HM45 help needed

[Cogsy]

Excellent info Peter. Thanks heaps!

I do think I'll make a similar drawbar, just got to work out the thread now (but it's probably in the manual anyway)

Cheers,

 

[ELM6061]

@Peter, that slide hammer/hand-wheel looks brilliant, though it does raise a couple of questions/concerns when you run the mill. It sounds as though there is quite a bit of vibration, which I think would be the shaft spinning inside the slide hammer.
(1) Is there really any vibration?
and if so;
(2) does this transfer down through the spindle, to the work piece being detrimental to fine finishes?
(3) hard on the bearings?
What are your thoughts and findings?
At the end of the day, as long as the shaft and hand wheel are balanced enough, the slide hammer can just be removed and replaced when needed. Doing this would also save any future wear between the slide hammer and shaft.

I may just try this on my HM50.

@Gus, They are some nice tools you have made Gus and looking at how you have fixed your chuck, has given me an idea on how to fix mine, thanks so much. Shame Al is in WA, those counter sinks in the blue box would be handy.

Ed

 

[petertha]

I was also going to chime in that it looked alot like my King RF-45, which was Taiwanese made, at least at the time. The current model looks like this, mine is '98 vintage but I think almost the same.
http://www.kingcanada.com/Products.htm?CD=36&ID=21734

The RF-45 uses R8 spindle tooling though, the HM45 is MT3 did you say?

My z-axis (downfeed) was uselessly innaccurate, I think most everyone with these mill/drills eventually adopts some sort of digital readout gizmo with a vernier retrofit (which I did) or full DRO. The X&Y axis dials were pretty good for accuracy but I ended up putting readouts on that just for sanity. Mine is also a bit of a noisy gearbox rattler. I'm told thats normal but I don't have others to compare against. I just hope its not bearings or gears because I dont feel like digging in there.

 

[AussieJimG]

Hi Peter, when I saw your link to a scheme to do away with the spanner/hammer, I thought "Great - I have been looking for something like that", and followed the link to find me demonstrating one of my daft ideas.

It seemed to work and might still be ok with a bit of fiddling. The problem was that the spindle accelerates so rapidly that the handwheel acts as a flywheel whose inertia unscrews the drawbar. When the spindle stops, it tightens up again. Meanwhile, the chuck is loose and wobbling around.

Because it tightens again, it took a while to figure what was going on. When I twigged, I gave it away and went back to spanner/hammer. Sigh!

Perhaps it just needs a handwheel large enough for the hand to apply sufficient torque while having minimum moment of inertia. Something with a thin aluminium ring on the periphery and most of the web removed might do it.

It was a bit of a shock to meet myself coming back though.

Jim

 

[Swifty]

Peter's idea is great so long as you are only drawing up a collet holder or drill chuck, would not work on R8 collets as these need to be spanner tightened to hold the cutters.
After over 40 years in the same toolroom, every one used a spanner to unlock the drawbar on the bridgeports and then used the same spanner to hit the end of the drawbar to release the collet. No swapping over to a hammer, and no broken spanners in all that time.

Paul.

 

[petertha]

..R8 collets as these need to be spanner tightened to hold the cutters...every one used a spanner to unlock the drawbar on the bridgeports and then used the same spanner to hit the end of the drawbar to release the collet. No swapping over to a hammer, and no broken spanners in all that time.
Paul.

Interesting comment. I have recently been noticing my RF-45 R8 drawbar threads seemed to be sticking just a bit lately as I hand screw it in. It has not had a hard life & I don't tighten it much harder than I have to.

It concerned me because I didnt want it stripping or buggering up a more expensive collet tool. I thought maybe a chip got inside the threads but it was clean. Then I got thinking about the 'knock' disengagement treatment (hammer, spanner or otherwise). One would think just the repeated jolt of this action would degrade threads. If I visualize hitting a 1/2" bolt engaged in a nut 1000 times, it would have to start degrading, no? Maybe my drawbar is just soft offshore iron & I should replace it before it takes out more expensive tooling.

On this note, I thought I could make one easy enough, but noticed what looks like a shear pin in the upper hex nut portion. Would this be a failsafe for the machine during running, or more for overtightening?

 

[ninefinger]

On this note, I thought I could make one easy enough, but noticed what looks like a shear pin in the upper hex nut portion. Would this be a failsafe for the machine during running, or more for overtightening?

I think what your referencing is the undercut at the head of the drawbar? If so its likely not for over torque as it would still require lots of force to break, and it won't protect the machine at all in the event of a crash (ask those who know...:fan: )

I believe its simply a stress reliever to prevent a crack from forming at a sharp corner, or to provide clearance for a sharp edge on the inside of the spindle, or both...

Mike

 

[Swifty]

On this note, I thought I could make one easy enough, but noticed what looks like a shear pin in the upper hex nut portion. Would this be a failsafe for the machine during running, or more for overtightening?

I think that the pin is just a method to hold the hex section onto the shaft. You will probably find the shaft is manufactured from 2 parts, the main drawbar and the hex head. This saves on machining and material when making the drawbar, use a shaft of the right diameter and put a thread on one end, then pin a hex head on the other.

Paul.