Author Topic: Leveling Denford lathe - has no levelling screws?  (Read 15054 times)

Offline loply

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Leveling Denford lathe - has no levelling screws?
« on: November 26, 2015, 02:28:46 PM »
Hi folks,

I'm trying to level (untwist) the bed on my Denford Viceroy lathe, but it turns out there are no leveling screws underneath the bed!

It's cutting quite a larger taper when I chucked up a 75mm x 200mm aluminum test bar. I haven't checked the head alignment but as I know the bed was removed from the cabinet by the previous owner, I'm assuming it's a twisted bed.

I lifted the bed off the steel cabinet today and found it was simply bolted down, one bolt in each corner, passing through a clearance hole in the chip pan. One of the bolts was missing altogether.

This is actually the second Viceroy I've owned and the previous one had a double-threaded widget in each corner which you used to jack the bed up and down.

Any idea what gives here? It looks to me like it was this way from the factory, because the chip pan holes aren't threaded. Should I just resort to using shims under one corner? Any idea why there are no leveling bolts?

Would appreciate any advice, would like to get this thing cutting straighter.

Here's the rubber washers which were squished between the chip pan and the bed:-

Offline Pete.

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #1 on: November 26, 2015, 02:42:08 PM »
I do believe that the Denford Viceroy is mounted on two feet at the headstock and one at the tailstock. No way to adjust for twist.

Offline loply

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #2 on: November 26, 2015, 02:52:30 PM »
Correct about the number of feet, but as I say my previous Viceroy had a "screw within a screw" system for twisting it, and the drawings and various bits of info on the internet all indicate this is the case too.

I'm just a bit mystified as to why it doesn't have any leveling feet, and if the designers somehow thought that it shouldn't need leveling.

I guess I'll just design & make some though? I suppose I only need one really... I can bolt three corners down tight and just use some kind of jack screw on the remaining corner?

Offline appletree

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #3 on: November 26, 2015, 02:58:00 PM »
I would have thought the bed was more rigid than the stand?
« Last Edit: November 27, 2015, 03:39:35 AM by appletree »

Offline DMIOM

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #4 on: November 26, 2015, 09:16:28 PM »
No help for the twisting issue but those 'squished' washers look to me like those used to seal the heads of the nails used to secure corrugated iron or asbestos roofing sheets.

Offline RussellT

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #5 on: November 27, 2015, 05:08:37 AM »
Is it possible that the rubber washers were intended to do the job - just squash as required?  Having said that I think that would be a lousy idea.

I'm not sure I understand about the number of mounting feet.  Surely a single mount at the tailstock end would mean that you can't adjust for twist anyway.

If you can I think the first thing to try would be bolting it down solidly at the headstock end and see how it sits at the tailstock - can you get a feeler gauge in?  Can you raise a corner of the cabinet and does that make a difference?

Russell

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Offline loply

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #6 on: November 27, 2015, 06:35:25 AM »
That's exactly what the washers are - they're made by 'SPAT' according to the text imprinted on them, Googling for that reveals they're usually used for roofing.

My thinking is that only one corner really needs a leveling screw - 3 points will always make a flat plane, so just one corner should need adjusting in theory (like putting a beer mat under the one wobbly corner of a table). Just need to find which one it is.

For what it's worth though I think I'm just going to make 4 - I'm going to drill & tap the chip pan M16 and make some hollow M16 widgets through which I can bolt the thing. Then by screwing the M16 thing up or down I'm jacking the lathe up or down from the chip pan. This is what is per the drawings/manuals for the lathe.

I would assume the leveling screws have simply been lost but the fact that the chip pan isn't threaded seems to preclude that, I guess for whatever reason they just stopped fitting these at the factory. Seems surprising but also seems the only possibility.


Thanks,
Rich

Offline Manxmodder

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #7 on: November 27, 2015, 07:19:05 AM »
Loply, my previous reading of issues concerning bed twist/head misalignment causing tapers is that bed twist itself would need to be quite pronounced to produce significant loss of paralellness.

