Helical head for 8" jointer?

[Zach Duran]

hello all.
I have an 8" Powermatic jointer with a 3 straight knife cutterhead. I have been considering buying a helical head for it, but I am wondering if the money would be wisely spent? Seeing as how the jointer is the first tool for lumber to hit, doesn't the benefit of the smooth cuts of a helical head get lost down the line of milling? After milling the first face flat, and then getting a true 90 degree edge, the lumber is further milled down with a planer and table saw. Once it hits the planer, I mill it to thickness, flipping the board over after each pass to remove the same amount of wood from each face. Therefore there will be no inconsistency with moisture content from each face. So that first face flattened by jointer is irrelevant, right?
So wouldn't the investment into a helical head be better served for the planer? In a perfect world, I suppose I would have both, but I'm afraid the wallet will not allow for that. What are your thoughts?

[Allan Speers]

As you say, not needed in terms of surface quality. Although I suppose with some highly figured woods, you might get deeper tera-out than you'd want to deal with, even if that surface will later be planed.

The main reasons to go helical, IMO are noise & easier chip collection.

If you're not in a garage-shop, with neighbors that complain, and you have at least a 3 HP cyclone, then I'd probably say keep the knives.

Of course, there's also the issue of knife maintenance, so....

[Zach Duran]

Ahhhh knife maintenance. Probably the best reason to just pull the trigger on a helical head. Thanks for that reminder of reality!

[Andrew Hughes]

There’s a lot more feed pressure with the helical Head. So if your facing boards too thin you might find it tricky to get them flat.
Carbide doesn’t get as sharp as good HHS .
I have a one in my planer and sold the jointer with a hh Head.
So I give it a thumbs down.

[Matt Day]

Save the money for the planer, if anything. How often do you really change knives? And if you have some mechanical ability and understand how the machine works, knife changes really don’t take that long.

Wasted money in the jointer if you ask me, unless you have enough money sitting around that you’re not worried about wasting it.

[Dave Zellers]

It seems to me you answered your questions and answered them correctly. I have always operated with the opinion that a jointer cut will almost never survive to the final project. My 8" jointer is used to flatten stock and from there the stock is almost always thicknessed on the planer both sides. Often using numerous passes as I sneak up on the final thickness. As Andrew said, sharp steel knives give amazing results. If you don't have the means to sharpen your own knives, buy a second set and send the dull ones out to be sharpened right after you swap them out.

[Mark Carlson]

Planer would be better. I faced the same choice years ago and upgraded my jointer only because I hated adjusting jointer knives. Still havn't rotated the inserts but its getting close to time.

[Daniel Dioguardi]

There have been times the finish of the cut has been appreciated.. like when I made some drawers a smidge too tight to fit and instead of sanding them all I was able to bring them to size with a light pass or two on the jointer.. no harm to my joinery which I was rather fond of. And the shavings are smaller and less likely to clog my ductwork. Straight knives will certainly do the job, but every so often I am thankful to have the helical.

[Brad Chenoweth]

There’s a lot more feed pressure with the helical Head. So if your facing boards too thin you might find it tricky to get them flat.
Carbide doesn’t get as sharp as good HHS .
I have a one in my planer and sold the jointer with a hh Head.
So I give it a thumbs down.

Hi Andrew,

This is an oft-repeated statement that I don't quite understand. I've always considered carbide saw blades and router blades to be sharper than the equivalent HSS ones. Also, my 38 years of machining experience (albeit in metals) leads me to the same conclusion. We often have to "stone" or slightly dull carbide tooling in order to prevent chatter that is the result of the tool being "too sharp" The same tool made from HSS does not require this step. I think this is one of those things that has become accepted as fact because it's so often repeated. I'm not sure it would stand up to actual testing. Qualifier: I don't have any experience with a helical head on the jointer.

Brad

[Mark e Kessler]

There is more resistance on feeding a jointer with a helical head for sure but I have a 16" J/P with Helical and do not find it that big of a deal and that is facing a 15" board.

I get pretty much zero tear out, I dont hardly ever even pay attention to grain direction anymore, and it is amazingly quiet...

If I was buying separates my jointer more than likely would be a straight knife and planer a Helical unless maybe I had a wide belt then probably straight on both.

also if you do a retrofit buy a true helical like the Hermance HelixHead...


mk

[Robert Engel]

As with many things, a lot depends on your method of work. I'm not concerned about a perfect surface as I run it though a drum sander.

For me, the biggest advantage is not worrying as much about grain direction. Example, when jointing for a panel glue up, I typically do "face in face out". I can run either face against fence without worrying about edge grain direction.

Another advantage is the cutterheads last much, much longer than blades. I didn't rotate mine until almost a year of use.

Yes they theoretically require more power, but I've never seen an issue with that I'm never taking more than 1/16 per pass.

I agree re: more advantageous in a planer, but in my case a 20" helical is ~$1K.

[Andrew Hughes]

It’s more complex then the carbide or hss steel used .
In a nut shell a insert head doesn’t have as much forward rake.
If you feel like geeking out on how a knife jointer cuts and a insert head cuts. Start buy figuring out what hook angle your jointer head is. Then what sharpness angle is on your knives then what the clearance is between the wood and the bevel.

Then apply the findings to a insert head.
Heres a pic to get you started.

[Brad Chenoweth]

Andrew,

All good points. As a manufacturing engineer, I do have a grasp of the rake angle, clearance angles, etc. I admit, I never considered that that the rake angle is less for the carbide inserts (I don't know what that exact angle is for the insert heads). They do usually incorporate a shear angle as well, which helps. My comments about tooling for brass, steel, etc. relate to tooling with the exact same cutting geometry, just different base materials.

I still don't agree that carbide isn't as "sharp" as HSS.

My experience indicates otherwise.

[Andrew Hughes]

Fair enough Brad I respect your understanding. I can see how your understanding would apply to the machining of metals.
I have my experience in wood both hand tools and machinery for wood.
I wish I had more experience with metal machining.
But I don’t

Good Luck

[Rob Damon]

I have a 8" PM that came with straight knives that I changed to Byrd head.
- Huge difference in sound level.
- No difference in pressure needed to push the wood. Would be on the 16" jointer I also have.
- Not as concerned about grain direction anymore
- The 2 hp motor is more than enough power to drive the bryd head
- Would never go back
- I use jointer to face joint first face but it is never the final face surface as I flip the board when planing and finish scrap/ sand prior to finishing
After upgrading the jointer I upgrade my 20" PM planer.