S7 Newall DRO v Taper Turning attachment

Hello,

Sorry to drag up an old thread, but it contains posts by two members who I believe can answer my question.

Just purchased all of the Newall components to add a DRO to my Myford S7. Researching this forum I found several references to the problem of moving the carriage lock to the front of the saddle. Two photos show what appears to be the right hand counterbored location of the front saddle gib strip being used to lock the saddle. In the Myford factory DRO installation, it appears that they added another SHCS to the left of the original location to hold the front gib strip and shim with the original location being used as a lock.

My question is: Did Myford just use the original front gib strip to lock the carriage or did they actually use something similar to the original lock?

The original counterbore for the right hand gib strip SHCS is too far from the bed to use that location for a similar to the original design carriage locking device. There appears to be room to the right of this location (end of the front gib strip) to install something. Would love to hear about what others have done to solve the problem. I would like to keep my new carriage lock on the saddle.

Please see photo in next post below.

Thanks!

Regards,

Mike

Edited By Michael O'Connor on 01/01/2015 01:28:07

Here is a photo of the Myford Factory Newall DRO installation with front mounted carriage lock. Note the counterbored SHCS to the left of what appears to be the original location of the right hand SHCS to secure the front gib strip. The use of the original location (with a sleeve to fill the counterbore?) to lock the saddle by squeezing the front gib strip? Does anyone have any knowledge of this modification?

Thanks,

Mike

Hello Mike. The photo you posted is of my lathe when it was new and is one I posted to my album when this topic came up before.

I have read and re-read you penultimate post and confess I can’t understand it, especially the reference to socket head cap screws securing the gib. The gib on the saddle is not made in the same way as that on the Super 7 cross-slide. The counterbored cap screws are to secure the apron to the saddle, not the gib to the saddle. The gib is rectangular and is free to float, being pushed into contact with the front shear by the three screws in the front of the saddle that have locking nuts.

The saddle lock is the hexagon head screw that sticks up above the top of the saddle, with the oil nipple immediately behind it. When Myford fitted the Newall DRO and moved the saddle lock to the front, they used a similar construction of saddle lock. The rear lock has a thick mild steel disc that sits in a counterbore in the underside of the saddle. The disc and counterbore are offset to the screw so that one side of the disc extends under the shear to clamp the saddle when the screw is tightened. In its front incarnation, it’s a rectangular block instead of a disc.

The problem is that in the front position, mine just doesn’t work. I have lost count of the number of times that I have moved the saddle with the handwheel, not realising that the lock is still applied – which tells you how ineffective it is. A closer look showed that the screw is too far away from the front shear to apply enough clamping force – the geometry is not good. The reason is that the gib strip must pass between the screw and the front shear, which of course doesn’t apply when the lock is at the back of the saddle. A further thing I don’t like is that there isn’t room to swap the screw for a lever with a decent enough handle without fouling the DRO encoder. It means I have to use a spanner every time and often the screw is hidden from view under the topslide. Very inconvenient for an operation that will be done countless times in the life of the lathe.

Making an alternative lock has been on my to-do list for a while. There was a design for an external saddle clamp in MEW 163. I like the idea of using the thread dial indicator stud as a fixing for the clamp but I thought other aspects were a bit Heath Robinson. Another approach would be to drill and tap for a fourth gib adjusting screw and fit a handle so it locks the gib up tight, similar to that on the Myford top slide (and cross-slide of the ML7, not Super 7). The lever would be conveniently on the front of the saddle but it would involve a major strip-down to install.

If anyone can think of any other good solution, I would be glad to hear of it.

Andrew M

Edited By Andrew Moyes 1 on 01/01/2015 11:38:42

I would agree 100% with Andrew re the re-positioned saddle clamp, not vey good, and inconveniently located - it always seems to hide under the cross slide every time I want to use it!

But I must disagree 100% with his comments on this one:

I've lived with this for nearly 20 years (I didn't make it, it came fitted to the lathe) and have found it to be very effective and very convenient - a nice solution to a tricky problem, and I can recomend it without hesitation. Here's the original design by Don Ainley, from ME:

I'm currently making one for my Connoisseur, alongside a friend making one for his PCF S7B - unfortunately we've found that the few dimensions given aren't quite right for a PCF machine, the position of the indicator stud seems to have been shifted slightly on green and blue machines compared to grey ones. I should have the right dimensions before too long, but this is a relatively slow process as it's being used as a teaching exercise for my friend, who's new to model engineering, and progress only happens one afternoon a week. And for some reason has completely stopped over the last couple of weeks!

Thank you Andrew for the very detailed and informative response to my post. Your confusion is due to my incorrectly referring to the Saddle Strip (Front) Myford KA7 #A9185 as a "Front Gib Strip". What I was wondering was if your lathe was using the Saddle Strip to lock the carriage. Sorry for the confusion. Thanks for the insight.

Thank you Cabeng for documenting your Myford S7 Newall DRO installation in MEW No.87 (Dec.2002/ Jan.2003) and for your response to my carriage lock question. It looks like an external lock may be the best solution.

Kind regards,

Mike

Thanks Cabeng for the drawing of the Don Ainley lock. To my eyes, that's more elegant than the version I referred to in MEW163. I'll go with your recommendation and will move it up my to-do list!

Mike - thanks for your explanation. I see where you were coming from now.

Andrew M

I see that I made an invalid assumption that it was the Ainley design to which you were referring - Wrong again! So my apologies for disagreeing with you Andrew!

Some time ago (see above) I posted re. a saddle clamp designed in 1992 by Don Ainley, and said that I would provide drawings when I’d finished manufacturing one for my lathe. Colin Rawson has reminded me that I’ve forgotten about this promise (thank you Colin!), so I’ve now put the drawing in an album, along with a copy of Don Ainsley’s original M.E. submission and a couple of photographs. Here’s the drawing:

A mixture of imperial & metric units - I normally work in metric, but the measurements of the mounting stud position were taken using imperial measuring equipment! Anyone intending to make one of these clamps should note the note about dimensions and surfaces shown in red, and the panel top left of the drawing showing relevant measurements taken from my S7 & Connoisseur machines – it would appear that all Myfords are not created equal, and these dimensions do affect the performance of the clamp. It has been tried on grey, green & blue machines and works on all of them, but clamping is noticeably better on the blue one, for which it was made. The effect of variations in the Myford dimensions can be seen here:

The gap between the clamp and the front of the shear is greater on the grey one, the top lip isn't perfectly flat on the bed, and the clamp plate is more horizontal – so as the note on the drawing says, you should adjust the red dimensions to suit your machine.

To find the position of the mounting stud relative to the front of the bed a 1” parallel was clamped to the bed, distances between the parallel and the stud were then determined using slip gauges for the vertical position and a feeler gauges for the horizontal distance:

Apart from the 'red' items, none of the other dimensions are critical, so I haven't shown them, those that are shown are for information, and do not need to be slavishly followed!

Hi Cabeng, do you have the issue number please for the saddle lock article?

Regards, Martin