Troubleshooting Moulder Tearout

Pros help a shop owner figure out the problem with his moulder. October 8, 2005

I am experiencing significant tearout from the reference engraver on my moulder. We use it to dress staves for edge glued panels. Needless to say, chunks missing from the edge of the board doesn’t make the best looking glue joint.

The engraver is a carbide tipped 4 wing generic import type. The moulder is a Bridgewood. The wood being run through is 3/4" white pine. For the last batch we ran, the cutter was brand new. We are hogging approx 1/4" off the back side, and the same on the left side.

Forum Responses
(Solid Wood Machining Forum)
From Dave Rankin, forum technical advisor:
There are a few possible problems that you may be having:
1. Misaligned infeed fence.
2. Misaligned infeed table.
Both of these would cause the wood to be out of control as it passes the engraver.
3. Misaligned Spindle.
If the bottom spindle is misaligned then the engraver is not parallel to the table and the cut will vary.
4. Dull cutter.

This could be the engraver or the bottom head. If either is dull you will lose control of the wood and can experience tearout.
5. Incorrect hook angle or attack angle with the cutter.
The wrong angle will cause finish problems.
6. Dull feed rollers or misaligned feed rollers.
Once again this can cause lose of control of the work piece.
7. Misaligned table rollers.
This can cause the wood to raise up or jam, in either case tearout can be a result.
8. Insufficient side control.
The work piece has to be held against the fence to prevent loss of control, which results in tearout.

From contributor A:
To the original questioner: Dave makes a lot of good points. I want to tell you first I am not familiar with your brand of moulder, so I might be a little off base here. The alignment I will describe is for a Weinig moulder. I hope they are similar.

First, lock and tag out. Take a 8' straight edge and put it against the infeed fence on the infeed table. Put the infeed fence at "0" position. Push the straight edge forward to the rebate guide. The rebate guide should be about 1/32" behind the alignment of the infeed fence at "0" position. The reason for this is, if you were using the moulder for, say, surface only top and bottom, and you were taking nothing off the left and right spindle, the rebate cutter would not come into play. I trust the rest of the fences are aligned properly with the infeed fence "0". If not fix that first!

Next, take a 12" straight edge put it against the rebate cutter guide piece (usually bolted to moulder). Slowly turn the cutterhead by hand till the rebate cutters vertical cutter just barely touches the straight edge. If it touches too much, move the spindle back. If it doesn’t touch at all, move spindle foward till it does. Remember it should just barely touch.

Next, take that same 12" straight edge put it on the bedplate after the first bottom spindle. Rotate the 1st bottom cutterhead by hand till it just touches the blade of the 1st bottom cutter (blade or knife).

Lastly, and most important, take that 12" straight edge and put it on top of the rebate cutter guide. Slowly turn the first bottom cutterhead and make sure that the horizontal cutter on the rebate cutter pushes your straight edge up in the air. It is crucial that the horizontal cutter takes enough wood off to clear the top of the rebate cutter guide.

If it does not clear, pull the cutterhead off and lower the knives in the cutterhead and repeat the alignment for the first bottom cutter to the bedplate after the cutterhead. Then check the alignment of the rebate cutter again. The horizontal cutter must cut above the rebate cutter guide, otherwise it will pull the lumber away from the fence and cause tearout from the rebate cutter. Dave's point of hook angle of cutterhead should be looked at as well. Feed rate of no more than 30 feet per minute.

As I said, I am not familiar with your brand of moulder but they all work basically the same way. If that doesn’t work, try one of Dave's theories. This is just one of the basics that is missed quite often.

From contributor B:
I'm not familiar with your moulder, but I'm not 100% convinced that the engraver is your problem.

Try this - take an 8' piece of whatever you are running and feed it in. When you have a foot or so sticking out on each end of the machine, shut it down. Back everything out of the way and pull the piece out. Usually you can tell right away where the problem is by looking at the wood.

From contributor C:
I agree with contributor A that it sounds as though the cutter is simply not adjusted correctly. A few other things to check are:
Does your #1 jointer head make a continuous cut right up to your rebate cutter? If there is a little space where the two meet it could be leaving a tiny line of wood that is getting smashed and ripped off by the fences and bedplates.

