Recommendation? I'm having a time with my grinder!

Dragons Breath Knives

Dragons Breath Knives

Joined
Aug 24, 2014
Messages
765
Good day to all!! I'm a new guy here and I look to the wisdom from those willing to share. I have a KMG grinder and I am running a flat platen. I am having an issue I sure could use some help with. I profile, bevel, and go to a finer belt to finish-up the grind and plunge line, and my belt will" lunge" towards the scales so I'm "chasing" the plunge back into the choil. I hope that makes sense. I ordered another tension spring, which should be here in a couple of days. Suggestions?

PS, I have a Northridge on order!
Thanks for all the help in advance!
Jim
DBK
 
Sounds like you don't have enough tension in your belt. Depress the tensioning lever with the arm unlocked, pull all the slack out of the belt with the platen and arm, and THEN tighten the arm and release the tensioning lever. You want that belt pretty darn tight.
 
Thanks Matthew!! That's why I ordered that tension spring for the control alarm because I think that after a couple years of use it's gone a little bit a weak. New springs and some new bearings since I'm gonna tear into it. Thank you Sir!
 
Another consideration that many guys have done is to eliminate the spring entirely and use a gas strut. At this point, I'm not sure who to credit for this, but I think it was either David Sharp or Brian Fellhoelter, but here's the parts list from McMaster Carr:


9416K11 Gas Spring with Threaded Ends, 40 Force, 5.90" Extended Length, 2.36" Stroke



9416K29 C-Style Eyelet Bracket for .24" Eyelet Diameter, Gas Spring with Threaded Ends



9416K84 Zinc Eyelet End Fitting for M6 Thread, Gas Spring with Threaded Ends


Some prefer to use higher force struts. They're cheap enough to try a couple until you find what you like, I guess.
 
I agree that lunging on contact is almost always too little tension. I think what happens is the belt engages the knife and begins to spool above it, which effectively changes the length of the belt. If the pressure is uneven, that length change is greater where the pressure is higher, one side of the belt or the other, which pulls it in that direction.

It's worse with fine grit J-flex belts because they're so much more flexible.
 
I don't have a omg, but had the same issue with my grinder. I put a spring about twice the recommended size on, and it's been flawless since.

I'd also suggest checking the wheels. The aluminum tracking wheels tend to wear the crown off. I've already had to recrown mine once, and it's worn again.... I'll be making a hardened steel wheel to replace it before too long.
 
i have noticed the finer the belt i use, and the lighter the backing, the more tension i need on the belt otherwise it will not go all the way over to the right side of the platen with the tracking wheel all the way down to its stopping point. i took my tracking wheel pivot arm off, and ground away the contact point so it could go lower. this helped because i did not have to pull the arm out as far as possible before tightening it. and like yourself, if the tension is way low, the belt moves to the left as soon as i apply pressure.
 
Mypatches1 said:
You guys are GREAT! Thanks!!
Click to expand...
hello
if nothing else works, try to verify wheel alignment.
is very important that the wheels track properly meaning a totally precision line up.
sometimes a misalignment happens after replacing bearings or bushings however a worn bearing will also do this-check for a heating bearing.
sometimes after the machine is tipped over(kids and younger brothers are good at this lol
 
Replaced two bearings, tension spring also. Had to shim a couple of areas to get my platen to line up with my belt. Things visually line up good now, I hope to put it to the test today! Dealing with KMG customer service left me not so warm and fuzzy. Where is my new Northridge??????
 
Mypatches1 said:
Replaced two bearings, tension spring also. Had to shim a couple of areas to get my platen to line up with my belt. Things visually line up good now, I hope to put it to the test today! Dealing with KMG customer service left me not so warm and fuzzy. Where is my new Northridge??????
Click to expand...

Glad I'm not the only one.... Their quality seems to be slipping too, at least from some parts I've ordered...
 
Matthew Gregory said:
Another consideration that many guys have done is to eliminate the spring entirely and use a gas strut. At this point, I'm not sure who to credit for this, but I think it was either David Sharp or Brian Fellhoelter, but here's the parts list from McMaster Carr:


9416K11 Gas Spring with Threaded Ends, 40 Force, 5.90" Extended Length, 2.36" Stroke



9416K29 C-Style Eyelet Bracket for .24" Eyelet Diameter, Gas Spring with Threaded Ends



9416K84 Zinc Eyelet End Fitting for M6 Thread, Gas Spring with Threaded Ends


Some prefer to use higher force struts. They're cheap enough to try a couple until you find what you like, I guess.
Click to expand...

I have also wondered who was the first. I used one in 2009 on my kmg clone. But I did not get the idea from seeing it done. I was looking through McMaster under springs and noticed the gas springs and thought I would give it a try and it worked amazing. My only issue with it and its more of a KMG issue is the short stroke of the tension arm. I don't like having to depress the arm and pull the wheel forward then reach over and tighten the tool arm. But the spring worked amazing for me up until a few screws vibrated loose and the tracking arm came off and bet the gas spring.
 
Bet that changes. Erik Markman says that even rough grinding is better on his Northridge.
 
Could always leave the kmg set up with something specific such as small wheels or a slack belt, and use the new grinder for everything else
 
That's what I did with my first less than stellar grinder build. Flipped it on its side and leave the small wheels on it. Very convenient.
 
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