Running Baseboard and Casing in One Pass
Can you run baseboard moulding or casing on a four-head moulder, using the first knife to create the necessary back-relief? October 14, 2006
Is it possible to run a four head moulder for casing and baseboard and run the back relief cut on the first bottom head? This way you could run your casing material in one pass. I realize that the first head is usually used for truing up the stock and that the throat does not move back. The relief cut, however, does not have to be too deep - maybe an eighth of an inch. I am looking at a used four head machine and the ability to do this in one pass would make a difference to me.
(Solid Wood Machining Forum)
From contributor R:
That depends on who you ask. It is not recommended by most manufacturers, but it can be done. I have made them to fit the Weinig Quatromatt 23, but only 1/16 of an inch deep on the backout. There are a few things to keep in mind, though. Most backouts I make are made with versatility in mind, so they can be used for a number of mouldings just by shifting the axial movement on the cutterhead shaft. This design concept can't be incorporated on the first bottom if there is a rebated cutter in play. The rebate cutter needs to be in a fixed position so it works as designed on the rebate guide. This limits you in your design of the cutter. So you will most likely have a few more backout knives than most people.
Second thing that comes to mind is more for the experienced operator. You would need a four wing cutter to make this happen, all the same hook angle. Two pockets 9" straight knives as normal. The other two pockets just the straight knife for the backout section raised 1 corrugation above the straight knives in the other two pockets, giving you a 1/16" cut above your planer knives making a backout. There are a few things you would have to do to make it work. Balance is critical and you would need some filler stock to fill the other sections of the cutterhead with no knife steel in it. Also, you would have to sharpen the edges of the knife at least 1/4" down on the edge, or bevel the edges with 45* angle off the straight part. Now you have more flexibility on what you can do and it is less expensive as well. Remember when you set the head, set to the straight (planer blades), not the backout. As I mentioned, it is more for the experienced operator, but it does work.
From contributor E:
I used to run a small 4 head machine with insert cutters that cut the back out on the first head. A Terminus style head might work well for this application, although the back out is quite deep in the Terminus. We use Terminus on our 5 head Weinig because of the simple adjustability.
From Dave Rankin, forum technical advisor:
I have run many moulders with the backout on the first bottom head. Both contributor R and E make valid points. I would add that when you run profiles on the first bottom, it is common to remove a small amount of material from the table for clearance. If you find out that this is required, I would contact the machine manufacturer for complete instructions. I personally use a corrugated head with a pair of long knives and a pair of short knives for the actual backout.
From the original questioner:
Thanks everyone for the information. Very helpful advice.
From contributor G:
Contributor R, is this okay? When we had a 5 head, we used a serrated head (2 knives) that we dressed and took out the back relief at the same time. We only cut a small back relief.
From contributor R:
If I understand your post correctly, I would say that's fine, but you would have to take out the shim under your last bottom bedplate to eliminate snipe. There is a .020" shim under the last bottom, which makes that bedplate higher. The purpose for this is to get any lubrication off the wood that was used on the bedplates. The reason for .020" is that is the least amount of cut you can take to create enough wood chip flow to keep the knife cool.
From contributor B:
I use the 1st bottom head all the time. Most of my mouldings are made from dimensioned pine (3/4"), so I use the bottom head solely to cut out the relief, not to surface the material as well. The setup is much simpler for this application, as the depth of the cut is controlled by the position of the infeed table. My moulder has a reference engraver, so as contributor R said, you will have to design the backout knife with this in mind. My application is for just a few profiles that we run 1000's to 10's of thousands LF for in-house use. Not sure I'd want to do very small runs or custom work with the 4 head.