Hi Joe:

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I’m pretty sure you meant David B., but since he was replying agreement to my post I thought I’d take a risk and reply myself. In my reply, I absolutely don’t mean to patronise — you probably already know all this stuff. Forgive me if I go over known ground…

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If a board is already flat, then “light forces with shallow passes” will probably get the job done. I say “probably” because the hard timber we get in Australia won’t pass nicely over the cutterhead without some serious drive help from the feeder, especially for wider pieces (say 300mm and wider). But let’s say the timber is of reasonable species, reasonable dimensions, and reasonably flat. A single pass of 1mm or 2mm will flatten the board, all-at-once, so it doesn’t matter whether the feeder is adjusted for a light force or a strong one. The key is that the job was done “all-at-once”.

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If a board is significantly not-flat — bowed, cupped, twisted — then any full length pass must get the majority of the “not-flatness” out, otherwise, a couple of things will likely happen:

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1. If the power feeder is adjusted so there is reasonable force pinning the board to the jointer surface, it is very likely the feeder pressure will partially flatten the board while it is being machined, only for the board to spring back after it is ejected from the feeder.

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2. This is especially the case for a bowed board (which looks “curved” when viewed on-edge). In this instance, after the machine passes over the cutterhead, and under the feeder, it will “spring” back into its natural curved state. It doesn’t take much pressure to distort a bowed board, especially one of some length — say 2m or longer. All that has been achieved in this instance is that the board’s surface has been smoothed; but the board itself is still bowed.

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3. This problem of spring back occurs less for cupped material (unless it is really thin) because even a strongly set power feeder will not unduly flatten a cupped board across its width during machining. So there is no, or less, spring back.

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4. For a twisted board, it doesn’t really matter whether the feeder is adjusted lightly or strongly. Light passes will not correct the twist as the board is likely to rock one way to the other as it passes under the feeder wheels (especially for short boards), or else corkscrew or propeller through as long boards are pinned under the feeder but twist through the cut as it extends off the end of the outfeed table. In other words, a twisted board is unstable unless it is manually flattened (e.g. David B’s suggestion with the scrub plane), machine flattened (by hand beside the feeder or with the feeder moved out of the way), or the depth of cut is sufficient enough to flatten the board all-at-once (at least to 75% flat).

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In summary, and in theory, a lightly adjusted feeder and light passes will work just fine for flat or nearly flat timber. And in theory, a lightly adjusted feeder will flatten badly warped boards, as long as the board is not thin, does not rock while being fed, and does not stick/stall because more drive pressure is required. Joe, this may be what you’re thinking?

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But in practice, boards need a reasonable amount of drive pressure from the feeder to work its way through the cutterhead. This is especially the case for cantankerous Australian timbers, and timbers of large dimensions. And this pressure will usually distort a warped board as it passes under the feeder wheels. If the depth of cut is not sufficient to obtain that 75% all-at-once flatness, or better, then the machinist will be chasing his/her/them tail, and never achieve flatness.

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I hope this helps.

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Warm regards,

Lucky

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On 23 Mar 2021, at 6:48 am, Joe Jensen <joe.jensen@...> wrote:

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David, why would “light forces with shallow passes” not get the job done. Would this not be like using a hand plan?? Why does pressing a board flat with the feeder not press some of the bow out before it passes the cutter?

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From:?[email protected]?<[email protected]>?On Behalf Of?david@...?via?
Sent:?Sunday, March 21, 2021 6:14 PM
To:?[email protected]
Subject:?Re: [FOG] PF Wheel Durometer for Shaper and Jointer?

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I’m with Lucky on this. ?For rough material, I first lay it on the sliding table of the saw, and check the amount of twist and bow. ?If the twist is under 3mm and the board lays flat, I set the jointer to 3+mm depth of cut, set the feeder over the outfeed table and adjust the height for 4mm of expected upward wheel displacement, and let it rip. ?Say the rough material is 25mm, I set the feeder tires 18-19mm above the outfeed table, infeed table to 3mm DOC. ?One pass, plenty of downward force on the outfeed table, and the board is ready for the thicknesser. ?Light forces with multiple shallow passes isn’t going to get the surface flat. ?If the material has more than 3mm twist, I cut it into shorter pieces or work off the high corners with a scrub plane first. ?The outfeed table has to be slick - I use Waxlit on top of Renaissance wax on the tables. ? This is one reason I optioned my Dual 51 with a 13HP motor, and I’ve done lots of 16” wide cherry in this manner. ? For thicker rough material (12/4 Oak for instance), I pay equal attention to bow and twist, and if the bow is substantial, with convex side down, bring down thickness at both ends, stopping part way through, then doing end-for-end swap, until the bow is less than 2mm or so, then revert to the process mentioned above.

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David Best

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On Mar 21, 2021, at 2:42 PM, David Luckensmeyer <dhluckens@...> wrote:

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Hi Imran:

There is a common misperception that “minimum down force” is desirable for a jointer.?

I think this is wrong thinking arising from users who take many light passes to flatten a board. In such a scenario, where a light pass is taken that does not flatten a board all-at-once, the board being machined would not rest flat against the outfeed table, and therefore be forced flat under the feeder, only to spring back afterwards. This leads to frustrating results.?

Best practice for jointer machinists, using a feeder, is to set the depth of cut to flatten the board all-at-once, to approx 75% of the board’s surface. This achieves a flat board very quickly, and good down pressure can be used with the feeder. This is safer (no slip) and the results are superior (i.e. flat, consistent results).

For scenarios where the jointer’s capacity is not up to the job (e.g. minimal horsepower, or the cup/bow/twist is beyond the jointer’s maximum depth of cut), then the offending board should be machined partially by hand, by moving the feeder aside (or working beside the feeder if there’s space) and machining part way along the ends (twist or bow), or pushing the board all the way through (cup — concave side down). The former is done easily by pushing a board through say 1/4 to 1/3 of the way, then lifting the board off the cutterhead, swapping end for end, and machining 1/4 to 1/3 of the other end, to eliminate most of the twist or bow. The latter is easy enough to do, even for large boards, because most of the board is not engaged in the cut (only the outer edges of the cupped board), and so can be pushed through manually.

This process prepares the worst boards to a “flatness” that allows the feeder to be used for that single, final feeder pass, which gets the board flat. By the way, short boards, say 600mm or shorter, which cannot be flattened all-at-once, should be discarded from the shop and project, or they should be partially flattened by hand (scrub plane). Short boards should not be partially machined by hand in the above manner, as the operator is working too close to the cutter head. User discretion required here.?

Minimum down force is irrelevant.?


Warm regards,
David Lucky

On 21 Mar 2021, at 11:21 pm, imranindiana via??<imranindiana@...> wrote:

?Apparently, a modification is offered by Western Roller where a belt can be installed on PF - pic from their website



Would this work better on PF for jointer where one wants minimum down force?

Imran

On Mar 21, 2021, at 9:01 AM, imranindiana via??<imranindiana@...> wrote:

?There are lots of msgs here and it appears durometer 60 is the most common recommendation. However, I saw durometer 50 is also available.

I need to replace wheels on shaper and jointer PF. Both have factory wheels. What is the durometer recommendation?

Axiom Industries and Western Roller Corp are the 2 places recommended.

If we have a sort on consensus, I can create a hashtag msg with details so it is easy to find.

Imran












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