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TK-2000 Tension Shaft Problems

Started by Larry, April 11, 2015, 11:04:18 AM

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Larry

I got a call from another forum member the other day.  He has a TK-2000 like my machine.  He said the shaft that tensions the band had locked up in the nut.  I told him it was a known problem.  After hearing about the problem from a different member I always dabbed a bit of grease or maybe a squirt of oil on my shaft and it has not locked up.  I'm sure not much lubricant made it to the needed point.  Decided to make a quick check just to make sure my shaft was still ok.

A close look revealed the shaft on my mill is very worn and close to failure.  I pulled it out, cleaned it up, and re-installed.  It should work ok for the short term.  Called TK to check on a replacement.  $87 plus shipping for a shaft and nut the same as what I have is not even an option.

When I had the thread out I closely looked at it.  Its apparent the thread is stretched towards the band.  I imagine when the thread finally breaks that is what locks the shaft in place.  I think obvious that a "V" thread is not strong enough in this application.

The fix seemed simple.  Put in an acme thread and make a new nut block to accept the thread.  Problem is I don't have an acme tap and they are expensive.  I suppose I could get a machine shop to tap the block.  I would do that but I'm in uncharted territory.  The "V" thread is a ¾ – 10 while a 3/4" acme thread will either be a 6 or 8 pitch.  With a coarser pitch that might make the crank a lot harder to turn...maybe even too hard, I just don't know.  Any thoughts on that?

Woke up this morning with another idea.  Weld the end of the acme thread in the old nut block.  Put an off the shelf nut on the outboard side.  Modify the crank arm to turn the nut.  I'm wondering if a brass nut would work better than a steel nut.

I hope to make up my mind on which way to go this weekend so I can get an order off to McMaster-Carr for supplies.  Any ideas will be appreciated.



In this picture right in the center of the thread if you look closely, it looks like the peaks of the thread are stretched to the left.  I'm not sure if that is from wear or pressure from the band acting on weak steel.



In the middle of this picture the peaks of the thread are gone from it rubbing on the clearance hole.  With all the wear it looks like an acme thread.



This picture shows how far from the center of the nut block the clearance hole is.  I'll fix that by off center drilling my new block.



This is the nut block I've been talking about.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

LeeB

The 1200 I had several years back had issues with the tensioner bolt too. Smae issue you are having. I fixed it a couple of times and ended up putting a bigger bolt of higher grade in it and made a new block by welding nuts on block of steel with a hole bored in it.
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, JD 3032 tractor, JD 5410 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

valley ranch

Greetings, Please excuse my saying: The bolt and block served for years? In that case replacing the bolt and block together { the same thread} with the use of the lube you have been using all along would be my choice. I mean by this: Make them, tap the block.
I say this because while I see pressure ware on the bolt it looks a good way from failure.

Hope you don't mind my posting.

Richard

Larry

I'm hoping to get a lot of posts, especially from owners that say they have never had a problem.  Current problems could be caused by Chinese steel, or improper machining of the nut block.  I would love to go back to the factory setup because I can get a piece of ¾ – 10 grade 8 all thread from McMaster for $7 and last night while Stairway to Heaven was playing I knocked out a new nut block.



It corrects the miss-alignment and introduces a new concept known as a grease zerk.  Made out of a piece of John Deere draw bar I'm obligated to paint it green before installation if I go back to factory.

To answer you question I bought the mill near new in 10 and it has had light use with low hours.  For the tension screw to show the kind of wear it does is unacceptable, with such light use.

If the shaft would lock up while I'm out on one of my few custom jobs it has the potential to make a complete washout for the day.  The only way to make repairs is cut out the shaft with a grinder.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

LeeB

Larry, you old hippy you. Looks good. The grease zirk is a nice addition. I actually twisted my rod off when it locked up the last time. That's the reason I went with a bigger size. It's what I had on hand. To me, the 3/4" is just to small.
'98 LT40HDD/Lombardini, Case 580L, Cat D4C, JD 3032 tractor, JD 5410 tractor, Husky 346, 372 and 562XP's. Stihl MS180 and MS361, 1998 and 2006 3/4 Ton 5.9 Cummins 4x4's, 1989 Dodge D100 w/ 318, and a 1966 Chevy C60 w/ dump bed.

