Drawbar accident

[ARM]

Hi Guys
This is quite embarrassing, but we have to get it out in the open and rectified.

Whilst working with our Asian BP clone we left the Spanner, some of U Guys call it a wrench, in the DRAWBAR and turned the machine on without realising what we had done. Definitely was not intentional as we were totally engrossed in the problems with the job at hand. Well crash boom bang !!! ~!@#$%^&*()_+{ This was a first and a shocker for us !!! Had a Millwright remove the stuck DRAWBAR, albeit he could not trace any serious damage nor reduce the noise in High Speeds. Regrettably this happened a second time and we managed to remove the DRAWBAR ourselves, seemingly without having done too much damage ???

However, having now acquired a nice GMT R8 Integral Keyless Chuck which we tried in the machine today, we noticed that the DRAWBAR had to be SCREWED really deep to fully engage in the Spindle. With a drill bit mounted in this new Chuck, it ran beautifully true visually, without being clocked, in direct contrast to the last Fong Kong one we had to return to the local Supplier. Reading some other threads here as well we note that some of the original BP Drawbars have WASHERS etc.

Now the obvious questions that need be addressed here would be :-

1. How much and what damage have we done to the Machine ???
2. Would using Washers resolve our deep threading problem ???
3. Would we need to re-open the complete top of the Machine Head to access intricate Parts ???
4. Have we crushed any Bearings above the Spindle, although the Spindle seems to be functioning normal ???
5. And finally, what would be the best bet in eliminating such a recurrence, without having to change the complete HEAD and installing an AUTO FEED, like the later Models. ( Or changing the Operator !! )

We could take pics and upload if necessary. However, we must make it very clear here that we will definitely not be able to take chances and attempt any mechanical corrections as that would be way beyond our meagre capabilities. It would be obvious from these incidents that we are indeed rookies trying to get work done on a sophisticated machine without prior training or qualified Supervision. We would love to restore our Machine to its original smooth quiet running, even if we have to solicit professional help.

Your advices would be immensely appreciated.
aRM

 

[darkzero]

having now acquired a nice GMT R8 Integral Keyless Chuck which we tried in the machine today, we noticed that the DRAWBAR had to be SCREWED really deep to fully engage in the Spindle.

For this very same reason I made my replacement draw bar with two nuts to allow me to adjust how far I want to screw the drawbar into the arbor. My import bench mill came with a POS draw bar with the same style so I just copied it. I have that same chuck too BTW & I'm pretty happy with it especially for the price.

 

[Jeff in Pa]

Regardless of any machine damage, that is a very serious safety issue. Both drawbar wrenches (spanners) and chuck keys should never be left in a machine. They stay in your hand and when your hand comes off of them, it's to put them in their storage position.

Since the person did not learn from his first mistake, they need a stern talking to about shop safety. Their lack of following proper safe working techniques not only put himself in danger but also anybody in the immediate vicinity.

If I see anybody leaving wrenches or chuck keys in tools, they get their "ear chewed on". I've been a machinist for over 30 years and I do not tolerate unsafe working conditions at all.

Jeff

 

[8ntsane]

Sorry to hear of you misfortune. It isn't clear if the noise your hearing started with the first, or second time around.

As far as the adjustable draw bar, that has already been covered, and looks to be a very nice solution to the problem. So that part may take care of that problem without doing too much work.

By the sounds of it, your not ready to add on a power draw bar just yet. There is other ways to get around this. One that comes to mind is something I had seen on a mill in a fab shop. It was a very simple device that had only 3 parts. There was a base plate that bolted down in the same location as a power draw bar. Its was bored to take a round sleeve that was machined with a step on the bottom. The base plate was bored to fit the sleeve, and the sleeve was installed up through the bottom of the plate.

This plate had simple spacers to hold it up about 3/4 inch up off the head, so longer fasteners will be required. The sleeve was machined to take a coil spring to drop over the top and a simple hose clamp to retain it. Im sure most people would make up something much nicer than the hose clamp, but this did work just fine.

The way it worked was, the sleeve would cover the draw bar, and when the operater was to loosen the draw bar, he must push down on the spring loaded sleeve to get the wrench to engage. It was still done one handed, so it was easy to operate. As soon as he took pressure off the wrench, the spring would force the sleeve up, and disengage the wrench.

