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Mill table wonky

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Steve35526/10/2021 21:31:32
128 forum posts
87 photos

I know it must seem like I’m always asking questions on here, but I’ve solved loads of other problems on my own, honest!

While trying to work out why my mill table was wobbling (which I think is fixed now) I noticed that the vise didn’t seem square, so I put an indicator on the mill table. Lo and behold, it didn’t seem square to the base - about .015 movement across about 2/3 of the width.

So I took it to bits again, and it turns out the the ways are not parallel. 3.0” at one and and 2.973 at the other. In fact, you can actually see this difference from the outside. I’ve put this all in pics below. Only thing is, I’m not 100% sure that the indicator movement is in the same direction as the slideway parallel difference, it something is definitely wrong.

I guess, Dore Westburys being originally a user built kit, it was an error in the original build.

Before I start messing around trying to re-bore the countersunk screw holes in the slideway to put them in the right place, I would ask here for opinions on what to do (if anything). And ideas on how to do it, that doesn’t involve using a milling machine, cos it is in bits again.

Thanks

Steve

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Edited By Steve355 on 26/10/2021 21:32:32

Edited By Steve355 on 26/10/2021 21:34:26

John P26/10/2021 22:16:32
359 forum posts
238 photos

If the edge of the table is not parallel to the direction of travel which seems to be what you are saying here, it is not anything to do with the slide way strip that you have shown in the photo with the caliper reading of 2.973" .The guide strip that is screwed to the underside of the table the one the gib strip runs on controls the position of the table ,you would need to check that the guiding edges of this strip are in line with table edge.

In any event apart from from a nuisance does not affect the operation of the machine in any way ,for what it is worth you would probably need to replace the strip rather than try to reposition the countersunk holes any distortion to the existing strip is likely to lead to more problems.

John

Howard Lewis26/10/2021 22:37:40
5528 forum posts
13 photos

If the strips on the underside of the table are out (Both? Maybe only one )

Could you make a new strip?

Clamp to the table, clock so that the edge is parallel to the table movement, and then drill and countersink the holes

Alternatively could you remove all but one of the screws and adjust the position until the edges of the strips are parallel. Hopefully one edge IS parallel to to to where it should be, and can be used as a datum.

You need to find which one, or you may remove the wobble but have a table which runs out by several thou relative to cutter when traversed.

I would feel inclined to start by clocking the T slots on the table when it is pulled /pushed against one of the locating strips, so that the slots are running true. In this way, you ahould be able to decide which of the strips need to be remade / adjusted..

Once the strip has been adjusted parallel to the datum strip, it can be located with dowels or rollpins, before drilling and tapping new holes and countersinks

The strip is located by the dowel, rather than the countersink, which is then only to provide clearance for the screwhead.

Where are you located?

Maybe someone on here could give some face to face help Seeing things rather than just looking at pictures might give a better understanding of the problem area and how to overcome it.

Howard

Andrew Johnston26/10/2021 22:46:42
avatar
6315 forum posts
677 photos

It would be a help if the pictures were zoomed out a bit. Otherwise it's difficult to see what is being measured. It's not essential that the sides of the table are parallel to the ways, but it's an all round PITA if they're not as then they cannot be used as reference surfaces.

Andrew

Steve35526/10/2021 23:51:43
128 forum posts
87 photos
Posted by John P on 26/10/2021 22:16:32:

If the edge of the table is not parallel to the direction of travel which seems to be what you are saying here, it is not anything to do with the slide way strip that you have shown in the photo with the caliper reading of 2.973" .The guide strip that is screwed to the underside of the table the one the gib strip runs on controls the position of the table ,you would need to check that the guiding edges of this strip are in line with table edge.

In any event apart from from a nuisance does not affect the operation of the machine in any way ,for what it is worth you would probably need to replace the strip rather than try to reposition the countersunk holes any distortion to the existing strip is likely to lead to more problems.

John

You are absolutely right, the gib strip (located under the display of the calliper) pushes the table against the guide rail, which is located under the right arm of the calliper in the pic. I need to look into this more.

Steve35526/10/2021 23:52:37
128 forum posts
87 photos

Thanks for the ideas chaps, I will take a closer look in the morning.

Steve35527/10/2021 10:34:11
128 forum posts
87 photos

Right, I spent some time on this before work today.

This all started on Sunday night, when I wanted to start to make some vise jaws (missing from vise I bought on eBay). I decided to mill a test piece to check for square before I started squaring the ends of the stock for the jaws. It wasn’t square.

I think to some extent I am chasing ghosts. I’ve been measuring with reference to the base. I’m not sure this is relevant.

Is this statement true? :- It doesn’t matter if the milling table is not square to the base of the mill (within reason). The milling cutter is round. What matters is that the X, Y and Z axes run perpendicular. Tramming ensures the Z axis is perpendicular. The X and Y axis should be perpendicular by manufacture of the table.

