[tcom-frazzled]

Folks,

I sent a spindle out for a grind, chrome, regrind. When it came back from the grinding, the newly refinished taper looked great, but the clearance gap between the top of the toolholder and the spindle face seemed excessive. Since I don't have any dimensioned drawings for the spindle on this Miyano TSV-35, I can't know if it is correct. The grinder insists that it is, but I'm now having problems with occasional misses in the ATC, where it will close the retention collet too high on the pull stud and the tool won't be seated properly in the taper. Occasionally, it'll even be out of the drive dogs. What should the standard clearance be? Right now, it's about 80 thou.




As you can also see, the drive dog engagement isn't all that great either, which also bothers me. Can anyone tell me if this is normal and I should be focused on readjusting the Drawbar transition point, or should I be looking for another shop to do another regrind? Or both?

Thanks!

[underthetire]

I'd run it. Check the atc height, make sure the v flange lines up, you may need to adjust the z axis to compensate. The only way you will know for sure is with a $$gage$$ tool(testbar).

[tcom-frazzled]

The way the ATC toolholder fork catches the v flange makes it a real pain to check alignment, but I'll take a crack at it. Everything is about mechanical timing on this machine, so i cant just tweak it in software.

When I sent it in, the taper was worn to the extent that the top of the V flange was hitting the spindle face and the drawbar would hit its upper limit stop before the taper would be fully engaged. To think it was worn that badly is almost unimaginable. Yes, this is a used machine that was bought to bring back to life. :-)

The mechanical timing of this thing is enough to make a watchmaker curse it. Just wish there was some kind of adjustment procedure doc.

[handlewanker]

Hi, get the spindle out and send a tool holder with the spindle to the grinder and STATE what dimension you want the tool holder to have when it's in the taper.....the customer is ALWAYS right when he is paying the bill.

Take advice as given but use your judgement.

The tool needs to be in the spindle with some clearance on the face when it's locked up and I'd reset the ATC (as in remount or adjust it's position) to line up with the tool collar.

The tool in the spindle is the first most important part to be fitted.
Ian.

[tcom-frazzled]

I sent it back to the guy once already with a toolholder and he still insists that its correct. I just want someone to confirm whether that amount of clearance is correct/normal for a bt30 spindle that isn't a big plus configuration.

If it is correct, I'll go to town adjusting the ATC mechanics, but I didn't want to start that process until I was sure the taper grinding was correct.

[Riddersholm]

I belive the correct distance from the tool to the spindle is 0.0079 on a BT30.

[underthetire]

There is no "standard" from the flange to the spindle nose i'm aware of. Every builder is different from what i've seen. Considering builders like Mori use a through spindle coolant plungers between the face of the spindle and the tool holder flange, I can see that dimension vary greatly. The distance your showing really looks right to me. Most tool holders have a flat right about that point from the taper to the flange. If yours was smaller to begin with, i'm betting someone re ground that spindle in the machine, if not more than once.

[The Swede]

The distance should be 2 mm. So your about 0,080 inch is correct

Adjustment ATC and/or tool change height is unavoidable

[nakatome]

first get some hi-spot ink / impression blue, very litey put some on tool holder, clamp tool in spindle remove tool check tool holder for contact should be 80%+ , with pull stud removed is tool going in spindle same distance , if spindle tapper had much metal removed draw bar tension changed and stroke .

[RICHARD ZASTROW]

Try this www.tools-n-gizmos.com/specs/Tapers.html#BT

Dick Z

[handlewanker]

Hi, if the spindle bore has been chromed and reground to give the clearance recomended, then I'd check the condition of the draw bar end and it's position and the position of the ATC as the next move.
Ian.

[tcom-frazzled]

I got lucky and one of the shop guys at centerline was able to shed some light on this. The tolerance for this clearance is 0.045 to 0.079, so a newly ground spindle should be toward the high end. Since the taper appears to be in order, I can get started on the ATC adjustments. I just wanted to make sure I wasn't about to spend an inordinate amount of time adjusting the ATC to match an out of spec spindle dimension.

Thanks for all of the responses.

[handlewanker]

Hi, I couldn't imagine why they make the drive dogs on the spindle so short when there is more depth to engage on, probably to make sure the drive dogs don't run out of slot length in the tool......mine are about 20mm long through the tool collar on all the tooling I have for my mill.

I'd also investigate if the end face of the drive dogs........which are slip in keys held in with cap screws......are not worn down and "re-finished" by the previous owner, seeing as how the bore of the spindle was so worn.