Tom the Sawyer

My mill is a B-20, the predecessor of the TK 2000.  It uses the same tension bolt but the block was somewhat different.  Mine had the zerk installed from the factory, as did the one I replaced it with at about 350 hours TT (both bolt and block replaced as a unit).
07 TK B-20, Custom log arch, 20' trailer w/log loading arch, F350 flatbed dually dump.  Piggy-back forklift.  LS tractor w/FEL, Bobcat S250 w/grapple, Stihl 025C 16", Husky 372XP 24/30" bars, Grizzly 20" planer, Nyle L200M DH kiln.
If you call and my wife says, "He's sawin logs", I ain't snoring.

ladylake

 

  Mine went out also at maybe 1000 hours, I took the block to a machine shop who bored out the hole and installed some hardened threads in it, now 9500 hours later it still works like new.  TK you need to make the block out of hardened steel.  Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

redbeard

Iam on my second one and the threads on the new threaded bar are wearing out also. Nice job Larry think I will make a new one like yours next round.
Whidbey Woodworks and Custom Milling  2019 Cooks AC 3662T High production band mill and a Hud-son 60 Diesel wide cut bandmill  JD 2240 50hp Tractor with 145 loader IR 1044 all terrain fork lift  Cooks sharp

xlogger

I'm the one that called Larry, the machine shop has it now and waiting for a harden bolt to come in Monday or Tuesday. I'm going to call them first thing Monday and see if he will do what Steve did with his. So I get a few days off, Steve (ladylake) jokes with me about my excuses for not sawing today :D.  I'm got just under 1000 hours on my machine now.
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

Ga Mtn Man

As I recall mine failed at somewhere around 350 hours, but I did not grease it as frequently as I should have. 

Question:  If you use hardened threads on the block but not on the threaded rod don't you still have the same issue?
"If the women don't find you handsome they should at least find you handy." - Red Green


2012 LT40HDG29 with "Superized" hydraulics,  2 LogRite cant hooks, home-built log arch.

xlogger

In my case he is waiting on the harden threaded bolt that I need, he was out of that the other day. So if he does what Steve suggested both will be harden.
Timberking 2000, Turbo slabber Mill, 584 Case, Bobcat 773, solar kiln, Nyle L-53 DH kiln

ladylake

 

I think the rod on the B20 is hardened good, don't know about the TK2000.   Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

Will_Johnson

Thanks for all of the input and interest here.

We did at one time harden these. The challenge here is two fold. First of all hardening can deform -- which can cause the threads of bolt and nut to be out of line with each other from the get-go and cause instant cross-threading. The second was of back then when a guy had an issue he'd complain bitterly that because the components were hardened they were unable to re-cut the threads on nut and bolt and they had to buy a new part!

Danged if we do, danged if we don't in some ways. :)

When we introduced the present design our goal was to have something that would last long (it usually does), be able to be recut by the customer, but also be relatively inexpensive to replace if this became necessary.

That's the target we need to hit to get the best over-all part for our customers. We are always open to better ways of doing things, and often the best ideas come from customers. So keep the ideas coming but I wanted to give some back-ground on the present design.


red oaks lumber

the problems i see, you can't have 2 wear surfaces. in high use areas the nut or insert is usally a bearing bronze type material, that way the threads don't wear down to a sharp point leading to thread failure
the experts think i do things wrong
over 18 million b.f. processed and 7341 happy customers i disagree

Larry

Will, I think you can see from the posts this has been an ongoing problem for some years.  I hope you correct post haste for future buyers.

I just placed an order with McMaster-Carr for a chunk of 4140 steel and a 1" - 8 grade 8 all thread.  Cost was $36 plus shipping.  The cost to move up from a 3/4" shaft to a 1" shaft was minimal.  It will take a lot more work to make the retro-fit as I will have to turn down the shaft on one end from 1"to 3/4" to fit in the bronze spring bushings.  I have to move the holes on the nut block apart to make room for the larger shaft.  That means I'll have to tap new holes in the nut block mounting plate.  With the 4140 steel I can harden the nut block....can't argue with Steves 9,500 hours.  I'll also put in a grease zerk.

