Wandering mill table

[Steve355Participant @steve355]

[Steve355Participant @steve355]

Hi

Now trying to learn to set up my Dore Westbury mill (got from eBay and refurbed)

I trammed the head yesterday and got it to .001 – happy with that.

I need to make some jaws for the vise, and I have some gauge plate for that. Before I cut the gauge plate I thought I’d indicate in the vise so I can mill the end of the gauge plate square. But I find that when I put the DTI on the vise and wind the table from left to right, the table wanders by about .005 on each turn of the wheel. I have tightened up the gibs but it seemed to make no difference. I had the table apart, nothing is obviously worn and everything seems in very good condition. I cleaned and oiled it and put it back together.

it seems to happen more when the table is at either extremity.

Is there something I don’t know about tightening gibs? When I tighten the gibs on the lathe carriage, I can’t move it. But on the mill, it still runs smoothly. Something doesn’t seem quite right.

Any ideas?

Thanks

Steve

[Anonymous]

How do you know that it's the table and not the vice that is off?

Andrew

[DalboyParticipant @dalboy]

Have you checked the Y axis

[Steve355Participant @steve355]

Posted by Andrew Johnston on 22/10/2021 23:06:24:

How do you know that it's the table and not the vice that is off?

Andrew

before I took it to bits, I was getting about .010 movement. I could see the corner of the table wandering, also, it corresponded with a stiffness at a particular point when I turned the wheel.

I also used some gauge plate for the DTI. I wasn’t sure if the “outer jaws” of the vise were flat enough, they have some grinding marks on them,

So I’m pretty sure it’s the table and something to do with the gibs/feed screw

 

Steve

 

Edited By JasonB on 23/10/2021 07:10:58

[Clive FosterParticipant @clivefoster55965]

If its a regular cyclic error as you turn the feed handle then +1 for Y axis slack as suggested by Derek.

Moving the handle creates a couple that will take up any cleasrances in the Y-axis generating the shift.

More of an issue with smaller amchines with, inevitably, lighter slides and smaller bearing areas but my Bridgeport is pretty decent yet the glass scale DRO is sensitive enough to pick up a similar tenth thou / micron level shifts. Such errors are academic of course.

Clive

[Steve355Participant @steve355]

Posted by Clive Foster on 22/10/2021 23:26:54:

If its a regular cyclic error as you turn the feed handle then +1 for Y axis slack as suggested by Derek.

Moving the handle creates a couple that will take up any cleasrances in the Y-axis generating the shift.

More of an issue with smaller amchines with, inevitably, lighter slides and smaller bearing areas but my Bridgeport is pretty decent yet the glass scale DRO is sensitive enough to pick up a similar tenth thou / micron level shifts. Such errors are academic of course.

Clive

I’m pretty sure I locked the Y axis but I will have a closer look in the morning

Thanks for the thoughts

Steve

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Steve355 on 22/10/2021 23:23:24:

[…]

So I’m pretty sure it’s the table and something to do with the gibs/feed screw

 

 

.

That looks like you have a lot of weight acting in cantilever

I would try setting the gib-screws with the table unloaded.

[ or have you already done that ? ]

MichaelG.

.

Edit:

It’s perhaps worth noting the proportions of this machine :

http://modelengineeringnorge.weebly.com/dore-westbury-mill.html

http://www.lathes.co.uk/dore-westbury/

Edited By Michael Gilligan on 23/10/2021 05:05:36

[JasonBModerator @jasonb]

What's holding that bit of bar you have the clock running against? looks like it's just stood on top of the fixed jaw.

To take out some variables try it with the clock on the edge of the central tee slot.

Can you also confirm that when you say 0.005" movement you are talking of wobble or just the steady change in reading from one point to another.

I assume you are loosening the locknuts then adjusting teh gib screws before finally locking the nuts again? If they are making no difference then something is wrong as they should lock the table if done up too tight.

It's a large vice for that machine, at least consider taking it off the swivel base if for nothing else to regain some Z height.

