[Beginner] How do I adjust the gibs on a milling machine?

[choochoo_balooParticipant @choochoo_baloo]

After a while spent cleaning and re-oiling my Senior M1 mill, I was hoping for guidance on how to correctly setup the 3 axes' gibs.
Here are my thoughts so far. Please bear in mind I am *not* an engineer, so please make it idiot proof.

• Ive read posts that say one need to account for unequal wear on any s/h machine (most in the middle portion vs ends of travel). Not sure How I account for that in practical terms.
• The x-axis (table) has two gibs (~2:1 length ratio). Seems unusual yet obviously an engineering reason.
• Does the z-axis (column) need a different approach, due the large weight it carries, plus being a vertical surface fighting against gravity
• To do this set up properly, will I need expensive clocks/gauges whatever, or can it all be done by feel?

Whilst typing this post, I just found this video from Keith Rucker. It seems appropriate, can anyone confirm that his method applies to all mills?

Thanks in advance chaps. A peaceful Easter to you all.

[choochoo_balooParticipant @choochoo_baloo]

[SteviegtrParticipant @steviegtr]

Tonight I have had to adjust the x axis on my Tom Senior vertical light. It had chatter after I had taken it off to fit a power feed. I had not adjusted it correctly. You are right that at the full travel you may encounter it being a bit tight due to central wear. Unless you are doing full length mills that really does not matter. I readjusted mine so there was no play & the wheel was tighter ,only just than when it was slack.

No matter even when they are set correctly as someone will be along shortly to advise you. It is still important to lock the axis you are not using. The Z I adjusted until it was smooth but not tight. Same for all really. I guess the proper way is with a dial gauge set up on the parts. Probably no help but you will get a definitive answer.

Steve.

[Kiwi BlokeParticipant @kiwibloke62605]

Haven't yet seen the video to which the link was provided.

Semi-random thoughts, hints & tips…

If there is enough wear to make an appreciable difference to the freedom of movement of a slideway, along its length of travel, once it's adjusted optimally, the machine really needs attention, eg scraping the ways. (Big subject – plenty on the 'net, including videos.) Of course, this makes adjustment impossible, except for over a limited length of travel.

Lubricate the ways with slideway oil before you begin. This special oil minimizes the 'stick-slip' phenomenon. It makes a big difference to properly adjusted slideways. People who claim otherwise are misled. If the slide is badly adjusted, and too loose, anything vaguely oily would appear to be OK. The aim is to get the adjustment as tight as possible, whilst allowing free movement.

The freedom of movement to be aimed for can't easily be judged by twiddling handwheels. It's best to remove the feedscrew, then push and pull the table, saddle, whatever, and slightly slacken the adjusters from gently bound to smooth movement. On a Senior-sized machine, with chunky feedscrews, you could aim for a force of a couple of pounds (or more) required to move the sliding member. It's a matter of adjust, test, adjust, test, rinse and repeat.

When replacing the feedscrew, screw it in as far as it can go, so that its nut is as close to the screw's mounting plate as possible. Bring the sliding member back towards the mounting plate, then tighten the mounting plate screws, whilst being sensitive to the position of the screw – the aim is for it to be central in its range of lateral wobble. (Does this make sense?)

The vertical knee is much the same, although judging freedom of movement is made difficult by the considerable weight. Suggest adjusting it before mounting the saddle. Or arrange a counterweight (improvise!).

You can use indicators, but you'll drive yourself crazy trying to get consistent results, when you're getting below a thou. The oil film is one problem.

[Kiwi BlokeParticipant @kiwibloke62605]

Just looked at the video – well, skipped through it, actually. Blimey! Can't some Americans talk? There must be more concise videos covering the topic…

KR is talking about taper gibs. Some Senior gibs are taper, others are the multiple-screw type (working from unreliable memory here, so don't know what you're dealing with). When adjusting taper gibs, be sure to lock the gib gently with the lock screw, otherwise the gib strip can be free to move and act like a wedge, to lock up the slide, at worst, or give hopelessly inconsistent results, at best.

