Saw Hammering

Jeff · October 18, 2020, 08:18:51 AM

Loosen the nut, remove the sheer pins, rotate the saw 180° put the pins back in and reclamp. Remember to always pull out any movement by rocking the saw back before tightening. Dont over tighten!

Don P · October 18, 2020, 08:25:11 AM

Yup, what Jeff said better.
What I was wondering on the bearings is whether they are putting any bind or arc on the mandrel, I kind of doubt that is what's going on but look and see if there is any vibration showing in it between the bearings at speed. I just emailed the scan on Enterprise Mills.

Farm Mechanic · October 18, 2020, 09:12:27 AM

Thanks for the help, I'll try it today and report back.

mike_belben · October 18, 2020, 11:42:57 AM

Quote from: Jeff on October 18, 2020, 08:18:51 AM
Loosen the nut, remove the sheer pins, rotate the saw 180° put the pins back in and reclamp. Remember to always pull out any movement by rocking the saw back before tightening. Dont over tighten!

Youre saying to roll the blade back opposite of rotation until it takes up all clearance and engages the dowels as if under load, right?

mike_belben · October 18, 2020, 11:51:58 AM

Quote from: Farm Mechanic on October 18, 2020, 07:37:14 AM
I varied the RPM the full range i could with the tractor, seemed to wobble the least at 500-540. I am not sure if the bearings are self centering, they are double tapered roller I believe. When you say try the blade 180 do you mean put it in backwards?

If possible, indicate the shaft runout at both ends and the center while in the bearings, and also in vee blocks. Marking the high and low readings in two different color sharpie. This will help you separate the runout in the shaft and any runout induced by the bearings.

If this issue persists and your dial indicator and machinist square cant find the issue, consider a dynamic balance test. Any (good) nearby company that services industrial hvac and conveyor/blower/collector systems should have or know who locally has the fancy balance testing equipment. I worked on blowers up to 50hp for pistol range dust collection and we subbed that out on the stuff i couldnt determine with static measurement. Hed hook up in a few minutes, power the unit up and walla... Theres your bad part making the whole hood system shake.

Try your tractor pto shaft both ways and see if that helps. If the two joint arent straight in line either dig ruts or chock up on planks until it is. Single cardan joints must be at equal angles or they cannot cancel out the acceleration rates of the different operating angles. Only a double cardan can do that. One joint bent and one joint straight wont work smooth on single cardans.

Farm Mechanic · October 18, 2020, 12:10:44 PM

This is a friction feed mill, the drive wheel for the feed runs on the mandrel and slides back and fourth to drive the carriage. I had a new mandrel made because the original was shot, the old was 2 3/8" the new 2 7/16" so I had to have the drive wheel bored to proper diameter. I believe this wasn't not done accurately and has caused the wheel to not run true. Would this be my issue? I think it's shaking everything.

mike_belben · October 18, 2020, 12:29:34 PM

Indicate the friction wheel too.

If it was bored on a 3 jaw lathe the bore hole should be concentric to whatever surface they chucked. If they used a 4 jaw or milling machine then all bets are off as it will only be as concentric as they took the time to indicate and center it to. Could be perfect or off quite a bit.

Farm Mechanic · October 18, 2020, 03:16:18 PM

It was bored with a milling machine.

moodnacreek · October 22, 2020, 09:32:45 AM

The runout on the tight collar at the outer edge should not be more than .002. That is not to say that you could not run with more but that could require wider teeth and maybe more lead. (and more power) If you have type E bearings there is just a little self aligning. Spherical roller bearing types have alot. Between the dial indicator and different saws you will find the wobble. As you know something way out of balance on the mandrel can shake the saw. The saw will wobble bad around half speed then run true at hammered speed.

Farm Mechanic · October 23, 2020, 07:46:02 PM

Mike,

Correct me if I am wrong but as long as the tractor pto shaft and the saw mandrel are parallel to one another The equal angles Of the u-joints should cancel out the induced velocity correct?

moodnacreek · October 23, 2020, 08:41:53 PM

I can not answer that . I wonder what happens when you turn the saw with one finger and watch the guides. If something is way out of balance you would feel it in the husk. If it is the pto shaft I think you could see it . At any rate the saw must run flat at hammered speed. Did you try other saws?

mike_belben · October 24, 2020, 09:01:11 AM

Quote from: Farm Mechanic on October 23, 2020, 07:46:02 PM
Mike,

Correct me if I am wrong but as long as the tractor pto shaft and the saw mandrel are parallel to one another The equal angles Of the u-joints should cancel out the induced velocity correct?