Looking closely at the Dore Westbury table, one of the slideways is precision located with dowel pins on a ground surface. It looks to me that this is supposed to be a perpendicular reference surface. The other slideway isn’t so important.

TABLE

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BASE

Looking at the base it sits on below, there is a perpendicular ground surface. That looks like it should mate with the precision perpendicular surfaces on the table. This would guarantee that the table and the base run parallel.

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However, they don’t. See below how it is…. The non-precision located slideway is against the ground guide.

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And clearly, this is how it should be….

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So basically, it looks like the table was installed the wrong way round. In fairness to the bloke who built it, he does seem to have followed the drawing.

This would explain why the table is wonky, and why I’m not getting square parts.

I’d appreciate any views on this. Am I right?

Cheers

Steve

Howard Lewis27/10/2021 11:29:48
5528 forum posts
13 photos

The two ground surfaces should be running against each other.

But, the Ground face fixed to the table should ensure that the table moves in a plane, X axis, left to right, perpendicular to the Y axis, to and from the operator.

It seems that you are likely to to be in a situation which is the reverse of the way that things are normally done,, by needing to align the ground face of the strip so that it is parallel to the Tee slots

I would suggest removing both strips and fitting to ground strip,(but not yet dowelling it ) so that it rides against the ground face on the bed of the machine. Adjust the table relative to the strip, until the T slots clock true. A copper/hide mallet is going to be useful for this.

When the strip is aligned drill and dowel / rollpin to maintain that alignment.. This may mean that new holes have to be drilled, countersunk, and tapped at new points along the strip.

Once you have achieved that condition, the problem of the 0.027" variation can be addressed and correcte on the other strip, in similar manner.

(You need the Tee slots to be in the same plane as the motion of the table, or will always have to clock the vice to set the jaws parallel to the line of the cut. Once the T slots and line of travel are the same, the vice can be aligned to the table with keys, or an alignment fixture ).

Howard

Steve35527/10/2021 12:49:34
128 forum posts
87 photos

What I’m hoping Howard (optimistically) is that if I turn around the table and everything is suddenly aligned the way it should be, I could take a test cut and check if it’s square. If it is, I just need to drill a couple of holes in the end of the table to fit the hand wheel. If not, I have a bigger problem! And will be looking at the kind of things you suggest above.

Steve

John P27/10/2021 13:27:56
359 forum posts
238 photos

Posted by Steve 355 27/10/2021 10:34:11

Is this statement true? :- It doesn’t matter if the milling table is not square to
the base of the mill (within reason). The milling cutter is round. What matters
is that the X, Y and Z axes run perpendicular. Tramming ensures the Z axis
is perpendicular. The X and Y axis should be perpendicular by
manufacture of the table.

Yes it is true , except for the last part after i had built my Dore westbury
the squareness of the X and Y was off by few thousanth's of an inch,
it is possible to re-machine the Dore westbury XY cross slide on a Myford 7
lathe cross slide because this is how i corrected mine.


There is little point to having the tee slots in line with the travel of the table
because of, 1 the longitudinal slots at each end are too short in all probability
to be able to mount any additional accessories (vice) without using some of the
other slots in either side of the table ,2 the tee slots in a Dore westbury are cast
in and not machined and are useless as a reference unless reworked
for that purpose.

As it is the 1st photo that you have posted showing the underside of the
table the dowels are in the correct slideway/ guide ,as you have surmised the table
has been fitted the wrong way round, however fitting the table as in the last photo
which is the correct way round also puts the guiding slide with the dowels on the
correct side, it is worth noting that if you remove either of the 2 guide strips from the
underside of the table they may be shimmed as this is the normal method on these
machines to control the table lift /clearance.

John

Edited By John P on 27/10/2021 13:35:41

Steve35527/10/2021 14:07:24
128 forum posts
87 photos

Thanks John, it’s really helpful to know I’m not just going mad. I’m very new to all of this and it’s particularly difficult with a machine that wasn’t professionally built in the first place, to know what’s right and what isn’t.

I just turned the table around and threw an indicator on it, moving it manually. Even without the gibs or hand wheel installed, I can see that it is way better than before.

I also may have found the source of the “wobble” and hand wheel stiffness. If you look at the pic above of the table the wrong way around, you can see that the screw holes that attach the handwheel tray are poorly placed. This would place stress on the lead screw - causing the same effect as it being bent, I would expect. So I can sort that out too.

Now I’ve just got to work out how to drill accurate holes in the end of that table. Luckily I have a big pillar drill!

Cheers

Steve

Howard Lewis27/10/2021 18:50:16
5528 forum posts
13 photos

Steve,

Try attaching the bearing for the leadscrew with one or two setscrews, Hopefully after a number of combinations the tapping that is out of position will be obvious.

You then have a choice.of solutions, depending on how far out the hole is.

1. Open up the hole to clearance around the odd man out.

2 Using the bearing block as a jig, drill a jig, but with the rogue hole only drilled to thread size (Probably 1/4 BSF )

Open up the hole to tapping size for 3/8 BSF, 8,25 mm 

Using the jig to drill the rogue hole out to 8.25 mm and tap 3/8 BSF.

