Thread: Another Problem with my Hafco HM-46 Mill Drill

Originally Posted by Dave J

Heavier oil might do the trick, you would have to give it a try.

With the quill drop I have heard a few people talk about this. On my mill (HM52) there is a clock spring which is adjustable for the rack gear. I have mine set up to raise the quill if I let go of the handle. This way the quill is always pushing back on the rack and doesn't drop at all.

Without this adjusted I could see where the quill would drop, so if you have the spring, give it an adjustment. Mine has 2 holes in the out case after taking the chrome cover off and has a screw under the head which locks it in place. I place a small allen key in one of the holes while undoning the screw and then rotate it anti clockwise for mine to put more tension on it.

Dave

Thanks Dave

Yes I have played with the tension spring and it works where the rack and pinion is working more or less ok.

However. This may not be the best explanation but there will always be a point where the whole mechanism plays catch up and drops over 1mm. Nothing can really stop that. It's almost like a tipping point.

My pinion seems to force the quill across to some extent so there is a limit of how much tension would allow the quill to return unaided.

Of course you don't need to use all the travel but the tension is such that it works over a partial range. If the spring was tensioned enough to return at full extension it would require more preload than I could wind on.

I messed around with preload using a big lump of high density foam and found that there was still parts of the travel that no amount of preload would improve. You would still get a "step change".

Cheers

Justin

Interesting as I don't have that problem at all, I posted my setup over in the other thread.

Dave

Just a thought - that clunk - have you checked the fit of the keys in shafts to handles, pinions etc? It sounds like back lash of some sort, where when a shaft gets to a certain rotational point gravity means that something is pulled forward rather than pushed back. (I would hope that keys are being used rather than grub screws)

Another cause of the jump could be a missing tooth on the pinion or rack, but that would be far more than a mm.
Michael

I thought I would post it here as well, since it's to do with this mill and not cutters.

On my mill, on the opposite side of the head to the fine down feed the shaft from gear comes through the head and there is a clock spring on the end of it.

Do your mills have something like this, if not this is the problem with the quill dropping.

Dave

After looking at the grizzly parts manual below, I see it is the same set up as mine with the clock spring.
http://cdn0.grizzly.com/partslists/g0519_pl.pdf

I also checked the slop between the rack and gear and mine has about 0.5mm movement up and down at the quill. My quill is heavy enough to fall on it's own, by the sound of it your quills are getting hung up on something. I also grease my quill to help with some of the play, and even with that it drops down no problem.

For mating the gear to the rack better, I do have pictures etc of one guys method where he bored the head casting to take bushes, and then he bored the bushes off set to give adjustment of the mesh of the gear. This will only work if the gear will mesh with the rack without and play, so you would have to do a bench test to see what it's like.

The only other thing I can think of is to place a spring on the quill to help hold it up. This would stop it dropping down.

Dave

Hello Jarh73,
I have explained my solution to this problem before but at the risk of boring everyone here I go again.
On my mill (Zay7045FG/2) the play is between the Quill rack and pinion, as on other machines. I found that when I released the Quill clamp, the two cast iron slugs which pressed against the Quill did not release immediately, but when I started to lower the Quill the clamp released which caused the Quill to drop and produce the "clunk" sound. I turned the ends of the two "slugs down and pressed brass end pieces onto them. I now keep the Quill clamp nipped up slightly and the brass end pieces do not grab onto the Quill and do not score the Quill surface. I also replaced the grub screw which locates in the slot down the side of the Quill, with a bolt with a phosphor-bronze end piece, and I keep this tightened slightly also. I don't have any problems with the quill dropping now . I have fitted a vertical digital scale to the Quill which I think is necessary to show exactly how far the Quill has moved .
Russell

Originally Posted by rusty steel

Hello Jarh73,
I have explained my solution to this problem before but at the risk of boring everyone here I go again.
On my mill (Zay7045FG/2) the play is between the Quill rack and pinion, as on other machines. I found that when I released the Quill clamp, the two cast iron slugs which pressed against the Quill did not release immediately, but when I started to lower the Quill the clamp released which caused the Quill to drop and produce the "clunk" sound. I turned the ends of the two "slugs down and pressed brass end pieces onto them. I now keep the Quill clamp nipped up slightly and the brass end pieces do not grab onto the Quill and do not score the Quill surface. I also replaced the grub screw which locates in the slot down the side of the Quill, with a bolt with a phosphor-bronze end piece, and I keep this tightened slightly also. I don't have any problems with the quill dropping now . I have fitted a vertical digital scale to the Quill which I think is necessary to show exactly how far the Quill has moved .
Russell

I'm fairly sure I know what you mean.

Did you have any pictures handy or a link to your solution?

I have had the odd problem of changed height of quill when it's undone.

On another note the leak is fixed for the moment.

Cheers

Justin