carbide inserts, why I don't change

[tablesawtom]

In the METAL CUTTING  industry the rule of thumb for horse power needed for carbide inserts  is 1 1/2 horse power per insert.  A 3 inserted face mill then requires 4 1/2 horse power to use the cutter efficiently. There are other things that factor in also, like depth of cut and feed rate. The feed rate calculated by chip load per tooth times the number of teeth times the rpm. and to drive the cutter. Therefore, the deeper the cut the more power power  is needed to drive both the spindle RPMs and power at the gear box. IN other words the more weight you are going to haul, the bigger the truck you should have. There are a lot of other things that  factor in, like how to remove cubic feet of metal the fastest like less depth of cut verses much faster feed rates and modern cutter technologies. 

High speed cutters on the other hand are sharper than inserted carbide cutters therefore requiring less horse power. And because the cutter is sharper it also requires less horse power to feed the cutter. And lighter depth of cut requires even less horse power to drive the feed rate. Fact: it is easier to cut yourself installing a a high speed jointer knife than changing a carbide insert on the cutter head.

I hope everyone will agree with me on the fact that a board can not be flattened on a planner. If a board is cupped, bowed, or twisted going in to a planner it it will be cupped bowed or twisted coming out of the planner. The reason being that the pressure rollers and the cutter head flatten the board in the planner but only mechanically. The bow for example return once the pressure is relieved.

The only time I actually tried out a carbide cutter on a jointer i noticed how much more pressure it took to move the wood a crossed the cutter. In other words it takes more downward pressure to move the wood a crossed the cutter. I watch some on TV and it looks like they have their elbows locked when using it. Now, one can remove a cup from a board with this method and if careful a twist somewhat as long not as to much pressure is used, but if you have to apply any downward pressure at all in the bowed section while running it a crossed a jointer then,  when a bowed board is flattened on the jointer table during the cut ( the same thing happens  as in the planner ) and the bow will return when the downward pressure is released. 

My jointer is a 8 inch from Sunhill. It is at least 30 years old. It came with what I believe is a 1 1/2 HP motor. It is possible it could be a 2 HP motor because it is 220 volt but i don't think so. It is snowing right now and my shop is a mile away and unheated and I don't feel like going over to an unheated shop and move the jointer out of its position so I can take the back of the machine off just to find out. MY point is today the inserted cutter head machines are 3 HP not 1 1/2 or 2.  And before you jump to conclusions and say the straight knife machines are also 3 HP it is because they use the same motor and pass the extra cost on to you and pass it as an upgraded  ( Better) selling advantage.

I indicate my knives in so there is no more difference in height that 2 thousandths in total runout on my indicator. they are also indicated in straight with the outfeed table. In other words I have all three cutters working and I don't have 2 sharp cutters and one dull cutter that is doing all the work. Once my fence is squared to the outfeed table it will remain squared to the table until I change knives.

My depth of cut is .015 ( 2 passes is a 32th. And I use a push stick like on a table saw and can push a board as long as my infeed table is with one hand.

And this is why I will not spend an extra $400 plus for a carbide upgrade for my jointer bit I will spend$275 for a dispozablade system. disposablade.com

[tablesawtom]

An inserted carbide cutter head on a thickness planner is a different story It would be nice to have.

Tom

[merced]

That's is a lot of good information, and a few things I hadn't thought about (but should have).

My introduction to woodworking one or two hundred years ago was in junior high and high school shop class.  The first semester was limited to work with hand tools, mostly so we could practice not injuring ourselves with dangerous things like pencils, or for some of us, erasers.  The tools were fiddly and kind of awkward to use, and we had our hands on them just long enough to get to a result that looked something like what we set out to do.  We never really learned how the tools worked, how to tune them, or how to take care of them.  Then we moved on to power tools.  So easy to use!  Clean cuts every time!  That introduction reinforced the mindset that brute force could always make up for a lack of finesse.

I've gotten reasonably good at hand tool work.  It only took me a few decades of futzing around to figure out that it's worth the trouble of setting up a tool to do its best to get the best results, and that how you go about doing something makes a difference.  Using a plane or a chisel that is right for the purpose, maintained and adjusted to do what it was designed for, is a joy.  

Naturally, because I'm an obedient customer of the tool industry, I have a shop full of power tools with more than enough horsepower for anything I'll ever need to do.  They're fun to use.  But you remind me that they're just tools, and even beyond setting them square and using them safely, you need to think about how they do what they do, and why.  Of course that's something I've known for a long time.  Still, it's all too easy to slide back into the mindset that having a powerful machine relieves you of having to understand what will happen to your lovely piece of wood when you let it do its thing.  Apart from giving me some solid new-to-me technical information, your post is a great reminder that thoughtful woodworking is good woodworking.

Thanks Tom.

Dave

[Woodshop]

I have carbide cutters on my jointer have no problems. But on my push blocks I have GRR-RIP BLOCK Smart Pushblock they have hooks on the end that hook the back edge of the board. so you use one to hold the front down and the back one to push. very safe with light pressure works great.
love the carbide cutters the seem to stay sharp forever. but you are correct they do take a bit more HP. My old 20" planer came with a 3 hp . I put on a 5 hp when I add the carbide head. now it kicks but.
Don

[lift mechanic]

I have the spiral cutter head on both my jointer and planer. When I notice jointer getting a little harder to push the material over the bed I give it a spray of lube. Makes all the difference in the world. I normally spray the infeed and out feed tables and fence at the beginning of each large project. I have tried several products. Lami-Lube III works well, Bostik's GlideCoat seems to work the best and I tried ProtecTool works good but is harder to buff out after applying. All of this stuff wears off after some use and needs to be reapplied.  The reasons to rotate the cutters is noticing some tear out or a line on the planed surface meaning a nicked insert.

[Aram]

My jointer came with knives, which I used for years, then upgraded to Byrd. It's harder to push a board, sure. But if I keep the beds waxed, it doesn't take excessive pressure. I've straightened wide, bowed boards on it. No issues so far. YYMV.

[BC in CT]

I use the jointer to flaten one face and true up an edge. After that the final psses on both sides of the board will be with the planer, so I don't see the need for using carbide inserts on the jointer. Just my perspective.

[®smpr_fi_mac®]

Meh.

Okay.

I'll put a carbide head in my jointer eventually because they handle curly wood very well.

I have a carbide head in my planer and friggin love it because it performs well AND it's quiet.

My jointer has a 5hp motor, my planer a 3hp.

The 16" PM planer I'm getting later this year has a 5hp motor. I'll put a carbide head in it, too.

[EdL]

20+ miles out of my way to get sharpening done.....insert head on the jointer was an easy choice.

Ed