If the drive dogs are a concern you could make new ones slightly longer, but they need to be case hardened and ground for a decent job.

I just went out to the workshop and measured the drive dogs on my Ajax mill which has ISO 40 taper.....the tool in it has a collar of 15mm thick, but the drive dogs only engage for 5mm, so I tried another ER32 chuck I just bought and this has a collar of 10mm thick but the drive dogs stilll engage for only the first 5mm, same clearance behind the colla retc.

That's a puzzle, but as the machine was designed that way I'll not fret over it, the forces driving even a big cutter probably won't be enough to shear the drive dogs off.

Best of luck with the ATC.
Ian.

[handlewanker]

Hi again, just had a thought, check the condition of the drive dogs and the tooling you have to go with the machine.

If the drive dogs are in poor condition, IE, if they have the corners badly worn off so that you are just engaging the drive dogs in the collar slots with a rounded edge as oppossed to a flat face, you could get an effect that would cause the tool to be jacked out of the taper as the engagement edge acts like a taper wedge against the tool slot edge/face under drive forces.

This would only be in extreme drive conditions where you were driving something like a big facing cutter, but it could explain why the bore was so badly worn......tooling pulling out of the taper and forcing the draw bar gripper then turning in the taper bore etc.

I can't think of any other way the bore could get damaged as once the tool is locked into the drive slots there is no further motion.......it is a possibility that the original owner drove a tool without the drive dogs so allowing easy tool insertion from the ATC if he was getting trouble in that quarter.

The machine spindle would have to be orientated 100% to the drive dogs and tooling slots to allow the tool to be entered by the ATC, so if the previous owner had the dogs out this would explain the bore damage..... tool rotating in the taper etc.......he probably re-inserted the drive dogs when he sold it to you, so they would probably be in pristine condition in that case........just a suspicion.....LOL.

I would not be surprised if you get a lot of trouble orientating the tooling with the ATC and the drive slots once you get it alligned.

Not knowing the set-up, how does your system orientate the drive dogs and tool slots when using the ATC?

If there is significent wear on the drive dog end faces, not the sides or drive faces, then it would appear that the ATC presses the tool up against the drive dogs and the spindle rotates slowly until the slots are engaged and the tool "clicks" in.

I don't think the draw bar would get a hold before the drive dogs are in the slots.

One question I would ask and that is how could the machine function with the ATC as it is for the previous owner, and why is it out of allignment.
Ian.

[tcom-frazzled]

This is service on a machine that I never got to see under power in its previous home. The drive dogs that you see in the picture aren't keyed and bolted to the spindle, they are integral. The ends have a slight chamfer, but it isn't so severe that I would expect a tool to jump out once it has seated in the taper. The problem only occurs when the tool is initially being grabbed by the drawbar. The spindle orientation isn't a problem, and the tool holder arms are keyed to the drive dogs in such a way that toolholder a shouldn't be able to rotate.

I'm pretty sure the problem is related to timing the retraction of the tool holder arm from the spindle nose. I don't think it is holding it far enough/tight enough in the spindle taper when the motion begins to transition to retracting the arm.

[handlewanker]

Hi, then it would seem that there was some swarf getting into the taper to get it damaged and require chroming and a re-grind......how else would the tapered bore, once it is in contact with the tool taper and locked, get damaged?
Ian.

[underthetire]

Gotta ask, you sure you have the correct retention knobs?

[tcom-frazzled]

I'm sure it was any number of atrocities. Swarf, worn toolholders, excessively heavy side milling causing the toolholders to pull loose in the taper while machining, and probably at least one or two regrinds before the machine landed in front of me to bring back to life.

Really, my focus is on understanding how it should be and there isn't exactly a ton of documentation floating around out there. I have the original manuals, but about all you're getting from those is an invitation to call Miyano (Mectron) and have them either try to sell you a new machine or tell you to fly a kite. I've tried... Drawings, why shoud a MTB that no longer supports a machine provide info like that? That's just silliness.

Based on everything I've heard, the taper is within a standard spec, so the rest has to be ATC adjustment. I have a few weeks out of town to give it some thought and when I get back to the shop, I'll figure out exactly what is going on with it.

[tcom-frazzled]

Yeah, at least the manuals specified those. All of the pull studs are new and I went so far as to check them with a digital protractor to make sure there wasn't some kind of mixup.

[tcom-frazzled]

For what it's worth, it's also an intermittent problem that is only happening maybe once every 50-60 toolchanges. One position on the ATC carousel appears to be more susceptible, but its pretty random.