Simple to build, easy to use. You could not ever forget to leave the wrench on the drawbar again with this item. I watched them changing toolin with this setup, and noticed that they were using a small hammer with a socket welded on one end. The spring loaded sleeve would just move downward when they were tapping on the draw bar to release the collet.

Im not sure what type of head your mill has. If its a Vari-speed head, then you could have a few things to look at. If step pulley, its much less complicated for sure. Before you get too crazy tearing the head down looking, I would start with removing the drawbar completely, and run the machine at several speeds.
Don't for get, when doing this, remove any tooling that's in the spindle too.

On my Vari-speed head, I was almost convinced the plastic bushings on the sheeves had worn out, and replacement time was near. But I found that the rattling noise was indeed the drawbar wobbling around. it also had evidence marks on the drawbar from doing so. Made up a new bar, problem solved. This may not be your problem, but removing the drawbar and running the machine would give you a quick yes or no real fast.

Good luck

 

[ARM]

Regardless of any machine damage, that is a very serious safety issue. Both drawbar wrenches (spanners) and chuck keys should never be left in a machine. They stay in your hand and when your hand comes off of them, it's to put them in their storage position.

If I see anybody leaving wrenches or chuck keys in tools, they get their "ear chewed on". I've been a machinist for over 30 years and I do not tolerate unsafe working conditions at all.

Jeff

JEFF
U are absolutely right and justified in what U say. We have now implemented harsh shop Rules amongst ourselves to avoid such a recurrence.
aRM

 

[ARM]

Sorry to hear of you misfortune. It isn't clear if the noise your hearing started with the first, or second time around.

As far as the adjustable draw bar, that has already been covered, and looks to be a very nice solution to the problem. So that part may take care of that problem without doing too much work.

By the sounds of it, your not ready to add on a power draw bar just yet. There is other ways to get around this. One that comes to mind is something I had seen on a mill in a fab shop. It was a very simple device that had only 3 parts. There was a base plate that bolted down in the same location as a power draw bar. Its was bored to take a round sleeve that was machined with a step on the bottom. The base plate was bored to fit the sleeve, and the sleeve was installed up through the bottom of the plate.

This plate had simple spacers to hold it up about 3/4 inch up off the head, so longer fasteners will be required. The sleeve was machined to take a coil spring to drop over the top and a simple hose clamp to retain it. I'm sure most people would make up something much nicer than the hose clamp, but this did work just fine.

The way it worked was, the sleeve would cover the draw bar, and when the operator was to loosen the draw bar, he must push down on the spring loaded sleeve to get the wrench to engage. It was still done one handed, so it was easy to operate. As soon as he took pressure off the wrench, the spring would force the sleeve up, and disengage the wrench.

Simple to build, easy to use. You could not ever forget to leave the wrench on the drawbar again with this item. I watched them changing tooling with this setup, and noticed that they were using a small hammer with a socket welded on one end. The spring loaded sleeve would just move downward when they were tapping on the draw bar to release the collet.

I'm not sure what type of head your mill has. If its a Vari-speed head, then you could have a few things to look at. If step pulley, its much less complicated for sure. Before you get too crazy tearing the head down looking, I would start with removing the drawbar completely, and run the machine at several speeds.
Don't for get, when doing this, remove any tooling that's in the spindle too.

On my Vari-speed head, I was almost convinced the plastic bushings on the sheeves had worn out, and replacement time was near. But I found that the rattling noise was indeed the drawbar wobbling around. it also had evidence marks on the drawbar from doing so. Made up a new bar, problem solved. This may not be your problem, but removing the drawbar and running the machine would give you a quick yes or no real fast.

Good luck

PAUL
At the outset allow me to say a gracious THANK YOU for this highly enlightening solution.
Just some more clarifications, if U may.
The noise did commence the first time around.
If U are referring to the earlier post on the adjustable Draw Bars then we have another problem in that we don't exactly know what the IMPERIAL THREADS are for our DRAW BAR, to make another ??? U see we work with METRIC here and even on inquiring from the Machine Supplier previously, we failed to elicit a positive response. I think they are NF, but what size exactly, we reckon U Masters should know better. We will be able to get those Dies locally to Duplicate our Bar and harden it.