ROL is absolutly right about the bearing materials, that's why I asked about using a brass nut in my first post.  I've been thinking a lot about the best way to go here.   With the 4140 steel I can harden to any level so I thought I would keep it a little softer than the grade 8 shaft.  I'll run the thread extra long and coupled with a grease zerk I think I can avoid problems.  I did look at bronze flange nuts while browsing at McMaster.  Besides being really expensive it would be hard to fit one.  I think the coarser thread of the larger shaft will also help.  Of course it would be different if I was building the machine from scratch...acme thread probably in a cast bearing block would be my choice.

With the 8 pitch all thread I don't think cross threading will be a problem.  Might take a bit more effort to tighten as the factory thread is a 10 pitch.

I'm sure this plan is way way over the top, but I don't ever want to re-visit this problem.  I'm guessing it will take 3-4 hours shop time to do the machine work.  I'll put on more Zeppelin...time goes by fast and what's an old guy to do for fun?

Probably be a few weeks until I get it done but I'll take picture for you guys and report back.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

red oaks lumber

larry
you could have just the thread tips induction hardened, that would give you more thread life but,it wouldn't stop you from re threading later if need be. good luck with your fix :)
the experts think i do things wrong
over 18 million b.f. processed and 7341 happy customers i disagree

ladylake



I don't know how hard the insert is the my machine shop put in the block on my B20 is but it has been in there for over 9000 hours with no problems.  I think he threaded it by hand after putting it in the block.   Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

coppolajc10

Mine failed too, currently machine shop is fixing replacing shaft, helical in block with a washer welded on front to keep helical from backing out. This is the $40 option, so was worth a try.  If this doesn't hold up, I was going to have them make an acme one like Larry pointed out, doesn't seem like the right application for a normal threaded rod.  Though, previous owner of mine went too long without grease causing failure I think.  Just curious, how's this done on other mills?

Larry

A lot of mills use a hydraulic tensioner.  It works similar to a hydraulic jack.  I had one on my old Kasco mill.  The only problem I've ever heard with any of them no matter who makes the mill is a "O" ring may go out.  10 cent fix plus labor.  With a gauge they give a really good indication of what the blade is doing.

I like the spring better because it provides a cushion if a piece of bark or something gets between the band and the wheel.

I think the ultimate is an air bag used on some of the WM industrial mills.  I even seen air tension on re-saws and shop bandsaws...all high dollar machines.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

Will_Johnson

Well again the challenge is to build something that will last a decent amount of time, be easy to fix, and, if necessary, easy and inexpensive to replace. It's a balance.

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.

This is a part that gets a massive amount of stress on it, so it is going to need to be replaced at some point. It's what I would call a long term wear part. I don't know all of the specifics of these different mills, but if after a period of time ("1,000 hours" and "years" were mentioned) one of the major stress-bearing parts of the machine needs to be repaired/replaced I'm not thrilled about it -- we never want anything to wear or fail -- but I don't think it's totally out of line. The reality of all equipment is that things do wear. To my mind the test then is how simple and inexpensive is the repair?

And folks who have worked with us know that if there's a truly premature and inappropriate failure we will always work with customers to address the problem fairly. Within the warranty period and, within reason, beyond it.

All of that said, I have way too much respect for this forum and the folks on it not to share this thread with our design and service folks. We do listen, but again we have to balance many many factors in design.

coppolajc10

Will, simplicity of your mill is one of the main reasons I chose the TK B-20 (hydraulics are nice too  ;D) and drove from western new york to alabama to pick up a used one ... after doing my research a used B-20 was the mill for me and it has yet to disappoint me.  I appreciate that this part is not expensive to fix, like most things on a TK you can easily buy parts local or fabricate a fix, and if it has to be fixed every 500 hours so be it.  I called and spoke to Mike and the price to replace it wasn't worth it when I could have it repaired for less than $60.  I paid $18 in parts and $40 at a local machine shop.  I was going to call TK for this question, but since you're involved in it already, is there a mechanical disadvantage to an acme screw for this part?  You mentioned the importance of "spring," would an acme screw fail in that regard?  Thanks, Jake.

valley ranch

That block looks real good!


