Fitting a DRO to a Tom Senior Mill

[Chipswitheverything]

Have just recently finished off the job of fitting a three axis optical r/o DRO to the larger of my two Tom Senior mills.  This mill has got metric feed screws, and I like to work in Imperial for my model engineering.  I have had the machine for about five years, it required a great deal of sorting out ( details for anyone interested are elsewhere, on the Tom Senior Yahoo forum).
  Though I had used DRO's a great deal at my former place of work, and was in no doubt as to their usefulness, I had a reluctance to do the fitting to this "classic" machine.  I thought that the visual appearance of the added apparatus would not please me very much.  Also I had to consider the cost / use equation a little.
  Anyway, Machine DRO were doing one of their limited time price offers back in the autumn, and they were attending the Brooklands Show which enabled me to pick the purchase up for free ( courtesy of a lift with JR72, thanks John! ), so it seemed a good time to chew on bringing myself into the 21st century.

  When I was heading for the car just about carrying the large and surprisingly heavy box with all the bits in it, some guy passing by remarked, "You'll have a load of fun fitting all that lot!".  His remark was about spot-on!

  I spent quite a while conjecturing how best to use the assorted one-size-fits-all brackets and bobs that came along with the main items.  I ended up moving the existing electrics attached to the mill column, and putting the z axis slider on that side.  I'd have quite liked to have tucked that slider and head on the L/H side, but the opening door and the locking handle for the Y axis made that a poor option.

  As can be seen in some photos, I made up a number of brackets and read-out holders from stock aluminium, to supplement the supplied brackets - most of them did need a certain amount of hacking about too, as might be expected.
  I was a bit torn as to whether to spend extra time painting the bracketry and covers to match the mill paint scheme, but I think that doing so did make a good deal of difference to the overall appearance, and has helped to minimise the visual intrusion.   DRO fitting can end up looking a bit as if a scaffolder has been let loose on what was an attractive older machine tool.

  The nice ball handle lock on the X axis had to go, though, hidden by the cover plate, and I made up a new locking lever based on an Allen bolt with a flat lever attached , with a split clamp, to the turned down ( ie. knurling removed ) bolt head.
  In use, like any other DRO, it's marvellous!, good bye to all that blooming conversion to metric, and 16 turns of the handle ( or was it 17 ! ) and the backlash nonsense too.  So, well worth it in the end..
  Dave

[Ramon Wilson]

That's a real nice looking mill you have there Dave - looking at that lever on the right hand side does it have power feed to the quill?
Ah I wish 

A nice conversion too that fits right in and looks 'part of the machine' - as you say, it will bring huge benefits in future use

If I may say so though, I would be inclined  to replace the cable tie with a tight fitting P clip and screw (on both cables) just to be certain no accidental strain goes direct on the readers 

Looking at these recent posts on here I am beginning to feel an itch 

Regards - Ramon

[sco]

Think that lever is the quick action feed to the quill, the handle on the front is the fine feed.

I too covert one of those Tom Senior mills - my dad has one that he never uses so I live in hope!

Simon.

[Chipswitheverything]

Thanks for the replies, Ramon and Simon.    No, there's no power feed to the quill, just the usual hand lever that can be adjusted for position, and on the other side the tapered knob locks in or out the fine feed on the ball ended handle.

  I will find out in due course whether the extra elaboration in fitting the Z axis with the optical read-out has been worth the added work.  I did it partly because I liked the 3 axis LCD screen monitor that Machine-DRO offered as a package with the three optic bars.  I had wondered about using axis 3 for a small travel readout mounted on the quill. But it might be neater, if I want a read out on that, to just fit one of the small battery powered digital read-outs that are quite cheap.
  The cover plate mounted on the front of the table would have been better if it could have been set down a little, to leave a bit of table edge available for offering up a square.  But I was already as far down as I could go with fitting the optical bar and leaving access to the locking screw hole.  I'll have to square off the back of the table, or from a parallel fence in a Tee -slot.     Dave

[JR72]

Hi David

Another superb job very well done, I must admit I was a bit I was a bit sceptical when you told me you wanted to paint the brackets and fixings. But now that I have seen your photos well I have to admit that it was well worth the trouble as it  looks as if the DRO is factory fitted,  in fact if you took the DRO off now of the machine it would look rather bare. Well done Dave.

John

[Holt]

I will find out in due course whether the extra elaboration in fitting the Z axis with the optical read-out has been worth the added work.  I did it partly because I liked the 3 axis LCD screen monitor that Machine-DRO offered as a package with the three optic bars.  I had wondered about using axis 3 for a small travel readout mounted on the quill. But it might be neater, if I want a read out on that, to just fit one of the small battery powered digital read-outs that are quite cheap.
    Dave

If you got rid of the Machine-DRO controller. and hooked your scales up to a almost free TouchDRO controller, you could hook up two scales to the same readout, so it would count the same regardless if you lowered the quill or raised the table, see THAT is a feature you don't see very often, in fact I dont think I have seen it elsewhere
Very nice mill and setup by the way
.

