Is some planer snipe to be expected?

2761 Views 79 Replies 23 Participants Last post by alphonse53, 2 mo ago

extech26

Discussion Starter · 3 mo ago

Hi - I bought a Dewalt 735 in January and just getting around to setting it up. I've only run a couple of boards through but there is noticeable snipe at the beginning and end of the boards. I have never owned a planer before and am curious if some snipe is to be expected . I guess I am wondering if something might be wrong / need adjustment on this planer. Appreciate any inputs. - Thanks.

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Rick Christopherson

· #4 · 3 mo ago

Contrary to popular belief, snipe is not caused by the bed or tables, but by the drive rollers of the head, which indirectly causes flex in the rest of the machine. This is why sniping always occurs at a precise location on the workpiece, which is equal to the distance between the cutter head and the infeed/outfeed drive rollers.

In simpler terms, snipe is the opposite of what most people think. It isn't a thinning of the end(s) of the board, but actually a thickening of the center of the board. When both infeed and outfeed rollers are in contact with the board, their downard pressure pushes up on the head and/or down on the bed (depending on whether the planer uses a fixed bed versus adjustable bed). In other words, the bed and the head get pushed apart while the center of the board is passing through, but relax slightly when only one of the rollers is applying force.

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Rick Christopherson

· #9 · 3 mo ago

DrRobert said:
Ricks explanation is interesting I’ll have to think about it, but it doesn’t explane how the remedies can help.

Actually, it does explain it, but the reasons are probably reversed from what most people think. If you're interested, I would love to have one of those "change my mind" type of debates with you on this. I think we could pull that off. Would you like to try?

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Rick Christopherson

· #10 · 3 mo ago

DrRobert said:
...I’ll have to think about it,...

By the way, here's an animated graphic I created 25 years ago (using chisels and stone tablets) to show the movement of the head. I wrote an article on the topic back then, but didn't publish it because I didn't have the graphics capability to show it better (hence this crappy animated gif).

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Rick Christopherson

· #13 · 3 mo ago (Edited)

DrRobert said:
I might see it on a portable machine, but how the head flexes upward on a stationary cast iron machine? I dont think so …… 🤔

Because the planer is not one solid piece of cast iron...there's a lot going on in there. On planers with a fixed bed and overhead motor (like Delta and most benchtop planers), leadscrew backlash is one of the predominate contributors. Gravity pulls the leadscrew nuts low in the threads, while drive roller pressure pushes them high in the threads.

But even on fixed-head machines (like my Jet 15" planer) there is still some flexibility in the mechanisms, just not as much.
Edit to Add: On most of the cast iron planers, there are bed rollers located directly below the drive rollers. These will be a point of flexure, prompting many woodworkers to conclude they are the root cause, when they are really just an ancillary cause. Nevertheless, lowering them is a mitigation remedy.

DrRobert said:
And why would extended tables and lifting the board help?

Lifting the boards has the effect of "pre-loading" the head (or whatever else is flexing).

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Rick Christopherson

· #15 · 3 mo ago

calabrese55 said:
YouTube has as mentioned tons of info on this.

This comes as a pleasant surprise for me to hear. When I first brought these principles up 25 years ago, woodworking lynch mobs were amassed to take my head for the blasphemy I was espousing. 😱 🔥 🤣 Glad to hear times have changed a little.

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Rick Christopherson

· #20 · 3 mo ago

DrRobert said:
Backlash would explain a board getting thicker as it runs, but not snipe - the last 3” of a board - that’s a board hanging off the outfeed and roller springs not strong enough to hold it down. As soon as it clears the infeed roller - bam! Snipe.

If snipe was due to a sagging board hanging off the planer, then butting an extra board to the end of your workpiece would not eliminate the snipe, as so many people have reported.

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Rick Christopherson

· #26 · 3 mo ago

My Jet 15" didn't have snipe from the factory, but when I replaced the knives I ended up with some at the tails. I readjusted the roller heights and pressures, but not until I readjusted the chip breaker (pressure bar) did the snipe disappear again. The only supports I use are my hands and the flimsy factory rollers.

Wood Engineering Gas Toolroom Machine tool

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Rick Christopherson

· #28 · 3 mo ago

Half Fast Eddie said:
Is that a picture of your planer? Why do you have a stick between two of the legs?

Because I was too lazy to readjust the leg heights 25 years ago, and this stopped it from rocking. Hey, out of sight, out of mind. 🤣

We don't need no stinkin' machine maintenance here!!

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Rick Christopherson

· #53 · 3 mo ago

DrRobert said:
You never answered why picking up in the board can eliminate snipe.

This would be easier to explain with a graphic, so let me know if it doesn't make sense to you. As I said at the very beginning, snipe isn't actually a thinning of the ends of a board, but a thickening of the middle. What you're actually doing when you lift the board at the beginning or end, is "pre-loading" the head.

Using some random (hypothetical) numbers, let's say each roller applies 100 pounds of down-force to the board in order to drive it. Therefore, when both rollers are engaged, there is a total of 200 pounds of down-force on the board, and by Newton's law, that means 200 pounds of lifting force on the head. (Technically 200 pounds of force pushing the head and/or bed away from each other.)

By lifting the board, you are pre-loading that first roller to achieve the entire 200 pounds of force from the very beginning.

DrRobert said:
Or how a head mounted to a cast iron body can flex. Are you referring to portable machines?

If anything, wouldn‘t the bed be pushed downward? I’ve seen the height wheel on my planer turn a little while feeding. Only hard wood. I attribute this to dull blades pushing the board downward.

I have a fixed-head planer. So yes, I can adjust the snipe out of my machine. Fixed-bed planers, such as Delta's 15", are more problematic, because leadscrew backlash is switching between gravity pulling the head down and roller forces pushing the head up.

Nevertheless, the forces involved with the rollers are pretty large. If you feed a board into my planer titled upward, it snaps down hard when it hits the first roller. And trust me, it hurts like hell if your finger happens to be between the board and the extension roller.

Yes, even though I say the head flexes (for simplicity), I have been sort of careful to also mention that its actually both the head and the bed (and all other components in between) that are getting pushed apart. Keep in mind that these are all moving parts, and they have interferences, play, and flexibility.

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Rick Christopherson

· #56 · 3 mo ago

alphonse53 said:
Your applecart reminds me of Oliver Douglas' blown head gasket that Lisa's hot cakes were used to save the day!

I had to google that to see what the heck you were talking about. Your sens of humor is even weirder than @DrRobert 's

But just in case anyone didn't get the reference, it came from his previous post.

DrRobert said:
You tripped me and now all my apple fell out of my cart. I hope you’re happy. 😆😆

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Rick Christopherson

· #72 · 3 mo ago

No, I believe he was politely telling you you don't have a clue and he's not going to argue with you any more. Well, that's my guess.

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