Surface Planer Design Question

[Brian Backner]

Hi all,

Several weeks ago I spent four or five hours tuning up my Jet 15" planer. Despite multiple attempts using dial indicators and what not I still ended up with some snipe.

Reviewing much of the literature, it would appear that the problem occurs when the wood is held by only one feed roller as it either enters or exits the cutterhead.

This begs the question - has anyone ever built a planer using double or even triple in/outfeed rollers? Seems like that would go a long way to minimizing, if not eliminating, snipe.

Then again, if it did work, why has no manufacturer ever offered such a machine? I recently acquired a late 1940's vintage Crescent P-24 (subject of a future "Gloat" posting) and it also has only single in/outfeed rollers but does a much better job than the Jet. I suspect this is due to the shear mass of the Crescent (3,100# vs maybe 300# for the Jet).

Anyone have any thoughts about this?

Brian
Taxachusetts

[Chris Parks]

Understanding what causes the snipe is the first step. It is the timber not level with the tables as it either enters the cutters or leaves them. This is caused by either operator error not having the timber sitting flat on the tables or the bottom rollers are usually too high and the timber drops or rises as it passes over the first or last set with no support from the other end rollers and they also need to be level side to side. Also remember that you have planed the board thinner so the outfeed top roller needs to be lower than the infeed top roller a point that escapes many. If it isn't lower it won't contact the board with proper force. The bottom rollers need to be level with the tables not above. If you put a straight edge over them there should be no light showing between the straight edge and the table and they should still roll if the straight edge is pushed over them. This is a delicate balance to get right.

As for operator error keep the board flat. For some peculiar reason this seems hard to do for a lot of users. Some build an extended table to remedy this and it seems to work. Practice also works if you are aware of what is happening. When tuned right and used right there is no snipe. Others may tell it differently but that is my experience.

[Chris Friesen]

The bottom rollers need to be level with the tables not above.

While setting the rollers level with the table may help reduce snipe, it also completely obviates the whole point of the rollers. Unless the rollers are slightly above the table they may as well not be there.

According to my planer manual the rollers should be a couple thou higher than the table, higher for rough lumber.

[Steven Satur]

I have a 18" Rockwell planer with adj. bed rollers. With the rollers set just a hair above the table, I do not get any snipe at all. Rebuild the Crescent and sell the Jet. I used a 24 Crescent years ago, that this was a beast.

[Rod Sheridan]

Hi all,

Several weeks ago I spent four or five hours tuning up my Jet 15" planer. Despite multiple attempts using dial indicators and what not I still ended up with some snipe.

Reviewing much of the literature, it would appear that the problem occurs when the wood is held by only one feed roller as it either enters or exits the cutterhead.

This begs the question - has anyone ever built a planer using double or even triple in/outfeed rollers? Seems like that would go a long way to minimizing, if not eliminating, snipe.

Then again, if it did work, why has no manufacturer ever offered such a machine? I recently acquired a late 1940's vintage Crescent P-24 (subject of a future "Gloat" posting) and it also has only single in/outfeed rollers but does a much better job than the Jet. I suspect this is due to the shear mass of the Crescent (3,100# vs maybe 300# for the Jet).

Anyone have any thoughts about this?

Brian
Taxachusetts

I have a Hammer A3-31, it has 0.01mm snipe (about 0.0008").

That's without holding the board in any special way, just feed it by hand until it is captured, then walk around the planer and take it away.

The planer has a single in and out feed roller, no bed rollers.

Commercial planers often have a lever or electrical switch so the bed rollers can be raised, or dropped below the surface.

One of the big differences between planers is the amount of solid bed before and after the feed rollers, this helps prevent the board from tipping in the planer.

Regards, Rod.

[Chip Lindley]

Well.....I've used the same Rockwell RC33 13-1/8" planer for over 20 years. I seldom if ever, plane any rough lumber. All is face jointed at least on one side. Bed rolls are set .002" above the bed, just to keep stock from picking at the slots. The flat bed supports stock as it passes through, with no in- or out-feed tables.

