Adjustment Problem - Cross slide lifting

[Metal_slicer]

Hello All,

I am brand new here and I just bought a HF 7 x 10 mini lathe. I have been using Sherline's cnc milling machine for over a year and have made several 3d parts. I have wanted to add a mini lathe to go along with the mill but didn't want to spend $700 on a aluminum lathe so I got the one from HF.

I have made several adjustments to my new lathe but I can't get the cross slide to not lift toward the chuck. I have the ways set so there is no rocking when twisting the slide right and left, and no lifting when lifting towards the splash guard forward and back, but it rocks a lot when I grab the compound slide and lift towards the chuck. Its like the metal strip in cross slide is rotating when lifting towards the chuck? I can eliminate this lift by tightening the 3 set screws but no mater how careful I am, it always ends up so tight I cant turn the handle. If I back off the screws to allow the slide to begin to move freely again with the hand wheel, it starts to rock again. There is no middle ground, either it is ultra tight or loosey goosey. I have it adjusted now where perpendicular cuts should be no problem but facing may be an issue.

Anyone?

 

[pete]

I'm not sure how to say this without sounding like a jerk.

'But didn't want to spend $700 on a aluminum lathe. Over and above the material choice, your also paying directly for the care, accuracy, and quality of the machine tools build. You can bet Sherline tests each and every component so it passes there quality control. The manufacter who built your HF lathe? Probably not, to very unlikely.

But just maybe you can do some repairs. I'd disassemble your cross slide, clean all the parts to a spotless condition, I'd bet your gib strip that's supposed to be adjusted for the play between the female and male dovetail is anything but straight. You either need to hand lap that gib strip, or build a new one so it's straight. Possibly? your dovetails were machined incorrectly and the problem can't be fixed. It's impossible to say that for sure. Asking here was the correct thing to do though.

Pete

 

[jirvin_4505]

Search the Internet for mini lathe 7x12 and you will find a wealth of info on the common shortcomings of the Chinese laths and their possible fixes.

I have a 7x12 and a little finishing work has resulted in a usefull lathe

Already having a mill will help greatly with the fine tuning of your 7x10

Cheers Jeff

 

[goldstar31]

As Pete says elsewhere that you could do a lot worse than get a copy of GH Thomas's views.
What GHT said about gibs was that they moved about. Not in so many words but brother they do!

What is needed in the first instance is to try pegging the gibs and or making better gibs to stop things going up and down 'like a fiddler's elbow'

 

[Metal_slicer]

pete,

I bought the sherline mill as a turn key setup because I didn't want to bother with tweaks and mods. I wanted to focus on learning the ropes. However, after learning how to use the machine, I have come to realize issues with rigidness and parts working loose. Sherlines are fine for tinny parts, but machining a 2" x 2" block of aluminum has some limitations.

I bought the HF lathe knowing its a china product and I knew I would need to do some tweaks/mods. I already know what aluminum machines are all about, want to try cast iron now which is why I have decided to go the rout I did. If you love sherline go with sherline, people have choices I have notheing personal against sherline products. I chose to pay 399 for the hf lathe and with the savings buy more tools.

I have also googled about mods for this lathe and that has lead me to these forums only to be told to go back to google? Anyway I appreciate the help I will google for procedures on how to fix my issues.

 

[wackyvorlon]

That's the thing with the 7x10, it's not a finished lathe - it's more of a kit. Now, there's nothing wrong with that. One just has to be mentally prepared. I know I bought a chinese 9x20 with QC gearbox. It took some work, but I've got it to the point where it does some decent work.

What you are experiencing seems to indicate an issue of fit. One must figure out *where* it's binding. One way is with bluing. This is a blue compound(also known as Prussian blue) that doesn't dry. You apply a very thin layer on the ways, and wind the carriage past it. Then take things apart and see where the blue has been rubbed off or on to a mating part. This shows where they are making contact. If you can post pics, I can see if I can give some thoughts. The fact that the carriage will push down at the front, but not lift up, points to the problem being toward tail stock end.

