How much cross-slide play is ok? Can't seem to properly adjust the gibs on my Sieg C3

[seethe]

Hi,

I'm a machining newbie, and am having trouble adjusting the cross-slide gib on my Sieg C3 mini-lathe: I have tightened the gibs to the point where it is difficult to move the cross-slide handle, and yet I am still getting a visible 0.05mm of play when I push down on the compound.

I have followed some other guides, and have given the gib screws cone tips, have replaced the standard steel gib strip with a brass one, and polished the gib. I haven't properly polished the surfaces of the cross-slide itself yet though.

Per the attached photos, I have attached a short piece of aluminium plate to the cross slide to simulate the compound and for a bit of leverage, and when I press firmly firmly down on the lever the other side of the cross-slide lift off its ways by a visible amount of about 0.05mm. I'm not sure if this is actually entirely normal and as good as I should be expecting? My thinking is that this amount of deflection will be noticeable when turning and may also be behind my difficulty in parting off (the parting tool always digs in and jams) - but after an afternoon of adjusting I can't seem to get it any better than this.


I've also attached a close-up of the gaps I can see between the cross-slide bed, ways and gibs, to see if these are all normal or perhaps theres something else involved in this excessive amount of play that is bothering me.



Thanks in advance for any assistance!

Cheers.

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[dharmic]

Only 0.05? You're doing well.

You'll also probably find the carriage wants to lift off the main bed at the front too, pulling down the tool if you're going in hard. Then the compounds on these things are made of cheese. Look at them sternly and they deflect. And just wait until you have a hundred hours on it, just don't look at the spindle runout because you'll cry.

This is the kind of difference to expect between a SIEG that cost fifteen thousand rand or so vs a mikuni or something at three hundred thousand. If you're like me and only using it for rough-and-ready jobs in the shed then it doesn't seem to matter so much if it's only a couple thou off when you load it up - get in close-ish and the last couple of skimming passes with very little load will get you to within a thou or two of the finished diameter you wanted.

[Superman]

My gut feeling is telling me, it has clearances in the wrong areas, and too much side clearance for the gib

The top slide should have contact with the base & angle wall of the dovetail only, ( where you have the R/H arrow pointing, 2nd pic)
- currently, as you tighten the gib, you are pushing the outer part down, into the carriage bed while pushing the gib upwards....tightening the gib would only lock up the cross-slide without getting rid of the play

Minimum rework would be....
The key needs to be ...... gib height lowered a tad ( so the screw doesn't push the key up onto the top slide), & L/H lower corner of the gib given more clearance ( remove any pivoting action)

I'd made a new key, a bit wider, not as high.... & must have clearance in the corners

[oregondave]

Hi I created an account because I have the same problem and searched and found this.

Did you find a solution?