Turn up a bush with a 3/8 BSF external thread, and an internal thread (Presumed to be 1/4 BSF)

Screw the bush into the hole, ensuring that it not above flush. Use thread locker if you wish.

When the anaerobic has cured, reassemble, and hopefully table movement should be as wanted.

Howard

Steve35527/10/2021 20:06:33
128 forum posts
87 photos

Hi Howard

If I’m understanding you correctly, I am in the lucky position of not needing to, I think.

First, I have the drawings for the Dore Westbury mill, so I can look up exactly where the holes need to go.

Second, because the ****** person who built the mill installed the table the wrong way round, there are NO HOLES in the end (see pic) that actually should have had the lead screw/handwheel attached. So I can drill completely new ones, in exactly the right places.

And I feel vindicated now because when I came home to face my wife last summer with a 6ft tall Jones and Shipman pillar drill I got for £10 on eBay, she said a drill that big would never be any use. How wrong she was.

4a4cc131-a908-4239-8302-f3669d4ec9f4.jpeg

b4f78b19-ffb6-4724-ac7a-32000ab672c2.jpeg

John P27/10/2021 20:32:26
359 forum posts
238 photos

Posted by Steve 355 27/10/2021 14:07:24

Now I’ve just got to work out how to drill accurate holes in the end of that table.

Luckily I have a big pillar drill!

The easiest way to do this is to remove the XY slide from the machine,
lay the table upside down on a bench fit the X leadscrew nut in position
on the XY slide fit the XY slide on the table fit and adjust the gib in place ,
screw in the leadscrew and end bracket as far in towards the nut as it
will go ,if you view down alongside the table the leadscrew should be
visable and it will be easy to see if the leadscrew is parallel with the
slideways then looking down from the top likewise the leadscrew
will be in line with the slide bars.
Probably easiest to just fix the end bracket to the table with a dab of epoxy
glue let it set ,make up a long centre punch that fits in the holes of
the end bracket ,if the glue will hold you can carefully traverse the
XY slide along the table before marking the 2 hole positions to test
the position.
When satisfied with the positioning use the punch to mark the
hole positions drill and tap for the 1/4 bsw fixing screws if they are
still this size they are on mine.

John

John P27/10/2021 21:07:21
359 forum posts
238 photos

Hi Steve,

just as a postcript to the previous posting that i made be careful about following the drawings as it appears from the third photo down on your posting at 10:34:11 today that the 3 holes that hold the leadscrew nut may also not be in the correct position , that extra little cast in lug on the XY slide is for that third screw ,as far as i can remember the tapped hole sits more to the left and a little higher in that position.Would be worth checking before drilling any holes.

John

Steve35527/10/2021 21:32:02
128 forum posts
87 photos

John, do you mean this bit?

48a125ae-8724-4f44-b458-fa6ae8eeb48a.jpeg

John P27/10/2021 22:01:25
359 forum posts
238 photos

Hi Steve,

Yes those three holes , it would be as well to assemble the parts as suggested earlier just to check the positioning before drilling the holes in the end of the table as if any of the the existing positioning is off it will lead to an error.

(because the ****** person who built the mill) as you had written earlier had obviously got some things wrong like having the table the wrong way round.

John

Steve35527/10/2021 22:26:13
128 forum posts
87 photos

Yes, good idea, I will check it very carefully. I had another play with the table on the mill this evening and it seems like it will indeed run true, which is a good result. I think I’ll have a good look at the Y axis mechanism too to see if I can identify any further faults while it’s all apart. I’m sure there are more problems to find.

Steve35505/11/2021 20:23:42
128 forum posts
87 photos
Posted by John P on 27/10/2021 22:01:25:

Hi Steve,

Yes those three holes , it would be as well to assemble the parts as suggested earlier just to check the positioning before drilling the holes in the end of the table as if any of the the existing positioning is off it will lead to an error.

(because the ****** person who built the mill) as you had written earlier had obviously got some things wrong like having the table the wrong way round.

John

Hi John

I dont know if you are around but I’m still having significant problems with the table wobbling by a couple of thou, The good news is that turning the table the right way round has ensured squareness and there is very very little play in the horizontal plane, once the gibs are tightened.

But there is play in the vertical plane. With the table central, I can quite easily lift it by a couple of thou using my fingers under one end. And if I turn the handwheel it has the same effect.

Most slideways are dovetail, so secure a table in the horizontal and vertical plane at the same time. But the Dore Westbury is not, the only securing force from the gibs is in the horizontal plane. I find it difficult to believe that this isn’t accounted for in the design somehow. I am wondering if I am missing shims somewhere or something?

if you have any thoughts I’d be glad of them (or indeed anybody else!)

Cheers

Steve

Dave Halford05/11/2021 20:55:21
1816 forum posts
19 photos

Under one end or both?

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