ML7 – Zeroing the Topslide?

[Martin KyteParticipant @martinkyte99762]

When machining to a shoulder I set a carriage stop just shy of the end of the work. Face off the end so the stop is exactly registered to the end. Wind the tool clear and advance the top slide to the length of the shoulder. Machine the shoulder to size with the crosslide and saddle taking a final indeed cut to square the shoulder. If the top slide is within a degree the shoulder length will be accurate to our purposes as has been mentioned. I tend to only use the topslide for short tapers where often a matching reamer can be turned at the same setting to finish the female component so again bang on setting is not required. Admittedly I have a Super 7 which I can set to better than 1/4 degree by eye but mostly that’s unnecessary as I say. I do have a micrometer carriage handwheel too which gives me other ways to skin the cat.

Topslides on Myford are not terribly good for turning I have found mainly due to the short dovetail slides. Turning the handwheel tends to produce a slight rocking which varies the cut. I did make George Thomas’ retractable topslide which has a bigger micrometer dial and a gear interposed between the handwheel and the lead screw which eliminates some of the rock and is much easier to set.

For very accurate spacing down a shaft when using limited or less than perfect kit I would make up a series of accurate spacers to use a stops.
Sometime we have to spend a bit of effort to achieve accuracy rather than just relying on the built in capability of the machine tool.

You could of course just throw money at the problem and buy more expensive kit but it’s not always possible or even justified.

One of the reasons why I find Model Engineering so interesting is learning how the engineers of the past achieved high precision without the modern high tech equipment. Old George Thomas said it’s amazing how much high quality work can be done on antiquated and worn machines provided you understand their limitations.

Happy Machining

Martin

[Dave HalfordParticipant @davehalford22513]

Posted by JasonB on 14/03/2023 07:01:03:

I mounted Dti on some part of the lathe and run the saddle up and down.

I use mine all the time to know how much of a cut I have put on or to position the tool as the saddle handwheel is not accurate and you are guessing anything much less than 10thou.

Not having any kind of a handwheel on my saddle I used mine to set a sliding cut length. Since getting a DRO I use it to make cuts right up to the chuck by locking the saddle where the tool just misses the jaws at full travel of the top slide. Stops all those crashes.

[JasonBModerator @jasonb]

This is how I do it on my flat sided topslide, just loosen the bolts and give it a gentle tap until it reads the same at both ends, far quicker than doing similar to a vice, etc in the mill as the carriage moves a lot faster. Less that half a thou over 7" is good enough for most things

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 14/03/2023 12:13:13:

This is how I do it on my flat sided topslide, just loosen the bolts and give it a gentle tap until it reads the same at both ends, far quicker than doing similar to a vice, etc in the mill as the carriage moves a lot faster. Less that half a thou over 7" is good enough for most things

That's exactly what I want to be able to do.

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