Holt

[Chipswitheverything]

Thanks, John, for the kind comments, when my workshop has improved on the 37 degrees F that it seems to be at at the moment! you can come and have a play with the new toy.
  Holt, thanks for the ingenious idea re. the coupling of the read-outs, and for the appreciation.  But realistically, having hardly used the new LCD display just yet - I need to have a play around with some of the tricks that it can do - , and having just paid about £350 for it, I have no plans to be dispensing with it any time soon!

 On the Tom Senior mill, though the main axes are metric on this machine, the quill head has a down feed calibrated in Imperial.  They never did bother to market the accessory head with a metric arrangement.  So, conversion wise, I'm already calibrated in my preferred units.
 
 The main trouble that I find with the quill downfeed, - and others will surely have met with the same snag, - is that because the spring return is on the shaft of the pinion ( like any drilling machine ), the quill is able to "float" to the extent of the backlash in the rack and pinion.  Depending on the "stiction" of oil or grease in the quill housing, or weight of the tooling being used in the taper, the quill body may be "up" or "down" in respect of the backlash.  Might be contacting either the upper side, or lower side if the pinion tooth. When the quill lock is released to put on a feed increment, you may get a drop down of the quill - not a great help - or your added few thou of feed on the handle may just be operating in fresh air, as the pinion turns within the backlash  ( which could be 15 thou or so )
 Admittedly, a separate digital read out on the quill could be a help in knowing what has gone on, but the operation remains a bit random.
   If it's safe to do so, I manually push the quill up hard against the pinon when adding feed.  Possibly on better and/or  larger mills they have some sort of split pinion or double rack that can be adjusted to take out the backlash?
  A certain way around this is to use the depth stop ( quite well made on the Senior ) to set an increment of down feed, using feelers or some sort of gauge, drill shank for instance.
 On my smaller Westbury mill, the quill has a strong tension spring that operates directly between quill and the cast housing. Though the appearance is a bit crude perhaps, the action of it is  entirely certain, and actually a better bet for a milling , as opposed to a drilling machine quill.
  So, I will probably now tend to add feed increments using the Z axis DRO read out, even though that Z slider is seldom wanted for charting considerable movements in the way that the X and Y slides are constantly used.
  Sorry that this has gone on a bit, but I would be interested in comments about ideas on this common problem with quill downfeeds.   Dave

[Nick_G]

.
I have 2 of those LCD displays. One on the mill and one on the lathe. The functions are very intuitive and easy to use (I use the PCD function quite a lot on the mill) with the initial setup being very configureable.

Had them about 2 years now and as you would expect have performed flawlessly. 

Only issue I have had was my fault when I did the initial install and had left one of the reading heads not tightened properly. ........... 

Nick

[MJM460]

A very neat installation.  Well done on the painting decision, really makes the job.

I put the vertical DRO on the quill of my mill/ drill which also has that slack you describe.  It works very well in that position.

Thirty seven degrees, eh?  We had 37 degrees for Christmas too.  Thirty seven C.  The son's pool was a great location for the family celebration. 

MJM

[Chipswitheverything]

Thanks for your comments, guys.   MJM, I'd settle for splitting the difference between my 37F. and your 37C. !, that would come out at just about a nice temperature for doing a bit of workshop engineering.

  Nick, pleased to hear that you have found the LCD displays to be reliable. Certainly it is a nice display to use, very easy to see at a glance.
 Do you do the reference locating procedure for each axis that the handbook suggests doing when the device is used? , or does it only matter if a job is on the machine for quite a while?  I haven't really had time to play about with investigating more than the basic working yet.
  Had an enjoyable look back over your posts, Nick, some terrific stuff there that I don't seem to have spotted first time round.  That's an interesting German made Q/C type of toolpost that you have fitted to the Boxford lathe, looks like a very good bit of kit.
  cheers, Dave

[pgp001]

Dave

I had a similar problem with controlling the down feed on the Z axis of my little Boley & Leinen jig borer.
I have installed a 2 axis readout for the X & Y axis, but there was not enough room for the Z axis so I made a micrometer dead stop system instead, I have to say it works extremely well and allows a very controlled cut to be applied regardless of feed screw engagement or slide friction etc.

I initially thought it might be a bit of a faf around to keep setting it to zero, but in reality it only takes a few seconds, and I use it all the time.





Phil

[Chipswitheverything]

Hmmm, well, that really is a nice bit of gadgetry, Phil, and it fits on the lovely little jig borer as if it was part of the B + L accessory package.  Like that a lot.  Dave