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Size is jumping during cylindrical grind

Good to have a dresser mounted in the setup so you can redress at needed intervals by just traveling to the dresser.
For solid carbide and the correct feed rate there should be little wheel wear for a scheduled number of parts (perhaps 5 or what) parts?
For a +- 005rad I just use a pocket scope and hand bump on a rad..
 
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Does the graph reverse with more parts?
Very common for me is that the machine starts out big in the morning.
Size dives as the wheels, spindle and such heat up and grow.
At about 10 parts things stabilize and I turn on the auto wheel wear adjust.
You know this will happen so important not to chase the first few and know the whats up.
On most parts we put notes in the program of behavior on cold start.
 

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Using as 16" wheel of much width for a .170 x .030" grind with a radius spec would be a lot of wheel to dress and diamonds going into the waste. Hopfully you have a narrow wheel, if not a 8 or 10" x 1/4"wheel would save some money.
and if it is long run part it seems it could be pressed and sintered closer than +.03"
 
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QT op ( I was under the impression carbide doesn't really load up the wheel like steel)
Correct carbide dosent load the wheel like steel but some wheel have harder bonding and the bond fills the room for chips. so it dosent hurt to stick a diamind wheel grinding carbide.
Proper siicking does not disrupt the diamonds, just lowers the bond.
 
Using as 16" wheel of much width for a .170 x .030" grind with a radius spec would be a lot of wheel to dress and diamonds going into the waste. Hopfully you have a narrow wheel, if not a 8 or 10" x 1/4"wheel would save some money.
and if it is long run part it seems it could be pressed and sintered closer than +.03"
My wheel is a 120 grit, 16"x0.5" wheel at the moment. I am wanting to switch to a 180 grit 18"x0.25" wheel.

I agree on the press and sintered part as well.
 
I had a made for grinding duble back tape that i bught back in the 70s that would be good
I dont see it marketed any more. It was a paper like tape and pretty thick, .004 or so. But using tape along with a hold down would be time consuming.for what should be a fast grid job.
 
Double sided carpet tape works.
We sometimes use it on the Blanchard.
Since I am trying to use this vise now, I don't think the tape would be necessary?
Does the graph reverse with more parts?
Very common for me is that the machine starts out big in the morning.
Size dives as the wheels, spindle and such heat up and grow.
At about 10 parts things stabilize and I turn on the auto wheel wear adjust.
You know this will happen so important not to chase the first few and know the whats up.
On most parts we put notes in the program of behavior on cold start.
I ran 10 parts and the graph did not reverse... I am still having the issue of these parts getting smaller the more I grind.
 
Since I am trying to use this vise now, I don't think the tape would be necessary?

I ran 10 parts and the graph did not reverse... I am still having the issue of these parts getting smaller the more I grind.

Keep going until it stabilizes? Something isn't right. Wheels wear, they don't grow. Could there be a bearing issue in the workhead?

And no, not necessary if you're using a vise. I think Buck was still thinking about the part flat on the faceplate with the center.
 
Keep going until it stabilizes? Something isn't right. Wheels wear, they don't grow. Could there be a bearing issue in the workhead?

And no, not necessary if you're using a vise. I think Buck was still thinking about the part flat on the faceplate with the center.
Maybe mechanical but doubtful. Would there be anyway to check this?

I wish I could run more. But these parts are pricey, and most my test pieces are coming out scrap

I just checked the runout of the wheel. It’s around 0.0008”, can this be giving me issues? Or is that not a big deal.
 
Maybe mechanical but doubtful. Would there be anyway to check this?

I wish I could run more. But these parts are pricey, and most my test pieces are coming out scrap

I just checked the runout of the wheel. It’s around 0.0008”, can this be giving me issues? Or is that not a big deal.

Put something round and true in the workhead and dial it in, see if it indicates true. Check for deflection and maybe end play by applying some pressure.

The wheel runout is not ideal, but I don't see it causing size changes unless your wheel is not stable. Are you absolutely sure it's tight? How are you dressing?
 
Put something round and true in the workhead and dial it in, see if it indicates true. Check for deflection and maybe end play by applying some pressure.

