Just had my spindle reground by Spindle Grinding Service!

[Edster]

I just had my VMC15's spindle taper reground by Spindle Grinding Service. Very nice people to deal with. My spindle went from 30% contact area and .0001 runout to 96% contact area and <.00005 runout. It would have been 100% but there was a small gouge at the small end of the taper left from a crash by the previous owner. It's a pretty cool process. Their fixture moves up and down with hydraulics and holds a tool post grinder. They turn the machine spindle on and use the y axis to adjust the ammount they are removing. Their grinder does the rest. My spindle was hourglass shaped and it was very easy to see the grinding wheel start to take material off in the middle before the ends. It took about 4 hours for everything. They checked the drawbar pressure before and after, checked the fit by blueing and checked runout with a tool and without. They even checked the drawbar pressure on my new TM-1 for free. It ended up costing $300 plus drive time, and the tech lives 20 minutes from me so that isn't too bad. I haven't tested it yet, but I'm sure there will be a huge improvement.

www.spindlegrinding.com

no affiliation just a happy customer.

[fpworks]

I'm more curious as to how is affects your tool length repeatability. (I would imagine that it is much better now)

Do you know your tool length repeatability before the spindle grinding?

...and just curious, how much did they remove on the spindle taper? (referenced from the gage line)

Justin

[Walt@SGS.Inc]

Edster,
Thank you for the post. I hope you do indeed realize an inprovement it the operation of your machine.
Be aware, you may have to adjust you Z axis home position. With your runout readings before and after, adjustment of your boring bars should not be necessary.
If we can be of further assistance feel free to call.
Regards, Walt Spindle Grinding Service Inc.
PS Again, thanks for the post.

[miljnor]

That cool man.

I wonder with all of that contact if you'll have tools sticking from the added friction.

I don't think the machines have that good of contact from the factory! I remeber when I was at my last job we did a spindle check on got a little touch at the base and a little at the draw bar end.

All though in all fairness it could have been the tool holders as my last boss was a cheap guy and bought the low dollard end.

[Geof]

Originally Posted by miljnor I wonder with all of that contact if you'll have tools sticking from the added friction.

That thought went through my mind. We had a lot of problems with a tool sticking in a VF-0 on a particular part with a very heav metal removal sequence. Eventually found a holder that did not have a really good fit in the taper; it solved the sticking problem.

Although on reflection I suppose every time we use that holder on that job we are beating the piss out of the spindle taper. Still the machine has paid for itself about tenfold and the parts still come out in tolerance. It is nice only having to work to +/-0.001".

[Ken_Shea]

Michael T,
I was thinking yet not knowing the same thing at first, yet with further thought my suspect is that the tendency for sticking would be caused from any high and low spots, when they are not there it should be less.


Walt ?

[miljnor]

hey ken

Tapers lock because of friction (acording to some book I read long ago) and thus if more surface contact more friction, ergo more lock-up.

This isn't a bad thing. just have to be aware of it. And all this locking up can be cured by a light oil coating. Probably makes the tool cut with less chatter and last longer too.

[Walt@SGS.Inc]

Some one mentioned sticking tools. I think they answered there own question when they mentioned heavy metal removal. Full contact in a taper spreads the pounds per square inch over the entire tool. Some people seem to think relieving the tool holder in the middle helps the tool sticking problem, I'm not so sure. Many many times, sticking tools can be traced to not enough tool knock out and or heat coming from either the bearings or from the cutting tool itself. (Heavy metal removal) Bear in mind, the heat in the spindle can be coming from the tool prior. Then the 2nd tool sticks and everyone looks at the sticking tool and forgets where the heat came from.
Some times the black oxide tools seem to stick more. Sometimes a little oil helps.
I think the use of oil is just a step in the direction of keeping toolholders clean. Keeping tool holders clean never hurt anything.
Regards Walt....

[Neal]

Fadal Spindles are designed to have a slight[B] concave form on the taper of the spindle. This is to avoid the "wringing" of the tapers together. It is designed to contact at the top of the taper and at the bottom of the taper.
Also, grinding too much out of the spindle WILL affect the Z axis zero position and also possibly the functionality of the Bellville Stack that hold the tool into the taper.
I state this just as a caution not to get over zealous about regrinding tapers.

Neal

[Edster]

fpworks, I don't know the repetability, but the machine was working ok for the parts (+/- .001) I do. They say that they usually don't take more than .002 out. I'm not sure where they measure the two thou from. I didn't think to ask how much they acutally took out of my spindle, but it wasn't out of round or anything. He did say that to correct out of round from a crash would need more material removed.

I also asked how many times can you grind the spindle, and they told me until the drawbar looses pressure on the tool, or when the face of the tool holder contacts the spindle face. Since there is a mile between the face of the tool and the spindle on my machine I think the drawbar would be the limiting factor. They measure the drawbar pressure before and after to make sure everything is working properly. The pressure of my drawbar was 810# that's with new bellville washers and a new drawbar a few months ago. Just a fyi my new Haas Tm-1 had 1004# of pressure. The tech did say the better machines like mazak were over 1500# of pressure.

I think the tools were sticking (making a loud popping noise when toolchanging not jamming) because of the low contact area at the big and small ends of the taper. Marks were being left in the middle of the toolholders that looked like little rust marks. I tried oiling the tools and it seemed to help the fadal, but on my new haas it made the tools stick tighter in the taper, go figure.

[Geof]

Originally Posted by Walt@SGS.Inc Some one mentioned sticking tools.... Some people seem to think relieving the tool holder in the middle helps the tool sticking problem, I'm not so sure. Many many times, sticking tools can be traced to not enough tool knock out.... Keeping tool holders clean never hurt anything. Regards Walt....

Based on my tool sticking experience and the way it was solved I think you can be very sure that relieving the middle does not help. Tools that fit very nicely along the length of the taper or which fit nicely at each end with less contact in the middle were prone to sticking. The tool that does not stick makes good contact at the small end but not so good contact at the large end. I cannot quantify 'not so good' any better than say it is less than the thickness of felt pen ink. My theory as to why it doesn't stick is that under a heavy cut it just wobbles a tiny bit and this stops it bedding in. But as a mention in my other post this is probably being a bit brutal on the spindle taper so it is probably not advisable on a machine that is expected to work to tenths.

[nervis1]

Those rust like marks could be galling from low drawbar pressure. 810# seems a bit low. I remember seeing in the manual drawbar pressure normals listed for the diferent spindles, don't remember one under 1000#, most were around 1200 I think. Could be wrong. You sure you have the full compliment of spring washers in there? Did not leave one or two out by mistake?