If the joints and slip shafting are tight, the joints clocked together, shaft straight, and both output and input shafts parallel to each other so that the operating angle at each joint is the same [typically equal and opposite] then yes, the shaft acceleration rates should cancel each other and run smooth.
My father has a very short dragster with a driveline issue where the car feels like the brakes are dragging and you cant push it with driveshaft in. Take shaft out and a kid can roll it. The bind has worn out a pinion and tailhousing bushing.
Try putting your pto in neutral and turning the saw blade with the shaft on and shaft off. See if theres much difference in effort, difference in coast down time and any feel of cogging between the two conditions. Hopefully that validates your driveline.

Farm Mechanic · October 24, 2020, 12:46:54 PM

I have a total blade run out at the rim of the saw of .036". The two extreme points are 180 degrees apart from one another. I indicated the shaft at the collar and it is perfect.

Farm Mechanic · October 24, 2020, 01:00:10 PM

I have .010" of run out at the center of the saw. I guess I need to remove the blade and check the newly machined collar.

moodnacreek · October 24, 2020, 08:04:25 PM

Mill saws are not perfect. I think your saw run out is acceptable . The man who hammers a saw has a certain amount of trade off between perfect flatness and equal tension. One of my saws is new and is no better than 2 of my older saws. If it looks good to the eye running between the guides is is good as far as being true.

Farm Mechanic · October 24, 2020, 08:38:13 PM

So runout Of .036" is acceptable? Also the saw is cutting towards the carriage a little. When it finishes the cut it will have about 3/8" gap between the can't and the blade. The bits are all new and the lead is approximately 1/16". What else could cause this?

moodnacreek · October 25, 2020, 08:56:26 AM

Sometimes the lead measurement is not telling you everything so take a little lead out. Always check for heat in the saw especially the center. Sounds like you are almost there. It would be best to saw short [8'] straight softwood logs at this time because the other kind spring while being sawn and this will confuse you.

Don P · October 25, 2020, 09:28:18 AM

If you mark it up you can paper shim it closer to see if that affects it.

moodnacreek · October 25, 2020, 09:39:49 AM

There are so many little things the will cause the saw to run off or appear to that no man could name them all. Things like sawdust being pulled back up in the cut or a little sun light hitting one side of the blade. Saw deep, big logs, with certain style saws will saw in every time. Some feeds will spring the mandrel and change the lead when pulling hard on the stick [ the crowd]. My sawmill will do this when gigging back and rub the saw on the log indicating trouble that is not there. A wood carriage can rack while in use. A cable feed not pulling straight is a really bad thing and will wear the guide wheels out quick. Most of all is the corners of the teeth. Most beginners can't see this. A few chipped [can be very small chips] teeth on one side and the saw pulls the other way. May not happen in all logs but will happen. Watch everything while sawing. Backing the carriage while sawing will show you where the saw is going in. Don't let the saw saw out as the log will have no clearance and rub the saw bad, heat it and start to ruin the last hammering job. Keep posting.

mike_belben · October 25, 2020, 09:43:50 AM

Note to self: never buy a circle saw problem.

Farm Mechanic · October 25, 2020, 10:57:56 AM

I'm going to pull the blade and check collar run out
and report back shortly.

Farm Mechanic · October 25, 2020, 12:52:27 PM

The out side rim of the fast collar has an approximate run out of .0025".

moodnacreek · October 25, 2020, 01:06:14 PM

Quote from: Don P on October 25, 2020, 09:28:18 AM
If you mark it up you can paper shim it closer to see if that affects it.

If the collars are not tapered [I think you said they where done correctly ] oiled paper rings can be used to make the collars only grip the saw around the outside. Or you can do one side or the other. The saw is not supposed to move in the guides when the nut is tightened . But I am thinking the collars are fixed and it's the adjustments of the husk to carriage causing it to saw in. If in fact the mandrel, it's collars and bearings [are running cool] are correct or very close to it then that part is done.

Farm Mechanic · October 25, 2020, 02:09:35 PM

Well bad news, after I checked the collars I notice some old build up at the eye of the saw, so I wire wheeled it clean and re installed. I then indicated the blade and now have double the run out at the rim, around .070". It wobbles very bad at full rpm now. I am not sure what's going on but i am going backwards not forward with this project now. The blade was just hammered.

moodnacreek · October 25, 2020, 02:43:05 PM

Darn. The very eye of the saw does not touch any thing so build up and rust mean nothing there. Only the outer rim of the collars touch leaving the eye to float. The run out of the collar [the fixed collar] can be as much as 2 thousands where it grips the saw and that part of the saw should be sanded clean both sides. Can you try another saw or rig up another way to spin the mandrel, in the air, to eliminate the pto shaft?