truing trouble

[skamath]

hi,
like i mentioned in another post, i hadn't used my supergrind 2006 much and recently started to.

i am having trouble truing with the older ADV-50D truing tool. i think i am following all the instructions both in the handbook, and Jeff's tips on this forum.

the stone i am getting seems to be slightly deeper (by about 0.006") on the honing wheel side of the stone. tried thrice today and thought i'll stop and ask. (like it is recommended for the planer jig, i am pressing down on the support before i lock it.)

the bronze tip of the tool has more than one wear angle mainly because i rotated it once to align the diamond stones to top side as recommended in the manual. not sure if this matters, but thought i'd mention.

btw, how much of run out is tolerable. if i look a the stone's side profile i see some lateral movement as the stone rotates.

thanks in advance!

[Jeff Farris]

I'm not sure that any grindstone surface could be held to a tolerance much tighter than six thousandths. Remember, it is going to wear immediately as you start to use it.  If it is cutting a true angle, it is possible that the stop bar is slightly twisted in some way. That would be worth a look.  Don't worry too much about the tip...it is normal for it to look a bit ragged and showing only a few cutting chips.

The Owner's Handbook lists the allowable tolerance for side to side run out.  It comes from the inside surface of the grindstone not mating perfectly with the inside washer.  You can minimize it by cleaning the hub area of your grindstone, assembling the unit, checking for run out and then, if run out is present, unlock the nut, turn the inside washer a quarter turn, without turning the grindstone or shaft, retighten the nut and check again.  Eventually you will find a "sweet spot" between the washer and grindstone where the run out is at its lowest.

[skamath]

thanks for the reply. i guess i was trying to make the stone flat enough to try the planer jig the 2nd time. (1st attempt with 6" jointer blades wasn't so good.  i get a bow)

maybe i should get the hang of the tormek more with the straight edge jig before trying the more complicated planer jig.

i'll try tonight by pressing down on the right (honing wheel) side of the truing tool stop bar when i tighten the right knob so it so it cuts less. when i had the stop bar sitting on a perfectly true surface i can see the right edge raised by a hair thickness. not sure if that would to translate to similar twist on the universal support.

btw, i am finding more and more that grinding isn't a simple process. it is sometimes hard to figure out why something is happening.

thanks again.

[Jeff Farris]

Most likely, the bow in your 6 inch blades came from either improperly setting the depth of cut or failing to grind to the point where the blade carrier was completely in contact with the support beam.

You're right, the planer blade attachment isn't the best place to start learning the system.

On the ADV-50D stop bar, look for casting slag or mold lines that might not have been completely cleaned up.

Hey, I'm grasping at straws.  This is not a problem we had often with that tool.

You might also consider upgrading to the TT-50 truing tool, which is a very much improved design.  It is available in an upgrade version where you can use the diamond tip out of your old ADV-50D.

[skamath]

tried truing again tonight. still have the angle on the grindstone. i tried pressing down on that end of the stop bar (before locking) to compensate, but the bar is pretty stiff (which is a good thing i guess) so it didn't really do anything.

Jeff, since you thought that 0.006" difference is good enough i left it at that for now and went back to the planer jig one more time. still no consistent grind, even though it seems the blade holder is touching the support.

i am not taking much of a bite mainly because i already have a burr all along the bevel. (btw the 1st blade that i did i took a 1/4 turn bite and that seems more consistent.)

one other thing. i moved the stops far out so i traverse the blade past the grindstone in both directions. when i am entering the grind stone i hear more grinding than when the entire blade is on the grindstone. is it possible that the corner of the blade cuts into the grindstone slightly causing a overgrind at the ends?

hoping i'll get the hang of things soon. thanks again for your prompt replies.

[ionut]

I hear the same sound but I consider it normal as lesser blade surface contacts the stone and the stone grinds more as the pressure on dimensional unit of the blade increases with decreasing blade surface on the stone. This sound should get more uniform as the grinding brings the blade holder to properly sit on the support. If you still hear the sound difference the depth of the cut was set to much considering the fact that you have a burr already. I usually seat my blades on the stone and do not use the dials to increase the depth of cut. I grind at this setting until I feel no grinding action happens anymore and check for the burr. If is there that's the setting I will use for the rest of the blades, if not I will increase it in smaller increments that the smallest gradation on the locking nuts.

You were saying that you move the blade pass the stone, I would personally not do that, if the depth setting is the smallest possible you can achieve the blade would dig in the stone every single time when would get in contact with it, which I think would lead to faster wear of the stone close to its edges and I am pretty sure the blade will not get straight at the end. I usually stop the blade at ½" of its end.

About the angle of the stone I wouldn't worry much when using the planer jig, the posts of the planer jigs are thinner and allows you more angle adjustment so you should be able to compensate for any difference compared with the universal support.

Ionut

[Jeff Farris]

...one other thing. i moved the stops far out so i traverse the blade past the grindstone in both directions. when i am entering the grind stone i hear more grinding than when the entire blade is on the grindstone. is it possible that the corner of the blade cuts into the grindstone slightly causing a overgrind at the ends?

hoping i'll get the hang of things soon. thanks again for your prompt replies.

That makes me think you've stopped too soon.  If your blade is "stepping up" onto the grindstone (which the increased sound indicates to me), you need to keep grinding.  It may visually appear that the blade carrier is on the support beam, but it would appear that there is still grinding going on.