540 or 600 RPM?

[Carpenter]

      Is there a huge advantage to run a mill at 600 rpm over 540?  This has been nagging me since we decided to convert the mill to pto.  Once we convert it to pto I will be able to use an 85 horsepower tractor so, if I have the right pulley set up I could run it at 600, but it looks so easy to hook it up direct to the arbor.  I just haven't had time to do anything with it lately, but I am taking Saturday off.  We have an 8  9 guage saw with 3" shanks, So, it is quite thin.  I am a little concerned with it not having enough centrifical force at 540 and so putting more pressure on the saw plate itself.  Is that a valid concern?  or have I over analized the situation?  Also, our arbor shaft is 2 3/16ths"  Is that a standard size?  One guy I talked with thought that 2 5/16ths was standard.  Anyway, I still haven't located what I need to convert it but at least I do have a plan. 

[DanG]

It is my understanding that there is a huge advantage to running the saw at the speed it is hammered for.  Any chance you could squeeze a few more RPMs out of that tractor for testing purposes?

[captain_crunch]

What I was told is by useing a jackshaft and belts was it takes pto shaft vibration off arbor. I am going to mill again today and will get some better pics of mine. We also built bracket and added another bearing outside of pully on my arbor

[Jeff]

As DanG commented on, the saw blade needs to be operated at the RPM it was hammered for.

Every saw I ran had 2 7/16s 3 bearing arbors, but they were all commercial operations.

[DanG]

My answer has led me to a  question of my own.  When you find yourself in the situation that Carpenter is in, having a blade hammered for an unknown RPM, is there really a good way to find out without a visit to a saw doc?  Is my suggestion that he just play with the RPM to see where it cuts best a valid one?  I hate to suggest something and then find out later that it was a rotten idea. :-[ :D

[Ron Wenrich]

If you run it too slow, it won't stand up straight.  That can be a problem where the board rubs the eye and it heats up some.  But, it may also cut in a little.

If you run too fast, it will lay over and open the saw up on the log side.  That will cause the saw to heat up even quicker.  You can control those problems somewhat with the saw guides, but its not recommended.

I had a saw that was hammered for 640.  I run it that way for a really long time, but could never get the performance.  Then I put a dial tack on it and found the RPM to be 690.  That made a difference, but I did saw quite a bit with the the lower RPM hammer job.  It just didn't saw like it should, and you had to make sure you were really sharp.

I also ran a mill where the owner had the RPM at 360.  You can't hammer a saw for that speed, so said my saw doc.  The slowest speed he could hammer for was 460 (I think).  It worked OK, but I really wanted to take the diesel off of idle and give it some juice.  The owner said no.  They went out of business in short order.

[bandmiller2]

Carpy,I'd have your headsaw hammered for 540 that gives you the leaway to drive it directly from the PTO.Its not exact, you can run a 540 hammered saw a little faster.Wile belts are good for power transmission they also impart side thrust on the arbor and also vibration especially when their cold.Thousands of Belsaws have been run with a direct PTO shaft for years so long as its balanced and not angled too steeply.Theirs a differance between part time handset mills and full time commercial mills,many times cost and what we have trumps the best engineering.Whats real important is maintaining saw speed in the cut,Your big diesel tractor with a good governor should have no problem.Frank C.

[r.man]

While on the topic, are blades that are hammered for a specific rpm marked with that on the blade or do you just have to know the history of it?

[Carpenter]

Thanks guys.  As long as 540 will work alright, the plan is to hook it up direct.  The blade is still at the saw doc's because we haven't gone to pick it up yet as it is a 6 hour drive.  He did hammer it for 540, I just thought if we would gain a lot by running it at 600 then we would have him change it and then get a set of pulleys.  The other problem I have been having as far as hooking the mill up direct is finding a yoke that will fit this shaft, or some sort of coupler.  
 

