Any tips for tuning a Tennsmith Shear

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Marty_Escarcega
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Any tips for tuning a Tennsmith Shear

Post by Marty_Escarcega » Tue Jun 01, 2004 7:09 am

I've had a 52" Tennsmith jump shear for quite a while. It was given to me as a trade for doing some work. Its never been adjusted properly. Too much space between the bed and the upper knife. How much of a job is it to adjust up any tips?

Marty
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Doug_C
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Re: Any tips for tuning a Tennsmith Shear

Post by Doug_C » Tue Jun 01, 2004 2:31 pm

Hi Marty,

There is no positive stop on the upper ram, this is controlled by the return spring tension.

The only adjustments I know of are as follows:


Rake Adjustments

Find the turnbuckles under the table. They are supposed to adjust the rake angle of the upper knife, but also adjust the foot pedal height.

First set the rake angle by placing 2 marks on the table. One 2" from the right end and then one mark 48" from there near the left end. The right end knife opening at the mark will be adjusted to 3/8" and the left end opening at the mark 1 3/4" respectively. Adjust each turnbuckle to get the rake dimensions set.

This works out to be a rake angle of 11/32(.343) per foot. Greater rake will reduce the force it takes to cut by reducing the amount of material in shear at any point durning the stroke, but also increases twist in the fall off piece. Flattening out the rake will decrease your capacity to cut material since too much material will be in shear at any point in the stroke. It also increases the likelyhood of folding material between the knives. There is a lot of other things that contribute to that too, but you get the picture for this discussion.

It is suggested to lock the gibb on the right end, once the 3/8" is achieved. Then make adjustments to the other turnbuckle for the 1 3/4". Then reset the gibb clearances. Make sure the machine is level first. I'd just as soon not mess with it if you don't have to. It is still possible to get the 1 3/8 difference in 48" without doing this.

Pedal height Adjustments

To adjust the pedal height. Lock the turnbuckles in place with the top screw locknut. Stroke the shear down and lock the upper knife in the down position with the middle gibb screws. Be sure that the left end of the knives cross by 1/8".

Disconnect the pedal from both turnbuckles and turn the lower screw of both equally turn for turn, up or down to put the pedal at a comfortable height and still have the knives cross on the left end before the bottom limit of the pedal. Re-attach the pedal to the turnbuckles, reset the gibb clearances and try out the setting.

Gibb Adjustments

Incidentally. setting the gibb clearance is done by first leveling the machine. Back off all gibb screws. Stroke the pedel and lock the ram at the bottom of the stroke with the middle gibb screws on each end. Then back off the gibb screws slowly, until the upper knife comes up on its own. Back off the scew 1/4 turn more and lock it with the jam nuts. Repeat this procedure with the rest of the gibb screws.

DC

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Steve_in_Mich
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Re: Any tips for tuning a Tennsmith Shear

Post by Steve_in_Mich » Tue Jun 01, 2004 3:50 pm

Gee Wizz Doug C, you could have saved me a whole day with that detail.

Great post!!!!!!!!!!!!!!!!!!!
Just because you don’t believe it - doesn’t mean it’s not so.

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Doug_C
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Re: Any tips for tuning a Tennsmith Shear

Post by Doug_C » Tue Jun 01, 2004 4:45 pm

Hope it helps someone now or in the future. Otherwise it's just useless information cluttering my experience banks. If I forget about what I used to know, I may need to return here to retrieve what I once knew off the cuff.

I saved the knife clearance adjustments for another day. I never did like the Tennsmith's procedure, but obviously it works.

DC

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Marty_Escarcega
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Re: Any tips for tuning a Tennsmith Shear

Post by Marty_Escarcega » Tue Jun 01, 2004 10:25 pm

Way cool Doug! Thanks. Would you believe that they replaced the table on this machine at one time! I don't think they ever went through the process of "tuning" it. They never liked the way it cut and it was replaced by an import machine.

