Harrison milling machine play

Good evening all.

On a harrison vertical mill the gib strips pull down the slide on to the knee casting. The axis is controled by vee; raisde on the knee and cut into the slide casting.

With the gib strips tightened so there is no lift the slide still wants to twist and pull itself up the vee.

I cannot get any measurable lift on the slide, but it still twists slightly from side to side. I dont want to flog the gibs down any tighter as I having tried that the motion becomes quite stiff.

Has anyone else experienced this? I have some gib strips out of an old lathe. I am considering milling slots in the vertical sides of the gib retaining slots, drilling and tapping holes and then fitting gib strips to control sideways movement.

Has anyone any experience of this, and another possible solution.

Are you referring to the Y axis gibs, when the table is moving in and out from the column. ?

I thought usually they are dovetailed both sides of the knee support.

Emgee

Yes, The axis that moves towards and away from the column. Dovetail on one side only. The left hand side.

Andy Pugh's video of his cnc conversion shows this single dovetail quite clearly.

That chap who invented the do everything lathe(70s?) had an alternative locking system he patented about 1982

Memory very hazy but I know I noted it for future reference because it was a simple clever system

If someone can remember his name, was it the universal lathe? It can be looked up

There's a thread with his system in here

AHA!

Impetus-Metalmaster
Universal Machine Tool

And the TRIANGULAR GIB STRIP

Not bad going for 8am on a sunday morning

Edited By Ady1 on 20/01/2019 08:14:35

Hi Marcel I thought that on these mills there was a V guide on the top of the knee casting to locate the axis. If this is the case that is whst you need to concentrate on check for play with feeler gauges when the table end is pulled and pushed when would put to one end. Check the amount of movement with a dial indicator and if the bed is lifting whilst rotating. If the bed is lifting you will have to remove the strips when the bed has been centralised to prevent over balancing inspect and possibly machining to flatten area, it depends what you find.

David

Hi Marcel,

If tightening the gib lifts it off the ways then you have a wear issue. Might be that it;s been run a while with the gib loose and worn a ridge that it's pulling up onto when the gib is snugged up.

Pop some photos up to show exactly where the problem is and you might get some good advice on how to improve it.

David, Pete,

Thanks for the input.

Centralising the bed? I can't get the bed to lift, but it does twist. are you suggesting that if the side furthest from the Vee is tightened first it will lift the other side of the bed slightly? It is a heavy old lump.

Initially I had the table (X Axis) off of the machine when I set the Y axis gibs and it was fine for a couple of passes. i have singe tightened up the gibs twice, I did it again this afternoon. the twist has gone for now, but if past experience is anything to go by it will re-appear.

All the ways appear to be true, as best as I can tell with a straight edge, and running the slide ove with blue does not show anything untowards. I dont think it is a wear issue as past experience has shown if gibs are adjusted in on position they have a tendency to bind at a different point on the ways, conversly if they ar tight a one spot they are slack at another. However this problem occures regardless of position.

I must admit I am finding adjusting this machine a bit of a trial, there is nothing in the manual.

Having said that I am going to try twisting the bed with a dial gague fitted to check for lift. That is for tomorow night.

I have now measured the twist on the slide which is reading 0.15mm on my dial gague. I can get no discernable lift though.

It was measured with the table moved pretty well to the end of its travel, I also had the table locked down.

I am trying to move this by hand though. Should I be clamping a bar on to the bed to give some extra leverage?

As said above I do not know the correct procedure for adjusting this. Just been going by trial and error.

I have just added an image but it is upside down. I cant find out how to resize it or rotate it.

Edited By Marcel Jolinon on 21/01/2019 23:17:06

Edited By Marcel Jolinon on 21/01/2019 23:18:15

Edited By Marcel Jolinon on 21/01/2019 23:27:07

Sorry Marcel I mis-read your opening post, plus I wasn't familiar with the arrangement despite David George's description .

Anyway, looking at the photos the inverted vee controls skew on the y-axis slide so if you're getting some then it suggests that the slide is not sitting fully on the vee. I would strip off the table and the cross-slide, clean it up and inspect the y-axis slideways. Could be it's riding on debris or might simply be wear in the vee ways. If it's wear you're going to have to scrape it some.

Hi Pete,

I have striped the machine down twice. No swarfe on anyof the slides.

Visual inspection with a straight edge and feelers leads me to think there is no apreciable wear, also normaly when wear is present it tends to be in the centre of the slides, or with lathes up near the headstock. My old Brown and Sharp lathe was pretty bad. When the gibs were adjusted up near the headstock it would jam up towards the tailstock.

This is not happening with the milling machine, which also leads me to think it is not a wear related problem. Also I believe that the slides are induction hardened, like the lathe beds, so almost impossible to scrape I think.

There is a gap (clearance) of around .9mm on either side between the knee and the slide, clearly there by design. The gib strips pull the slide down. I have adjusted the gibs again last night, the action is now quite tight and the twist has gone. However to me it seems too tight. I dont supose anyone knows what sort of torque would be required to turn the screw. That I can measure.

I think I am using the wrong procedure for adjustment. I am tightening the adjustment screws one at a time little more than finger tight and locking them up. Should I have all the locknuts slack adjust all the screws and then tightem all the locknuts? Should I be adjusting one side at a time, or perhaps going side to side, or perhaps even diagonally?

As I said I have no idea of the correct procedure for this.