[Tripp]

Carpenter,

What size is your blade? Mine is a 40 inch and I had it hammered to run at 600 rpm. My saw doc says a 40 inch is hammered to run flat with no dish at all speeds. I have found it definately cuts better at the hammered speed though. If I cut slower the blade wants to wobble a bit. I have heated the blade a few times cutting big dry oak so it might be time for a re hammer.

Tripp

[Carpenter]

Our blade is 50"

[captain_crunch]

Our mill sets on frame work so we need jackshaft to get pto lower here is the best pic I can find of it Notice added bearing at end of bellsaw arbor




Dan
In my limited experiance watch blade just below rated rpm it will wobble like crazy bring rpm up to where it just smothes out and check rpm not sure this is corect but how I bumble thru it. Then watch back of blade while in cut if it wobbles you need a few more rpms. On our Bellsaw running it this way I can take 1/2 a blade cut off a 16 ft cant so I figure that be good enough fer me
Brian

[bandmiller2]

Carpy.your arbor shaft is 2 3/16",one way you could hook it up would be to mount a sprocket on the end of the arbor flush.Anouther taper lock sprocket with the size of your yoke shaft, connect them with a double roller chain.Frank C.

[Joe Lallande]

After I converted my Belsaw from the flat belt drive to V belts and pulleys, I bought an inexpensive photo tach to check my math for the blade rpm. I have no tack on my diesel engine. I found the diffeerence between 500 and 550 rpm at the blade really improved my cutting. The blade needs to be run at its hammered speed. Also to connect the drive shaft to my saw arbor, I had a local machine shop make an adapter. I will post a picture if you like?

[Carpenter]

   Joe, could you post a pictures of the connection addapter?  I have a couple of ideas but some pictures would help. 

    Bandmiller, I never thought of making the connection with a double chain before, Thanks for the idea.

    Captain, That set up is what I would really like, I just haven't found matching pulley sheaves.  That was a really good idea to add a third bearing.  I can see that that would help with side pull, and vibration. 
     Our mill is set a little high as well because it is set on a cement pad and I wanted to leave extra room incase we ever decided to put a bigger blade on it so, if we can hook it up direct, I may have to pile up some dirt to put the tractor more inline.  But, we haven't built a saw shed yet so the shed can be built to accomodate the height.   Right now, if I use an 8' pto shaft and don't pile any dirt, the pto shaft will be at a 3" drop per foot. 

[Ron Wenrich]

While on the topic, are blades that are hammered for a specific rpm marked with that on the blade or do you just have to know the history of it?

The saws manufactured speed and hand are usually stamped on the newer blades.  I'm not sure about the older blades.

The saw docs have always told me they can hammer a saw for any speed and can take a right hand saw and flip it to a left hand saw.  Changing the rpm hammering hasn't been too much of a problem.  Changing from right to left has been a problem.  There's a thing called memory that the saws want to revert to.  I have gone to buying new saws mfg for my left hand mill.  They seem to work much better.

[bandmiller2]

RMan,You have to tell your sawdoc what you want for hammered speed,most keep records with your name, mill HP,hand,and type of bearings,and of course what they hammered it for.If you know the name of a mills previous owner and who hammered it good chance you can find what it was hammered for.To my knowledge sawsmiths don't stamp the speed on the plate mayby new saws but I've never been close enough to even sniff one of those.The guy before my had the "F" pattern 50" blade hammered for a little over 700 RPM with the diesel wide open,I dropped it back to 600 and slowed things down a little.As a rule of thumb the slower you run the less problems you have with tension,if you run too slow you can hear each tooth hit.Of course slow saw speed also cuts your production slightly, no biggie for part time sawyers. Frank C.

[bandmiller2]

Carpy,anouther idea on hooking up your shaft.Many times a drive shaft has a four bolt flange at the mill end.Get a taperloc sprocket and center and bolt the flange to it.Also I think you have a big cast flat pulley on the shaft now.Most of those have a long bearing surface on the shaft,move it off the end of the shaft enough for a stub shaft turned down to the yoke dia at the outer end.Whatever you do put a good guard around it.Frank C.

