HF 8x12 - Lathe - Apron handwheel - too much play

[gorlosky]

HF 8x12 Lathe - Apron handwheel - too much play

The HF 8x12 - Lathe - Apron hand wheel has way too much play. It is solid on the keyway, but I must be feeling the slop of the 2 gears 606 and 608. I guess if I am turning to or away from the chuck only, then it makes little matter, BUT if I am turning a recess then I would not want to use the calibration ring, but a dial indicator only ?

 

[sinebar]

It seems to me that you know the answer to your question. You might also set up a carriage stop.

 

[unioncreek]

My 8x12 doesn't have a calibration ring on the apron wheel. Are you sure you don't mean the cross slide or compound?

 

[Tony Wells]

It seems to be a common conception that all the dials on machines should have almost no backlash and the graduations relied on for all motion. That's simply not the case. There must be some clearance on the screws/nuts and gears involved. So there WILL be backlash. Even on CNC ballscrew machines, there is measurable backlash, although much less, and in most cases can be comped out in the control. In no instance should anyone rely on bi-directional movement based on machine dials. Either a DRO, or as stated, a dial indicator.

 

[unioncreek]

I see that the newer 8x12 has a calibration ring. I just learn to live with whatever backlash a machine has.

Bob

 

[gorlosky]

Thanks for the replies. I just was wondering if I really needed to take the gear box all apart to get the apron wheel gears set closer, but if there is no adjustment, and I am only hand driving the wheel, so minimal pressure, there should be no issue with slipping a tooth. And yes there is a calibration ring, similar to the tail stock ring.

 

[aaronad]

I just got my 8x12 last friday and have the same issue. I have about 15+ deg of slop in the apron wheel. Some is from the poor fit of the hand wheel, but most of looks like it is coming from the 2 apron gears and the rack. I have not stripped it down yet. I saw a post elsewhere about poor machining of the rack gear. Here is the link:
http://www.cnczone.com/forums/mini_lathe/95419-8x14_lathe_slow_mod-2.html#post705656

I wonder if this is an issue with this batch of machines. What's the serial number on your machine?

Aaron

 

[gorlosky]

My serial number is (off the little paper QUALITY CERTIFICATE - is it stamped on the machine anywhere ?) is either 130905 or B0905, can't quite tell.
On page 25 of the manual, I looked some more at what is causing all the slop by using a mirror and it seems the the play of the 627 Gear Shaft (which has the gear on the end) is about the width of the end of a tooth, so that is quite small.
Looking at the play of 622 Small Gear Shaft (which has a gear) with 624 Gear, there is quite a bit. I see that 624 is keyed onto 625 Sleeve which is keyed onto 627, and wonder if the keys or keyways are bad.
It appears that to really look at this, that the whole Apron box needs to come off, as to pull off 615 beside the Apron Hand wheel, would only let you see the Gear and Key as it supports the end of 627.
Now that I look at these drawings, neither is accurate, as my new lathe has the Lead Screw going through holes in the side of the case.

PS: I also have another Parts list and it shows New Model of Apron for HD210 HD250 and CQ6125, so I don't know which is the most recent as this manual does not show the Sleeve with inner and outer keys.

 

[gorlosky]

Ok - after further review, it appears that the 4 upper screws (2 per side) hold the lower case to the upper (Saddle). And the lead screw blocks are held by 2 screws each and a tapered pin for alignment, so reassembly should be easy and accurate. Additionally the driven end of the lead screw will need detached.

 

[aaronad]

Re: HF 8x12 Lathe - Apron handwheel - too much play

The S/N on my is 130902. Must have been a bad day at the factory. Maybe the first day back after Chinese New Year.