Shaper speeds?

[Beechwood Chip]

I've only ever used routers, but I'm considering getting a shaper instead of a router table.  I think I'm seeing some apples to oranges comparisons, which I hope someone can explain.

 

A Triton 3.25 HP Router is a good choice for a router table.  It has 3.25 HP, soft-start, 8,000 to 21,000 rpm variable speed.

 

The Grizzly 1035 shaper has 1.5 HP, and only two speeds: 7000 and 10,000 rpm.

 

Will the lower HP of the shaper be a problem?  Or is this a case of HP numbers not meaning much?  Will I miss the higher speeds when using smaller router bits in the shaper?  I imagine I'd need to use a slower feed rate to get a smooth cut.

 

It makes sense that you don't need "soft start" on a 200 lb stationary machine.

 

Thanks for any insight you can offer.

[dwacker]

First HP on routers is sort of fabricated. When you slow a router you no longer have near the stated HP.  No you will not want to run all router bits on a shaper. Some do well others do not. No the lower HP will not be a problem on the shaper as long as you don't try to run big cutters that need more HP. Most any carbide cutter can be run on a small shaper. I would suggest still having a small router table with something like a PC690 for those times that you need a router. Even a small wing added to the shaper is fine. You should not need a big router since you would have a shaper.

[Beechwood Chip]

Thanks, PB.  I figured that you could give me the straight dope.

[Eric.]

I was watching one of krtwood's videos last night, and his shaper bogged down cutting some simple finger joints...to the point where he had to back off and make several passes.  I don't know what model he has, but it surprised me...I thought even the smaller shapers were supposed to eat some material.

[dwacker]

I was watching one of krtwood's videos last night, and his shaper bogged down cutting some simple finger joints...to the point where he had to back off and make several passes.  I don't know what model he has, but it surprised me...I thought even the smaller shapers were supposed to eat some material.

 

Got a link?

[Dan S]

Got a link?

 

 

all end grain cherry, so I'm not surprised. A shaper isn't a miracle tool. 

[dwacker]

If you listen to the video you can tell that the cutters are dull and to small of diameter for the cut. The spindle looks to be maxed out or close to it. Either way he got the job done just needed an extra pass. 

[customwood montrose]

One thing to consider, a 3/4" router bit spinning at 20000 RPM compared to a 2" diameter shaper cutter at 10000 RPM. Tip speed will be about the same, I don't have the exact numbers though. On a small shaper of the size you are talking about, I run cutters up to 3" cutters with a small to medium cut depth and not have any problems. Cutting a raised panel profile, I would do it in steps of cut depth anyway. Power, a small shaper will out perform a router any day of the week. Dustin

[T-astragal]

I've never used a shaper smaller than 3 hp, so I don't know. But if you could spring for a bigger model you'd be most impressed. Get a corrugated knife head and buy used knives on eBay for pennies on the dollar.

Steve

[dwacker]

You have to keep these discussions in perspective to do anyone any good. These 1.5hp hobby shapers are great little machines. They are designed to run SINGLE hobby cutters. Fortunately today they are cheap and easy to find. You can waste brain cells doing all the math to optimize your set up but unless you have a regulated feed method and a wide range of cutter diameters available your wasting your time. This techno bable is for production work with shapers, moulders, and saws pretty much any cutting tool being power fed for extended runs. Not so much with shapers since they really are not a production machine.

The hobby cutter are all carbide. Carbide is never as sharp a HSS but will hold what edge it does have longer. The hobby cutters are actually dull by comparison. This does not mean they won't get the job done and do it better than any router. It means you can't go hog wild and fill up a spindle as shown in the video above. 

You can make up for lack of power and cutter quality by increasing rim speed as Dustin mentioned above. When you start stacking these hobby cutters on a hobby shaper you either have to take more passes or make up the difference. You can't add HP but you can add rim speed by adding cutter diameter. The cutters shown in the video are small groovers or rabbeting cutters designed to be used two at a time on edge/face work or one at a time as a groover. I have no idea what the diameter is probably under 3". Rim speed of a 3" cutter at 10K rpm is 7850 FPM. Upping the cutter diameter to 4" increases the cutter speed almost 3000FPM. In short if your going to push your small shaper and make these cuts in a single pass you need to increase something. You can't just go willie nillie and start stacking cutters without putting at least some thought into what you are doing.

Steve mentioned corrugated cutters and I agree they king on short runs but if you have or are thinking about a hobby machine just get it out of your head you can't run these cutter. The cutter blocks are heavy my smallest block weighs nearly 5 lbs They will destroy your spindles and spindle bearings very quick. Even if you took very light passes the weight will trash a little shaper.

A 1.5 HP shaper is plenty for most hobby folks but you just need to keep things in perspective and not loose sight of what your working with. 

[Eric.]

