Cross slide lifts when parting off

02/05/2011 13:39:56

http://www.arceurotrade.co.uk/Catalogue/Machines-Accessories/Lathes/Model-C3-Mini-Lathe/C3-Super-C3-Mini-Lathe-Accessories

Hi, I have a problem with the cross-slide lifting when Im parting off Mild Steel (EN1A free cutting).

I have tightened and aligned the adjuster at the side so that it's almost to tight to move the cross-slide - but it still lifts!

How can I stop this?

thanks

PS WM280VF lathe

maurice bennie

02/05/2011 14:37:57

164 forum posts
1 photos

Hi Martin. Have you checked that the carriage is not lifting.

best wishes Maurice.

john swift 1

02/05/2011 14:55:16

318 forum posts
183 photos

Hi Martin ,

my first attempts parting off on a CL300M minilathe didn't go well

the tool was deflected downwards even after tightening the gibs on the top and cross slides

re-grinding the tool to make it thinner helped

but in the end ,I replaced the original bent and miss shaped low grade steel gibbs with new brass ones from Arc Euro Trade

I also changed the method of adjusting the plates holding the saddle down to the bed

removing the 2 jacking screws from each plate and inserting a shim to set the clamping pressure between the saddle plate and the bed

this link shows the original saddle clamps

http://www.mini-lathe.com/Mini_lathe/Modifications/modifications.htm#brass_gibs

I don't know if brass gibbs are avialable for your machine but at least you need to check

the fit of the gibbs on you machine

Edited By john swift 1 on 02/05/2011 15:17:04

Edited By john swift 1 on 02/05/2011 15:18:07

Edited By john swift 1 on 02/05/2011 15:18:35

Edited By john swift 1 on 02/05/2011 15:27:04

02/05/2011 15:38:25

Posted by maurice bennie on 02/05/2011 14:37:57:

Hi Martin. Have you checked that the carriage is not lifting.

best wishes Maurice.

Hi, I can actually see the top slide moving up and down. But how exactly can I tighten up the main carraige as well?

thanks

02/05/2011 15:45:26

940 forum posts
30 photos

Hi John thanks for the reply and will ring Arc Euro tomorrow about the gibs

However a bit lost with the sadlle info you have mentioned... bit new to lathes. I am trying to look for info now.

thanks

Martin W

02/05/2011 15:54:27

Martin

Are you parting off from the front or from the rear like some advocate. If from the front then all the forces should be acting more or less into the bed of the machine, however if from the rear then there will be a lifting force. Using a similar but smaller version of this lathe I have had no problem parting from the front and so have not tried parting from the rear. I believe that at the rear of the saddle, under the rear edge, there are a set of gib adjusters that control the saddle clearance. Secondly is there a saddle locking screw which clamps the saddle securely to the bed, if so then it might be worth locking this when parting off.

Cheers

Martin

JasonB

02/05/2011 17:14:53

25215 forum posts
3105 photos
1 articles

I have the same lathe and don't have a problem parting off.

The saddle can be locked by tightening the allen screw that is just under the cross slide gib adjusting screws, the one nearest the bed of the three on the right top surface of the saddle though I seldom need to do this.

You may need to adjust the gibs on the cross slide if that is lifting, use the three screws that have the lock nuts, the one without a locknut is just to lock the cross slid ein a set position.

Check the tool is not above centre height as this will tend to push teh toolpost away from the work and lift the cross slide.

What type of parting tool are you using, what dia is the steel what speed and feed are you using and what cutting fluid? answer these and it will help us to help you.

You should not need to replace the gibs or saddle fixings.

Jason

Edited By JasonB on 02/05/2011 17:18:14

02/05/2011 17:52:54

Posted by JasonB on 02/05/2011 17:14:53:

Hi Jason, I have adjusted the gib screws but still no go. I am cutting off from the front and left hand side as I stand looking at the lathe. When cutting you can pysically see the toolpost dipping forwards. I have checked the toolpost etc an that is solid with no movement - however you can see the cross-slide lifting on the right side (were the gib is) I am using cutting fluid with a pump. The tool is spot on centre on the work piece, but when the post dips it makes the tool go lower than centre and then dig.

Cutting with a HSS blade that is very sharp - but also have a carbine insert system, but this does exactly the same.

I will try tightening the apron tomorrow but at the end of the day the cross-slide if definitely lifting.

02/05/2011 17:56:51

The steel I am using is EN1A feee cutting leaded steel at 20mm diameter. Speed at approx 120 rpm and using the finest feed "C" on my machine. When it does cut it does it lovely but I really think the movement is bodging it up most of the time.

