Router Experts: Adivce needed - bit selection

[Kent A Bathurst]

I use routers when I gotta use routers, not as a staple of my work process. So, appealing to you guys that know your way around this topic: 'splain something to me, if you would be so kind:

42" wide hardwood [QSWO] table top. Very serious $$$ gorgeous-grained wood. I will be machining tenons for breadboad ends. Failure is not an option.
> I may need 2 different bits, maybe 2 different diameters, and I have no problem with that if it is the best solution. The cost of a couple of bits is a rounding error compared to the cost of the wood.
> I have a pair of PC 690's - one of the traditional On-Off models, and one newer model with variable speed, and all 3 bases. Also, a Makita lam trimmer, but can't see how that comes into play here.
> I also have the excellent Betterley dust collecting bases, so there really isn't much of an issue with dust in the bottom of a slot, if that is a consideration.
> I understand the "multiple passes" game very well.......would go for 3/16" max depth-of-cut, unless a different scheme is warranted.

1] First issue - define the shoulders of the tenon. I would, of course, hope for zero tearout. My limited knowledge tells me to leave the up-cut spiral bits in the drawer. Beyond that, tho?? And - might be over-driving my headlights here, but it seems that a small diameter bit, with it's correspondingly lower tip speed, would be smart, but again....I dunno. Plus, with the VS, this shouldn't be an issue, but again.......I dunno.
2] Second - mill out to create the tenon faces. Flat bottom-of-cut is the goal. But - I don't need mirror-flat.
3] Strategy: cut the shoulders to final depth, then start at the outer edge, working in, to mill out the faces.

Thanks

Kent

EDIT: You can edit the post, but have to leave the lousy typing in the title................

[johnny means]

Larger diameter cutters yield cleaner cuts, because they exit the cut at a smaller angle. Tear out shouldn't be an issue going cross grain in quarter dawn, blow out at the end of the cut will. Be sure to use a sacrificial backing block at the end of the cut. You could just score your shoulder with a knife, than work progressively in towards the line. I wouldn't route the shoulder first because routing the waste could be get hairy once you get to the last bit. Little pieces like to go flying and can be unnerving.

[Dan Hintz]

No router expert here by any means, but I would think cutting out the majority of the wood in the first pass, followed by a second pass that just sliced off 1/16-1/32" would provide the cleanest edge. Of course, the down-spiral bit is a given.

[Bill White]

Absolutely score the line(s) before the cuts, a larger bit, and "sneak up" on the final cut. All good tips.
The trusty 690 is a good router. The VS feature is a must for large bits like a panel raiser. Not so important for what you're gonna do.
Bill

[Kent A Bathurst]

Suggested bit styles for the shoulder cut and the tenon faces?

[Brian Tymchak]

Suggested bit styles for the shoulder cut and the tenon faces?

Also not an expert but +1 on Dan's suggestion of the down-spiral bit for the shoulder cuts. To clear out the bulk of the material on the cheeks you can use a straight bit with a broad base to give you consistent depth of cut. I bought a 1/2" x 3/4" bit a couple years ago from woodcraft, when I built my workbench, that I'm fairly sure had cutting edges on the bottom of the bit. I used it to "plane" the tops of the leg assemblies level after I racked one of them slightly in the glue up. I can't find that bit on their website but if you are interested, I can check tonight when I get home from work.

[Kent A Bathurst]

No router expert here by any means, but I would think cutting out the majority of the wood in the first pass, followed by a second pass that just sliced off 1/16-1/32" would provide the cleanest edge. Of course, the down-spiral bit is a given.

Dan - my apologies - I wasn't ignoring your down-cut advice - I skimmed your post too quickly, and missed it entirely, until I just read Bryan's dope-slap.

Thanks to both of you.

Now then - the hard part - driving 10 mintues to Highland, and leaving with a down-cut spiral bit without - say - an Auriou in the bag as well. :D

[glenn bradley]

I use routers quite a bit in and out of the table. I agree on scoring your line with a couple passes of a razor or marking knife and the downcut spiral as a good combo. When I score across the grain the downcut becomes less important and I often opt for a larger bit (I am a member of the 'largest diameter you can' club) for cleaner results. You have the advantage that with the exception of the shoulder (and possibly the entrance and exit point depending on style) the result will be enclosed in your breadboard. ;-)

[Kent A Bathurst]

Glenn - Groovy. Thanks.

Johnny - ditto. Should have thanked you for the primer on bit diameter, the exit backer board, and the score the line - and Glenn is joined to you at the hip on these points.

I have no problem with keeping control of the tool on a short entry climb cut at the one end, which is how I'll deal with the end-of-cut tearout - I am glad you guys reminded me of that risk - I had not been thinking about that part, only the top-surface tear-out, and the down-cut addresses that. I'll get me a 1/2" dia and work it in shallow passes for the shoulder cut.

And, Glenn - you are correct about the tenon face being hidden. I'm proud of the fact that I have gotten good at figuring out how to build stuff so that the most likely point of screw-up will not be seen. After the shoulder is done, I will go to the far outboard end, and work my way in, so that I have a stable support for the router base.

I'm not shy about posting my opinions on things I think I know something about, and by the same token, I am not shy about asking questions on topics where IGNI. You guys are good.

Gratzi