                  Stairway to Heaven~ I have that on vinyl in a box up in storage.
                 
                  Was this playing on the radio?

ladylake

Quote from: Will_Johnson on April 14, 2015, 10:46:16 AM
Well again the challenge is to build something that will last a decent amount of time, be easy to fix, and, if necessary, easy and inexpensive to replace. It's a balance.

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.

This is a part that gets a massive amount of stress on it, so it is going to need to be replaced at some point. It's what I would call a long term wear part. I don't know all of the specifics of these different mills, but if after a period of time ("1,000 hours" and "years" were mentioned) one of the major stress-bearing parts of the machine needs to be repaired/replaced I'm not thrilled about it -- we never want anything to wear or fail -- but I don't think it's totally out of line. The reality of all equipment is that things do wear. To my mind the test then is how simple and inexpensive is the repair?

And folks who have worked with us know that if there's a truly premature and inappropriate failure we will always work with customers to address the problem fairly. Within the warranty period and, within reason, beyond it.

All of that said, I have way too much respect for this forum and the folks on it not to share this thread with our design and service folks. We do listen, but again we have to balance many many factors in design.



Will
  I really think you need to use a hardened block on your mills as mine has lasted over 9000 hours after putting a hardened insert in mine and it cost me around $50, no big deal.  If the treads strip out of the block it sure doesn't help to rethread it. 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. Your B20 is a great mill and I've picked up many customers  due to how good and fast it saws.   A TK 2000 might be in the future if you get the setworks so I can saw from the top down and change the thickness of a board on any cut, if sawing all the same size the 2000 setworks works just fine.  Also I think I heard the blade goes to 36" above the deck on your new mills, that's a huge improvement for those big logs.  Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

ladylake

Quote from: coppolajc10 on April 14, 2015, 10:58:44 AM
Will, simplicity of your mill is one of the main reasons I chose the TK B-20 (hydraulics are nice too  ;D) and drove from western new york to alabama to pick up a used one ... after doing my research a used B-20 was the mill for me and it has yet to disappoint me.  I appreciate that this part is not expensive to fix, like most things on a TK you can easily buy parts local or fabricate a fix, and if it has to be fixed every 500 hours so be it.  I called and spoke to Mike and the price to replace it wasn't worth it when I could have it repaired for less than $60.  I paid $18 in parts and $40 at a local machine shop.  I was going to call TK for this question, but since you're involved in it already, is there a mechanical disadvantage to an acme screw for this part?  You mentioned the importance of "spring," would an acme screw fail in that regard?  Thanks, Jake.


  Jake a acme screw might crank too hard as it has way fewer threads per inch, maybe long handles  would work with a acme tread.  Steve
Timberking B20  18000  hours +  Case75xt grapple + forks+8" snow bucket + dirt bucket   770 Oliver   Lots(too many) of chainsaws, Like the Echo saws and the Stihl and Husky     W5  Case loader   1  trailers  Wright sharpener     Suffolk  setter Volvo MCT125c skid loader

Larry

Quote from: valley ranch on April 14, 2015, 02:56:02 PM

                  Stairway to Heaven~ I have that on vinyl in a box up in storage.
                 
                  Was this playing on the radio?

I have all the music I like on the PC.  I'm not sure but maybe it is a MP3 something or other?  I found its really easy to bribe kids to do computer stuff when they come around. :D
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

coppolajc10

Quote from: Will_Johnson on April 14, 2015, 10:46:16 AMOne 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.

Quote from: ladylake on July 12, 1974, 07:53:54 PMI 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.

Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

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.
Larry, making useful and beautiful things out of the most environmental friendly material on the planet.

We need to insure our customers understand the importance of our craft.

Peter Drouin

Nice job you did. smiley_clapping
A&P saw Mill LLC.
45' of Wood Mizer, cutting since 1987.
License NH softwood grader.

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