Sieg SX2P x-axis gib

[Alex TsekenisParticipant @alextsekenis66517]

I have decommissioned my SX2P to try and improve on a few of its shortfalls.

I am focusing on the x-axis gib which does not sit properly on the dovetail. As you can see from the picture, the gib only touches the table dovetail on its edge. This has caused a pitted line on the gib due to wear. Fortunately replacement gibs are cheap.

I have read about people using brass gibs, reforming the gib screw points etc. I have not modified the stock gibs and gib screws in any way. The y and z axis gibs appear to make good contact, but I will be checking them for wear later.

What are your thoughts on this?

Edited By Alex Tsekenis on 28/01/2016 21:28:21

[Alex TsekenisParticipant @alextsekenis66517]

[John RuddParticipant @johnrudd16576]

Looking at your photo, the angles are different…..hence the wear line on the strip…

This is your decision on what to do about it….bottom line, the dovetails need matching.

[Frances IoMParticipant @francesiom58905]

I'm in process of modifying an SX1 mill to have some simplified CNC (I bought a 2nd such mill so I still had my original to machine any parts) – the first phase was to fettle the table as with the original I could never get free movement along the full length without some section being too loose – when I took off the gibs from the new table one of the gibs was banana shaped and would happily spin on a surface plate – I replaced this with a brass gib

and used a small amount of metal polish (a white paste with a little WD40 added) to give a smooth action

[Alex TsekenisParticipant @alextsekenis66517]

Yes, the gap between the dovetails needs bridging as clearly the stock gib is too thin. But even so, if the gib screws were impinging on the correct height (mid of dovetail) the undersized gib should make good contact. In other words, my evaluation is that unless the gib is a press-fit between the dovetails, the problem will still be present to some extent.

Frances, I too get movement when approaching the travel limit. This is particularly so for the x axis which has a shorter gib. It might the angle of the photo, but in your picture the brass gib seems to be at a significantly different angle too. I wonder if you have noticed any wear?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Alex Tsekenis on 28/01/2016 21:27:53:

What are your thoughts on this?

Edited By Alex Tsekenis on 28/01/2016 21:28:21

.

Alex.

As John says: 'the angles look different' … but … zooming-in on your photo; the angles on the castings look fairly well-matched, yet the gib-strip is standing more vertical.

This is all-the-more confusing when we note the [high] location of the ajusting screw !!

I suggest that you first look very carefully at the gib-strip and its adjusters … I suspect that something is binding, and not allowing the strip to sit correctly.

MichaelG.

[Alex TsekenisParticipant @alextsekenis66517]

Hi Michael, I'm pretty sure this is what John meant by angles being different, so I think we are on the same page.

Having to guess, I would say the gib screws impinge lower than they should; the picture perspective makes it look like they are higher. This would explain the gib misorientation. In any case the height different will be minuscule.

Right now the gib screws are flat-bottomed, but their sitting location on the gib is anything but flat. I remember seeing somewhere one forming the gib screws tips into rounded points as part of the general prep of this machine. Seems like that's the place to start.

Here are pictures of both faces of the gib.

[JasonBModerator @jasonb]

Same problem and the cure on MEM forum

You would probably have to narrow the gib unless you can deepen the relief

J

Edited By JasonB on 29/01/2016 07:28:55

[mechman48Participant @mechman48]

Had a similar problem with my WM 250V-F compound slide gib key; pics show the original gib & the new brass gib that I made, much improved movement…

OEM gib as supplied…just a piece of rough hand filed MS plate, couldn't even get the angles right…

New brass gib fitted…

As you can see slide castings are not the best to say the least, the undercut is far too big but at least the angles are the same so the new gib fits much better…

George.

Edited By mechman48 on 29/01/2016 09:47:15

[Neil WyattModerator @neilwyatt]

A little thought will show that the angle of the face the screws protrude from doesn't matter (as the strip should not be in contact with it!)

It's to do with the geometry of where the gib screws press on the gib causing it to tilt. You need to ensure the contact point is either higher (by using pointed screws) or closer to the rubbing surface (by milling pockets).

I encountered this problem once when i made a replacement gib, and creating pockets to move the screw tips closer to the rubbing face worked a treat.

Neil

[Alex TsekenisParticipant @alextsekenis66517]

Just off the phone with Ketan from Arc – this level of customer support makes me feel spoilt.

I will try out the great suggestions you all have made and report back on the results.

Thank you for the help so far!

Alex

[Alex TsekenisParticipant @alextsekenis66517]

Just reporting back with good news. It turned out the relief was adequate with plenty of clearance.

I ground the gib screws to a point and the gib contact on the table's dovetail is now much improved.

I ordered some cone-point grab screws and got a new gib strip. The gib strip does not have any dimples formed. I think I can improve the contact a bit more by milling vertical V-grooves on the new gib where the cone-point grab screws will sit in. This way I'm hoping the gib will assume its natural position on the dovetail.

Alex

[Peter KroghParticipant @peterkrogh76576]

It is my opinion the the correct way for gib screws to contact the gib is with a flat end in a flat-bottom pocket. Easily done by using a flat bottom drill the size for tapping the screws. Just drill through the screw holes to make the pockets and turn a few threads off the ends of the screws. It doesn't take any longer to do than all the others.

Pete

[Danny M2ZParticipant @dannym2z]

One modification that I did to my C3 minilathe top and cross-slide (yet to do the same to my X2 mill) was to replace the supplied gib screws with cup-point hex-socket grub screws and to slip a small (2mm) ball bearing between the screw and the gib indents. (The balls were rescued from a disc drive ball race and decent quality (ISO) set screws are readily available here in Oz).

The dovetails were blued and the high spots removed with a diamond lap and left slightly rough (to hold a smidgin of oil). Replacement gibs were machined from brass as the supplied cast iron ones were banana shaped. I did consider making tapered gibs but tried the easy way out first.

Imho, if you are going to fettle gibs, the dovetails should be true otherwise you are chasing your tail!

With a few shims under the handle collars backlash is now minimal (<0.005" )  yet with the gib screws done up fairly firmly things still move smoothly.

As the X2 mill is behaving nicely at the moment I am loathe to pull it apart, but when that day arrives, the same tweaks may be required.

* Danny M *

Edited By Danny M2Z on 03/02/2016 04:35:50

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