Edited By JasonB on 23/10/2021 07:34:46

Edited By JasonB on 23/10/2021 07:39:13

[Steve355Participant @steve355]

Posted by JasonB on 23/10/2021 07:15:47:

What's holding that bit of bar you have the clock running against? looks like it's just stood on top of the fixed jaw.

To take out some variables try it with the clock on the edge of the central tee slot.

Can you also confirm that when you say 0.005" movement you are talking of wobble or just the steady change in reading from one point to another.

I assume you are loosening the locknuts then adjusting teh gib screws before finally locking the nuts again? If they are making no difference then something is wrong as they should lock the table if done up too tight.

It's a large vice for that machine, at least consider taking it off the swivel base if for nothing else to regain some Z height.

Edited By JasonB on 23/10/2021 07:34:46

Edited By JasonB on 23/10/2021 07:39:13

>>What's holding that bit of bar you have the clock running against? looks like it's just stood on top of the fixed jaw.

nothing, it was just an experiment to check it wasn’t imperfections in the surface of the cast iron on the vise. Same results.

>>you are talking of wobble or just the steady change in reading from one point to another.

wobble, it is “wobbling around a steady change” if you see what I mean

as Michael also suggested I will take the vise off and eliminate that as a variable.

Thanks!

[John PParticipant @johnp77052]

Bit a of a long shot this its 40 years since i built my Dore wesbury mill, the two steel flat bars that are fitted to the underside of the table one of which provides the narrow guide for the gib strip to run on and sit under the two steel strips which form the bearing surface for the table to traverse on ,all of these strips of steel are attached with countersunk screws ,the guide strip should have a a couple of hollow spring dowels to secure the strip to the table .It may be worth checking if the guide strip that is fitted to the underside of the table is still secure and the screws are still tight as if the strip moves about the table would wobble as you have described.

John

[Steve355Participant @steve355]

Posted by John P on 23/10/2021 09:14:51:

Bit a of a long shot this its 40 years since i built my Dore wesbury mill, the two steel flat bars that are fitted to the underside of the table one of which provides the narrow guide for the gib strip to run on and sit under the two steel strips which form the bearing surface for the table to traverse on ,all of these strips of steel are attached with countersunk screws ,the guide strip should have a a couple of hollow spring dowels to secure the strip to the table .It may be worth checking if the guide strip that is fitted to the underside of the table is still secure and the screws are still tight as if the strip moves about the table would wobble as you have described.

John

John, you may just be a genius… certainly another line of investigation….

I have it apart again, the strips are all tight and seemingly in good nick. I am wondering about those spring dowels. I can’t seem to post pics of the drawings here, but I can’t find anything about them on the drawings except the holes in which they go.

see pic below, do you think that looks right? I can’t see the point of those holes myself, so Is something missing perhaps?

[Steve355Participant @steve355]

Posted by Michael Gilligan on 23/10/2021 04:50:51:

Posted by Steve355 on 22/10/2021 23:23:24:

[…]

So I’m pretty sure it’s the table and something to do with the gibs/feed screw

.

That looks like you have a lot of weight acting in cantilever

I would try setting the gib-screws with the table unloaded.

[ or have you already done that ? ]

MichaelG.

.

Edit:

It’s perhaps worth noting the proportions of this machine :

**LINK**

**LINK**

Edited By Michael Gilligan on 23/10/2021 05:05:36

done it now, same result, now 0.002 wobble on DTI. 😢

[JourneymanParticipant @journeyman]

From your photo it looks like the spring dowel or 'roll-pin' is in place.

John

[Dave HalfordParticipant @davehalford22513]

Going back to the gibs, does that locking screw (third hole) lock the table?

Not the pic journeymans reply 

Edited By Dave Halford on 23/10/2021 11:06:45

[John PParticipant @johnp77052]

That looks as if it is ok as noted previously by Journeyman , have you checked also the gib strip adjustment on the Y axis slide way, try the test with the Y axis lock tightened.

John

[Steve355Participant @steve355]

Posted by Dave Halford on 23/10/2021 10:59:50:

Going back to the gibs, does that locking screw (third hole) lock the table?