I will tune mine this weekend. Will be great not have to bounce my 240lbs up and down on the pedal to cut an 8" piece of sheet metal!

Marty
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Scott
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Re: Any tips for tuning a Tennsmith Shear

Post by Scott » Wed Jun 02, 2004 12:50 am

Doug,
I alway enjoyed your posts about shears from the old board. Heck I even enjoyed your posts with D. Thomas. [img]/ubb/images/graemlins/grin.gif"%20alt="[/img]

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Doug_C
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Re: Any tips for tuning a Tennsmith Shear

Post by Doug_C » Wed Jun 02, 2004 1:38 am

There should be 2 sets of holes in the pedal bars where the turnbuckles attach, The rear set of holes will gain you a mechanical advantage if the linkage is further back. These shears always need more force than what one would have expected.

Since you know the table was replaced, I will go into the knife clearance setting sooner than later.

The knife clearance should be set to .002. I start this with the table backed off. I want to know where the knives are in relation to each other before I stroke new knives together.

There are 2 locking bolts at each outside end of the table. There is also a bowing rod adjustment on the backside of the ram that will flex the upper knife.

The only place I check the clearance is a 2-3" area, both sides of where the knives cross during the stroke. I do this with the table backed off and use thin(.03-.06) aluminum burr free scraps as feeler gages. Verify the ends first by moving the table for equal clearance at both ends. Then check and adjust the center is parallel or slightly tighter using the bowing rod on the back of the ram.

As the pedal is slowly brought down, check the right end knife clearance at crossing, then the left end and snug the table in place. Check and adjust the center if needed. Better yet, checking every 3-6" with a feeler gage set will map out any tight spots that could prevent a .002 setting. After the knives are verified set parallel, they can be moved to the .002 setting or whatever may be realistic due to any previous finding that would prevent it otherwise. Crud, burrs, or kinks in the knife seats will make things interesting.

Keep in mind that these knives have only 2 useful edges each. This is due to them being a parallelogram? The upper knife seat is perpendicular to the table, but the lower knife seat is tilted to provide clearance below the cutting edge. This helps prevent trapping material between the back gage and the lower knife as it cuts. Installing either of the knives in bassackwards will cause all kinds of grief.

Tennsmith used to suggest setting the knife clearance with paper. I'd tend to think that by the time an inexperienced adjuster is finished......a new set of knives may be in order? LOL!

Let me know if anything needs clarification.

DC

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Doug_C
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Re: Any tips for tuning a Tennsmith Shear

Post by Doug_C » Wed Jun 02, 2004 1:52 am

EhhGadz [img]/ubb/images/graemlins/crazy.gif"%20alt="[/img], I was hoping that history was long and forgotten!

Not some of my prouder moments for sure...... [img]/ubb/images/graemlins/blush.gif"%20alt="[/img]

I must be jell'n? LOL!

DC

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Re: Any tips for tuning a Tennsmith Shear

Post by Grue » Wed Jun 02, 2004 4:03 pm

Terrific info Doug, Thanks muchly.

I've been looking for a difinitive statement about blade clearance for years,and have never found one. The word of mouth explanation that seems to be standard is to set the clearance to 5% of material thickness.

Your explanation for the Tennsmith at .002 would be in this ball park,as most of these shears would be used for metals in gauges 2*

I've worked on larger machines with a cutting capacity of up to 1/4" and these have a lever adjustment to adjust the clearance according to the thickness you are cutting. If you cut a piece of 10 gauge with the machine set to 1/4", you get an almighty burr, and doing the opposite really shortens the life of the knives.

Glenn
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Doug_C
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Re: Any tips for tuning a Tennsmith Shear

Post by Doug_C » Wed Jun 02, 2004 4:38 pm

Thanks Glenn,

I had opportunity in my past to installed and set up 10ga to 1" plate shears etc. across this great country doing field service work. Only recently have I had any exposure to toys, uh...I mean Tennsmiths.....LOL!

DC

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