My new lathe and why is the combound .002 per line

I got a grizzly lathe http://www.grizzly.com/products/13-x-40-Gunsmithing-Lathe-with-DRO/G0776, so why is dial .002 per line on the carriage, as I dial in or out. And how do I fix it to read .001 per line. I know it is in the lead screw. But iam not that smart about these stuff.Just need some info on it. Brett

Brett

Your dial is calibrated to give the amount cut off the diameter which is twice the infeed. Common on American market machines. Often called a "Direct Reading Dial".

Allegedly better for novice and casual users because you get the size change directly instead of needing to multiply the feed by two. Personally I think it downright confusing because the topside is still calibrated as feed so you have two systems. Easy to get muddled.

I guess your DRO system is set to read feed so the DRO changes by half as much as the dial to really get you mixed up. Most lathe DRO units have a multiply by 2 setting which will bring its cross slide reading into line with the dial.

Clive.

How get muddled? The cross slide takes off on the diameter, the top slide almost invariably on the length. .001 movement of the cross-slide takes .002 off the diamter; .001 on the top slide .001 off the length. So that marking is perfectly logical to me. When I got my first lathe which was metric, I was initially puzzled why it was only taking half as much off the diameter as I expected, having only read about machine tools up to that point and that you had to move the cross slide half the amount you wanted to take off the diameter.

My lathe, the Warco 220, (the Bulgarian Mashstroy C210T) also has this system whereby the dial directly indicates how much is taken off the diameter. To be fair, it took some while to get used to the fact that actual travel was half of what the dial said, but now it's second nature. For me, it was more a mental thing than a practical thing.

Perhaps a short piece of , eg, Dymotape, stuck somewhere near may help.

Peter G. Shaw

The potential for confusion comes when you want to machine a groove

... often specified by depth, rather than diameter.

MichaelG.

Agree that its easy enough to get used to a direct reading dial.

But given that everything else in the machine tool world works by depth of feed and that all the cutting parameters are, as they obviously have to be, specified by depth of feed it seems silly to have a different system for a trivial simplification. How hard is it to mentally multiply by 2?

If you have re-settable dials probably best answer to any confusion is to adjust things so you always finish with the dial at zero. Gets all the thinking out of the way first. None of this business of was it 0.375 or 0.357 to finish on. More professional as you get what you set too.

None of the "8@#€€ its 5 thou over" followed by scraping and scratching to get it down to size or, worse "8@#€€ its 5 thou under" followed by rapid trajectory into the scrap bin at about Mach1. If what you set isn't what you get then adjustment is easy until, after a rather short while you learn how to be right first time like the professionals.

Clive.

About as easy as it is to divide by two when you want to cut a groove on a direct reading machine. As you tend to do far more turning to diameter than plunging to depth the direct reading needs the least mental imput so reduced chance of errors.

Anyway if the lathe comes with a DRO why do you need to look at the handwheel dials?

FWIW the OP says it's the compound slide not the topslide.

Neil

Neil, I thought the compound slide and the top slide were interchangable names for the same thing

John

He also mentions it's " on the carrage"?

Grizzley give Cross slide as 0.002" per division direct reading = 0.2" off dia per rev and top/compound as 0.001" per division = 0.1" off length per rev in the manual.

Edited By JasonB on 19/02/2018 13:23:39

Perfectly true, but everyone has been discussing cross slides, which may well be what the OP meant but isn't what he typed!

Neil

Thanks for the info Brett

.

May I present strong circumstantial evidence on behalf of the defence yer 'onour ?

What Brett actually wrote was: " ... why is dial .002 per line on the carriage, as I dial in or out."

This looks very much like reference to cross slide, I would say.

MichaelG.

But the carriage is normally used to position the crosslide correctly along the bed, and the OP said it was the 'combound'.

I think that what engineers do is make what they want using what they have, so I think I'd better not comment further.

.

But the suitably positioned cross-slide is then moved "in or out"

... I rest my case.

The gratuitous debate is really not worth pursuing further.

MichaelG.