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Liger Zero
02-24-2009, 02:33 PM
Ok at the risk of starting another multi-page flamefest over accuracy issues... :D

http://littlemachineshop.com/products/product_view.php?ProductID=2222&category=-1536942993

This item from Little Machine Shop. It's a DRO kit for mini-lathes. Anyone have experience with this item? How easy is the install? Is it accurate for the price?

I'm not making nuclear or medical grade parts, mostly pipe-fittings and control knobs and other bits and pieces so I don't need sub-sub-micron *glares at you know who* or near-quantum resolution. :)

John Stevenson
02-24-2009, 02:46 PM
One thing and it's more a question of semantics over the term DRO.
Yes it is a digital readout but it measures the screw.
Most DRO's measure the slide. The difference being it doesn't take backlash into account.

The correct term is really Digital Dial Display.

Some people say they are no good as they don't take backlash into account but neither does a dial. With a dial you back off and come back again, same for these things.

So what advantages do they have you ask


?? Well ask then ..............

Ability to zero at any point on the travel at the touch of a button.
Ability to swap instantly between imperial and metric.
And probably the best reason in my book, no having to count turns.
Want 32.87mm off on an imperial lathe or 1.285" off on a metric lathe, just wind on that amount.

.

Liger Zero
02-24-2009, 02:51 PM
One thing and it's more a question of semantics over the term DRO.
Yes it is a digital readout but it measures the screw.
Most DRO's measure the slide. The difference being it doesn't take backlash into account.

The correct term is really Digital Dial Display.

Some people say they are no good as they don't take backlash into account but neither does a dial. With a dial you back off and come back again, same for these things.


Ok thanks for clearing that up. I've heard both terms, never knew the difference though.



So what advantages do they have you ask


?? Well ask then ..............

Ability to zero at any point on the travel at the touch of a button.
Ability to swap instantly between imperial and metric.
And probably the best reason in my book, no having to count turns.
Want 32.87mm off on an imperial lathe or 1.285" off on a metric lathe, just wind on that amount.

.

I'm looking at it and it seems to come with a new screw and nut for each axis... Wondering if these are "tighter" than what I have now... meaning less backlash.

And yes, not counting tick-marks is my goal. If I can get "reasonable" repeatability I'm happy.

I'm all about documenting processes and making them repeatable per setup. Saves time, lowers costs, makes customers and me happy.

John Stevenson
02-24-2009, 02:59 PM
They come with new screws and nuts as they are 20 tpi regardless of what you host machine has.
They have to be 20tpi for the encoder to count correctly.

In fact they will fit any machine if you can get them fitted and swap to 20 tpi.

They fit a Taig mill very easily as Taigs are already on 20 tpi [ 1/2" x 20 UNF ]

Liger Zero
02-24-2009, 03:04 PM
I have a Clark which is a "Typical 7X10 Import Lathe" like the Harbor Freight and Grizzly models.

Overall I'm happy with it, and I realize it'll never be on par with a Monarch (nor do I need it to be!) I'm just looking to optimize my processes at home. :)

Just Bob Again
02-24-2009, 03:59 PM
They're not expensive and they'll fit. Two marks in their favor. More tiny little unreadable LCD displays. One big black mark against. (rant/ Yes, power is lower. If I can't read the darn things it doesn't matter a bit how low the power is. Don't care if I need a cable direct to the Hoover Dam to run it, I want nice bright LED displays. /rant)

Anyway, if you want readouts for a mini-lathe not much else available except duct-taping a caliper on it. Or using calipers and a readout box. Costs as much as the lathe itself. I'd rather have the digital knobs.

oldtiffie
02-24-2009, 05:38 PM
One thing and it's more a question of semantics over the term DRO.
Yes it is a digital readout but it measures the screw.
Most DRO's measure the slide. The difference being it doesn't take backlash into account.

The correct term is really Digital Dial Display.

Some people say they are no good as they don't take backlash into account but neither does a dial. With a dial you back off and come back again, same for these things.

So what advantages do they have you ask


?? Well ask then ..............

