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Just a basic jointer question...

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2 hours ago, Unknown craftsman said:

I bet they don't stay sharp very long. Since insert heads are mostly a scraping cut just like a high angle scraping plane. 

Aj

Do you have literature on this? I don't understand how the cut angle could be forward to mimic that of a scraper when the bevel angle of the inserts is less than 90. I've done a lot of research to make sense of this claim and can't find anything.

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14 minutes ago, derekcohen said:

You could always just try feeding it from the left :o

Regards from Perth

Derek

I believe that would be a one time experience, if you managed to keep your fingers.

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2 minutes ago, RichardA said:

I believe that would be a one time experience, if you managed to keep your fingers.

Just wire it to spin the other way ;)

 

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1 hour ago, derekcohen said:

You could always just try feeding it from the left :o

Regards from Perth

Derek

In think they automatically spin the other direction when south of the equator.

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3 hours ago, Chestnut said:

Do you have literature on this? I don't understand how the cut angle could be forward to mimic that of a scraper when the bevel angle of the inserts is less than 90. I've done a lot of research to make sense of this claim and can't find anything.

I agree, it seems counter-intuitive.  These helical heads are supposed to cut smoother than knives, yet at least in wood turning a scraping cut leaves a much rougher surface than does a shear cut.

Also if you look at the helical head mounted in the machine from the side, the backs of those cutters are very nearly parellel to the wood surface which would give a shearing cut.

 

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1 minute ago, Llama said:

I get my toilet paper from woodworking magazines like a real man. :) 

So this is how they make their toilet paper? Man, that's amazing.

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@Chestnut I tried to find info on the Bryd head so I can better understand but it's just not available.

But I can share with you that adding a facebevel to jointer knives to reduce the cutting angle is easy info to find online.

I will now share why I compare a jointer to a handplane. We all know that handplanes have different bed angles that are better or worse on different woods.Jointers have what's called a hook angle. That's the angle that the knife or insert is held in the head. Since that cannot be changed someone who makes the head has to decide. Do we make it favor  hard or soft wood or something in between.Usually in between. Lower hook angles a better for hardwoods and the higher the hook angle for soft woods.

Here is a example of how I set up my jointer that has  a hook angle of 38 degrees.

I sharpen my primary bevel at 42 that gives me 10 degrees clearance in between the cutting circle and the wood. If I sharpen a 10 degree face bevel on my knife I can reduce the cutting angle to 28 and reduce tear out. But what happens is that bevel acts like a chip breaker. And in a way compress the wood fibers instead of scooping them out. This takes more feed pressure and motor power. And wears the knife faster more heat I think.

Theres other reasons I like straight knifes in a jointer.Thats for another day.

The beauty of the Bryd insert is skew angle and the slight radius on the edge. I like the Bryd head but only in a planer.

If you can figure out the hook angle in a Bryd head please share. I wouldn't  be surprised if it's somewhere between 0 and 10.

Aj

 

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Guest Randy

A lot of good answers and some, well maybe have some qualifications.

I owned a 6" jointer (and not even a long-bed jointer) for 30 years before upgrading to an 8" helical head jointer. I did just fine edge jointing and even face jointing some 6" or less boards. Was it easy? No. Did it always turn out perfect? No.

For at least the last 10 years I had a 13" planer. Sometimes I could get away with lightly planing the first side on wide boards; then the second side - continuing to plane each side lightly until at least one side was flat enough to finish plane the board. Did this always work? No, but often enough that I was successful doing this most times. I just was careful about the boards I selected for projects; nothing too warped, cupped, or twisted.

Can you face joint 6" of one side of a board wider than 6"? Sometimes this works as long as the board isn't more than 8" wide. It isn't the safest thing in the world to do but, with the proper push pads, it does work. It's not something I have done much but sometimes it was the best way to do it. Plus, recently I found the same opinion from several professionals online, so I think it's an OK thing to do once in awhile.

There are some who feel that ripping boards to 6" is a good idea anyway as it makes it less likely that they will cup over time. Maybe. Maybe not! It works but it probably isn't necessary with properly dried wood.

Is an 8" jointer a great tool? Absolutely and I would completely agree that, if you can afford it and have the space (although an 8" jointer really doesn't take up that much more space than a long-bed 6" jointer).

Regardless, I would also recommend buying the best jointer you can for the size  you select. For example, if you can afford a Powermatice helical head as opposed to a Jet helical head, I'd spend the extra money. Don't ask how I know. The less expensive Jet will do the job well, but the Powermatic is just a better machine and, I feel, made a little better.

None of these answers are meant to be the law but they have worked for me over the years. Always get the best machine you can afford or, if you can find a great used machine that doesn't require a lot of restoration work, that can be a great option also.

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On 11/9/2017 at 5:47 AM, gee-dub said:

I use a lot of figured material.  The prevention of tearout and the lower cost of ownership over time of an 8" helical head jointer and a helical head planer have long since paid for themselves and reaped benefits ever since. 

Topic tangent -- using a lot of figured material.  How is the best way or options to prevent tear out on figured wood?   I have been playing around with some highly figured walnut and some moderately figured Maple.  Pretty much resigned myself to foregoing the planer (regular head, no helical head) and just using many passes through a drum sander.

