Bandsaw Blade Speed

[glenn bradley]

Well, here's a question that I thought I answered the other day. My dad is putting a motor on his 55 year old Delta 14" BS. Current 14" saws seem to run 2900 to 3500 fpm. Suffolk suggests 4500 to 4800(?). With the current motor and pulleys my dad is moving the blade around 4200 fpm. Any comments on this? Too fast? Just right?

[glenn bradley]

Bump. Hmmm. no opinions? It must be the cycle of the moon or something ;-)

[Pete Bradley]

The 1951 catalog shows the speed as 2200 FPM and the 1957 catalog says 3000 FPM. I'd probably shoot for 3000. On that saw, I'd expect anything north of 3600 would be asking for trouble.

Standard motor was a 1725 RPM.

Pete

[Charlie Plesums]

My 24 inch bandsaw runs close to 5000 fpm. My 14 inch Grizzly G0555 is dual speed, 1500 and 3200 fpm. When I had a problem with a Timberwolf blade they first thought I must be running it on the low speed (which they considered bad). When I confirmed the higher speed, they replaced the blade, but their attitude was that even faster would be better for wood. Based on that data, I would shoot for something at least 3200 fpm, but might not go a lot faster because of bearings and other issues.

[Phil Pritchard]

I was under the impression that bandsaws should aim for around 2,000 m/min (circa 6650 ft/min). I've looked up speeds on older Wadkin bandsaws (admittedly much bigger machines in the main) and the blade velocities were as follows: 16in - 4,000fpm, 24in - 5,500fpm, 30in - 5650fpm and 36in - 6,780fpm. Machines from another manufacturer, Dominion, showed speeds as: 14in - 5,200fpm, 24in - 6,000fpm and 30in - 5,500fpm. So it looks like aiming for the higher speed will get you the best sawing results. The main question has to be if the bearings will be up to it

Phil

[Pete Bradley]

I was under the impression that bandsaws should aim for around 2,000 m/min (circa 6650 ft/min).

Not in general. There are some machines with very large wheels that operate in that range, but it's out there, and way beyond the design speed of this machine. Theoretically you could glue down the tires and let'er rip, but I expect it would be very hard on bands and the machine for little if any benefit.

Pete

[M Toupin]

The 2900 to 3300 sfpm is a good ballpark and jives with everything I've seen or heard. I can't believe Suffolk recommended 4500-4800 sfpm for a 14" saw. Those numbers run counter to everything I've ever seen AND their own website.

Snipped from the Suffolk Machinery website
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Examples of optimum Surface Feet Per Minute on vertical band saws running 1/8" to 1" wide blades. It is not considered wise to exceed these values.
WHEEL DIAMETER S.F.P.M. WHEEL DIAMETER S.F.P.M.
12"= 2,800 24"= 4,000
14"= 3,300 26"= 4,000
16"= 3,800 28"= 4,000
18"= 4,000 30"= 4,000
20"= 4,000 36"= 4,000

As you exceed the S.F.P.M. for a specific wheel diameter, you greatly increase the centrifugal force applied to the body of the blade traveling around the two wheels. This causes you to over-tension your blades in order to make them run stable. This WILL cause premature and excessive blade breakage.
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Mike

[Jerry Allen]

I think most stuff I've seen says ~3000 fpm, but I run mine at about 2000 fpm and seem to get better results. I think it all depends on the blade you are using, how powerful the motor is, and if everything is balanced and tuned. I'd just try it at different speeds and see how it feels.

[Phil Pritchard]

The 2900 to 3300 sfpm is a good ballpark and jives with everything I've seen or heard. I can't believe Suffolk recommended 4500-4800 sfpm for a 14" saw. .......
As you exceed the S.F.P.M. for a specific wheel diameter, you greatly increase the centrifugal force applied to the body of the blade traveling around the two wheels. This causes you to over-tension your blades in order to make them run stable. This WILL cause premature and excessive blade breakage.