No, it doesn’t seem to, and I can get them all as tight as they will reasonably go and the table will still move. Getting stiff, but it moves. I’m thinking perhaps the gibs are installed incorrectly.

[Tony Pratt 1Participant @tonypratt1]

Posted by Dave Halford on 23/10/2021 10:59:50:

Going back to the gibs, does that locking screw (third hole) lock the table?

Yes, from memory over 40 years ago when I made one. The OP said tightening the gib screws made no difference, they should certainly lock the table if snugged right up. The gib in my Dore Westbury was just a flat strip of metal so hard to make or fit incorrectly but possible?

Tony

Edited By Tony Pratt 1 on 23/10/2021 11:08:10

[Steve355Participant @steve355]

Looking at the drawing, perhaps the gib is supposed to be “raised”, when I’ve installed it it just slots in and settles on the bed. It feels right, but according to the drawing it isn’t. I will have a go at that next.

[Tony Pratt 1Participant @tonypratt1]

Steve355, the gib screws & the locking screw should go into dimples in the gib strip.

Tony

[Steve355Participant @steve355]

Posted by Tony Pratt 1 on 23/10/2021 12:44:24:

Steve355, the gib screws & the locking screw should go into dimples in the gib strip.

Tony

Yes indeed, but in this case it looks like they can sit in the dimples in two ways.

If the gibs sit on the bed, the gib screws will push the upper side of the dimple, and only the top inner corner of the gib will make contact with the slideway. Looks like that’s why the gibs weren’t locking the table.

if the gibs sit about 1mm above the bed, the screw fully engages in the dimple and the entire gib contacts the slideway, providing a lot more friction. I’ve now got it like this and the gibs can lock the table properly. I can also not move the table at all in the hoizontal plane.

But there is also a vertical component. I think I was turning the handle too roughly, which seems to flex the table – only very slightly, obviously. But it doesn’t take much to create a .002” movement on the DTI. The gauge plate I was using was very slightly off square to the table, so a slight vertical movement moved the DTI needle.

I think I’m getting there.

Steve

[Martin ConnellyParticipant @martinconnelly55370]

Not flexing the table but probably some induced rotation about a vertical axis, this is unavoidable unless you tighten the gibs to the point where the bed can't be moved. An advantage of a powered drive is that there is just torque applied to the leadscrew, no pushing and pulling at 90° to the leadscrew axis. It would be a good exercise to see if you can drive the bed with a variable speed drill to reduce the pushing and pulling that comes from hand cranking. That will give a truer indication of the set-up you are achieving. With a spoked wheel a simple fork shape in a chuck can be enough but it looks like you have solid wheels in the photos above.

Martin C

[Dave HalfordParticipant @davehalford22513]

Maybe a bent leadscrew?

[Steve355Participant @steve355]

Posted by Martin Connelly on 23/10/2021 15:25:30:

Not flexing the table but probably some induced rotation about a vertical axis, this is unavoidable unless you tighten the gibs to the point where the bed can't be moved. An advantage of a powered drive is that there is just torque applied to the leadscrew, no pushing and pulling at 90° to the leadscrew axis. It would be a good exercise to see if you can drive the bed with a variable speed drill to reduce the pushing and pulling that comes from hand cranking. That will give a truer indication of the set-up you are achieving. With a spoked wheel a simple fork shape in a chuck can be enough but it looks like you have solid wheels in the photos above.

Martin C

Actually the table wheels are spoked. I might give that a go.

I did have the best genius idea of putting some oil on it earlier and it seems to turn a lot more easily.

I am beginning to want to add a power feed already.

[Pete RimmerParticipant @peterimmer30576]

If the table is rotating simply from turning the handle either the ways are worn or the leadscrew is bent. It's also possible that the leadscrew nut is machined slightly too tall and the bed is riding on the leadscrew somewhat. Check for a bent leadscrew by turning it slowly by gripping the wheel not the handle. If it's bent it will move your dial regardless of how it's turned.

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