Also check the pins that press into the gib. On my lathe, there's a sets crew with a nut on it for locking. This pushes on a pin that transfers the force to the gib. I ran into problems because the pins had flat ends that were not angled to match the gib. This meant that the force was being focused on a small corner of the pin, and the pin itself was extremely soft. Over time the pins were deforming causing the gib to loosen. I made new pins out of drill rod, filing the end to a suitable angle and then hardening them. I didn't bother tempering, as they experience no shock.

If the gib needs to be squared up, you can manage that handily in your sherline mill.

 

[goldstar31]

I tend to agree with Wackyvorlon that the Chinese lathes are 'more of a kit' but I would reasonably expect that the kit of parts would be dimensionally straight but that the fitting left much to be desired. In other words, I would whip all the gibs out and scrape them in by hand, not on a Sherline mill or whatever.

What everyone will say that has done a bit of machine tool reconditioning is that one needs something called 'references' or pieces to scrape to. Whether it is a piece of float glass or a surface plate or a lathe bed, it matters not- you need it. You HAVE to scrape to your reference in scraping cycles, removing each high spot with a scraper that need only be a bit of old file-razor sharp or a carbide blade- with the provision to realise that it will soon blunt-- and you need something to put that cutting edge back( which you might not possess)

There is nothing mystical or secret about it. There are a lot of people who will advise you otherwise but each scraping cycle improves the fit. I mentioned things rocking about like a fiddler's elbow and this slowly reduces it.

I once had a lathe bed slideways ground professionally. One of the world's great experts( so he believed) asked me how it miked. I said the saddle sucked down with a ever so gentle sucking noise-- and he went away 'muttering' sweet nothings.

That is where you go- with the simplest of tools and a lot of work.

 

[MCRIPPPer]

i have the same issue with my littlemachineshop 7x12. i machined some flats into the gib and center drilled them, and refined the points on the set screws, and it is working ok until i machine a whole new gib out of steel and make some better set screws out of some 12.9 bolts. im going to make a gib that actually fills most of the space instead of the little tiny cast iron thing in there now. the 7x lathes are a project for sure, but i have mine set up ok now and it works good. i still have a long list of mods inside the front cover of my shop notebook tho. see my mod thread for some of the things i have done on my lathe.

http://www.homemodelenginemachinist.com/f28/my-mini-sx2-mill-mini-7x12-lathe-mods-so-far-20843/

 

[Metal_slicer]

MCRIPPPer,

Nice mods. I love the knurled handles. I want to do this eventually.

 

[chipenter]

ARC do a guide for setting up Chinese lathes http://www.arceurotrade.co.uk/Catal...Model-C3-Mini-Lathe/Model-Super-C3-Mini-Lathe

 

[Tin Falcon]

IMHO the gibs on these chines machines are often poorly fitted .
And HF version of the sieg has a reputation of being the ones left over after the other companies take there pick of the production run.

I have made several adjustments to my new lathe but I can't get the cross slide to not lift toward the chuck. I have the ways set so there is no rocking when twisting the slide right and left, and no lifting when lifting towards the splash guard forward and back, but it rocks a lot when I grab the compound slide and lift towards the chuck. Its like the metal strip in cross slide is rotating when lifting towards the chuck? I can eliminate this lift by tightening the 3 set screws but no mater how careful I am, it always ends up so tight I cant turn the handle. If I back off the screws to allow the slide to begin to move freely again with the hand wheel, it starts to rock again. There is no middle ground, either it is ultra tight or loosey goosey. I have it adjusted now where perpendicular cuts should be no problem but facing may be an issue.

I had a similar situation on my x-2 mill . My suggestion is make a brass or bronze if you can gib that fits. also debur the dovtails and you may want to lap the dovetails or smooth with some fine silicon carbide paper and oil.

IIRC chuck fellows did a write up on a wedge style gib that would be a considerable upgrade.

Here is a plan for a jig to make gibs

http://www.fignoggle.com/plans/figNoggle_gibStripViseBlock.pdf



Tin

 

[MCRIPPPer]

you can do taper gibs for the saddle but i think a taper gib for the other axis woudl be difficult. i guess you could machine one of the dovetails at an angle, assuming it would not make the parts too thin.