Mike

Suffolk's figures seem to be completely at odds with the speeds in almost every 18in and over saw built today! I've had a look through manufacturer's figures from a good selection of modern bandsaw makers (Centauro, ACM, Meber, Agazanni, Steton and Wadkin), together with some 1960s and 70s British machines (Wadkin, Robinson, Wilson, Pickles, Dominion and White), as well as some older (1930s) machines. Almost universally on narrow bandsaws the manufacturers are producing narrow bandsaws with cutting speeds in the area of 5,500 to 6,500 fpm for saws between 18in and 42in wheel sizes, with only some 16in and a few 20in machines running any slower (4,500 to 5,000 fpm). I don't think the centrifugal argument stands up for another reason - if a bandsaw can't tension a blade to the optimum beam strength (around 14 to 15,000psi in a carbon steel blade according to Starrett, Sandvik and Morse) then you will have to run the blade much slower to overcome the inability of the machine to tension the blade adequately. I believe that Louis Iturra of Iturra Design has found the tension springs on new Jet and Delta saws to be so inadequate that they will only tension the blade to between 6,000 and 8,000 psi.

Experience tells me that if a blade is undertensioned it is much more likely to be displaced backwards onto the rear thrust bearings, it will suffer from bellying in cut, it will twist or drift more and increased friction (as it will spend a lot of time rubbing against the bearings) will heat the blade more and potentially ruin the temper or detract from the sharpness. All these factors, combined with the welds being flexed around a tighter diameter wheel will result in earlier blade failure on smaller saws. This seems to be bourne out by my own experience: 28in machine in use over 5 years - no breakages (wore-out 30 or so blades, including two TCTs), 14in machine in the same period - 5 or 6 breakages in 3/8in and narrower blades (from a smaller number of blades). It strikes me that there's something here which doesn't appear correct when people are saying a 14in machine should be run well undertensioned (which detracts from the quality of cut when resawing/ripping) and at half the blade speed of larger saws. Perhaps someone would like to try explaining this discrepancy

Phil

[Phil Pritchard]

Not in general. There are some machines with very large wheels that operate in that range, but it's out there, and way beyond the design speed of this machine. Theoretically you could glue down the tires and let'er rip, but I expect it would be very hard on bands and the machine for little if any benefit.

Pete

Almost all the 18/20in and above machines I can find data on run in that speed range - it is not an anomaly.

Phil

[M Toupin]

Phil,
I'm not disputing your observations, but we're talking a 14" machine here, not a 24"+ machine. For example, your 28" machine is running at less than half the wheel RPM you would ask that poor little 14"er to run at to get the same sfpm. As for blades and tension, we're talking a 1/8" to 3/4" blade which is about the most your going to get tensioned properly on a 14" machine, not 1", 1 1/2" or wider common on larger machines. If you're saying you're 14" is running at the same sfpm as your 28" and breaking blades at the rate you claim, then I think you prove the point. Getting back to the original question, I think you might be inadvertently misleading Glen on his needs based on his 14" Delta.

Mike

[Phil Pritchard]

Hi Mike

What I'm trying to do is ascertain what the optimal speed for smaller saws should be. Should it follow the same rules as that applied for the bigger machines? After all a 14in machine running at 6,000 fpm has the wheels revolving at just under 1650 rpm which is hardly fast and all but corresponds to the speed which the wheels would turn at if the motor were a direct drive motor - as many modern small nbandsaws are. The 14in BS in my shop was replaced by a much larger cast-iron 16in machine late last year - that is a 56 year old machine (older than even me) and runs at 4,000 fpm, which just happens to be the optimal speed quoted by Suffolk. However I find that it doesn't cut as quickly as I'd like so when the bearings get pulled in a few months time I'll look into rebalancing the wheels and maybe upping the speed to get nearer to the 6,000 fpm figure.

As you say, though, Suffolk's own information is contradictory and is at odds both with that provided by three large blade manufacturers and by all the larger machines (i.e. 18in and over) I've ever come across. I wonder why this is?

As for blades and tension, we're talking a 1/8" to 3/4" blade which is about the most your going to get tensioned properly on a 14" machine, not 1", 1 1/2" or wider common on larger machines.

My take on that is that a 14in machine probably can't tension anything much wider than a 1/2in blade in any case. Certainly the average 24in fabricated machine cannot be guaranteed to tension much more than a 1-1/4in blade even if the wheels are 1-1/2in wide because the frame will flex. My current 16in machine has 1in wide wheels, but interestingly the manufacturer's own literature states that it should not be used with blades wider than 3/4in - and that's a machine with a one-piece cast iron frame.

The tension setting of 15,000 psi is an optimal figure for resawing or veneer cutting where only minimal drift and bow are acceptible. For curve sawing which requires less accuracy much less tension is needed.