If as you say the headstock has been previously removed then I would suspect the problem more likely to be head alignment on the bedways rather than bed twist.

That being said you are definitely going the right route in wanting to fit levelling screws....OZ.

PS: If you've checked across the bed at several points from the headstock with a precision level how much twist variance are you seeing?

Also worth considering what maybe an easy solution of just using shim stock between the feet and the base to effect a level when everything is tightened up.
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Offline DavidA

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #8 on: November 27, 2015, 07:41:09 AM »
This is straight from the manual for my Viceroy 12 speed Synchro.

Bench Model (without tray or cabinet).

The machine should be bolted down on a rigid level bench. Care must be taken not to over tighten the bolts and distort lathe bed.
After installation the machine must be accurately levelled with a precision level at the headstock and tail stock ends of the machine bed.

Cabinet model.

The machine can be free standing on a level solid surface. If the machine is bolted down care must be taken not to over tighten the foundation bolts. The same levelling procedure must be undertaken as described for the bench model.


Note, no mention of any levelling screws. So it seems that you have to use shims at the holding down screws to get the bed level.

Dave.

Offline Alan Haisley

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #9 on: November 27, 2015, 04:56:01 PM »
Before going further, please check the bed for twist. With the three mounting points, you can level the bed front to back at the headstock and left to right on both rails. You can't correct for bed twist though. It seems much more likely that the headstock is skewed to cause your taper. If that's the case and you try twisting the bed to correct the taper things will just go from bad to worse.

Alan

Offline loply

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #10 on: November 29, 2015, 05:46:11 PM »
Thanks for the advice everyone.

I got the precision level out today and checked the bed properly, it was twisted when bolted down just fingertight, with the tailstock end being I think about 0.3mm/m higher on the operator side.

Turns out I could undo this twist simply by tightening the bolts different amounts, so perhaps I don't need any adjuster screws after all! I think the sheet metal chip pan not being flat means it kind of acts like a spring.

The rest of the lathe is in bits so I can't check the headstock alignment at the moment.


Offline Kjelle

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #11 on: November 30, 2015, 08:52:14 AM »
As several others has said, check with a precision level if the bed is twisted. Also, if you are interested, there are loads og threads on Practical Machinist about twisted lathe beds and leveling... I'm not an expert, but I'm inclined to think that the bed/head intersection has some kind of problem, if the head has been off. It don't take much to upset the alignment there.

Kjelle (giving my 2 €-cent)

Offline bertie_bassett

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #12 on: November 30, 2015, 11:59:35 AM »
hmm you've got me wondering what my viceroy has now, wil have to brave the elements and get down in to the workshop!

I know it has three bolts through the base into the concrete floor, and I thought it had levelling feet on the actual lathe, but those "washers" look awfully familiar :s
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Offline DavidA

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #13 on: November 30, 2015, 03:49:02 PM »
Just been reading through my manual again.

I can't find any reference to alignment of the headstock to the bed.

There is the usual stuff about tailstock  and cross slide gibs etc, but not a mention that the headstock is in any way adjustable.
There is a mention of adjusting the main shaft bearings.
I suspect that the headstock is fixed.
Tomorrow I'll also brave the cold and go into the shed and have a good look at the machine.

Dave.

Offline loply

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #14 on: December 01, 2015, 05:34:56 AM »
Hi folks,

Sorry about the confusion, the headstock has never been removed as far as I know, I just said that the bed had been removed from the steel stand.

The headstock is bolted down onto the bed with 4 cap screws which you can access via the rear cover, on my old Viceroy there were then two taper pins hammered in, on my new one there is a bar bolted across the bedways in front of the headstock, plus there appears to be some kind of tight fitting key between the headstock and the bed at the rear end too.

I'm rebuilding the whole lathe at present & servicing all parts, once it's back up and running I'll take another test cut and check the head alignment.


Offline Will_D

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #15 on: December 01, 2015, 06:57:02 AM »
As we all know 3 point contact is perfect.

However if two points are fixed (end of bed and one at headstock end) then the third point ( adjustable  jacking screw) should then be able to untwist the bed?

