Planer Snipe

[paulrussell]

I have a Shopsmith planer, originally the SPT version, but now mounted on a power stand. I am getting horrible snipe no matter how I try to "help" the boards through.

I've read opinions that it could be due to low roller pressure, or even from having the original rubber roller. Has anyone tried either of these fixes, and what was the result. Oh, and on the matter of the metal infeed roller, the web page says it is for "For Stand-mounted Shopsmith Planers with serial #’s below 20,00." I'm not sure if that applies to my aluminum table, power stand mounted planer or not!

[JPG]

I have a Shopsmith planer, originally the SPT version, but now mounted on a power stand. I am getting horrible snipe no matter how I try to "help" the boards through.

I've read opinions that it could be due to low roller pressure, or even from having the original rubber roller. Has anyone tried either of these fixes, and what was the result. Oh, and on the matter of the metal infeed roller, the web page says it is for "For Stand-mounted Shopsmith Planers with serial #’s below 20,00." I'm not sure if that applies to my aluminum table, power stand mounted planer or not!

Look to see which infeed roller is there.

Is the blade height set correctly?

Describe your 'help'.

Finally snipe on leading edge or trailing edge, or both?

Interesting question re model/roller.

[dusty]

With the Shopsmith surface planers, snipe occurs when the work piece does not remain flush against the infeed/outfeed table.

The infeed and outfeed rollers serve a dual function. One of those functions is to keep the work piece down, flush to the table. If snipe is occurring, the work piece is being lifted off of the table.

With the Shopsmith planer and its relatively short table, managing the work piece can be difficult. With shorter piece, that should not be a problem; however, stock less than 12" long should probably not be planed with the Shopsmith planer.

You did not describe the work piece that you are planing. To help eliminate the sniping, I would first plane a piece about 2' long. This size allows the entire work piece to be supported mostly by the table. I attempt to put downward pressure on the work piece as I feed in into the planer. I do the same as it comes out of the planer. If this piece still exhibits the sniping, you need to work on the rollers; either the rollers or the four tension springs. Roller pressure may be inadequate (this would be my first guess).

Good look.

Keep your fingers out from under the hoods.

Incidentally, when I am working on a project that is really important to me, I cut to length only after I have done the surface planing. This allows me to cut off and discard the sniped ends.

[rjent]

My limited experience, for what it is worth, is the snipe is greatly reduced with smaller (thinner) cuts. The more material you are trying to take off, the more snipe you get. Try more passes taking less material.

[dusty]

My limited experience, for what it is worth, is the snipe is greatly reduced with smaller (thinner) cuts. The more material you are trying to take off, the more snipe you get. Try more passes taking less material.

This is oh so true but in the perfect world there would be NO snipe.

I simply attempt to adjust the planer as close as I can get to the perfect world and then help the rest of the way by holding the work piece down on the table.

If the work piece "NEVER" lifts up off of the table, snipe will be zero.

[JPG]

My conclusions regarding snipe with the SS planer.

As Dusty mentioned, snipe is created when the workpiece is not contacting the table. The rollers are intended to hold the workpiece tight to the table as well as feed it.

However the original rollers are resilient rubber.

As the workpiece enters the planer, it first contacts the infeed roller.

If the infeed roller is resilient, it will be compressed slightly. This adds a second spring constant to the force holding the workpiece.(the rollers are spring loaded downward to begin with).

Until the workpiece contacts the cutter blades, the infeed roller is the only thing contacting the top surface of the workpiece. The motion of the cutter blades will tend to lift the workpiece up off the table as it contacts the 'END' of the workpiece. Normal cutting action will also tend to raise the workpiece as the blade rises 'into' the uncut area. That resilient roller makes that lifting worse, hence the infeed roller 'upgrade'.

I have not yet installed the infeed roller upgrade, so my thinking reflects no experience with the steel roller.

That raising of the workpiece creates the snipe until the workpiece eventually contacts the outfeed roller. Although the outfeed roller is also resilient, the roller will become a second force applied to the top of the workpiece that pushes the workpiece down to the table consistent with the positioning for the remainder of the cut up until the workpiece exits the infeed roller.