Same question on resawing.  The place I buy stuff from cuts primarily 8/4, 10/4 and 12/4 stock so I am able to resaw into 3 or 4 pieces.  Any hints for avoiding tear out resawing on a band saw?

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13 hours ago, Unknown craftsman said:

If you can figure out the hook angle in a Bryd head please share. I wouldn't  be surprised if it's somewhere between 0 and 10.

I'd argue they are not very different if not the same. I couldn't find the Byrd patent but i found another segmented cutter head patent. Angle A in figure 1 is your hook angle and grinding a back bevel decreases that angle closer to zero. A scraping cut is a cut with an angle of zero or negative. Figure 10 shows the profile geometry of a spiral cutter head and figure 6 shows the angle on the face of the insert. The angle on the insert is greater than that of A in figure 1 but the top dead center of the cutter is about 10 degrees back making that angle slightly steeper.

If what you are saying were true it would take more power to do the same cut on my 735 and that is defiantly not the case. I honestly think the cutting angle on the segmented heads is shallower than that of a strait knife head because it takes less power to do the same cut on my 735. I wish i had an easy way to measure the angles but i don't so i rely on the parents and information i can find online.

 

cutterhead_knife_angles.jpg.ca562ab010d025bcf4dd3dbdd21c5e60.jpg

Figure 1.

US07708038-20100504-D00006.thumb.jpg.550dab576d7d2ba60880a2667957fc24.jpg

US07708038-20100504-D00005.thumb.jpg.70c29dfbc79a8c8bb7dd4edf48cc6cac.jpg

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22 minutes ago, SCPDX said:

Topic tangent -- using a lot of figured material.  How is the best way or options to prevent tear out on figured wood?   I have been playing around with some highly figured walnut and some moderately figured Maple.  Pretty much resigned myself to foregoing the planer (regular head, no helical head) and just using many passes through a drum sander.

Same question on resawing.  The place I buy stuff from cuts primarily 8/4, 10/4 and 12/4 stock so I am able to resaw into 3 or 4 pieces.  Any hints for avoiding tear out resawing on a band saw?

West Australian hardwoods are very interlocked. I've also just completed a kitchen using USA moderately figured Hard Maple. All these woods are easily thicknessed and planed with my Hammer A3-31 with spiral heads. These are true spiral heads, where the cutters are angled to the work, and cut with a slicing action.

If I did not have the Hammer, I would happily use hand planes. These will not only would much faster than any sander you care to use, and leave a finish that cannot be matched by a sander.

Regards from Perth

Derek

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1 hour ago, SCPDX said:

Topic tangent -- using a lot of figured material.  How is the best way or options to prevent tear out on figured wood?   I have been playing around with some highly figured walnut and some moderately figured Maple.  Pretty much resigned myself to foregoing the planer (regular head, no helical head) and just using many passes through a drum sander.

Same question on resawing.  The place I buy stuff from cuts primarily 8/4, 10/4 and 12/4 stock so I am able to resaw into 3 or 4 pieces.  Any hints for avoiding tear out resawing on a band saw?

Sounds like a job for a card scraper. I've had good success using card scrapers around knots and other highly figured wood locations, and they can be as fast or faster than sanding, without all the dust.

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3 hours ago, Chestnut said:

I'd argue they are not very different if not the same. I couldn't find the Byrd patent but i found another segmented cutter head patent. Angle A in figure 1 is your hook angle and grinding a back bevel decreases that angle closer to zero. A scraping cut is a cut with an angle of zero or negative. Figure 10 shows the profile geometry of a spiral cutter head and figure 6 shows the angle on the face of the insert. The angle on the insert is greater than that of A in figure 1 but the top dead center of the cutter is about 10 degrees back making that angle slightly steeper.

If what you are saying were true it would take more power to do the same cut on my 735 and that is defiantly not the case. I honestly think the cutting angle on the segmented heads is shallower than that of a strait knife head because it takes less power to do the same cut on my 735. I wish i had an easy way to measure the angles but i don't so i rely on the parents and information i can find online.

 

cutterhead_knife_angles.jpg.ca562ab010d025bcf4dd3dbdd21c5e60.jpg

Figure 1.

US07708038-20100504-D00006.thumb.jpg.550dab576d7d2ba60880a2667957fc24.jpg

US07708038-20100504-D00005.thumb.jpg.70c29dfbc79a8c8bb7dd4edf48cc6cac.jpg

I see what your saying,I should said the effective cutting angle. I think it's also called the rake angle.

I did measure the front bevel on a Bryd knife and it looks like it's somewhere around 30 degrees.

@derekcohen that's a nice machine I almost bought one. In the Manuel does it say what the max depth cut is ?

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6 hours ago, Unknown craftsman said:

that's a nice machine I almost bought one. In the Manuel does it say what the max depth cut is ?

I'd like to know this as well.

I looked through the Felder manual. I didn't see it in there because I think the answer is (as usual) it depends...

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I work with very hard woods. I hesitate to take a deeper cut that 1.5mm most of the time. I think that the maximum depth of cut is 3mm. 

Regards from Perth

Derek

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