Spiral vs helical vs straight knives

[Cian]

It sounds like you're saying if you have a helical head, you can skip the drum sander.  Is that right?

I have an 8" jointer with a Shelix head and also a Grizzly 15" planer with the factory helical head. The planer does the final surfacing of visible surfaces through the normal course of operations, and I often go straight to finishing with no sanding needed.  I primarily mean cabinet faces and drawer fronts.  However, I do use my drum sander for thinner materials as Frank mentioned or cleanup of reclaimed lumber.

[jteneyck]

I have an 8" jointer with a Shelix head and also a Grizzly 15" planer with the factory helical head. The planer does the final surfacing of visible surfaces through the normal course of operations, and I often go straight to finishing with no sanding needed.  I primarily mean cabinet faces and drawer fronts.  However, I do use my drum sander for thinner materials as Frank mentioned or cleanup of reclaimed lumber.

It's hard to imagine a planer of any type that doesn't leave compression marks in the wood.  With the segmented head they will be dispersed, rather than in a continuous line across the board like with straight knives, so maybe they are small enough not to notice.  Count me skeptical, however.  I'd love to see some photos of work you've stained or dyed.  

John

[Cian]

It's hard to imagine a planer of any type that doesn't leave compression marks in the wood.  With the segmented head they will be dispersed, rather than in a continuous line across the board like with straight knives, so maybe they are small enough not to notice.  Count me skeptical, however.  I'd love to see some photos of work you've stained or dyed.  

John

Hi John - 

Your skepticism is 100% warranted. I was coming from a straight blade jointer and portable planer too.  Also, likely my standards aren't as demanding as most, but here are pics of my shop built-in drawer fronts. I didn't want to obsess over them given they were just for the shop, but after they came out of the planer, I thought, "Wow, that's plenty good enough..." and just applied a finish. Admittedly the shellac may have smoothed them out even further but they had such an impressive sheen coming out of the planer like as if they were hand planed.  The last pic is some brazilian cherry (or walnut?) that was resawn and just put through the planer to remove the bandsaw blade marks.  Apologies but I normally do smaller pieces so maybe your assumptions are correct and that larger stained surfaces wouldnt pass the muster.

   

   

   

   

[Tapper]

I have an 8" jointer with a Shelix head and also a Grizzly 15" planer with the factory helical head. The planer does the final surfacing of visible surfaces through the normal course of operations, and I often go straight to finishing with no sanding needed.  I primarily mean cabinet faces and drawer fronts.  However, I do use my drum sander for thinner materials as Frank mentioned or cleanup of reclaimed lumber.

I have the same setup, Shopfox brand on both. Bought the 15" planer with the Grizzly head already installed. Bought the 8" jointer with straight knives; replaced it later with a Byrd cutterhead. Recently rotated the inserts on the Byrd head for the first time after many years of usage.

No discernable difference in the cut quality between the two IMO. Would NEVER go back.

Doug

[jteneyck]

Hi John - 

Your skepticism is 100% warranted. I was coming from a straight blade jointer and portable planer too.  Also, likely my standards aren't as demanding as most, but here are pics of my shop built-in drawer fronts. I didn't want to obsess over them given they were just for the shop, but after they came out of the planer, I thought, "Wow, that's plenty good enough..." and just applied a finish. Admittedly the shellac may have smoothed them out even further but they had such an impressive sheen coming out of the planer like as if they were hand planed.  The last pic is some brazilian cherry (or walnut?) that was resawn and just put through the planer to remove the bandsaw blade marks.  Apologies but I normally do smaller pieces so maybe your assumptions are correct and that larger stained surfaces wouldnt pass the muster.

Thanks for the response, Cian.  I certainly can't argue with how those pieces look, probably the best I've ever seen straight off a planer.  Your comment though about the "impressive sheen" gives me a little pause, however.  At least in a straight knife planer, that sheen is indicative of the knives compressing the wood fibers behind the cut.  It would be interesting to see how something coming off your planer responds to stain and dye compared to one that also was sanded.  

If it wasn't for the power limitation I have with the motor on my J/P, I might have to reconsider a segmented head.  MiniMax put a 3 KW motor on my 14" J/P, and you would think that would be enough, but it can't take off more than a little over 1/32" w/o bogging down.  It would be definite no go with a segmented head, so I'd have to replace the motor as well, and then I'm looking at a $2K investment.  Oh well, that's another story.  

Thanks again. 

John

[Cian]

It would be interesting to see how something coming off your planer responds to stain and dye compared to one that also was sanded.  

As a general rule, I do align with you and believe a sanded surface would embrace staining and dyes more agreeably than a planed surface - hand or machine.  However, I rarely if ever use stains and primarily stick (pun intended) with shellacs and poly which just sit on the surface. 

