Thumbnail Router bit

[Dennis Puskar]

How do you use a thumbnail router bit ( MLCS No. 8559 ) on a table ?


http://www.mlcswoodworking.com/orderstatus/html/smarthtml/pages/bit_table_edge.html

My Manual says do not use router bits over 2 1/8 " the router bit at MCLS is approx. 2 3/4 Dia.

Dennis

[glenn bradley]

I would obey your particular router's instructions. I spin 3-1/2" bits in the table with a router/lift and table that is designed to do so. I have variable speed to allow me to slow things down to around 10,000 rpm and my table router happens to have enough oomph. As to technique; on that type of profile I set the bit to full height, set the fence so that I am taking about 1/8" off, run the edge(s) being profiled, adjust the fence to take the next 1/8" and repeat. I leave a skinny 1/16" for the last pass which should just touch the bearing.

[Dennis Puskar]

Thanks Glenn for your input.

[John TenEyck]

If your router is single speed, like mine, you can buy a variable speed controller for it that will allow you to use those larger bits at their recommended rpm. The one I have works OK but the router losses torque, despite the advertised claims otherwise. So if you buy one I'd recommend you make sure it has a constant torque capability, and a 100% refund policy.

As for using a thumbnail bit, I like using mine freehand. I think it allows me greater control over the process and, most importantly, I can climb cut with it safely which gives a much nicer finish with almost no risk of tearout. I set the bit for a very shallow cut, take a pass with the bearing riding agains the work, then increase the depth, take another pass, etc.

[Dennis Puskar]

John
My router is a single speed, Porter Cable Mod. 690, 1 3/4 HP.
How do you use this oversize bit without the plastic base ?
Thanks for the info on the VSC.

[Myk Rian]

John
My router is a single speed, Porter Cable Mod. 690, 1 3/4 HP.
Isn't that a slow start router? I don't think a speed control can be used with it.

How do you use this oversize bit without the plastic base ?
For large bits, you need a router table.

[Dennis Puskar]

No its not a slow start Router.

[glenn bradley]

No its not a slow start Router.

OK, so you're good with a speed control (seems like they are about $15 to $35 depending on quality / sale price). With regard to the base plate, the opening would, of course, have to be a little larger than the bit. My lift has a 3-9/16" opening and the motor is very well centered so the 1/32" clearance is scary-tight but adequate.

How does your router mount to the tale? Directly? Plate? Lift? If it mounts directly, you probably have some opening size that you selected and I would be reluctant to cut a larger hole in a table without a plate or some other method of installing throat plates. If it mounts to a plate, the manufacturer decided on an opening size that was correct for that plate so I would acquire (or make) a different one that will handle the large bit and keep it around for times when i need to use that bit. If it mounts in a lift you are bound by the opening in the lift's built-on plate and again, I would acquire (or make) a different plate for this operation. Just my .02. Good luck and let us know your solution if you would.

[Dennis Puskar]

Glenn

We are getting a little confused the table that I am going to use this thumbnail router bit is 48" diameter so I have to route this freehand.

[Barry Richardson]

Just use a handheld. I've done it many times with a PC690. It just takes several passes. make a spare base plate with a bigger hole for use with it.

[Jim Neeley]

Dennis,

I understand that there comes a size whereby the only feasible approach is to bring the router to the bit even though it's not the desireable approach. Large bits should be used in router tables because with a table you can limit your amount of cut in a single pass. A 2-3/4" dia thumbnail bit is way too big to cut in a single pass.

First, assuming this is a 1/2" shank bit, the *max* cut you should make is 1/2" (measured from the perimeter of the table inwards, not vertically) since all of the stress on the bit get transmitted through the shank. If you so not have a large table w/fence to limit the depth of cut you could use an edge guide. Then take several revolutions around the table as necessary to complete the cut.

The larger thing a table does for you is to ensure the router doesn't tip and let the router dig deep in the stock. It's not ideal but you can reduce the risk by building yourself an eccentric router baseplate (perhaps 3/8" thick) that extends 6"-8" beyond the routers plate and mount a handle in it. To cut, place one hand on one router handle and the second on the plate's knob. While cutting, press downwards on the handle, holding the router flat on the table to prevent tipping.

I hope this isn't too confusing.

Jim

[John TenEyck]

I don't agree with the comment that you want to use thumbnail bits only in a router table. I find it easier to use them handheld with large workpieces. You control the depth of cut by how deep you set the bit through the base, so that you can still ride on the bearing with each pass, just as you would for smaller bearing bits. I hav the same PC 690 router. I make a separate base for it out of 1/2" BB plywood and size the opening for the bit I'm using. Takes just a few minutes. If you're worried about tipping the bit, make the base larger on one side and add a handhold to it so that you can hold it down on the work piece more easily. Like I said before, you can climb cut safely with the router handheld, not so in a router table, and that will minimize the chances of tearout.

[Dennis Puskar]

Jim
No not confusing at all sounds like plan to me.

Thanks to everybody for there input.

[glenn bradley]

I don't agree with the comment that you want to use thumbnail bits only in a router table.

The OP is talking about a bit that is 2-3/4" in diameter.

[Myk Rian]

There is no way I would use a 2-3/4" bit hand held.

[John TenEyck]

There is no way I would use a 2-3/4" bit hand held.

Once you slow the speed down to the correct rpm, the tip speed is no different than smaller bits at high speed. The only difference you will notice is a slight gyroscopic effect due to the mass of the spinning bit. I feel perfectly safe as long as I keep both hands on the router/base and take small cuts. Way better than trying to move something like a 48" dia. table top over a router table.

[johnny means]

Dennis,
A 2-3/4" dia thumbnail bit is way too big to cut in a single pass.



Jim

Not true, I have used just such bit in making spiral handrails (only way to do it). Probably about the trickiest profile cut in all of routerdom. Now I wouldn't recommend this to a newb, but cutting a simple thumbnail on a table top really isn't all that risky. The key is to get the work piece at a height where you can lean into it real good. A heavier router helps a lot. A router in a firm grip really won't get away from you like some people seem to think. Also, thumbnail bits don't dig deeper if the router tips, they leave high spots which can be routed on a second pass.

That warning about large router bits is typical corporate bull. How do they think dining room tables and conference tables get thumbnails? On giant 20 ft router tables? The typical way to rout this would be handheld, lowering the bit a little with each pass. Two or three should do it with very little force needed.