Will
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Offline loply

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #16 on: December 15, 2015, 05:06:15 PM »
Hi folks,

Well I finally finished rebuilding this lathe - fitted a new motor, all new electrics, replaced the gear head with a direct belt drive + VFD, added a lamp, hand scraped the saddle and compound, generally took every single thing apart and cleaned/lubed/rebuilt as required.

Lathe is turning really nicely but sadly is cutting a taper of 0.01mm per 25mm, ie half a thou per inch. Bit more than I hoped for! My last Viceroy lathe cut 0.00mm per 6 inches...

I tested this with a 7 inch length of 3 inch aluminum turned down in the 3 jaw. Pretty sure it's head alignment rather than bed wear or suchlike as the taper is so linear.

Maybe one day I will remove the head and rescrape/adjust to get it better. Will begrudgingly accept it for now!

Rich

Offline loply

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #17 on: December 15, 2015, 05:08:25 PM »
Oh I also made and fitted way wipers, and ground oil grooves in the bottom of both sides of the saddle and cross slide, and inserted oiler points which feed straight into these oil grooves.

Offline Alan Haisley

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #18 on: December 18, 2015, 12:15:55 PM »
Hi folks,

Well I finally finished rebuilding this lathe - fitted a new motor, all new electrics, replaced the gear head with a direct belt drive + VFD, added a lamp, hand scraped the saddle and compound, generally took every single thing apart and cleaned/lubed/rebuilt as required.

Lathe is turning really nicely but sadly is cutting a taper of 0.01mm per 25mm, ie half a thou per inch. Bit more than I hoped for! My last Viceroy lathe cut 0.00mm per 6 inches...

I tested this with a 7 inch length of 3 inch aluminum turned down in the 3 jaw. Pretty sure it's head alignment rather than bed wear or suchlike as the taper is so linear.

Maybe one day I will remove the head and rescrape/adjust to get it better. Will begrudgingly accept it for now!

Rich
Which way does the taper run? Might it be worn chuck jaws?

Offline DavidA

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #19 on: December 18, 2015, 02:26:55 PM »
I was thinking the same.

It's asking rather a lot of your chuck jaws to be more accurate than that.

Have you tried taking a cut across your face plate ? Or maybe just passing a dial g guage across it ?

If the cross slide is square to the bed then you should get a dead square cut or reading across the plate. Else it will be conical.

Dave.

Offline chipenter

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #20 on: December 18, 2015, 03:22:46 PM »
It can't be the chuck jaws he has taken a cut then mesured the run out , have you tested the bearings with a dial guage on the top and lifted the test piece .
Jeff

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #21 on: December 18, 2015, 04:11:31 PM »
Jeff

It could be if the jaws are bell mouthed and no tail stock support was used

As to facing a face plate it should be very slightly dished  , to make sure a faced item will sit down flat

Best have a read of Connely's book


I would bet it's the head stock not lined up with the bed

Stuart

Offline chipenter

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #22 on: December 18, 2015, 05:00:15 PM »
Loply I have E.F.Connely's book in PDF if it helps send a pm and I will forward it , how long was the test cut and was the taper even , I spent ten days scraping my Southbend's bed most of the whare was just under the chuck and it's a 42" bed .
Jeff

Offline DavidA

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #23 on: December 19, 2015, 01:21:17 PM »
Stuart,

..As to facing a face plate it should be very slightly dished  , to make sure a faced item will sit down flat..

How does having the faceplate dished make sure that anything bolted to it is flat ?

Let's say I have a piece of 1/2" thick plate six inch long by 2" wide.

I have a faceplate 10" diameter.

The job is to bore a 1" hole centered  2" from the end of the bar..

As one end of the bar would be 1" from the centre and the other end 4" from the centre on the opposite side, how will this hole be true to the surface ?

Surely the bar will not be square to anything as the 'short end' is down in the dish to a much greater extent than the 'long end'.

Dave.