I agree I should not need to change the gibs or saddle fixings, but I have tried adjusting until I am blue in the face

02/05/2011 17:59:58

BTW thanks for the replies - I am taking it all in slowly.

Been at it all day so going to try again tomorrow now. It just seems like the gibs mechanisn isnt doing much apart from making the cross-side stiffer to operate, it does not seem to be locking the topslide down much at all.

thanks again

JasonB

02/05/2011 18:02:01

25215 forum posts
3105 photos
1 articles

You have not said what dia the steel is or the speed and feed you are using.

I tend to use the slowest gear combination which is what the lathe comes set up with and the lever in the "C" position as this gives the finest feed rate, speed depends on dia but I can part off 1" steel at around 500rpm with a 3/32" wide Eclipse HSS blade.

Maybe take the cross slide off and check there is no muck under the gib strip stopping it seating properly- just keep winding it towards the back until the screw disengages with teh nut. If teh gibs are tight the slide should not be able to lift.

EDIT Cross post there, only other thing is to make sure the tool is perfectly at right angles to teh lathe axis so the sides are not rubbing.

Edited By JasonB on 02/05/2011 18:04:22

02/05/2011 18:08:15

http://phelum.net/info/CQ9325/modifications.htm

Hi Jason, my cutting blade is 2mm and is square (I square it with the chuck face).

500rpm - I can only dream of parting off at that speed LOL

I will take the cross-slide off tomorrow and clean it all out - thanks for the tips.

john swift 1

02/05/2011 22:10:33

318 forum posts
183 photos

Hi Martin ,

I failed to find the manual for your lathe but if you look at pictures 2 and 14 here :--

( they look more like your lathe than the CL300M !! )

you will see "L" shaped pieces that hold under the front and rear edges of the bed

assuming the parting off tool at the rear , have a look at the rear rear clamp adjusters ,

the 5 screws hidden underneath

see picture 14, may be easier with the rear splash guard removed

the front clamp looks its in 2 parts , looking at the marks in picture 10

these clamp just under the front inverted "V" on the bed

John

02/05/2011 23:45:11

http://www.tangi-flow.com/rollerboxes.odl

I haven't tried it yet but the turret lathe boxes always had a steady over the workpiece for parting off.

The problems are hundredths of a millimeter but they employ large forces and unless your lathe is "perfect" you will get issues.

A steady across the top of the workpiece apparently makes a huge difference for parting off. Nowadays instead of a block lubricated with whale oil and tallow we can use a couple of one dollar bearings to secure the workpiece.

2cents(buddy)

john swift 1

03/05/2011 00:31:27

318 forum posts
183 photos

Hi Martin ,

just a thought , you don't have the parting off tool too far out ??

if it is just long enough you reduce the leverage on the tool post

also don't part off too far away from the chuck or collet than you need to

Hi Ady ,

I've not seen steadys used when parting off

but have seen rollerboxes used to turn small diameters down in one pass

at school ( a long time ago !) the parting off tools on the Myford 7 lathes had a very short life

( 2 or 3 tools to partoff one piece )

years later I used an old Ward 2D capstan lathe once !

what a difference ,no deflection of the tool or workpiece

parted off several dozen parts without breaking the parting off tool

John

Edited By john swift 1 on 03/05/2011 00:35:41

03/05/2011 00:53:59

"Cross slide lifts when parting off"

This really shouldn't happen ever, for any reason.

Take it off and clean it up.

Edited By ady on 03/05/2011 00:59:13

These lathes aren't very old, they should be fine, a quarter of a ton with an MT4 spindle...holy smoke

Model No.
Distance between centers	700mm
Swing over bed	280mm
Swing over cross slide	165mm
Taper of spindle bore	MT4
Spindle bore	26mm
Number of spindle speeds	6/Variable
Range of spindle speeds	125~2000/50~2000rpm
Range of cross feeds	0.02~0.28mm/r
Range of longitudinal feeds	0.07-0.20mm/r
Range of inch threads	8-56T.P.I
Range of metric threads	0.2-3.5mm
Top Slide travel	50mm
Cross slide travel	140mm
Tailstock quill travel	80mm
Taper of tailstock quill	MT2
Motor	0.75/1.1KW
Packing size	1400 x 700 x 680mm
Net weight	210kgs

Edited By ady on 03/05/2011 01:02:17

03/05/2011 01:04:01

Give you a giant tip.

Lose the compound and replace with a big 4 way tool post. bolted directly to the cross slide.

Only ever use the compound for tapers.

Edited By ady on 03/05/2011 01:10:56

03/05/2011 01:14:50