping with routers.

As has been mentioned, you have a higher chance of chipping or tear out the more depth you are cutting.....so you may be better off uing other methonds to reduce the depth of the waste before flush trimming.

becsue of the hard timber you will need to ballance feed speed..too slow and the wood will burn too fast and it will chip......the sharper the bit the easier time you will have here....a blunt bit and you will not avoid burning or chipping.

The larger the diemter of the cutter the less trouble you will have all round......small flush trim bits tend to chip out far more than larger diameter ones.

If you are trying to do this work with a 1/2 cutter...you will struggle...step up to 3/4 or 1 inch cutter with a big bearing you will have a lower cutting anle to the line of cut, better chip clearance and a faster tip speed.....all far better.

as has been mentioned you could look at climb cutting.....but to do this safely and effectivly you need to be looking at a lighter cut...you need to be looking at a lighter cut anyway.

it may be worth looking at a trimming bit with a range of bearings, so you can take your waste away in steps.


as for sharpening flush trim bits.....it is unavoidable that a flush trim bits will not cut as flush after they are sharpened.

its come to a point where sharpening and buying new can be pretty close run thing.

back when I first started seriuos wood work it was a no brainer to take saw blades and router bits to a good sparpening service...these days you realy need to look at the price of a new bit.

cheers

[elanjacobs]

as for sharpening flush trim bits.....it is unavoidable that a flush trim bits will not cut as flush after they are sharpened.

its come to a point where sharpening and buying new can be pretty close run thing
Might also be worth looking into a flush trim bit with disposable inserts.

[soundman]

Yeh those replacable edge router bits may have been a viable thing at one time, but I think they too have been overtaken by the falling cost of router bits.

cheers

[chook]

If you are routing against the grain and there is no avoiding then
1. Make sure that you remove as little as possible with each pass. Millimetre or less
2. Bump cut along the line first. Bring the timber up against the bit and pull it away. Do this all the way along the piece and as close together as you can. Then go back over the cut to clean it up.

You can be sure that if timber can tear out then it will. It will happen with the most expensive piece of timber in the most conspicuous place.

[elanjacobs]

Yeh those replacable edge router bits may have been a viable thing at one time, but I think they too have been overtaken by the falling cost of router bits.

cheers
Yep, you're right. The Carbitool 40mm insert flush trim bit is $110 and inserts are $4.73, the equivalent solid bit (38mm) is $36. At that price it's almost not even worth sharpening them. Sad, really.

[soundman]

I havn't baught a carbitool router bit for over 20 years.

Carbatec house brand 1/2 inch flush trim bit 38mm blade length $22

It would cost about $15 to sharpen it plus the trip to the saw doctor twice.......unless the shw doctor was close by and you rode a pushbike .......its not looking good.

CMT 1/2 inch by 1/2 inch flush trim 1/4 inch shank.$37.
more like what the op needs
1/2 inch shank, 19mm diameter 16mm cutter $53

ya might get them sharpened.

Even at the prices of 20 years ago, insert tooling for router bits never took off.....on spindle moulder heads...ahh well that is another story all together.

You would have rocks in your head to buy fixed edge tooling for a spindle moulder if insert tooling heads where available.

cheers