My SOP is to flex stock upward slightly as soon as the infeed roller engages it, then release when the cutterhead begins to plane. While board is passing through the planer I move to the outfeed end, at the left side. When the trailing end of stock is about to pass the infeed roller, I flex upward on the board at the rear of the planer, using my right hand to push down, and left to pull up. This effectively holds the board against the bed and prevents all but the most minute amount of snipe; not objectionable, and easily sanded out.

Experiment with this technique, and develop "the touch"! See if your results don't improve.

[Chris Parks]

I new I would get criticised for that bit. It is what works for me on my machine and I don't get any snipe at all. In reality the rollers have to be up a bit to actually roll, I can't be bothered measuring it as it is all done by eye and feel with no visible light under the straight edge so it is not much.

[Peter Quinn]

Brian, read up on the terms "chip breaker" and "pressure bar". These are what separates the men from the boys, or the truly industrial machines from the toys in the planer world. A chip breaker sits right in front of the planer head and holds the stock firmly to the table, and as it turns out, breaks the chips. When I say right in front, I mean really close following the heads arc, so a second roller is not necessary. An industrial planer will generally have a segmented chip breaker with massive springs. Most little 15" iron imports have a chip breaker with springs of more or less effect. My little DC380 is ok in this regard.


The pressure bar sits just after the head, is curved to follow its arc, and pushes down like hell to resist the knives lifting action. This helps minimize the snipe on outfeed. No second roller set needed. No small planers that I know of have this feature, and that is why you can't always dial out the snipe. Pull up, push down, daisy chain, sacrifice a lamb, voodoo snipe dance, none of these things seems 100% effective to me. I always leave a little extra room and cut short parts to finished length from longer boards after planing.

[Chip Lindley]

Chris, No criticism intended. You have found what works for you, as I have also!

Planers are one machine in particular, if you finally *get it right*, don't mess with it. I have never reset the tension on my infeed or outfeed rollers in the 24 years I've used it. It still works for me, so, If it ain't broke....

I badly want to tear down the RC33 for a complete repainting and addition of jack screws to the cutterhead. I may fail to get it right upon reassembly, and that would be a real shame.

[Chris Parks]

I want to explain why I think the rollers don't need to be significantly above the table, they still roll but they are so close to the table height it really is not worth measuring. If the bottom roller(s) are significantly above the table and the board can rock on one or the other while it is only sitting on one during set up as in entry or exit it will cause snipe, it is nearly if not impossible to avoid. The board hits the entry roller and LIFTS even one thou you will get snipe, you can't get around that fact, it is common sense. I recently put a digital gauge on my planer and it is interesting to watch the table rise and fall during operation. This is no tin toy planer either, it is a heavy duty production planer. It doesn't move much but it sure as hell moves up and down. I know there is disbelief out there re this contention but think about it don't take what is written in a book as verbatum.

[Simon Dupay]

Some of the older planers like buss, Oliver and some euro planers like martian use 2 feed rollers. Most of those 15" planers are going to have snipe, their just not heavy duty enough to resist the forces in against the feed works.

[J.R. Rutter]

When I had a 20" 4-post import planer, I ended up making an auxilliary table with hardboard and laminate to get rid of the snipe (and still had to lift up the ends of longer boards on entry and exit. When I got a heavy duty machine and got the rollers adjusted barely above table level, snipe pretty much went away. I think Peter has it right - on better planers, the forces of the feed rollers and existence of (and high force on) chip breaker and pressure bar work very well.

[Brian Backner]

Thank you all for your comments.

While the Jet is an adequate planer, it simply isn't in the same class as the Crescent. I bet just the feed roller on the P24 weighs as much as the entire head assembly on the Jet! The chip breaker is hinged but not spring loaded - must weigh 150# by itself.

Length of the stock table is also much larger on the Crescent. The Jet is typical of the import planers - actual table is maybe 20" and has two bolt-on auxiliary "tables" that are nothing more than rollers held by some angle iron. The P24 has a massive cast iron table that appears to be one piece nearly five feet long.

I should be bringing the Crescent home next week - once I get it hooked up and running, the Jet will definitely be looking for a new home.

Now to find a 16"+ Crescent or Oliver Jointer to go with it ....

Brian
Taxachusetts