Band Saw questions

Page 1 of 3  
Is a .5hp motor a good size for a band saw? What other specs would you look for if planning to purchase? I ask due to someone selling a used one though the only specs thus far are the .5hp he lists and it stands 6 feet high. Otherwise, I will call for the rest of the info and questions I need to ask.
Thank you
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Good for a trial to see if you are going to really be interested in using one. I had a 1/2 hp BS once and it is ok for cutting thin soft woods, hardwoods not so good. Basically you can do better with a jig saw. I also like to resaw, if you are thinking of resawing buy one with 2 hp or more, my current BS has 4.5 hp.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

motor in it's place?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The saw may not be built to withstand the extra strain for a reasonable amount of time.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Valid thought.
Let's look at some numbers. My calculations show replacing a 1.5 HP motor with a 3.0 HP motor increases the maximum load on the lower wheel bearings by about 3%. Yep, that's 3 (three) percent. Don't believe it? Read on.
WARNING! Mathematics follows, continue at your own risk!
What are the forces on a bandsaw? First, understand that the maximum load on the upper wheel (assuming a 2 wheel saw) occurs when the blade is tensioned, but the saw is not running. When the saw is cutting, the load on the upper wheel is actually less than when the saw is not running. So we can ignore the upper wheel and its bearings when looking at the cutting loads supplied by the motor. However, the load on the lower wheel is increased by the cutting loads.
When the saw is cutting, the force necessary to pull the blade through the workpiece comes from the motor through the lower wheel. That force is applied to the blade by the lower wheel, transferred by the blade to the workpiece, and reacted by the bandsaw table support structure. So the load on the table acting downward is equal to the load acting upward on the lower wheel bearing. But what is that load?
First take the case of the motor developing its rated power at its rated speed. Further assume that all processes occur at 100% efficiency. That is a conservative assumption since lower efficiency means lower loads on the wheel bearing and table structure.
Assume a 3HP motor. That means the motor at 100% efficiency provides Power = 3 X 550 X 60 = 33,000 foot-pounds/minute
Assume the blade moves at 3000 feet/minute when the motor is turning at its rated speed. That value is from the specifications for my bandsaw and is, I believe, a fairly typical value for woodcutting bandsaws.
    Force on the blade = 33,000/3000 = 11 pounds.
So, a 3 HP motor developing is full rated power at its rated speed during a cut will pull downward on the table and upward on the lower wheel with a force of 11 pounds. Dividing by 3 (for a 1 HP motor) yields 3.667 pounds per horsepower load on the internal parts of the saw. Round it off to 4 pounds per horsepower for simplicity.
If you think that's a trivial load and can't possibly be the maximum load developed within an operating bandsaw, you are absolutely correct. The calculations used rated speed and power. The problem is the motor doesn't develop maximum torque at its rated speed. Maximum torque is developed when the motor is very nearly stalled out and is barely turning if it's turning at all. And it's the maximum torque that produces the maximum load on the bandsaw.
I'm no motor expert and don't know how much higher the maximum torque may be than the "rated" torque. But, capacitor start induction motors are built that way so they will have a high starting torque. For these purposes, I'm going to estimate that the maximum torque of a capacitor start, induction motor that would typically be used for a bandsaw would be on the order of 5 times the running torque. Perhaps a motor expert can improve on that estimate.
If the 5x estimate is anywhere close to the right ballpark, look for something on the order of 20 pounds per motor horsepower to be the maximum load applied to the table structure and lower wheel bearing by the motor.
1 HP = 20 pounds 2 HP = 40 pounds 3 HP = 60 pounds
So unless my estimated maximum torque is wildly low, the load added to the bandsaw components by the motor is really fairly small.
To get the full load in the lower wheel bearing, you have to take into account the load due to the blade tension. That load is proportional to the width and thickness of the blade and the tensile stress in the tensioned blade..
According to the guys at Suffolk Machinery, the makers of Timberwolf blades, the tension should be such that a stress of about 12,500 psi is developed in the blade.
So if we assume a 1" blade, .035 thick, 12500 psi equates to a tension load of 437.5 pounds. Since the blade has a wrap angle of 180 degrees on the wheel, the wheel bearing sees double that value, or 875 pounds of side loading.
With a static load of 875 pounds from the blade tension, the added maximum load of 60 pounds from a 3 HP or 30 pounds from a 1.5 HP motor doesn't seem to be anything to lose much sleep about. That's why I never hesitated to replace the 1.5 HP motor on my bandsaw with a 3 HP motor . It increases the load on the bandsaw wheel bearings from 905 pounds to 935 pounds - about a 3% increase.
Tom Veatch Wichita, KS USA
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I did not read it all, but did any of that take into account the increased ability to resaw much wider boards which would also put more strain on guides? Did it take into account faster feed rates which would also create more strain on bearings and guides. Did it take into account the ability to cut larger heavier pieces which might damage marginal trunions and or tables? I was sorta indicating premature failure because of the extra capacity during actual use, not just from turning the BS on. My old BS was pretty much all aluminum as far as the frame/housing was concerned. I viewed the smaller hp motor as being a safety measure to keep the frame from distorting and twisting, a condition that would be present when cutting heavier and thicker pieces of wood with a larger hp motor. I was pretty impress with your detail however. ;~) Perhaps a larger motor on a "fan" would not have as much potential to do harm.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

