Thread: Problem With a Hafco HM-46 Mill/Drill.

Originally Posted by RayG

Hi Dave, it might be that chicken fat that they grease the HM52's with...

Regards
Ray

LOL, yea and if it's from the chickens from over their, who knows whats in it.

Dave

I have the same problem and it's just sloppy tolerances in the worm drive.
The backlash is horrific.
I take all my rough cuts with the table rise then when I get to a finnishing cut whithout a DRO what I do is put a dial gauge under the spindle on zero for the last cut then work out what distance I need to come down to finnish to size and adjust the fine feed down that amount if it drops because of back lash you just go back up and come down again to the correct dial position and lock the spindle .
I know it's not a pro solution but it works for me better than using the fine feed graduations which are not accurate anyway.

Originally Posted by Retromilling

I have the same problem and it's just sloppy tolerances in the worm drive.
The backlash is horrific.
I take all my rough cuts with the table rise then when I get to a finnishing cut whithout a DRO what I do is put a dial gauge under the spindle on zero for the last cut then work out what distance I need to come down to finnish to size and adjust the fine feed down that amount if it drops because of back lash you just go back up and come down again to the correct dial position and lock the spindle .
I know it's not a pro solution but it works for me better than using the fine feed graduations which are not accurate anyway.

I agree with you but my issue has been that I have operated in only one direction and I get either no movement or way too much movement.

So I have a working tolerance of 0.5mm or no movement and if I'm in the right part of the system I get acceptable accuracy.

I'll definitely be putting a DRO on the quill not sure if I'll cut down a micrometer or just buy one ready made and mount it securely.

Hopefully on Sunday I'll have a better idea.

Cheers

Justin

I spent an hour or so Saturday morning testing out another milling machine to see how the quill fine feed worked.

Using my mitutoyo dial indicator I measured every 0.25mm over 60mm of quill travel. I found that 0.25 on the quill equals anywhere between 0.23 to 0.26mm. But is generally around 0.24 to 0.25mm. Obvioulsy the accuracy cycles due to the quill fine feed mechanism.

The accuracy and precision was what I had expected. No clunks and no strange excessive movements or zero movements.

Today (Sunday) I started to reassemble my milling machine. I cleaned out all the grease and lubricated with WD-40. I found the spindle dropped under it's own weight about 60mm after that it gets tight in it's barrel.

The only difference in reassembly was that I installed the pinion shaft 180 degrees around from it's orginal position. Very easy to do as the locating screw for the return spring is a very handy datum.

I then repeated the same testing I did on Saturday with another mill at the suppliers. Again I measured every 0.25mm for about 50mm. I found the variance was about 0.23 to 0.27mm but there was regular areas where 0.25mm on the quill fine feed was exactly 0.25mm on the dial indicator.

The clunk had totally gone and over 50mm of travel it responded as expected where movement of the fine feed always resulted in movement of the quill.

At 50mm movement of the fine feed did not result in movement of the quill. Movements of .75mm resulted in zero movement and another 0.25mm (total 1.0mm) finally resulted in 1.0mm of movement. I continued to fine feed 0.25mm and each time I pulled down on the quill and it moved more or less the correct amount.

It would seem that the tightness in the quill at plus 50mm total travel was stopping the quill from dropping.

At least I have 50mm of accurate travel to work with. More than enough.

I then did some milling and found it to be working very well able to take off material off in 0.1mm and even ~0.05mm cuts. No strange clunks or lack of movement or indeed to much movement occured.

The 180 indexing of the pinion shaft also as allowed the spring return to actually work when the spindle is fully extended using the hand wheel.

Now to do some milling!

Thanks all for your help and advice it all helped put the pieces together and determine a solution.

Cheers

Justin

Hi Justin,
Good to hear you have it worked out and the store let you test the other mill.
Just keep in mind what I said earlier about keeping the quill up as much as possible when milling.
If the tightness does start to bother you, you can always lap the quill in with some lapping paste.

Another check you might want to do before going to much further, is to check to make sure the X and the Y axis is square to each other. To do this get the fixed jaw of your vise running true to the X axis with an indicator. Then put a square in the vise and tighten it so it holds it firmly, and run the dial indicator along the Y axis edge while winding it back and fourth. If you have doubt about the square you can then flip it over the other side of the vise and compare the reading.
There are other checks as well like making sure the head movement on the column is square to the table top, and also the quill movement is square to those movements.
Knowing whats what in these measurements lets you work around them if need be.

Now you have it up and running we expect to see some of your projects.

Dave

Nothing like a little pressure, a Dave?....lol

I think I'm feeling a bit of pressure!

In the other forums I'm in any of my machine work looks good, this might be a tough audience.