Offline philf

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #24 on: December 19, 2015, 01:36:02 PM »
Stuart,

..As to facing a face plate it should be very slightly dished  , to make sure a faced item will sit down flat..

How does having the faceplate dished make sure that anything bolted to it is flat ?

Let's say I have a piece of 1/2" thick plate six inch long by 2" wide.

I have a faceplate 10" diameter.

The job is to bore a 1" hole centered  2" from the end of the bar..

As one end of the bar would be 1" from the centre and the other end 4" from the centre on the opposite side, how will this hole be true to the surface ?

Surely the bar will not be square to anything as the 'short end' is down in the dish to a much greater extent than the 'long end'.

Dave.

That's true David but the amount of dishing is small and could be zero.

There was some discussion on this subject a while ago.

http://madmodder.net/index.php?topic=7066.0

I posted:

I have a copy of Testing Machine Tools by Dr. Georg Schlesinger. (Schlesinger limits are/were often quoted in machine tools specs). In it are various figures given for the lathe facing accuracy.

"For Finish Turning Lathes": "Lathe faces (hollow or concave only) within 0 to 0.02 per 300mm in dia."

"For Toolroom Lathes (Highest Degree of Accuracy)": "Lathe faces (concave only) within 0 to 0.015 per 300mm in dia."


Phil.
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Offline DavidA

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #25 on: December 19, 2015, 02:09:39 PM »
Phil,

Yes, I remember well the last discussion we had.

My point is that you are starting out with a built in error, no matter how small.

If you are bolting something to the dished faceplate, then either the job has to bend or the faceplate does until the faces touch.  A fifteen thou dip in the middle of a 12" plate really is a lot.

I just can't see the doing in doing it.

Each to his own; of course.

Dave.

Offline philf

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #26 on: December 19, 2015, 02:30:19 PM »
Hi David,

It's not 15 thou - it's 0.015mm - just over 1/2 a thou.

It's incredibly difficult and therefore very expensive to get it exactly right. Convex is an absolute no-no because you'd never get a flat object bigger than the radius to sit in a stable position.

With your 1/2" thick bar the out of squareness would be a maximum of around 0.0004mm.

Phil.
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Offline Pete.

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #27 on: December 20, 2015, 05:14:22 AM »
You could easily  scrape a faceplate flat or with a much smaller dish than quoted above.

Bear in mind that a 300mm faceplate probably runs out more than the quoted figure above and will almost certainly distort more when you clamp an irregular shaped object to it.

Offline DavidA

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #28 on: December 20, 2015, 06:31:11 AM »
Phil,

You're right.  My apologies for that. I'm used to equating three places of decimals to Imperial. I didn't take into account the 300 mm next to it.

Dave

Offline Alan Haisley

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #29 on: December 20, 2015, 11:49:37 AM »
You could easily  scrape a faceplate flat or with a much smaller dish than quoted above.

Bear in mind that a 300mm faceplate probably runs out more than the quoted figure above and will almost certainly distort more when you clamp an irregular shaped object to it.
True, but the concern is what a lathe will do in facing off a piece of work. It could be a faceplate or it could be a surface of a properly held piece. The idea is that since we can't get the lathe to machine perfectly flat we may as well go for a slight concave which provides a more useful surface.

Offline loply

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Re: Leveling Denford lathe - has no levelling screws?
« Reply #30 on: December 20, 2015, 01:43:02 PM »
Hi folks,

I'm concious of the chuck jaws - I think the issue is that if the chuck isn't very good the workpiece can deflect a bit and (at long stickouts) you can get uneven turning.

Because the taper appears to be completely linear though I think that's unlikely to be the case here, especially given I was only taking small cuts. I am going to re-run the test using the 4 jaw at some point before I take the head off just to be sure though.

Luckily the head on these lathes is just bolted on to a flat section of bed, so no need to rescrape anything (unless it's vertical misalignment!). I will simply put a bar in the chuck, loosen the head up, then 'push' the bar using the cross slide to make the requisite realignment, then tighten back up. Shouldn't be a big deal I don't think.

Cheers,
Rich