Good info to have, Don.  But it kind of throws a wrench into the router vs. shaper debate, at least for me, since I thought one of the big advantages of the shaper was the ability to remove more meat at once without bogging down the machine.  So apparently to reach that goal we'll have to step up to a 3HP unit or larger, which means a more expensive machine and therefore a more lopsided comparison when considering which to purchase.  I really don't see the advantage of a small 1.5HP shaper if it's just as limited as a router in the power department and doesn't come with the advantages of a router table.

[Dan S]

Good info to have, Don.  But it kind of throws a wrench into the router vs. shaper debate, at least for me, since I thought one of the big advantages of the shaper was the ability to remove more meat at once without bogging down the machine.  So apparently to reach that goal we'll have to step up to a 3HP unit or larger, which means a more expensive machine and therefore a more lopsided comparison when considering which to purchase.  I really don't see the advantage of a small 1.5HP shaper if it's just as limited as a router in the power category and doesn't come with the advantages of a router table.

 

I have to agree, power is power. Hence the reason machinists talk about material removal rate, as its takes everything into account. The only way to not bog down a machine is to either feed slower, or take shallower cuts (assuming the same tooling).

[Vyrolan]

I would also agree with Eric. Seemingly a hobbyist would want a shaper to not have to make tons of tiny passes with the router...if that's not the case, I think the advantage starts to dwindle fast.

[dwacker]

Good info to have, Don.  But it kind of throws a wrench into the router vs. shaper debate, at least for me, since I thought one of the big advantages of the shaper was the ability to remove more meat at once without bogging down the machine.  So apparently to reach that goal we'll have to step up to a 3HP unit or larger, which means a more expensive machine and therefore a more lopsided comparison when considering which to purchase.  I really don't see the advantage of a small 1.5HP shaper if it's just as limited as a router in the power department and doesn't come with the advantages of a router table.

 

Not at all. In the case of the box joint video larger diameter cutters would take care of the issue easily. He maxed out the machine running it though end grain with a maxed out spindle with no regard to cutter diameter. Well maybe not no regard he may just not have larger cutters. This cut on that machine should have used 4" x 1/4 dado chippers on the 3/4" spindle and there would have been no issue. If he would have been using a hobby sized panel raiser he would have been able to do it in a single pass. Lastly the cut from larger cutters is far superior to that of a router. Its not a one size fits all like a router. Does take some learning.

[Dan S]

Not at all. In the case of the box joint video larger diameter cutters would take care of the issue easily. 

 

I have to disagree, as this statements runs against the basic laws of physics. The power required to remove a given volume of material at a given rate is purely dependent on the power of the tool. Either the tool has the power to remove the material at that rate or it doesn't.

 

 

This page has a simplified example of the equations used to calculate the power required to remove a given volume of material, all you need to know is the "unit power" of the material. I say simplified, as it doesn't take the type of cutter (hss or carbide read sharpness), or tooling geometry into question, but regardless they are both small factors compared to the power of the machine.

 

http://www.custompartnet.com/calculator/milling-horsepower

[dwacker]

I have to disagree, as this statements runs against the basic laws of physics. The power required to remove a given volume of material at a given rate is purely dependent on the power of the tool. Either the tool has the power to remove the material at that rate or it doesn't.

 

 

This page has a simplified example of the equations used to calculate the power required to remove a given volume of material, all you need to know is the "unit power" of the material. I say simplified, as it doesn't take the type of cutter (hss or carbide read sharpness), or tooling geometry into question, but regardless they are both small factors compared to the power of the machine.

 

http://www.custompartnet.com/calculator/milling-horsepower

 

Dan,

 

Let talk real world shaper use not armchair internet woodworking. Go fire up your shaper with a thee inch cutter and make a deep end grain groove. Switch the head out for a 4" then a 5" Come back and let us know what you find. 4" dado chippers are no different than running a contractors table saw with a dado blade. On the shaper the rpm is 10000 rpm 6000 more than a table saw the dado on the shaper will outperform the dado on the tablesaw easily even in end grain. 

[Dan S]

Dan,

 

Let talk real world shaper use not armchair internet woodworking. 

 

Call it whatever you like, the laws of physics still apply.

[Vyrolan]

I have to disagree, as this statements runs against the basic laws of physics. The power required to remove a given volume of material at a given rate is purely dependent on the power of the tool. Either the tool has the power to remove the material at that rate or it doesn't.

 

Doesn't the bigger, heavier cutter change the dynamic here?  Power required may be the same, but a larger diameter cutter does indeed have more power...the larger diameter means the outer edge has higher velocity at the same RPM...and so the energy is higher.

 

 

This page has a simplified example of the equations used to calculate the power required to remove a given volume of material, all you need to know is the "unit power" of the material. I say simplified, as it doesn't take the type of cutter (hss or carbide read sharpness), or tooling geometry into question, but regardless they are both small factors compared to the power of the machine.