Nonetheless I'll give it a go.

Cheers

Justin

No pressure,
I wouldn't worry about the guys on here, everybody enjoys seeing new ideas and projects.

Dave

Just a bit of an update.

As mentioned the mill was working "better" but proper proof is in the operation and there was still some issues so I have since investigated further.

The pinion shaft is "bent" and not just in one spot its a bit like a wiggly line different parts are bent differently at different points! Ranging from 0.25 to .5mm also the various machine diameters are not concentric with each other. The actual pinion gear is egg shaped by .3mm.

I suspect that if any one part was out of spec this would not effect the operation.

Going to get some machining done on it and if that improves the situation next stage is to make a new shaft.

I can get the shaft made and Nitrided (Nitrided just cause I can and the factory gear is heat treated too)) for free just have to pay to get the gear cut so chasing prices on gear cutting.

Cheers

Justin

Hi Justin,

I have only just noticed your thread and may well be very off track here but ...
I have a ZX-45 mill which I believe would be similar to yours.

You said :

At 50mm movement of the fine feed did not result in movement of the quill. Movements of .75mm resulted in zero movement and another 0.25mm (total 1.0mm) finally resulted in 1.0mm of movement. I continued to fine feed 0.25mm and each time I pulled down on the quill and it moved more or less the correct amount.

If I am reading this correctly you are moving the fine feed and letting the spindle/quill move under its own weight?
I always have some friction on the quill lock and feed against that friction. The rack/pinion needs to push the quill down and not relying on gravity pulling it down. There will be backlach when reversing direction but there should not be any areas of no movement once this backlash is taken up. I will check my machine later today for you but I think I need around 1-1.5mm of movement of the fine feed for it to change direction. Once this "slop" is taken up it works fine.

I always thought it was correct practice to machine this way for consistent results. You need enough friction on the quill/spindle that gravity or the cutter does not pull the quill down.

Someone please correct me if I'm wrong but I don't think there is anything wrong with your mill.

Like I said maybe I am way off track but just thought I would put these idead out there.

Regards,

Jayson.

Originally Posted by Jayson

Hi Justin,

I have only just noticed your thread and may well be very off track here but ...
I have a ZX-45 mill which I believe would be similar to yours.

You said :



If I am reading this correctly you are moving the fine feed and letting the spindle/quill move under its own weight?
I always have some friction on the quill lock and feed against that friction. The rack/pinion needs to push the quill down and not relying on gravity pulling it down. There will be backlach when reversing direction but there should not be any areas of no movement once this backlash is taken up. I will check my machine later today for you but I think I need around 1-1.5mm of movement of the fine feed for it to change direction. Once this "slop" is taken up it works fine.

I always thought it was correct practice to machine this way for consistent results. You need enough friction on the quill/spindle that gravity or the cutter does not pull the quill down.

Someone please correct me if I'm wrong but I don't think there is anything wrong with your mill.

Like I said maybe I am way off track but just thought I would put these idead out there.

Regards,

Jayson.

Yep all good points but the step change was the issue and inconsistency.

I had a quick check over with my straightened and machined shaft installed and everything "feels" more consistent. Will properly install tomorrow and see how it goes.

The thing that really annoys me is that if they made the shaft straight it would be fine and it would at least be consistent. The ones I tested at H&F were all consistent. Not perfect, but that's perfectly acceptable given the price range of the equipment, never expected perfect.

Rest of the machine is actually fine, no complaints.

Cheers

Justin

Originally Posted by Jayson

Hi Justin,

I always thought it was correct practice to machine this way for consistent results. You need enough friction on the quill/spindle that gravity or the cutter does not pull the quill down.

Regards,

Jayson.

Hi Jayson,

Trial and error and lead me down the same path. I do exactly the same thing. Also since I have installed the DRO on the quill, the above method and the DRO make it quite easy to overcome the problems. But then again I don't think I have a bent pinion either!

Simon

Thing is the "clunk" overrides any tension on the quill! (Obviously if its too tight you it won't override but you can't wind it down either!)

Its weird to say the least.

I'm at the stage now where I think I will make collar that ensures I don't accidentally run in the clunk zone.

Newly straightened and machine shaft is in and the clunk is still there but the quill now travels further more easily and can return using only the spring at almost full travel.

Interestingly I index the pinion shaft 4 x 90 degrees and since being straightened it makes no difference how you index the clunk is in the same spot.

Once out of the "clunk" zone it feels much smoother and more consistent.

Bottom line is IMHO that mesh between the quill rack and the pinion is most likely not correct and I will just live with it. a 10mm collar will prevent me operating in the clunk zone.

Cheers

Justin