The wheel runout is not ideal, but I don't see it causing size changes unless your wheel is not stable. Are you absolutely sure it's tight? How are you dressing?
Fairly certain it is tight, but I will check again. I dressed the wheel by grinding the faceplate diameter (steel)
 
Since I am trying to use this vise now, I don't think the tape would be necessary?

I ran 10 parts and the graph did not reverse... I am still having the issue of these parts getting smaller the more I grind.
One can put a 50 mill DTI on a mag base that sits on the table and touches the in/out table somewhere and watch it.
A continual forever going smaller says encoder or other problems. This can happen due to retract speed being higher than indeed but is very rare.
Also here is coupler or pulley slip, broken coupler, due to the accel and speed differences between in and out.
You can use a touch temp probe and check the temp of the wheel itself just behind the diamond layer to see if it is growing.
.0008 runout works but why is it there? Should have dressed true under .0001. Spindle bearings? Wheel not tight on flanges?
Checking runout on a 120 grit diamond wheel is not easy so not sure how done here. The wheel eats the indicator tip.
We rotate a lot of turns and let it eat a rad into the carbide indicator tip so that it settles down. Others put scotch tape on the wheel OD and ignore the bumps.
Now in a vise I'd think the end part is now round and not oblong? (IE: no lobing)
How is it dressed? Wheel stick after dress tried to open it up to full cutting?
 
.... I dressed the wheel by grinding the faceplate diameter (steel)
Oh....:eek:. That's a new wrinkle. We should have asked this true/dress question at the start. :wall:

Then you absolutely must stick the wheel after dress to open the bond and expose the diamonds.
Size control will be just this side of impossible without this.
Your grinding pressure must be huge dressing this way.
This grind steel method will true a diamond wheel slowly but it will not cut a worth crap until the bond is removed around the diamonds.
Also this leaves you with very dull diamonds. Good for a finer finish and sometimes done on purpose but higher pressures.
Does explain how you are getting away with a 120 grit wheel here which I found strange for this tolerance and a nice finish. I'd be in 320/400.

Another truing method is to put a moly stick in where the normal dressing diamond goes.
This also has to be opened up with a stick before use.

The only way you get away with no stick on a resin or vit bond wheel is using a motorized or brake controlled wheel dresser and even then the stone has to match the wheel in use.
Note to others: Never stick or try to dress/true a plated diamond wheel. Only one layer of diamond here.
 
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Oh....:eek:
Then you absolutely must stick the wheel after dress to open the bond and expose the diamonds.
Size control will be just this side of impossible without this.
I do stick the wheel after I dress with the steel plate. I don't stick the wheel after grinding carbide parts. Wheel looks open to me (correct me if I am wrong).
Image
One can put a 50 mill DTI on a mag base that sits on the table and touches the in/out table somewhere and watch it.
A continual forever going smaller says encoder or other problems. This can happen due to retract speed being higher than indeed but is very rare.
Also here is coupler or pulley slip, broken coupler, due to the accel and speed differences between in and out.
You can use a touch temp probe and check the temp of the wheel itself just behind the diamond layer to see if it is growing.
.0008 runout works but why is it there? Should have dressed true under .0001. Spindle bearings? Wheel not tight on flanges?
Checking runout on a 120 grit diamond wheel is not easy so not sure how done here. The wheel eats the indicator tip.
We rotate a lot of turns and let it eat a rad into the carbide indicator tip so that it settles down. Others put scotch tape on the wheel OD and ignore the bumps.
Now in a vise I'd think the end part is now round and not oblong? (IE: no lobing)
How is it dressed? Wheel stick after dress tried to open it up to full cutting?
This is where it gets weird. I put a DTI on the table, and wrote a program to rapid the wheel to the same spot and infeed a thou, rapid in X and Z and looped it 20 times -- the DTI repeated everytime and did not move. After this test I thought I could confidently eliminate any error from an encoder or ballscrew... am i wrong? *Note that the wheel was not spinning, nor the workhead*

The touch temp probe is an interesting idea, wonder if I have something like that.

Im checking the runout two ways, 1) masking tape on the wheel, 2) sacraficing a DTI tip. I think the runout is there because I got lazy, and only needed 0.17" of a 0.5" wheel dressed. I will get the runout out today.

You are correct the parts are very round after grind, on my tenth DTI i can not even see it move.
 








 
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