 

http://www.custompartnet.com/calculator/milling-horsepower

 

That page seems based on CNC machines, where the dynamic of "larger cutter diameter yielding faster edge velocity yielding more energy with a constant rate of material removal" could not exist because larger cutter diameter would also increase material removal rate in a CNC machine.

 

I think the "tooling geometry" matters a lot.  I would think the diameter of the cutter is like the length of a lever or the size of a gear.  If output is based purely on the power of the machine, why can I ride my bike up the hill in the lowest gear but not in the highest?   The power required to propel the bike up the hill is constant as is the power of my body to drive pedals.   In the lower gear, I have to pedal faster, but that's the same as the higher edge velocity of the larger diameter of the cutter.

[pghmyn]

Call it whatever you like, the laws of physics still apply.

I haven't done physics or dynamics for awhile, but this is how I look at it...

Power, as you bring up, is a function of work over time. (W dot)

Work, or using torque, is force multiplied by distance. Increase the distance (diameter), increase the torque (work).

Increase the work, increase the power.

Increase the power, increase ease of cut.

[Tpt life]

This may not factor, forgive if so. Velocity, mass, and horsepower ratings are some of the easiest to confuse. The best push mower I ever ran was a 1.5 HP two stroke. (I should note that restrictions all but killed the two stroke mower.) The next non two stroke that could compare was a 6.75 HP four stroke. They were both 21" machines. That 5 HP in between was meaningless because slow speeds don't work with this style cutter in grass. Slower speeds with HP in these ratings just did not have enough inertial energy. Once the motor had any reason to bog down it was worse. There are factors like this that color real world applications.

[Vyrolan]

In my shop the lights flicker when I use my table saw and yes, it does bog down.

 

I feel that pain... =(

[Dan S]

Doesn't the bigger, heavier cutter change the dynamic here?  Power required may be the same, but a larger diameter cutter does indeed have more power...the larger diameter means the outer edge has higher velocity at the same RPM...and so the energy is higher.

It will have higher rotational inertia, for a given rpm, but that only helps over a very short period of time.

The formula for horse power is:

HP = (Amps * Volts)/746 (assuming 100% efficiency)

so a quick example is shop vacs, they pretty much all run on 120 thus the max power you can get out of them is 20*120/746 = 3.2 HP (if we make a bunch of assumptions)

However you always see shop vacs listed with more power than that, mines listed at 6.5HP for example. The reason for this, because that Hp rating is calculated over a very short period of time and the motors inertia "helps" and allows for shall we say creative marketing.

The rotational inertia works against you as well, because once the rotating object gets slowed down, it takes even more power or time (depending on whats more important to you) to get it back up to speed.

 

why can I ride my bike up the hill in the lowest gear but not in the highest?   The power required to propel the bike up the hill is constant as is the power of my body to drive pedals.   In the lower gear, I have to pedal faster, but that's the same as the higher edge velocity of the larger diameter of the cutter.

You are trading off velocity for an increase in height, but your power output is most likely still the same.

In short the more material you want to remove continuously the more power you need. it doesn't mater if its a router, shaper, table saw lathe, milling machine etc, it all comes back to power. More importantly what can be sustained for more than a short burst.

[Vyrolan]

There are factors like this that color real world applications.

 

This is a good point...the number of variables is truly massive.  Some of them are completely intangible...for example even if I knew the quality of the cut was going to be good either way, I might make multiple small passes routing a big profile just to keep myself in the lower part of Eric's pucker scale.

[Vyrolan]

In short the more material you want to remove continuously the more power you need. it doesn't mater if its a router, shaper, table saw lathe, milling machine etc, it all comes back to power. More importantly what can be sustained for more than a short burst.

 

I can't explain why, but I just can't agree with that statement.  Maybe it's just too broad and/or vague.  But I read that as you are saying the only thing that matters is the power of the machine.  It's saying the sharpness of the blade or the cutter doesn't matter...that the geometry of the cutting edge doesn't matter...  That's just not true.  There are more factors than just the power.  

 

 

 

You are trading off velocity for an increase in height, but your power output is most likely still the same.

 

That doesn't explain the bike situation.  I'm saying the power required to move the bike is constant (just as the power required to remove a given amount of material) and that the power output of my legs is constant (just like the power output of the machine's motor)...  However, in a low gear I pedal easily but quickly (faster edge velocity of larger diameter cutter)...and in a high gear I struggle to pedal slowly (bogging down with a smaller cutter). 

[Tpt life]

Dan is totally correct with one caveat. There is a place where the power required to make the cut does not overbalance the motor. This may be what inertial energy gains you with a larger diameter cutting wood. The additional cutter speed may overcome the force required to make the wood sheer.