If you're saying you're 14" is running at the same sfpm as your 28" and breaking blades at the rate you claim, then I think you prove the point.

On the contrary. Smaller saws fracture blade welds at a higher rate due to the nature of their use - the smaller radius which a blade is flexed/unflexed around is what causes the problems, together with the blade bowing back when not under sufficient pressure. Think of it rather like bending and straightening a piece of aluminium strip. The ally will break much more quickly if you are bending it across a sharp radiused edge such as a kitchen counter top edge than it would if you were doing the same over a softer edge of larger radius, such as a bowling ball. As I stated my saw supplier has stated that their experience over many years with narrow bandsaws is that breakage and kinking is much more likely to occur if the blades on a narrow bandsaw are insufficiently tensioned. As most small machines can't pull sufficient tension and are in any case seem to have grossly over-optimistic tension gauges that is more likely to be a contributory factor than running too fast.

Glen

Sorry if this is turning into a bit of a discussion, but I keep hearing very low blade speed rates being quoted whilst at te same tame many people complain about the poor quality of cut they are achieving with smaller saws. We also have here a major retail supplier who is contradicting themselves in their own advice and many machine manufacturers who seem to have adopted speeds in a different league to those advised here and elsewhere. I'm just trying to find out why and what the real situation is.

Regards

Phil

[Pete Bradley]

Almost all the 18/20in and above machines I can find data on run in that speed range - it is not an anomaly.
Phil

Phil, you're citing a narrow segment of the market. None of the present Deltas, Griz, or Jets in the 18/20 range run anywhere near 6650.

Regardless, my post was quite clearly about the proper speed for the 50 year old Delta 14" that started this thread. For comparison, the Delta 20" of that time (I own one) runs at 4500.

Some time ago I spoke to someone at Suffolk about their speed table topping out at 4K, since my machine exceeds that. I was told that the table was conservative, and their bands should be fine on my machine (as they have been). They weren't as comfortable with the old ships saws that run at very high speeds.

Pete

[Jim C Bradley]

Hi to all of you who responded to Glenn's thread.

I am the dad and proud possessor of the Delta described in Glenn's thread. The Delta is cast iron. Has 14" wheels with new tires. It is equipped with new Carter guides. Using the formula I was given, it is running at 4,215 sfpm.
Formula used: Motor RPM * Motor pulley diameter / driven pulley diameter * bandsaw wheel diameter * Pi / 12
4,500 * 2" / 6" * 14" * 3.1416 / 12 = SFPM

I am using a new Carter 1/2" 3 TPI blade. Tension is set at the Delta 1/2" mark. The saw runs quietly, smoothly, cuts cleanly and smoothly.

I have used a bandsaw for this and that for many years (it took me 20 minutes to get the table saw out to where I could use it so I would use the bandsaw). However, at that time I was not trying to do anything fancier than cut construction lumber.
Now I am finally getting a wood shop set up where I can get to all tools. The tools are all very finely tuned. With the saw set up as it is, I can easily cut 1/16" thick slices off of 4" thick wood. The slices were cut using a Rockler fence on a Rockler bandsaw table. The cuts are clean, no burns, and no indication of drift. The slices were 1/16" x 3.75" x 42". This is the first time in my life I tried to make a thin slice, so my success has nothing to do with experience.

I would be happy as the proverbial Lark if I didn't know the speeds advertised on Laguna, Delta, Jet, Grizzly, etc. 14" bandsaws.

I have two other, new Carter blades, 1/4" and 3/8" and another 1/4" blade with more teeth (can't remember make and number of teeth. It was removed from the original package a few weeks ago. However, it is probably 10 years old). The odds are very high that the 1/2" Carter will remain on the saw and the others in the drawer.

I am sure that all of you know more about this than you want to at this point. I certainly read all of your responses. I appreciate the time and effort you made in my behalf. My current posture is that I will continue to use the saw as it is now configured unless someone proves to me that I am going to ruin a good saw.

Oh yes, I am sending this info. to Carter to see what their response is to the "dilemma."

Enjoy,

Jim

[M Toupin]

The saw runs quietly, smoothly, cuts cleanly and smoothly.

Well there you go Jim, if it ain't broke don't fix it!

Sometimes we loose sight of the important stuff, making our particular machine run well. Like many things in life, theory doesn't always translate to real world results. It sounds like you have your particular machine tuned well and you're getting good results with it so stick with it

Mike