Upon leaving the infeed roller, the only thing holding the workpiece down is the resilient outfeed roller. That allows the blade to resume pulling up on the workpiece again due to normal cutting action. Difference is now the trailing end lifts up off the table.

My limited experience using the older rollers is to slightly lift up on the workpiece trailing end as it enters the infeed roller until the outfeed roller engages the workpiece, and lift up on the leading end as the workpiece leaves the infeed roller. Both actions prevent(minimizes) the lifting of the workpiece up off the table at the ends.

I believe the soft rollers compress fully due to the larger spring force of the roller support arms.

Thus pulling up on the ends of the workpiece does not cause additional compression of the rollers. At entry the manually applied upward force causes the workpiece to pivot about the roller and the leading end remains contacting the table. Ditto at the other end of the operation with the trailing end.

This is the opposite of what Dusty described above. I think pulling up on the ends is more effective in holding the other end tight to the table.

The upward lifting is very slight. Just enough to take up the slop so to speak.

JMHO

[drl]

I agree that lifting the piece as JMHO suggest greatly reduces or will eliminate snipe. Standard operating procedure for me.

Regards,
Dwight

[charlese]

One thing that is forgotten by many woodworkers is the forces present as blades slice off pieces of wood. Sounds silly, I know, but it's true. We tend to go to mechanical adjustments to our tools because that's what we mostly understand.

When any blade is forced to slice into wood, the wood is pushed in an equal but opposite direction. For a simple example - remember the forces caused by a small router bit as wood is cut - When wood is passed from right to left against a fence of a router table, the wood is pulled into the fence. Without a fence, the bit will "try" to cut deeply into the wood. A sharp router bit cuts (slices) with less force.

The knife forces in a thickness planer are similar, but the knives are quite a bit larger. The lifting force of the blades is similar, but greater than a router bit. In a planer, the knives are fixed, so the forces tend to pull the wood into the blades. ONCE AGAIN - SHARP BLADES WILL RESULT IN A DECREASED FORCE.

Yes, machine adjustment to proper settings is necessary, But SO IS BLADE SHARPNESS! This consideration should not be forgotten!

---

[BuckeyeDennis]

Matthias Wandel has an outstanding illustrated explanation of the causes of planer snipe, here: http://woodgears.ca/jointer/planer_snipe.html.

Allowing the end of the workpiece to lift off of the table is only one of the two primary causes of snipe. Like JPG, I avoid this problem by lifting the opposite end of the board very slightly, as it enters and exits the planer (until well balanced on the table).

The other primary cause occurs during the transition from single-roller engagement to two-roller engagement (and vice versa), and has nothing to do with operator technique. The rollers press downward on the table (via the workpiece) with considerable force. When the second roller engages, that force doubles. Because no structure is infinitely stiff, this causes the machine to flex internally, moving the cutterhead slightly farther away from the table, and thus increasing the cutting thickness. Matthias makes a convincing case that this structural flexure is the primary cause of snipe. And not surprisingly, it is a bigger problem on cheaper planers, with lighter frames and fewer jackscrews. (Mathias also has a clever technique for eliminating flexural snipe.)

After tuning up my Pro Planer, I get snipe in the range of 0.002" to 0.005". Pretty good, and indicative of a good rigid frame.

If a Shopsmith planer is generating a lot of snipe, I'd start looking for something wrong with it. I don't see much that could go wrong with the frame itself. But the table jack-screw adjustment could easily be out of whack. The load is supposed to be evenly shared amongst all four screws. But if mis-adjusted, it could be primarily supported by only two screws, cutting the table-system stiffness roughly in half. Worse, it could "tilt" between one or the other of the remaining two screws as the load shifts, causing even larger relative motion.

I think I recall a report of a loose jackscrew on this forum, as well. Anything that compromises the structural rigidity of the machine could cause excessive snipe.

[forrestb]

I have the infeed roller upgrade installed and it does help with leading edge snipe, but it is still there.

I agree with JPG and Dennis to lift the board up at entry and at exit to (almost) eliminate snipe. I haven't played with the rollers pressure but will try that in the future.

And a big YES to having sharp blades!

BTW the metal infeed roller means that you NEVER run a board through a second time without height change. Unless, of course, you want the nice pattern of lines across your board. Don't ask why I know this.

Forrest