Drill Morse Taper off-centre

[Chris152]

OK, let me try again. I used this setup, with the v-blocks where the bearings would be, and rotated the spindle.



(I've actually inverted the photo so it's the same orientation as the original readings.)
The readings are underlined in blue here (below the original readings). The two figures to the right are the ID and OD of the internal MT.



Is it safe to say that the spindle is bent at the splined / pulley end? And would that bend at the top of the spindle, above the bearings, account for runout at the bottom of the spindle, below the bearings?

If so, what is the best way to set about straightening it? We have a hydraulic press, but what would the setup look like?

Thanks.

 

[Smouser]

I can't help but I find the troubleshooting and advice from other members interesting.

Thanks for posting and keep us up to date.

Good luck with getting it sorted!

 

[bricol]

Using vee blocks is not an accurate may of measuring actual run out - you need to hold it in a collet - see attached.

This was a bit of an mind-blower when this came up in GD&T training a few years ago - but makes sense when you get your head around it. Which mine isn't today . . .

 

[Brad93]

Using vee blocks is not an accurate may of measuring actual run out - you need to hold it in a collet - see attached.

This was a bit of a mind-blower when this came up in GD&T training a few years ago - but makes sense when you get your head around it. Which mine isn't today . . .

Thats nonsense

 

[Brad93]

We don't care about shaft centreline or DATUM.

We care about the concentricity of the taper in relation to two points on the shaft, the bearing seats.

 

[Chris152]

I'm pretty sure we've found the point at which a bend starts (tho we'll double check everything). Does this setup look like it may work? (I've based it on the method in this vid, which uses a pull-down straightening tool:

The press would bear down on the high point of the bend. It will need around 0.07mm of movement to achieve straight (ish!).

 

[voipio]

I would be inclined to support the spindle at the top bearing point and at the bottom end of the spindle, and then apply the force at the point where the lower bearing would be, since the original bending force is likely to have been applied to the end, via the chuck, and the lower bearing would have resisted that force, and acted as the fulcrum, where the force was concentrated. Measure the runout at the lower bearing position, as the spindle is rotated, and mark the high point with a felt tip pen. That way, the spindle can be returned to the same orientation for any further fine adjustments. The required deflection should equal half the runout. The spindle will tend to spring back, when the pressure in the press is released, so several cycles of applying press force, relaxing it and measuring, may be needed. Go carefully, increasing the deflection a little bit each time, until the desired result is achieved.

An altogether more crude method would involve reassembling the spindle in its working position, finding the runout and marking the "high" point, and then applying force to the end of the spindle at the "high" point, using gradually increasing strength club hammer blows through a piece of wood placed against the end of the spindle, using the same piece of wood in the same orientation each time, until the runout has been minimised.

 

[Chris152]

I would be inclined to support the spindle at the top bearing point and at the bottom end of the spindle, and then apply the force at the point where the lower bearing would be, since the original bending force is likely to have been applied to the end, via the chuck, and the lower bearing would have resisted that force, and acted as the fulcrum, where the force was concentrated. Measure the runout at the lower bearing position, as the spindle is rotated, and mark the high point with a felt tip pen. That way, the spindle can be returned to the same orientation for any further fine adjustments. The required deflection should equal half the runout. The spindle will tend to spring back, when the pressure in the press is released, so several cycles of applying press force, relaxing it and measuring, may be needed. Go carefully, increasing the deflection a little bit each time, until the desired result is achieved.

An altogether more crude method would involve reassembling the spindle in its working position, finding the runout and marking the "high" point, and then applying force to the end of the spindle at the "high" point, using gradually increasing strength club hammer blows through a piece of wood placed against the end of the spindle, using the same piece of wood in the same orientation each time, until the runout has been minimised.

Thanks Voipio. In the pic you can see indicated the two bearing positions (1 and 2). The bend seems to be at the point of the top bearing (1), which is odd? As you say, I'd expect the original bending force to have been at the bottom. But, according to my last measurements, it seems to be straight from the top bearing (1) to the bottom of the MT.

 

[voipio]

Could that mean that the drill bit snatched in a workpiece, and the drive pulley got jerked, resulting in the bending of the spindle?

Is there little or no runout at the chuck end of the spindle?

 

[brightspark]

must have been hit knocked before he bought it. jerking a belt wouldnt bend that .stalled mine loads of times only bent the taper once when the drill grabbed the job and spun round with the vice straitened it back up with a copper hammer and a clock gauge all good now

 

[Chris152]

Could that mean that the drill bit snatched in a workpiece, and the drive pulley got jerked, resulting in the bending of the spindle?

Is there little or no runout at the chuck end of the spindle?

The runout is at the chuck end (which is why it bothers us) but I guess the bend at the top bearing point is what's throwing the chuck out at the bottom? I'm assuming it makes no difference which end caused the problem, that so long as we correct the bend, it'll improve things.

That said, I can't picture how, with both bearings fitting the lower half of the spindle well (which they seem to be) and that part of the spindle through to the MT being straight, it's possible for the chuck end to run out. I'd have thought regardless of what's happening above the top bearing, the spindle below the top bearing would have to run true. But that's probably because I don't understand these things!

 

[voipio]

If the spindle between the bearings is perfectly true, and the bearings themselves are concentric and smooth, and are a good fit, then the cause of the runout at the chuck is going to be something below the bearings. Mis-machining of the morse taper might be one of those possible causes, based on your earlier observations.

 

[Brad93]

is the lower bearing and angular contact?

 

[Chris152]

Well, some success! The spindle is still not completely straight - 0.08mm out at the pulley end (it was 0.24 out) - but at the chuck end it's way better. On the exposed bit of the MT (see pic) it's down to 0.02mm runout, but still approaching 0.1mm at the bottom of the chuck. That's a huge improvement - we'll have a go at getting it closer to straight later today (it's only on the drill atm to check to see if the improvement in the spindle measurement made a difference in practice, which it clearly does). And it's the first time we've used the press, happy days!



Thanks for the help and suggestions all

 

[bricol]

Thats nonsense

Which was exactly our response too.

When it's explained by someone who knows what they are doing (not me) it makes sense.

 

[Brad93]

Which was exactly our response too.

When it's explained by someone who knows what they are doing (not me) it makes sense.

I'll have to take your word for it.

For shaft straightening and alignment i've always used two v blocks