Top Slide

Adjusting the top slide of my myford 7R to cut 60 degree threads or 55 degree threads is very difficult to see the mark and the graduations. There only seems to be one mark on the top slide can I put an extra mark on where it is easily seen and where would the best place be to put it.

Hope this makes sense and as always thanks in advance for any help and advice you can give.

Alan

Alan,

My first thought was to put a single new radial line at 30° or at 27.5° rotation from the existing fiducial mark.

Decisions ... Decisions !!

Then I wondered: Might it be best to engrave a short arc, with one end identifying each angle?

Does that make sense ?

MichaelG.

Hello Alan,

​The top slide is fitted to a circular base which is in turn bolted down to the cross slide it sits on; the bolts are fitted through two curved slots on the top slide base. The whole is located by a peg through the underside into a close fitting hole in the cross slide.

There should be a 45 - 0 - 45 degree scale on that circular base which is referenced back to a fine fiducial mark on the centre line of the cross slide. Setting angles on the top slide is from that fine mark.

If the mark is not present , you can re-establish it the following way.

Remove the top slide complete, fit a faceplate or the catch plate to the spindle nose and then a wide parallel can be butted up to the faceplate so that it is aligned along the mid point of the top slide, being sure it bisects the location hole for the top slide. Now scratch a mark which reaches beyond the point where the base of the top slide will have left a faint circular witness mark on the flat top of the cross slide. That scratch will be your new fiducial mark

I hope that helps you

Regards Brian.

Whilst you are at it, make sure the new mark is mirrored to the tailstock side of the cross slide as well, useful when cutting LH threads!

I wonder if the top slide assembly has been fitted back-top-front? The marks are only on one side but I think the base is otherwise symmetrical.

In any case, the important detail is to get the tool itself exactly at right angles to the spindle axis (assuming that it has been ground 'square'  )

If the offset angle is not enough the 'back' edge of the tool will take a tiny shaving, and if too much then one face of the thread will have ridges. So, a bit less than the 'correct' angle is much better than a bit too much.

I think

Cheers, Tim

Edited By Tim Stevens on 22/08/2016 09:38:13 to remove a silly face!

Edited By Tim Stevens on 22/08/2016 09:39:04

Edited By Tim Stevens on 22/08/2016 09:39:39

Hello Tim,

​That had occurred to me as well, but the feed screw nut would then be on the wrong side, ie chuck side, and probably beyond the reach of the feed screw anyway.

Regards

Brian

.

I may be wrong [it has been known]; but I think the discussion is drifting away from Alan's stated problem:

As I see it; he has a scale, and he has the standard fiducial line, located in the standard position ... It's just that [when angling the top slide for screw-cutting] he finds it difficult to see the reading.

The question is two-stage:

• can I put an extra mark on [where it is easily seen] ? ... Answer: Yes
• and where would the best place be to put it ? ... Answer: At 27.5° and/or 30° rotation from the original. [and mirrored for left hand threads if you so wish]

Done as I suggested earlier, this provides alternative fiducial marks, with minimal modification.

Am I 'barking up the wrong tree' ? ... or just 'barking mad' ?

MichaelG.

Hi, I have the same problem ( as will anyone with a similar Myford) my solution which is drifting is to use the protractor from a combination set against the chuck or face plate and the side of the top slide quick and easy cheers

I agree with all that Michael G suggests, but I too own a similarly equipped Myford,. The engraved markings on the vertical face of the circular base are clear and easy to read, just as they are on a second top slide I bought with a special project in mind, so I am rather puzzled as to what the problem is that Alan G and Alan L are having.

I accept that the graduation marks are fine, but my eyesight was severely compromised years ago by retinal repair and I can read them using ordinary reading glasses. Decent lighting helps and I still have the option of magnification to fall back on when I can no longer resolve them.

Alan Lightfoot's idea could be enhanced by making simple fixed angle plates cut to the two angles (three if you include BA) so that no reading of marks or divisions is then necessary

Regards

Brian

When I was making parts for agricultural machinery that we were building, I had a number of angle plates that I could fit between the face of the chuck and the top slide, just a few seconds to set the angle, and just requires some scrap sheet metal.

Ian S C

Thanks for all the different methods, I have found them very useful. Micahel thanks for putting everyone back on track again, Alan.