[Carpenter]

     My dad suggested today that I just have the end of the shaft turned down and splined so that a pto shaft will slip on.  Also, I looked online and I can get a slip clutch that will go on a splined end and has a splined end for a pto shaft,  It has a splined male and female end.  I guess, I over looked the odvious.  We are only talking about machining down the last 6" of the shaft or so to
1 3/8" so that it matches a standard 540 pto shaft.  It should not weaken the shaft as it will still be 2 3/16ths between the bearings.  I think its a Dang good idea.  What do you guys think?

[bandmiller2]

Carpy,your idea will work but setting up the shaft to cut a spline is a time consuming job and finding a machine shop with a lathe that can handle that long a shaft is likewise not easy.They make a PTO shaft adapter for the old fords that had 1 1/8 female one end and 1 3/8 male on the outher,the OD over the female end is large and probibly close to your shaft dia.That could be welded to a coupling or taperloc sprocket.Have a look at some PTO farm implements most have a slip clutch and could be adaptable.Frank C.

[Joe Lallande]

Here is a picture of the hub adapter a local machine shop made for me. I have the drive shaft disconneted in this picture. When connected, the shaft is almost level.

[DanG]

Probably modifying the clutch to fit the shaft would be a lot more practical in every way, but it takes all the fun out of it.  If you want to set up a real triumph for yourself, build a lathe around that shaft and mill it in place. ;D :D 8)  Hey, the hard part is already done for you, since it is already "chucked" in the bearings it will live in.  Just set up a milling machine around the end of it and Bob's yer Uncle.  You could even use the blade as a reduction pully to turn the thing with.  How's that for inventive? :D :D

Now back to the serious side;  Since the original question isn't quite like we understood it at first, I don't think it ever got answered in its new form.  We didn't understand that the blade is already at the saw doc, and Carpenter wanted to know what speed to have it hammered for, rather than what speed to run it at.  I didn't ever get cleared up on that, and my curiosity is up.  Is there an ideal speed for a blade of a certain size to be hammered for and operated at, or do you just pick a number and go with it?  I don't know saw blades like some of you do, but I know my stiff little blade has a safe operating limit of 1200 rpm and we run it at 1100, which seems right in the ballpark since that blade is twice as big as mine. :P

[Carpenter]

     Dan, believe it or not, I did consider ways to hold a cutting tool against the shaft and spin the shaft.  The saw doc showed me a tool that he uses to touch up collars while on the mill.  It was a machinists vice on a couple of threaded rods with handles on the rods.  Somehow he would mount the base of the vice solid, clamp a lathe bit in it, and turn the mill and since the vice could be moved two ways with the threaded rod he could machine the collars in place.  I'm sure the same thing could be done to turn the other end down. 
     And, yes my original question was should I run the mill at 540 or speed it up and now since the blade is at the saw docs and he only works on blades part time and isn't finished with ours yet, I could speed it up and have it hammered to match.  Anything is possible right now, since I really haven't done anything yet. 

[DanG]

Yeah, that was a kinda half-joke, or a half-a$$ joke, whichever you want to take it. :D  I'm sure it could be done though, since all the lathe really does is turn the piece against a tool.

The 540 speed is probably going to be most practical for you using the tractor for power.  I was just wondering what would be best for max saw efficiency, mostly for the sake of this great thread.

[bandmiller2]

Chattahoochee Dan,I'am sure there is an optimum speed for each size saw I don't know it.The smaller the blade the faster you can spin it.The faster you turn a saw the more critical the tension becomes.Modern mills spin the saw fast to up production usally they have a big honken diesel or large electric motor and many teeth on the saw.Older headsaws had fewer teeth and were designed to be turned at slower speeds common with water or steam power.Older blades tended to have softer steel and don't hold tension like the newer saws.For most of us back yard Wyerhousers we have little to gain running the saw speed up.I've got one saw hammered for 540 and the outher for 600 can't see any differance.Frank C.