 

[Forestgnome]

My suggestion would be to stop trying to lift the carriage towards the chuck. A carriage is designed for downforce, not upforce.

 

[Metal_slicer]

My suggestion would be to stop trying to lift the carriage towards the chuck. A carriage is designed for downforce, not upforce.

When the cutting tool contacts the rotating stock it is moved down causing the cross slide to move up on the gib side, not the non gib side. You must be thinking of something else because it lifts (on it's own) when cutting. The carriage doesn't move, the compound slide doesn't move, however the cross slide moves on the gib side. This only happens when the cutting tool is positioned in-line with the stock and a facing operation is done.

 

[Metal_slicer]

just a quick update. I adjusted the gib tighter and most of the play is gone but the slide is very very firm. for now it will have to be this way until I can lap or make new gibs. I appreciate the help guys.

 

[Sshire]

I did this procedure on my 10x22 a few years ago. Made a big difference.
http://www.mini-lathe.com/Lapping/mt_lap.htm

 

[wackyvorlon]

Wow, that would take a lot of time. Mothers is pretty fine stuff. Now, the compound you might want to consider is what's called Timesavers. It's designed to break down as you lap, causing the particles to become smaller. You can then start out with it relatively coarse(making the process faster), them it becomes finer and finer. It also reduces the need to make sure you clean everything thoroughly.

An alternative is scraping. The thing is, you don't want a perfect fit between the two surfaces. A perfect fit will push out oil and stick like crazy. Ever wrung together gauge blocks? Same thing. The idea with scraping is to have so many bearing points per inch. It can retain oil and slide easily, while still sliding precisely.

I recommend having a surface plate too. There's a couple options here. 2" thick by one foot square surface plates can be had for about $50. You can call up a local monument maker and ask if he has a scrap tombstone. These are very flat and precise, and made from granite. Sometimes the engraving goes wrong and you can pick up a fairly large chunk very cheaply. Alternatively, you can make your own.

How do I make my own surface plate without the proper measuring instruments, you may ask? Geometry! It's a very cool trick. The proviso however is that you need to make *three*. You can use steel, cast iron, granite, what have you. Pick up some abrasive like clover compound. Label the plates A, B and C. You're going to lap them to each other. Do it in a figure eight, and don't push down. Gravity will apply plenty pressure. You're just pushing in a figure eight, no vertical force at all. Lap plate A to B, then B to C and C to A. Keep going around in this fashion. As you do this, all three will get flatter and flatter. You can check them against each other will toolmakers blue.

 

[Forestgnome]

When the cutting tool contacts the rotating stock it is moved down causing the cross slide to move up on the gib side, not the non gib side. You must be thinking of something else because it lifts (on it's own) when cutting. The carriage doesn't move, the compound slide doesn't move, however the cross slide moves on the gib side. This only happens when the cutting tool is positioned in-line with the stock and a facing operation is done.

If you have enough side force to lift your cross slide then your tools are ground incorrectly. The majority of the force should be downwards, turning or facing. Tool post position should direct the downforce between the flats your cross slide rides on. Gibs shouldn't need to be tight in most turning situations. Just enough to keep the wheels from turning on their own. Otherwise you wouldn't get the accuracy we get.

 

[Forestgnome]

Actually I just looked at a picture of the mini lathe. I'm used to larger lathes. Considering the short distance between flats on the cross slide, I would think a lantern tool post would be better geometry-wise. Not much space there to get the tool tip balanced over the cross slide using a QC tool post, unless it was a teeny one.

 

[Metal_slicer]

Actually I just looked at a picture of the mini lathe. I'm used to larger lathes. Considering the short distance between flats on the cross slide, I would think a lantern tool post would be better geometry-wise. Not much space there to get the tool tip balanced over the cross slide using a QC tool post, unless it was a teeny one.

Yeah its a tiny tiny lathe. Another problem I have is a broken cutting tip, with a sharper tip it will cut with less effort. I did adjust the gibs to the point it should not lift unless I am really taking deep cuts.