An easy technique to use for diagnosing problems is to run a workpiece 1/2 way into the machine, stop the machine and spread apart the machine and remove the piece. You can then see how each spindle is cutting and exactly where your tear out is occurring. It will also show you if the rebate cutter is not adjusted correctly.

Another thing to check is that your first inside vertical spindle is flush with the outfeed fence directly behind it. Your rebate cutter is not really intended to make a finish cut. It is this first inside spindle cutters job to do that. If your spindle is adjusted too far back you can still pick up the cut from the rebate cutter head even though you are taking 1/4" off the side.

Last, take off the outfeed fence right behind the first inside vertical spindle. (Takes about 2 bolts and 2 minutes). Make sure there is no accumulated crud making this fence misaligned. Any time this fence is adjusted forward or back to bring it closer to the cutterhead, it should be taken off and cleaned, not just simply slid back and forth. That is how build up occurs.

From Dave Rankin, forum technical advisor
I agree with the additions of the other folks here. There are many things that can cause your problem. Contributor A makes a good point about the engraver alignment.

From the original questioner:
I found two of the mentioned conditions that I hope are the culprit.

First the feed speed was way too fast. It's a variable step pulley, but doesn't have a meter to tell you how fast it's actually going. So I counted the number of revolutions the feed wheel made in one minute which was 47, and multiplied that by pi x 5.5" wheel diameter which is 17.27" x 47 which is 811 inches/min = 67 ft/min. I had thought the max feed speed was only 60 ft/min and the pulley was set in the middle of its range.

The reference engraver was cutting below the level of the engraver fence behind it also. The boards are already s2s so I'm not making a cut with the bottom cutterhead, so I dialed it down below the table about.06". I raised it up as high as I could without the teeth making a cut. Now the engraver's cutting circle is above the fenceline, although it's only about .02". Can you run your bottom spindle with just the reference engraver and spacers instead of a cutterhead?

I'll let you know this works out. I'm thinking the feed speed probably has the most to do with it.

From contributor A:
I’m glad you found something useful to help with your problems. The .020" above the fence behind the rebate cutter should work out just fine.When you put your cutterhead on the shaft, does the edge of the cutterhead touch the vertical cutter of the rebate cutter? Check this with a feeler gauge.

If it does, you will need to insert some small shims in between the rebate cutter and the cutterhaed that holds the knives. You are taking a big risk of spinning a cutterhead if this is the case. The reason for this is, when you tighten the spindle nut, the cutterhead is being tightened against the tips of the vertical cutters on the rebate cutter leaving a small gap between the bodies of the cutterheads. If the tips of the rebate cutter break, your cutterheads will spin and weld themselves to the shaft costing you thousands of dollars in repairs and down time. You might want to make sure you have some shims between the two cutterheads. This is another scenario that is quite often missed.

Regarding your question about running without the cutterhead, I would run just like you are. .020" above the rebate fence should be just fine. I would be very concerned about whether your cutterhead touches the vertical cutters of the rebate cutter.

From contributor E:
Assuming the inserts are sharp, the first thing I would check is the relationship of the inserts on the rebate cutter. The vertically mounted spurs must be a few thousandths "proud” of the edge of the planer inserts. The spurs score the wood and define the vertical cut and the square planing inserts hog out everything else, much the same as a stacked dado set.

If you will check the alignment of the rebate cutter to the rebate guide fence just behind it, as contributor A explained, only one or both of the spurs should make contact (more often than not just one). The sides of the planing inserts should not touch. If they do you will have tearout.

To adjust, put a 2-4/1000" shim between the straight edge and the guide fence and axially adjust the rebate cutter so that the spurs are just making contact, then remove the shim and shift the planing inserts in the cutterhead until they are lightly touching as well. This will set the edge of the inserts the thickness of the shims back from the spurs. Retighten the inserts in this position. You will then have to realign the spurs to the guide fence without the shim by axially adjusting the spindle again.

There are a lot of issues regarding the rebate cutter and guide. If they are not 100% correct as pointed out in the other posts you will have problems.

The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
To avoid tear out you can also change the angle of the tip of your knives. We use a 25 degree bevel on our knives when we run pine, then I go back through and just touch it with a 20 degree for my final pass. It works every time.