TK-2000 Tension Shaft Problems

[coppolajc10]

One of the great virtues of this design is that it's simple, it has spring to it (which is vitally important to have the give that's not found on other designs) and on the whole it's dependable, easy to fix.

I like the design with the spring as it offers cushion which hydraulic tensioners don't have unless they have a air pocket built in.

Steve, thanx for clearing that up, thought Will was referring to spring in the choice of threaded rod  ???  Thanks also for advice on acme screw, Jake.

[Larry]

Modification complete.  The tension screw is 1", roughly 1/3 bigger than stock.  Screw and tension nut block have been hardened.  Grease zerks added to keep things moving smoothly.



Added a bushing where the shaft comes through the frame for added stability. 



I've been sawing without a gauge for three or four years and quite happy with that procedure.  I thought maybe the next guy with this mill might want a gauge so.....   Took the "O" ring out of the gauge cylinder and welded it to my new bushing.  Put the "O" rings back in and a plug where the gauge goes.  Since I'm happy measuring the spring compression I won't put a gauge back in until time for the mill to go down the road.



Replaced thrust bearing and washers with all new.  I was hoping a bronze oil-lite thrust bearing would work but it was to much friction.  A standard needle thrust bearing works fine...its surprising how cheap those are and made in the USA.  I would like to try a plastic thrust bearing to see how that would work.



A little something extra.  When a band breaks the slide goes to the right driven by the spring decompressing.  The band wheel hits the housing sometimes easily, and other times like a freight train crash.  I don't know that it causes a problem, but it could be a factor in premature gauge failures.  In any case it can't be good for the wheel bearing.

With the knurled nut I can spin it up to the frame after I tension the band.  It keeps the spring from decompressing in the event a band breaks.  No drama at all.

I haven't had the luck to test it with a broke band yet, but it appears to work.  The nut is just a standard grade  2 nut I turned down and knurled.  If it works I'll make a larger nut that will be a bit more user friendly.  The big question is if I will use it each and every time or will I neglect it after a while.

[pine]

If I understand the nut you added for band breakage.  While it sounds good, if you you use it, will it stiffen the tension so that the blade does not have any "spring" for lack of the correct term from the compression spring.  If the blade is tensioned to a set level and receives a shock the tension spring has a bit of  give to lessen the direct shock to the blade.  With the nut in place that seems to go away and I wonder if it could result in more broken blades due to shock loading.

Of course I may not understand exactly how that is set up. 
Either way nice workmanship.  You must have a nice metal mill to turn the nut and knurl it. Metal and wood mills.  Perfect world.

Since you are using the spring measurement method instead of the gauge, any idea what psi you are running on the blade tension  TK had me turn mine up tighter as they recently changed the manual specified tension. 1300-1500 psi versus the older 1200 psi.

[Larry]

Looking at the plate from the back, its free to move to the left under control of the spring so the cushion is still there.

A couple of times a year I check band tension with a Lenox tension gauge (WM sells the same one) directly on the band.  With 1 7/8" compression on the spring I get a band tension of 18,000 psi.  That works good for what I saw with most bands and is still taking it easy on the machine.  The band manufacture can tell you what they want you to run on the band.  WM wants 19 to 22,000 psi.  Lenox is I think the highest and they want 24,000 psi.  My spring won't give those higher values until it is near total compression.  There are some down in the 16,000 psi range but I can't remember right off hand which ones.

[Peter Drouin]

Nice job you did. smiley_clapping