The perfect solution U presented makes absolute sense. However, without the specifics in dimensions and or drawings we will need take this to our Toolmaker to have made up.

Ours is a STEP PULLEY belt driven Spindle and we will, first thing in the morning run the Machine as U suggested and ascertain the source and type of noise. That should be enlightening.

Once again an appreciative THANK YOU for these kind assistances.
LORD BLESS
aRM

 

[OldMachinist]

The threads in R8 tooling is 7/16"-20 UNF.

 

[darkzero]

If U are referring to the earlier post on the adjustable Draw Bars then we have another problem in that we don't exactly know what the IMPERIAL THREADS are for our DRAW BAR, to make another ??? U see we work with METRIC here and even on inquiring from the Machine Supplier previously, we failed to elicit a positive response. I think they are NF, but what size exactly, we reckon U Masters should know better.

If your spindle is R8, it should be 7/16"-20. I believe all R8 arbors are 7/16"-20, regardless where they are made.

When I was making my drawbar I was researching about what type of steel I should use & if it should be hardened. Some use 4140 & some just use 1018. The points made that I saw was that the draw bar does not need to be hardened as it would be considered a "consumable". Cheaper to replace a damaged drawbar than a damaged arbor especially if that arbor is integrated with the tool. A draw bar should not get damaged unless it's abused as there's no need to really crank down on them.

Dorian drawbars are made of 4140 & heat treated. I just made mine out of 1144 with hardend flange nuts & called it a day. Time will tell how it holds up but so far I can't see it getting damaged or worn out at my rate. But I'm just a home shop machinist, in a production environment or where multiple people use the same machine as it sounds like in your case it may be a different story.

 

[Tony Wells]

While the spring loaded sleeve certainly is workable, it may be easier to implement a spring loaded socket on a breakover. Same basic principle, but might be easier to put together. If you can find a spring that is just a bit smaller than the across flats dimension of the hex socket, just peel back, or unwind a coil or two on the end that you will insert into the socket. That will serve to retain it in the socket. You'll have to experiment with strength and length to make that work. Operators won't like having to hold the wrench down to tighten/loosen the drawbar, but it will be safer.

I've only powered up a knee mill with the wrench on it once (I'm partial to a box end wrench), it was in the direction that merely loosened the drawbar as soon as I turned the machine on. It could just as easily been the other way, and I suspect would have either stalled out the motor, slipped the belt, or possibly even broke the drawbar. More than once, though, I have been caught by lowering the quill to check for proper clearance or something, touching off a surface, etc., and had the wrench disengage and fall off. Better than powering the machine, but if you're in the wrong place, you get a nice knot on the head. Or a dong on the table or workpiece. If lowering the quill becomes a habit, the wrench hitting the head will "impress" the point about not leaving the wrench on the drawbar. Of course, as stated above, the best way is to become accustomed to never letting the wrench leave your hand unless you are setting on the workbench or hanging it on a hook or something. Just like a chuck key on a drill press or lathe. If you're not actually using it at that particular moment, it should be in its storage place.

As far as damage, it's hard to say. The spindle is pretty robust, so it's possible that no serious damage was done. As someone else suggested, run the machine with no drawbar and an empty spindle (no tooling in the taper). If the noise is still there, and you want to make sure there is nothing going on that will build into a major breakdown, which absolutely must occur during a most critical operation, you may have to tear it down and see if the bearings are damaged. It's possible they were.

 

[ARM]

A draw bar should not get damaged unless it's abused as there's no need to really crank down on them.

But I'm just a home shop machinist, in a production environment or where multiple people use the same machine as it sounds like in your case it may be a different story.

WILL
And that's exactly the other problem - we had to "really crank down" on the bar when mounting that new chuck. We hope in heaven's name we had not cross threaded the Tool, but did reverse and start a couple of times over from the beginning.

If we understand our problem correctly, we would need to shorten the Length of ours either by making a new one or inserting an appropriately sized turned COLLAR just above the Spindle Bore ???

We are Custom Knifemakers, Son Full time and me part-time sharing the shop, and only we two use the same machine.
So there's no one else to blame except meself !!!
aRM