saw collar

1wkinsley · November 11, 2015, 06:34:49 PM

Greetings,

What are some different methods for refacing saw collars on a circular mill? I just got my blade hammered and my mandrel is level and in good shape but my blade wobbles when it runs. My guess is that the collars are my problem.

Wynn

Kbeitz · November 11, 2015, 06:46:14 PM

I have a machine shop and i was ask to do a job like this.
We took the moveing crossfeed off our lathe and bolted it down to the mill.
We then machined the collar right on the shaft... No run out this way.

1wkinsley · November 11, 2015, 08:56:15 PM

Is there any redneck way of doing it if you dont have a machine shop?

Gearbox · November 11, 2015, 09:54:39 PM

First is your saw up to speed . They will wobble till you get up to hammered speed .I think I would dial indicate the inside collar first . you may lay a shoe box size cardboard between the outer collar and the saw . Also are your saw guides within a 1/16 of the saw when up to speed . Mine are within a 32 nd on the outside when shut down . Gearbox

dgdrls · November 11, 2015, 09:54:58 PM

http://209.164.108.37/board/index.php?topic=70562.0

Check here, Dave has run the gamut with his mill.

Dan

beenthere · November 12, 2015, 12:19:34 AM

Quote from: 1wkinsley on November 11, 2015, 06:34:49 PM
Greetings,

What are some different methods for refacing saw collars on a circular mill? I just got my blade hammered and my mandrel is level and in good shape but my blade wobbles when it runs. My guess is that the collars are my problem.

Wynn

Maybe first put a dial gauge on it and see how far out it is. Might take out the "guess" to your problem.

bandmiller2 · November 12, 2015, 07:21:19 AM

Wynn, good advice given, there is a way to machine the fast collar shown in Stan Lunstroms on line booklet page 19 they are not just machined flat. Many hammersmiths have a portable tool to true up collars, if yours doesn't he will know someone who will do it right. Circular mills are simple machines but everything must be right or they will haunt you day and night. How is your arbor driven, belts will take a set and especially long flat ones that flap will make the saw chatter in the guides . with multiple Vee belts it will usually go away when they run a wile and get warm. Frank C.

1wkinsley · November 12, 2015, 08:19:33 AM

Frank,

I have v belts on it but I think they were not tight enough the last time i tried it so i have since tightened those. Also, there was some rust around the collar and on the face of the collar when I took it off. Could that be a good indicator that something is wrong with my collars?

1wkinsley · November 12, 2015, 08:29:59 AM

In Lunstroms booklet it just says "collars should be machined", and it shows you how to measure it but no how to on the machining.

Kbeitz · November 12, 2015, 06:20:10 PM

Quote from: 1wkinsley on November 12, 2015, 08:29:59 AM
In Lunstroms booklet it just says "collars should be machined", and it shows you how to measure it but no how to on the machining.

And it's best to machine them on the shaft where they belong.

1wkinsley · November 12, 2015, 06:40:35 PM

How do I machine them? I do not have a machine shop and I would like it done by Sunday.

Stuart Caruk · November 12, 2015, 06:52:56 PM

I've made several saw collars for the local mills. I fail to see the point of machining the collar on the saw, since the first time you remove them to reinstall a blade they would NEVER go back on in exactly the same place.

The real problem is how they are often made. Many shops simply chuck up stock in a lathe and bust out the first side of the collar, flip it, and finish the collar. If you measure the runout, it will often be 0.005" simply because the jaws don't line up with the centerline of their lathe. The first half of the collar this isn't important, since you generally finish one half of the collar (the most critical side) complete. For the 2nd half we always mount and machine a set of soft jaws to ensure that the last op is held in jaws that are perfectly concentric and parallel to the lathe centerline. IF you don't have a lathe fret not, there should be dozens of machine shops that can do the work for you.

I'd ask the shop if they bore softjaws to finish the part though, and if not, I'd be very suspect of the final product.