Along these lines, there was a debate a long time ago about the surface quality produced by different index cutter head designs - angled vs skewed, more teeth vs less, etc.  The head in my jointer is a genuine Shelix with the skewed teeth. My planer head is also like the Shelix in that the cutters are askew slightly in relation to the direction of the feed.  It was early on in the appearance of these "fancy" heads when I first bought the planer, but this was one of the main reasons why I chose this particular Grizzly model vs others in their lineup simply based on Shelix' marketing - valid or otherwise (plus I got info from a knowledgeable source that this particular planer was produced on the same factory line as the PM equivalent but that's another matter).  Over time, I think the conclusion was made that the variation in output quality between index head designs was neglible. 

   

[Bob Vaughan]

Straight knives take a whole lot less horsepower when sharp.
Straight knives get a bad rap because the users don't change them often enough.
A week ago I changed the knives in my 8" jointer.  I hit go on a stop watch and walked over to the jointer.  Forty minutes later the jointer was buttoned up and ready to go.  The actual changing time using a dial indicator was about twenty minutes.  My 18" planer takes nearly an hour to change knives if the settings haven't changed.

Below is what sharp knives in a 6" jointer product from hard maple. (I just happened to have this photo since this was on a jointer I was selling)

   

[jteneyck]

Straight knives take a whole lot less horsepower when sharp.
Straight knives get a bad rap because the users don't change them often enough.
A week ago I changed the knives in my 8" jointer.  I hit go on a stop watch and walked over to the jointer.  Forty minutes later the jointer was buttoned up and ready to go.  The actual changing time using a dial indicator was about twenty minutes.  My 18" planer takes nearly an hour to change knives if the settings haven't changed.

Below is what sharp knives in a 6" jointer product from hard maple. (I just happened to have this photo since this was on a jointer I was selling)

No question sharp, straight knives use less HP than a spiral head and, in friendly wood, produce a finish at least as good and usually better.  The benefit of a segmented head is it's quieter than straight knives and produces less tear out in difficult wood.  

My experience changing the knives in my 14" MiniMax J/P is consistent with your experience, maybe a little faster.  It takes about 30-40 to take out the three knives, sharpen them on a knife grinder, and reinstall them.  If I'm installing fresh knives, it's 15 minutes.  The machine has its own knife setting jig, so it's nearly a fool proof process.  I've tried using fresh knives in wood where the old knives were causing tear out.  There was less tear out, but still some.  I get around the problem by stopping short and finishing the thicknessing on my drum sander.  That works, but clearly there's an advantage for a spiral head.  

John

[Derek Cohen]

I have had a Hammer A3-31 for close on 8 or 9 years now. This is still on the original set of carbide inserts, with one more turning to go. The finish is very superior, without any suggestion of snipe, and all this in very hard and abrasive West Australian hardwoods.

The digital gauge on the thickness-planer means that sizing is super accurate and repeatable.

The fact that the finish is flawless is also not as important as it may appear since I hand plane or sand all final surfaces.

Regards from Perth

Derek

[tablesawtom]

I am a Tool and Die Maker by trade. I have a lot of experience with indexable carbide inserts, but my experience is in cutting metal not wood. Interrupted cuts are the worst , which is what a jointer and planners are. If one is uses one to side mill with, the surface finish looks' like Bucky Beaver chewed it off. Before you even get started I am not talking about production CNCs with 25-50 HP at the spindle and through the tooling cooling with enough pressure to blow the chips out. I am talking about manual machining which is how you are doing it.  If you think that every pocket of every cutter head will be exactly the same it is imposable. And inserts are sintered and are as sharp as they are going to be when the manufacturing process is complete.

The datum on a jointer is the outfeed table, not the cutter head, but the cutter head determines everything.  The cutter head may or may not be in line without feed table. With the planner the datum is the machine bed not the cutter. If you actually measure each side of a board you will find the board is not as parallel as you thought.  I could write a book on this but, you can read between the lines.

Actually I have two planners ( a 15 and a i3 inch ) with straight knives and two jointers (a 8 and a 6) with straight knives. I am rebuilding the 6 and I am trying to decide if I want to purchase a inserted cutter head or not. I tried a jointer with an inserted cutter head and I found it took a lot more pressure both down as well as feed pressure in the cut. Know all three my knives are set parallel to the outfeed table within .002 TIR (total indicator read out run out) and my infeed table is set .0156 below the outfeed table. I would rather take lighter cut which require no or very little downward pressure and the feed pressure is with one hand. (this is finish passes not roughing) If you are going to rough ,rough everything, if you are going to finish, finish. they have nothing in common.

I prefer knives and probably won't change. Probably because of age verses cost. I sharpen my own knives on a surface grinder so there is no cost. If I were to get an inserted cutter head it would be on the planner, that is where most of the material is removed and high speed knives get duller faster. 

There are advantages and disadvantaged to each type of cutter head. Some people can't or don't want to change knives so it is a another reason for an inserted cutter and if so it is the way to go.

So in closing if you have the money and want either type buy it. 

Tom