If you had plowed through all that, I'd be tempted to advise you to "get a life". 8-)

No, I didn't consider the weight of the workpiece on the table and trunnions, or the effect on the guides, just the additional loads that a larger motor could possibly apply to the structure during a cut that used the motor to its maximum power/torque output.
To be honest about it, I was surprised to find, especially with the largest blade my bandsaw is "rated" to use, the structural load due to tensioning the blade is huge! So large, in fact, that the added loads on a bandsaw from cutting at maximum developed motor power/torque fades almost to insignificance.
But, it's important to note that those numbers are not blanket justification for arbitrarily or thoughtlessly increasing motor power on any tool, bandsaw or otherwise. Your cautionary statement is still very much on point and valid.
At the very least, when someone modifies a tool by increasing the motor size, or any other significant change for that matter, they can toss the warrantee in the burn barrel. And on the other end of the spectrum, they could very easily increase the risk of serious damage to the tool and themselves. We, as customers, rarely know the basis for all the sizing decisions made by the tool designers.
Tom Veatch Wichita, KS USA
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tom Veatch wrote:

I didn't read it all either, other than skim it. I would wonder if the dynamic analysis of the loads during heavier usage wouldn't factor in over the static analysis...just a thought; I've really not considered it in great detail.
There is one self-limiting factor I'll agree with, though, and that is the maximum tension force one can manage to apply to a small saw is limited by the small blade capacity. If one were to try to put a large resaw blade and tension it properly on such a small saw, it's at least a decent chance you'd collapse the frame before ever starting so the motor hp to pull it wouldn't matter... :)
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Agreed!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Especially when it's a Craftsman. <G>
Max
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That's a mistake. The value, 33,000 foot-pounds/minute, is for a 1 HP motor. 3 HP = 99,000 foot-pounds per minute. (as an explanation for the error, I can only offer the though that it was written in the wee hours of the morning during a bout of insomnia)
That means all the motor loads in my previous treatise should be multiplied by 3.
1 HP = 60 pounds 2 HP = 120 pounds 3 HP = 180 pounds
Also, the calculation of the percentage increase in loads from increasing motor is as follows:
Load in the lower bearing from blade tension = 875 pounds (no change from the original post)
Load in the bearing from maximum cutting load with 1.5 HP motor = 90 pounds. 3 HP motor = 180 pounds.
Total load with 1.5 HP motor = 875 + 90 = 965 pounds Total load with 3.0 HP motor = 875 + 180 = 1055 pounds
Percent increase = (1055/965) - 1 = 9.3%
So instead of a 3% increase, there's almost a 10% increase in load on the bearings. That is beyond calling it a trivial increase, but still should be well within design margins of the saws structure.
I am embarrassed by, and apologize for, the arithmetic error. If it were possible, I would delete the previous post and replace it with a corrected version.
Tom Veatch Wichita, KS USA
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tom Veatch wrote:

That seems in realm; no slight intended and I didn't look at it hard enough to catch the arithmetic but it did somehow just seem to have too little of an effect.
The strength of usenet is also at times a weakness--once it's in the ether, it's never to be reclaimed... :) [and :( ; I've more than once wished for the same facility]
--
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

What power you need depends on how you will use the saw. Many bandsaws are 1 HP. More important than power is accuracy of cut. Bandsaws are notorious for getting out of tune, so you will have long-term benefits by buying quality.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Half hp would be a pretty small BS, maybe a desktop unit, good for small work like model making or pattern cutting thin stock, etc.
Main spec of a BS is the throat. You'll see something like 14" or 18". This indicates the distance from the blade to the backbone, or how wide you can cut on the restricted side. A bigger numer is generally a better saw (not exactly but generally bigger is better. 6 feet high doesn't mean anything. You could configure a 12" bandsaw to be 6 feet high.
A typical starting size for a serious bandsaw is 14" and a 20" is industrial grade and bigger than that is only for sepcialized ops (IMNSHO). A typical 14" will have at least 3/4 hp. 18" are pretty much the standard for top end garage models and will have 2 or 3HP.
I get by with a 14" but have my eye out for an 18 or 20 but I don't bandsaw much but would like to do some resaw in the future.
The other capacity is depth. 6" is pretty standard for the small sized models. You can get extensions to raise the head and increase that dimesnion but if you really want to resaw, just buy a bigger, more stable saw.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

