Recommended router bit for a planer sled configured for slab flattening

I would recommend this one if it’s specifically for planing. If it would ever need to be used to plunge though, you’ll want a bottom cleaning bit.

There are also inserted bits available now that are like the Whiteside I linked but use indexable carbide inserts. If I were going to be using the sled a lot, I’d probably go that route.

-- Kenny, SW VA, Go Hokies!!!

Not enough information?
Can almost use most any flat cutter, even a standard 1/2” carbide spiral up cut?

If you have plunge to start cut; then use a mortise style bit:
https://www.whitesiderouterbits.com/collections/mortising
Can get these with replaceable heads for high volume work.

I would suggest you start with smaller diameter bit and get feel for your planer sled and wood being machined?
The harder the lumber, or more it tends to splinter; the more careful you need to be about bit selection.

Start with 1” OD cutter like this:
https://www.whitesiderouterbits.com/collections/cnc-spoilboard-surfacing/products/6210
and then try larger 6220 already mentioned.

The challenge with larger CNC bits is keeping a constant feed rate. CNC spoil board surfacing bits have large gaps between cutters and don’t have anti-kick back protection found on common router bit for hand use. Push to fast, and they will grab wood aggressively and chatter.

For really large CNC tables, they use large bits like the $400 4” OD cutter with inserts from Whiteside:
https://www.whitesiderouterbits.com/collections/cnc-spoilboard-surfacing/products/sbu40-3
But I would not attempt to use these beast bits by hand.

If you find that bits with sharp corners are leaving witness lines with every pass (due play in router fixturing), then can use bowl & tray bit with radius corners, such as this one:
https://www.whitesiderouterbits.com/products/1376

IMHO – There is no ONE answer to how to machine wood with a planer sled?
Hope this helps.

Best Luck.

-- I'm an engineer not a woodworker, but I can randomly find useful tools and furniture inside a pile of lumber!

With a router that has a 2 1/4 Hp motor as your Bosch 1617EVSPK has I would suggest not going with a HAWG sized bit, but rather limit it to 1 1/2” diameter at the big end.

A 3+ Hp hawg router, then jump on up, and put in a hawg bit.

Your router will tank you for it by running longer.

-- Think safe, be safe

Thanks for the advice guys! I will prob purchase a the smaller diameter surfacing bit and see how it works and feels.

I have done this with the same router. Think I used a 2” dia bit (have to measure it) as well as smaller ones. Depth of cut as well as cutter dia controls whether a given router can do a cut. I would not want any larger bit than I used controlling the router by hand. Mine is square cornered, highly recommend a radiused bit to prevent cut lines – just about impossible to prevent with a non cnc set up. Pau attention to the amount of tearout you get. I abandoned the method due to that. I was flattening panels not slabs. For slabs its a good rough flattener, then use handplanes to remove the tearout and cut lines if any.

My router mounts to a steel bar slide mechanism sliding on bearings and is mounted to a all steel frame so the router doesn’t just slide in a slotted opening does that make a difference?

I’d be interested in some pictures of your sled if you wouldn’t mind posting a few :-)

-- Kenny, SW VA, Go Hokies!!!

I use this bit also, it works well. Just be sure to use a bit that cuts on the bottom and slow your router down to the proper speed for the diameter of the bit. The type of sled you use will not matter

My router mounts to a steel bar slide mechanism sliding on bearings and is mounted to a all steel frame so the router doesn t just slide in a slotted opening does that make a difference?

- DHapp

Should be a lot better if executed well. Stiffness in the z vertical direction, smoothness of movement in x y horizontal.

I use this bit also, it works well. Just be sure to use a bit that cuts on the bottom and slow your router down to the proper speed for the diameter of the bit. The type of sled you use will not matter

- Davevand

I use a similar bit that is shown here. 1-1/2” with a 1/2” shank. I am using a Dewalt DW618 router, and it handles the bit with now problem. I feel I could upgrade to a larger bit if I wanted too.
The key to using the larger bits is to take lite cuts. I don’t think I have ever taken more than a 1/16” at a time.

-- John