Professional Machine Fettling

[Bill PhinnParticipant @billphinn90025]

Dr G, it might be a good idea at this stage if you removed the offending gib strip and had a close look at it and the channel it sits in.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Bill Phinn on 02/07/2023 13:44:00:

Dr G, it might be a good idea at this stage if you removed the offending gib strip and had a close look at it and the channel it sits in.

I appreciate the advice, but I give up with the thing. It’s never been great even at side milling mild steel, and the z-axis control seems flawed in terms of backlash. In fact this morning while working on a steam engine part, the cutter dragged into my milling vice and took a chunk out of it. The axis was locked, but obviously not tight enough. The vibration of side milling probably loosened it. Whatever the cause (my fault or the machine) I’m ready to give it up as a dead loss at this point. The other odd thing about it is that to get the z-axis central over the x-y table, the table has to be extended so it’s significantly overhanging the guides. Presumably this doesn’t help with stiffness, and has the knock-on effect that my milling vice also overhangs the x-axis, partially obscuring the y-axis locking lever (that I fitted myself).

[Anonymous]

Out of idle curiosity I measured the movement of my vertical mill table when at one end of its travel. The table is 48" long and the saddle is 18" wide. With one end of the table lined up with the edge of the saddle that gives an overhang the other side of 30". With a reasonable push I could get a DTI on the edge, at the end, of the table to move ±0.1mm. I didn't lock the Y axis so that could be both X & Y movement combined. Dunno if that is good or bad, never measured it before and certainly never worried about it. Given that the cutter is operating in the centre of the saddle I can't see that smallish movements at the end of the table have any effect.

Andrew

[JasonBModerator @jasonb]

I'll measure mine later, there is some movement there but not felt the need to measure it before. As you need room for the oil film there will always have to be some clearance so no movement is going to be almost impossible

[SillyOldDufferModerator @sillyoldduffer]

Posted by Dr_GMJN on 02/07/2023 14:08:44:

Posted by Bill Phinn on 02/07/2023 13:44:00:

Dr G, it might be a good idea at this stage if you removed the offending gib strip and had a close look at it and the channel it sits in.

I appreciate the advice, but I give up with the thing. It’s never been great even at side milling mild steel, and the z-axis control seems flawed in terms of backlash. In fact this morning while working on a steam engine part, the cutter dragged into my milling vice and took a chunk out of it. The axis was locked, but obviously not tight enough. The vibration of side milling probably loosened it. Whatever the cause (my fault or the machine) I’m ready to give it up as a dead loss at this point. The other odd thing about it is that to get the z-axis central over the x-y table, the table has to be extended so it’s significantly overhanging the guides. Presumably this doesn’t help with stiffness, and has the knock-on effect that my milling vice also overhangs the x-axis, partially obscuring the y-axis locking lever (that I fitted myself).

Only a lost cause when the owner surrenders! Taking a break is allowed but Model Engineers never give in.

The faults that frustrate me most are those that have me going round in circles. This could be an example.

• One cause is a level of skill and judgement is needed that I haven't attained yet. The only cure is to acquire the skill by patient practice. (Or get outside help, which is why clubs are recommended!)
• Most difficult are an interacting combination of two or more faults. Adjusting 'A' puts 'B' out of kilter, which upsets 'C', and 'C' being wrong misaligns 'A'. Problems like this can take a long time to diagnose. They occur most with older equipment due to wear, damage, or bodged repairs. Rarer on new equipment, but assembly errors and faulty parts do happen. Also caused when a new owner dismantles a new toy to see see how it works or to improve it, without quite knowing how to put the thing back together again! (You can guess how I know, blush..) Cure is to identify and eliminate all the faults one by one, which may require several serious debugging sessions.

Unfortunately it's rather easy to get things wrong when fixing machine tools – they appear simple but have hidden depths. Issues are easier to diagnose when one has a dollop of experience. In the absence of experience, assume nothing and ask the forum! Photos plus full lists of all faults and what's already been done to the machine would help.

I empathise. I'd much rather make things than waste time fixing tools.

Dave

[Dr_GMJNParticipant @dr_gmjn]

Thanks all.

Jason & Andrew – my assumption was that there should be minimal (ideally zero) play in the slides once adjusted properly. Obviously you can’t eliminate deflection through material/oil film reasons, but I thought that machining loads and/or axis locks would cause deflections not registered on the DRO and cause significant errors. If this (within reason) isn’t the case, then OK – I’m having un-realistic expectations of what’s normal.

Dave – believe me I don’t give up easily. But there comes a point when everything fails to resolve an issue, and you just have to throw the towel in. I’ve been battling this machine since I got it, in terms of achieving my expectations of how a machine tool should perform (ie comparable with my 1966 ML7), and have failed. I’ve posted many questions, issues and potential solutions on here over many months, and have taken on board advice given. I have used it to build my first ever M.E. Project (a Stuart 10V), and I was happy with the results. Now on my second engine (Princess Royal), which is more complicated and requires much more use of the mill. When it’s – literally – a drag to use, it takes some of the enjoyment out of the hobby. I only have limited hours to spend in the workshop, hence the real frustration.

Cheers.

[JasonBModerator @jasonb]

Here you go, table almost all the way to the left and axis unlocked. I would say +/- 0.002" (0.05mm) which is about half of what Andrew gets and what I would hope as the table is about half the length. And there may be some flex in the wooden bench it is sitting on.

It's probably a bit freer in the middle but even that varies slightly depending on time of year

 

Edited By JasonB on 02/07/2023 16:55:38

[Anonymous]

Posted by Dr_GMJN on 02/07/2023 16:11:19:

…there should be minimal (ideally zero) play in the slides once adjusted properly.

Maybe I have misunderstood what measurement you are making. Let's say the table is central around the saddle. Where are you measuring to get your results; in the centre of the table, or outboard at one end?

Andrew

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 02/07/2023 16:52:30:

Here you go, table almost all the way to the left and axis unlocked. I would say +/- 0.002" (0.05mm) which is about half of what Andrew gets and what I would hope as the table is about half the length. And there may be some flex in the wooden bench it is sitting on.

It's probably a bit freer in the middle but even that varies slightly depending on time of year

Edited By JasonB on 02/07/2023 16:55:38

Thanks Jason. Mine’s worse than that even when ‘sticky’ at the wheel.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Andrew Johnston on 02/07/2023 16:53:56:

Posted by Dr_GMJN on 02/07/2023 16:11:19:

…there should be minimal (ideally zero) play in the slides once adjusted properly.

Maybe I have misunderstood what measurement you are making. Let's say the table is central around the saddle. Where are you measuring to get your results; in the centre of the table, or outboard at one end?

Andrew

Pretty much as per Jason’s video above.

[Anonymous]

Posted by Dr_GMJN on 02/07/2023 19:55:23:

Pretty much as per Jason’s video…

Exactly what I measured. With the exception of the DTI sitting conveniently on the adjacent milling machine, which is heavier than the machine being measured.

The result is never going to be zero. Considering the results that Jason and I see, the obvious question is how does it affect the milling process? I think the answer is not much, if at all. Since the milling cutter is fixed in the centre of the saddle even if the table pivots around the end of the saddle the movement will be reduced by a factor of four or so, in my case. Assuming that cutting parameters stay constant then cutting forces will be constant, so the table won't be moving in and out with the cut.

My vertical mill is probably around 50 years old and consequently is fairly worn. So I expect that the same test with the table centred may well be worse. But until now i've never noticed, or worried about, the table rocking during a cut.

Andrew

[Author]

Posts