Also, properly designed, the part of the collar that meets the blade is not parallel to the blade except for a very small distance. Ideally the collar has a relief of around .005" in and inch or so.

Another thing to check is to see if the blade is really flat, and or tensioned properly. Unlevel plate, excessive drop, to much or to little tension will cause the blade to wander as well.

bandmiller2 · November 12, 2015, 07:59:05 PM

Wynn, what I was referring to was the shape of the collar face with just the outer 1/2" or so clamping the saw and the center recessed. You should clean the face of the fast collar and as recommended put a dial indicator on it and see how much runout you have. I'am not sure how much run out is acceptable. Its best to machine it with the proper tool. If it was my mill and it was running out much more than .005 I would take my straight shaft grinder with a 6" grinding wheel dressed flat. I would run the arbor and carefully brace the grinder and just let it kiss the high spots at a slight angle. Worth a try if your going to have to have it machined anyways. Frank C.

Kbeitz · November 12, 2015, 09:29:54 PM

The back or the first collar on the shaft works so much better if it's locked to the shaft so it can't turn.
The arbors I have worked with had the collar heat shrunk to the shaft.
Then machine it. The front collar will automatically line up to the fixed collar.
A few thousand's out on the collar really makes a difference at the end of the blade.

dustyhat · November 12, 2015, 09:44:40 PM

Two or three thousands on both collars is what we always put.

ETSawyer · November 20, 2015, 11:07:53 PM

Had ours done over the summer. Was told by saw doc and guy that machined them on the mill if you think you have a collar problem you do lol. He said he like to see 4 thousand in the collars. Found problem after heating saws and irregular cuts. Checked with dial indicator at collars and rim of saws. Can be checked with plumb bob hanging over a shoulder of the saw. Rotate saw and check every few teeth. If the strings hangs away from opposite tooth or touches holding out of plumb its a good sign there's a problem. Not as accurate as a dial but if the collars are out it will show in one spot on the saw and head you in the right direction. Ours were done with a jig that clamped to frame of the mill. Grinding wheel mounted on lathe slide clamped with desired taper for collars. Hope this helps.

ddcuning · November 21, 2015, 07:18:26 PM

While you are working on finding someone to machine the collar, paper it for now and see if that helps. If you paper it and you see a noticeable reduction in wobble, that is a clear indication that you need the collars machined. I papered mine before I replaced it and saw improvement. Of course, reading my thread you can see my mandrel was bent, bearings bad, etc. etc. so machining the collars was a mute point.

Dave C

Lambee10 · November 23, 2015, 02:09:17 PM

Quote from: ddcuning on November 21, 2015, 07:18:26 PM
While you are working on finding someone to machine the collar, paper it for now and see if that helps. If you paper it and you see a noticeable reduction in wobble, that is a clear indication that you need the collars machined. I papered mine before I replaced it and saw improvement. Of course, reading my thread you can see my mandrel was bent, bearings bad, etc. etc. so machining the collars was a mute point.

Dave C

Dave- what do you mean by Paper It?

beenthere · November 23, 2015, 03:05:58 PM

May be helpful to read up on collars in this circular sawmill booklet, linked in .pdf format.

http://www.fpl.fs.fed.us/documnts/misc/circsaw.pdf

Ron Wenrich · November 23, 2015, 03:35:11 PM

When you paper your collar, you're using a shim. But, you have to know where to put the paper. You can make it worse.

You need to open your saw guides up and find where the saw is hanging in the center. Then you advance the saw at each tooth. As it moves off center, you add a + sign if it goes to the right, and a o if it goes to the left. A - is center. The further it moves away, you add more + or o signs. The farthermost point might have 4 or 5 signs on it. After you do the whole saw, you can figure out where to put the shim.

If you take the saw and rotate it 180°, the marks should be the opposite. If not, it's in the saw, not the collars or shaft.