KR's machine was obviously pretty badly adjusted. The fact that he was using it for 2 years says something… You can try his 'lean on it sideways and look for the movement' approach, but, on smaller machines, everything is so much smaller and tighter (or should be). I maintain that it's easier and more reliable to judge gib adjustment by the effect it has on freedom of movement of the sliding member (in the desired direction, of course).

All these remarks assume the ways are not significantly worn and the gib strip isn't a banana.

If you're hunting wear, then you'll need expensive metrology gear…

I don't understand your remark 'The x-axis (table) has two gibs (~2:1 length ratio)'. Please could you explain? Never seen that…or am I being thick?

[Anonymous]

Posted by Kiwi Bloke on 12/04/2020 12:36:06:

Blimey! Can't some Americans talk? There must be more concise videos covering the topic…

Too right! That's one reason I don't watch much on Youtube. In a 30 minute video you get an introductory 15 minutes of waffle and not a machine tool in sight. At which point I've usually lost the will to live.

With the exception of the lathe top slide all my machine tool gibs are tapered. I adjust for a slight drag when using the handle. I always check full movement as it's not uncommon for me to use full table travel. On the Bridgeport things get tight at the ends, but I'm pretty sure that's due to the leadscrew/nuts not the slideways.

Andrew

[old martParticipant @oldmart]

The Tom Senior light vertical has only one X axis taper gib, I cannot figure out how two would work on an M1.

The Y axis has a strange one piece gib which is held in two planes. I think it is a bit of trial and error to get it right by slackening the plain bolts a little and then adjusting the screws and nuts. The plain bolts have to be tightened and then the movement is checked. It needs to be just a tiny bit tight, but movable over the full range with only slight extra tightening at the ends of the travel.

The knee gib is similar to the Y axis in design. Practice with getting the Y axis adjusted first. The knee is likely to get tighter near the bottom of its travel.

[choochoo_balooParticipant @choochoo_baloo]

Posted by Kiwi Bloke on 12/04/2020 12:36:06:

I don't understand your remark 'The x-axis (table) has two gibs (~2:1 length ratio)'. Please could you explain? Never seen that…or am I being thick?

Yeah wasn't very clear was I! Photo below should explain all. I meant why is there not a one gib covering the entire dovetail. Perhaps it affords more control to central wear, having 2 gibs?

[old martParticipant @oldmart]

Your M1 with the power X feed has a very different setup to the light vertical. Your gibs are conventional screw and locknut adjusted type, the lv uses a sliding tapered gib. Have you taken the gibs out? There is a possibility that it started life as one piece and broke, it should be easy to check.

[Peter Simpson 1Participant @petersimpson1]

I have a Light vertical and an M1 both gibs are identical, Not sure about the age of the M1 photoed above but it's not the same as mine. Both of my machines have the long X axis gib which is adjusted with two large headed screws which work from both ends of the table and lock the gib into position.

[Peter Simpson 1Participant @petersimpson1]

I have a Light vertical and an M1 both gibs are identical, Not sure about the age of the M1 photoed above but it's not the same as mine. Both of my machines have the long X axis gib which is adjusted with two large headed screws which work from both ends of the table and lock the gib into position.

[Kiwi BlokeParticipant @kiwibloke62605]

Strange. I've never seen a gib strip in two pieces, like the pic. The manual for an earlier version of the M1 identifies only a single gib strip for the table. Sometimes one gets the impression that no two Senior machines are the same, however I think yours is probably non-original, or has been broken (and then fettled?).

I don't see why a two-piece gib strip shouldn't work OK in this application. If you think about it, gib strips are not very stiff, so the bit between where the screws bear really isn't doing much. This is in contrast to tapered gibs, in which there is well-fitted contact on both of its surfaces – and they're easier to adjust too. Altogether preferable.

I suggest you get the machine up and running, and then you can have the satisfaction of making a new gib strip…

Gib strips need to be restrained from moving lengthways. IIRC, and as the pic suggests, each of the Senior's screws locates in a pocket in the strip. However, if there were only one pocket doing the restraining (and the other screws have, for example, a ball end which bears on the strip's surface), the non-pocketed bit of your two-part strip could move.

Incidentally, I think the pic suggests that the correct oil level should be low enough not to worry about gaskets, etc.

Edited By Kiwi Bloke on 14/04/2020 00:20:33

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