Anomaly with LTAGA Grinder

[quadracutter222]

Hello all.  I have completed the factory refurbish on the used LTAGA I purchased and am noticing a strange occurrence.  On the first pass, the stone only hits every third tooth on the face grind.  If I try to get all teeth in one pass its grinds every third far too heavy.  

Is it possible that every third tooth there is a change in forward feed amount?  Or perhaps the stones are out of wack?  Or grinder motor arbour wore out?

Cheers and thanks!!

[Tom the Sawyer]

Up front I would admit I have never seen one of those... but, if it is hitting on every third tooth, I would check to make sure the grind stone is perfectly perpendicular to the band.  If it were off a tiny bit, it would hit the teeth that were set in its direction first.

[donbj]

I own one of those and still use it. It works well except a bit under powered and should have more rpm but gets the job done. It's weird it only hits every third tooth. The push mechanism should push each tooth to the exact same position under the grind wheel.

You say on just the first pass? Is it good after that? If so it almost seems like your tooth spacing is different. Something odd here.

[donbj]

Looking at Tom the Sawyers post more I think he may have your answer as every third tooth is set in the same direction or a raker. 

[Cutting Edge]

On the first pass, the stone only hits every third tooth on the face grind.  If I try to get all teeth in one pass its grinds every third far too heavy.  

- Is it possible that every third tooth there is a change in forward feed amount?  

- Or perhaps the stones are out of wack?  Or grinder motor arbour wore out?

quadracutter222,

What you are trying to deal with are blades that are most likely manufactured using a die punch process.  The die is beginning to wear on the leading cutter.  It is possible with other manufacturing methods as material indexing is involved to advance material.  Regardless of the process, this is every so slightly changing the spacing of the offending tooth.

The blades should equal out and be more consistent on the second pass as you've removed the majority of the offending material on the first pass.  By the second sharpening, the blade should be consistent from tooth to tooth with equal material removed each and every time.

The fact you have refurbished the sharpener eliminates almost any wear issues associated with these machines.  

Even if a stone is slightly out of round or "off" in either axis of rotation, the rpm's (rim speed) that it turns, would not effect the indexing/sharpening of every 3rd tooth.  Same goes for the motor arbor.

Be mindful of wheel wear as you sharpen each blade.  Be diligent with dressing of the wheel to maintain the profile needed from blade to blade and you'll get many years of satisfactory service out of it with good maintenance.

Hope this helps ya out.

[donbj]

On the first pass, the stone only hits every third tooth on the face grind.  If I try to get all teeth in one pass its grinds every third far too heavy.  

- Is it possible that every third tooth there is a change in forward feed amount?  

- Or perhaps the stones are out of wack?  Or grinder motor arbour wore out?

quadracutter222,

What you are trying to deal with are blades that are most likely manufactured using a die punch process.  The die is beginning to wear on the leading cutter.  It is possible with other manufacturing methods as material indexing is involved to advance material.  Regardless of the process, this is every so slightly changing the spacing of the offending tooth.

The blades should equal out and be more consistent on the second pass as you've removed the majority of the offending material on the first pass.  By the second sharpening, the blade should be consistent from tooth to tooth with equal material removed each and every time.

The fact you have refurbished the sharpener eliminates almost any wear issues associated with these machines.  

Even if a stone is slightly out of round or "off" in either axis of rotation, the rpm's (rim speed) that it turns, would not effect the indexing/sharpening of every 3rd tooth.  Same goes for the motor arbor.

Be mindful of wheel wear as you sharpen each blade.  Be diligent with dressing of the wheel to maintain the profile needed from blade to blade and you'll get many years of satisfactory service out of it with good maintenance.

Hope this helps ya out.

Cutting Edge, maybe I'm missing something but wouldn't the push arm position each tooth in exactly the same spot under the wheel? A 7/8" spaced blade with the proper cam would position each tooth in the same spot regardless of the slight discrepency you mention wouldn't it? Just trying to wrap my head around this.

[pineywoods]

Most likely one of the hidden gotchas on this unit. Look at the pusher arm closely. There is a small pin that contacts the face of the tooth to advance the blade. Most likely there is a notch worn in the pin where it contacts the face of the tooth. The notch will be exactly as wide as the thickness of the blade. The pin is a press-in roll pin. replace it. There is enough slop in the pusher arm to allow some teeth to fall into the notch, some don't.

[Cutting Edge]

donbj,

The push finger only contacts the tooth at the very bottom of the profile.  The largest percentage of extra metal being removed is above the push finger on the face... towards the tip.

The best way to confirm this is to adjust it to where the offending 3rd tooth is barely, BARELY being contacted on the face and see where the grinding wheel has polished it.

The fact it is consistently every 3rd tooth, almost confirms that there was an issue in manufacturing.  If the machine had a problem, it is highly unlikely that it could produce this result with consistent/repeatable issues.  It would be far more eratic....  Ex - Grind (2) heavy, next (3) perfect, following (2) barely, (7) perfect and so on.

If like in the example given... then the pushfinger itself needs looked at.  Like pineywoods mentioned... the roll pin for starters, but the bronze bushing where it attaches to the cam is the other culprit.

[donbj]

Thanks Cutting Edge.

It would be interesting to have him throw a blade on from a different brand or batch. That would be very telling

[quadracutter222]

On the first pass, the stone only hits every third tooth on the face grind.  If I try to get all teeth in one pass its grinds every third far too heavy.  

- Is it possible that every third tooth there is a change in forward feed amount?  

- Or perhaps the stones are out of wack?  Or grinder motor arbour wore out?

quadracutter222,

What you are trying to deal with are blades that are most likely manufactured using a die punch process.  The die is beginning to wear on the leading cutter.  It is possible with other manufacturing methods as material indexing is involved to advance material.  Regardless of the process, this is every so slightly changing the spacing of the offending tooth.

The blades should equal out and be more consistent on the second pass as you've removed the majority of the offending material on the first pass.  By the second sharpening, the blade should be consistent from tooth to tooth with equal material removed each and every time.

The fact you have refurbished the sharpener eliminates almost any wear issues associated with these machines.  

Even if a stone is slightly out of round or "off" in either axis of rotation, the rpm's (rim speed) that it turns, would not effect the indexing/sharpening of every 3rd tooth.  Same goes for the motor arbor.

Be mindful of wheel wear as you sharpen each blade.  Be diligent with dressing of the wheel to maintain the profile needed from blade to blade and you'll get many years of satisfactory service out of it with good maintenance.

Hope this helps ya out.

Thanks Guys! What I did replace was the cam and pawl, bronze bushings in both the push arm and lift assembly among a few other non critical items.
How crucial is the bolt that holds the main up/down pivot?  The one that goes thru the two bronze bushings. I did notice it had some wear spots.
Are there any other items that stand out to be replaced?
Also the previous owner had modified the roll pin to have a piece of carbide on the end of the threaded rod, I wonder if this is causing some slop too?

[Pabene]

The most important in a grinder is: The feed pin HAS to feed just that tooth as the wheel will grind. So, if the feed arm/pin would feed the tooth before (to the right of) the tooth as the wheel will cut, you will have a lot of problem. It is also good if the end of the feed pin/arm is sliding on a support surface so the feed pin always will hit the tooth face on its stright part. It is not good if the feed pin starts the feed movment in the bottom of the gullets, then slides along the radius and finaly push the tooth to its grinding position.