Ability to zero at any point on the travel at the touch of a button.
Ability to swap instantly between imperial and metric.
And probably the best reason in my book, no having to count turns.
Want 32.87mm off on an imperial lathe or 1.285" off on a metric lathe, just wind on that amount.

.

Thanks John.

Good sense.

I took the liberty of emphasising one part of your post as it can be a real "trap" for the unwary.


The difference being it doesn't take backlash into account.

I suspect that some may think that there is no need to "come back on" to a cut or position if there is either or both back-lash and/or end play in a drive and rely on the DRO and perhaps neglect to use the slide clamps. Those will not be issues on a good well set-up CNC machine with good and pre-loaded ball-screws and thrust pads.

Next, those "RDO's" at LMS have a "resolution" of 0.0001" (a "tenth") but have an "accuracy" or 0.001" (a "thou"). That "thou" can be a "trap" and a PITA as it acts on the job radius (because of the 0.001" in-feed) and so has a diameter accuracy limited to twice that ie:

0.001" (in-feed) x 2 = 0.002" (diameter).

I would still use a micrometer and an dial indicator on the tool-post to "finish off".

But, perhaps I've mis-read this.

lazlo
02-24-2009, 05:53 PM
To add to what Bob said, David Cofer did a nice job of mounting a caliper to his 7x10. The pictures seem 404, but I'd imagine David still has them:

$52 Mini lathe DRO.. (http://bbs.homeshopmachinist.net/showthread.php?t=32226)

Roy Andrews
02-24-2009, 10:26 PM
if your at all competent at electronics. digital machinist did an article on making a similar readout that is bigger and plugs in so no batteries. it doesn't change the handles but puts an encoder cup and led switches on the back of the screw. it would involve a little work but i think it would be a fun project. but i like electronics. if you would like a copy of the article i could mail it to you. i plan on making it for the cross slide and the lead screw then i will put a hand wheel on the lead screw and have readings both ways

S_J_H
02-24-2009, 10:30 PM
They are just digital dials. You would get much more functionality by fitting cheap digital scales to the slides.

Steve

dp
02-24-2009, 11:38 PM
Analyzed from a "what problem does it solve" perspective:

- It replaces your dials, feed screws, and nuts.

Well, that's about it, actually. How important is that?

Secondary effects are the new screws and nuts may be better than what you have in terms of slack; the pitch of the new screws may be better suited than the original. Or not.

Nuisance potential: These indicators appear to always be on even when turned off. That causes battery life to be short. Plan ahead.

If the little computer in there goes gunnysack you have no alternative but to go to the vendor and hope they still have that model in stock. Otherwise it is a start-over project. And that assumes they even still support your lathe with the newest model. Over the life of the lathe. Or you put your old parts back on. Remember where you left them?

The slide position/motion sensors are true add-ons. They don't replace anything so if it all breaks you just fall back to what your first shop teacher taught you.

David Powell
02-24-2009, 11:40 PM
I have an arrangement so that I have a 1" travel indicator mounted on a slotted piece of angle iron ,fixed to the saddle. The plunger contacts a steel plate bolted on the topslide. The indicator is held by one ( large ) thunbscrew so can be reset easily if needed( The slide has about 4" travel). Yes, I know that dial indicators are comparators and not really measuring devices, but mine ( $15, from Princess Auto, sometimes less) seem within a thou in an inch whenever I have tested them with Joe blocks. In work I have an Accurite readout on the lathe, on my other lathe a Shooting Star readout. Of the three I prefer the dial gauge. Provided my tools are sharp I can, confidently work to half a thou by moving the finger a quarter of a division. The lathe is a Canadian made Standard Modern 9". Hope this helps David Powell.

David Powell
02-24-2009, 11:43 PM
Just realise, I wrote topslide, I meant cross slide. Regards David Powell.

oldtiffie
02-24-2009, 11:43 PM
A good combination of "worst state scenario" and "what if" analysis Dennis.

Steve's and David Powell's solutions are the best in every in every respect - so far.

Liger Zero
02-25-2009, 11:51 AM
Ok thanks for the advice everyone, I'm going to give this item a pass for the time being.