Panels, Space Balls, and (Whiteside) Slot Cutters

[andrew whicker]

Hi,

Maybe I'm confusing myself, but I'm planning on making a panel and using the router table instead of the tablesaw. This is new for me, I have only used my tablesaw / dadoes. I want the slot to be 1/4" to fit 1/4" Space Balls.

What I find confusing is that I assumed a panel with a 1/4" long tongue would be common resulting in a groove of 1/4" (tongue) + 3/16" (1/16" space ball squish) = 7/16" groove depth. However, Whiteside doesn't make a bearing for their arbors that result in a 7/16" groove depth.

What then are the standard frame and panel cutting dimensions when using 1/4" space balls?


As far as Whiteside goes, I made a table in an attempt to de-confuse things. Hope this helps. For my needs it looks I would have to use bearings B20 and B25 for a cutting depth of 9/16" and 3/8", respectively. Whiteside makes it extra confusing by selling their arbors with a B5 bearing.. a bearing size that isn't even mentioned on their slot cutter page. They also don't give the buyer info on the slot cutter diameter, requiring the buyer to back calculate.

Whiteside Router slot cutters.png

[Richard Coers]

Use a 1/2" deep cutter and make the panel another 1/8" wider

[Phillip Mitchell]

Is this for a cabinet sized door? Seems like it based on 1/4” thick panel/groove. How wide is the panel and is it solid wood or ply?

I don’t use space balls, but instead use close cell foam backer rod that I typically cut to fit the size I need for my grooves. You can buy long rolls of it in various diameters (1/4” and up) and cut it to fit very quickly with basically infinite flexibility of different groove widths/depths.

My panel and groove width calculations are a little more, well, calculated when doing solid wood panels to account for expansion and contraction so I don’t have an easy answer for you regarding what’s “standard” there.

If for a cabinet door and using a ply / sheet stock panel that won’t expand or contract then the calculation is easier and I shoot for ~ 1/4” of panel going into each groove, but I don’t know if that’s what anyone else does or is standard.

There is also usually the variable of what your joinery for the door stiles and rails is ie: stub tenon, etc and typically size the depth of my grooves based on what I want for the joinery. I usually do at least 1/2” deep with cabinet door stub tenons and sometimes more if it’s a bigger or tall door and just increase the panel size a bit and use a bit more foam in the groove. Kinda depends...

[Mark Bolton]

3/8" tenon is industry standard

[andrew whicker]

Thanks much!

Still learning my around cabinetry and this discussion helps a lot. This is a ply panel into real wood rails and stiles. It's not a cabinet door. One panel / frame will be on a head board and the other on a foot board. I like the idea of the backer rod vs space balls.

[andrew whicker]

Another question: do you make the panel tongue slightly undersized then? There is an option for a slot cutter that is 0.281" thick. Sounds like this might be a good option to keep the panel tongue at 0.250" and make the groove 0.281".

[Paul F Franklin]

I find the groove has to be a little oversized or the panel a little undersized or it's a real pain come assembly time. 30 thou seems a bit much to me, but for a large panel like you are talking here, probably ok.

Just make sure you have the plywood you are using for the panel in hand since 1/4 ply cabinet ply is often a little under size. And don't forget to allow for finish thickness assuming you are pre-finishing the panels.

[andrew whicker]

I am using 1/2" ply that I'm rabbeting to a 1/4" tongue.. so I could make it small by a tad pretty easily.

[Mel Fulks]

I always kept a small wood sample of each pair of panel cutters ,that means one sample and keeping it with the cutters. Not making new
sample unless it was somehow used differently for a particular job that would be done at one time. We made the panel tongue fit so that
it pretty much seated with a 1/16th space left over. Panels would pretty much seat properly, but some would need tap or two to be
equidistant all around. You have to remember that that a small panel sample just 2 or 3 inches wide must seem a little loose with a proper
fit . A whole panel ain’t gonna slide in as easy as sample . Some customers like to see a little flat perimeter , but I’ve found most like
to see a fit that shows no flat and seems , seamless.

[Eric Arnsdorff]

I used space balls not long ago for the first time. I wasn't sure about the recommended gap for the space balls so I made a test assembly then squeezed it in by hand. This was a very qualitative assessment. I came pretty close to the recommended values on the space balls package.
I used maybe 1/32" less than the recommended value.

My assessment is to just use the amount they recommend (error on a little less). Determine the panel width based on this and the groove depth your bit will but. You have variable depths based on the bearing size so I'd use about 3x the clearance recommended from the resulting space ball squeeze distance.

[Mark Bolton]

Another question: do you make the panel tongue slightly undersized then? There is an option for a slot cutter that is 0.281" thick. Sounds like this might be a good option to keep the panel tongue at 0.250" and make the groove 0.281".

If its a ply panel you dont need spaceballs. Just cut the panel for a close fit and glue it in. The only time you need spaceballs is with a solid wood panel that needs room to move and you want to keep it centered.

[Kevin Jenness]

When using spaceballs I leave 3/16" around the perimeter and size the panel accordingly. Cope/stick sets vary in groove depth so your tongue length will vary. I use a 1/2" stub tenon for square edge cabinet doors. Large doors get spline tenons as well.

Using a 9/32" cutter means the spaceballs will fall out of the groove. They are sized for a friction fit in a 1/4" groove. Since you are using a 1/2" panel, rabbet the panel so that the (prefinished) tongue is a slip fit in a 1/4" groove. As Mel said, a full size panel needs a bit more clearance than a small sample would lead you to believe. With a reasonable fit the spaceballs will center the panel on assembly, otherwise you will have to tap or lever the panel to get an even reveal around the rabbet at the back of the frame.

I usually leave at least a 1/8" reveal at the rabbet. Any tighter and you have to be very precise about dimensiong the panels to match the frame size. When required to leave a 1/16" gap I have used spacers while assembling to get the reveal correct at the rails.

[Robert Engel]

My CMT bit makes a 7/16" deep groove. Whiteside 1/2".

I use 1/4" Panel line strips, principle is the same. I subtract 1/4" to the calculated width to allow for 1/16 compression either side.

If the total with groove bottom to groove bottom is 10", then subtracting 1/2" (1/4 + 1/4) and adding back 1/4 = 1/4" meaning subtract 1/4 from the total width, in this case I want a panel 9 3/4" wide.

But there's a "but". You have to take into account season. In the winter, I subtract something like 3/16, summer I want it tight so I might only subtract 1/8. Depends on the width of panel. Anything under 12" I don't worry about.

All that said, I'm not going to use them anymore. If I'm worried about equal movement I'll just pin or glue the middle of the panel to the groove on the back side.

Problem solved!! ;-)

[Kevin Jenness]

For me, using spaceballs (or in the case of thicker grooves self-adhesive foam)is a means to save time centering the panel. Otherwise I have to knock or pry the panel into a centered position.

[Larry Edgerton]

For me, using spaceballs (or in the case of thicker grooves self-adhesive foam)is a means to save time centering the panel. Otherwise I have to knock or pry the panel into a centered position.

Ditto. .....