1/2 HP is too small for serious work with hardwoods.
Other specs:
Wheel diameter - bandsaws for hobbyist woodshops will usually run in the 12" to 18" range with the most common probably the 14" size. Versatility/usability is directly related to the wheel diameter. The throat dimension (distance from the backbone to the blade and the largest circle, similar to the throw dimension in drill presses) and usually the maximum resaw dimension - cutting height above the table - increases with wheel diameter.
Resaw height - runs from about 6" to 12" typically for hobbyist type machines. Most of the 14" machines with cast iron frames require a riser block to reach 12". With the newer welded steel frames, what you get is all you have. There's no provision for riser blocks. Bigger is better if you plan on resawing, but using the larger capacity requires more power.
Motor horsepower - normally as the bandsaw size increases, the power of the standard motor also increases. Don't know all the specs for all the saws, but my 16" came with a 1.5 HP motor which I burned up resawing some green maple. Replaced it with a 3 HP Baldor Industrial motor ($$$) and now it works fine.
Minimum and maximum blade widths the saw will handle. The width you'll use is dependent on what you're doing. Narrow blades down to 1/4" for tight curve cutting, wider blades for straight cuts and resawing. Many folks recommend as wide a blade as possible for resawing. 1/2" blades work fine. Wider isn't really necessary. If the saw will tension a 3/4" blade properly, that's all you'll probably ever need.
Blade Length - There are several "standard" lengths in bandsaw blades. In general, the larger the saw, the longer the blade. If the length required is not one of the common standards, blades will have to be custom ordered. That not as bad as it may sound, because many, if not most, suppliers of quality blades weld blades to order even for the "standard" lengths. However, a non-common blade length may prevent your dropping into your local borg and picking up a blade off the shelf.
Number of wheels - virtually all the current crop of bandsaws are two wheel saws. There are some three wheel models out they are relatively rare. They will generally have larger throats and resaw capacity that a 2 wheel saw with the same diameter wheels. I understand they tend to break blades more often than comparable 2 wheel saws but have no experience with them. I surmise that, along with non-"standard" blade lengths may be why they are not very popular.
Whatever you're planning on doing with the bandsaw, consider that you'll wind up wanting to do more and bigger things as you gain expertise with the saw. Plan accordingly.
Tom Veatch Wichita, KS USA
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Great post.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I must be fooling myself about the seriousness of my work, then. 1/2 HP is just fine. The blade makes much more difference in the quality and ability to cut. Certainly a larger motor is nice, but mostly, it's a matter of marketing and pandering to consumer bias.
(I saw your earlier analysis. Can't say I can find fault with it. ;)

Folks tend to forget it's not just the riser block that limits the resaw height. I'm more limited by what I can flatten on the 6" jointer. (Serious work, indeed.)

It does depend on what you're cutting, of course. And the blade you use.

Yes, I'm an affirmed member of the holy church of best blade for the job. I need not worry about having to drop in at the borg for mediocre blades, though. I have a small collection of superior quality blades, and any one of them will substitute in a pinch if the "best" blade happens to break, prove dull, etc. I'm not on a production schedule, you see, and FedEx rings my doorbell even on Saturdays.
But here's the punchline. Every single blade I use for wood is plain, ordinary high carbon steel. No bi-metal, no high speed steel, no welded carbide teeth.

Phooey on that. ;) Thinking back only the 12 years since they made my bandsaw, only the marketing focus has changed, not the work or the material.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Have you resawed a 6" wide piece of hard maple on a Laguna LT16 HD with a 1.25" wide Resaw King blade yet? If not and you get the chance to do so you might rethink some of your above answers.
Before getting a Laguna BS I resawed 6" hard maple on a 12" 1/2 hp BS with a brand new 3 tpi premium quality steel blade. It took approximately 2-3 minutes to make a single pass to resaw the 24" long pieces.
I did the same a few months ago with the Laguna taking about 10 seconds per pass to resaw a 6" wide, 48" long piece piece of hard maple.
I also did this with the Laguna and a 1.3 tpi steel blade in about the same amount of time but the smoothness of the cut dropped dramitically. With the bi-metal ResawKing I was able to get more pieces from the 3/4" stock.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Sort of, and more or less routinely. Not a big deal. Not quite 6"; 5-1/2" is about all that will fit under the guard. Despite all that, I haven't felt limited by the tool.

I haven't had the pleasure. Is that an invite?

For sure, a 48" pass in 10 seconds is doing justice! But maybe we part company on the need to do so. A worthwhile slab that benefits from resawing to veneers is an unusual find. The money I didn't spend on machinery and diamond studded blades buys a lot of bookmatched flitches. ;) But I do understand your doing so. Just having the tool, I expect I would welcome the opportunity to put it through its paces.
I have a basically stock 14" Delta open stand made mid-90 something. Setting it up for resaw, I take paper thin cuts on whatever I have on hand to prove out the fence drift and setup. That's as good as I need it work. It's worth repeating, as it was the point I was trying to make in my original post: I don't feel limited by my bandsaw. The jointer is a bit small sometimes, but even that matches the bandsaw.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yeah! Come'on down. ;~)

Actually I just needed thick veneers for the refacing of the kitchen cabinet face frames. I basically turned 2, 8' 1x6 s4s pieces of hard maple into 10. I did not want to resaw 5 in half and plane to 3/16"

I had my old BS for about 20 years and seldom used it. The new one is such a pleasure to use with limitless posibilities that I use it much more often. I found that I can quickly cut up dried firewood for my BBQ smoker and often find prize pieces when doing so. ;~)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.