Was turning a set of soft jaws. Stopped for a measurement and had 5.670 with a target of 5.750. Took 4 more 0.010 cuts and took another measurement. 5.745! Yeikes I thought I had another 0.020 to go? Brain had defulted to making it smaller, but I was making it bigger! Slow 0.002 final pass and on the money!
Almost f-up today.
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Torque&Recoil
Well-known member
Aw, that happens. We've all been there. Glad to hear that you were able to get it perfect with the final pass.
On a lathe 0.010" on the cross slide is 0.020" on the diameter...
slowtwitch73
Well-known member
My latest pooch screw was edge finding on the mill and forgetting to subtract .1 for the .2 dia edge finder tip. Doh!
nadogail
Well-known member
Sometimes i get things 100% correct, most days I m lucky to be "Close Enough".
This is true on most of them. But by no means a rule.
Whut?
If you set-up a 0.01" deep cut it will change the diameter by 0.02".
Please explain when that's not correct
This is correct. But there are (although not as common) lathes that have taken this into account and have the dials allready reading 2x the cut.
Luckily I had enough time into this that I was being overly cautious!
Been there!
Jim greengo
Well-known member
My tape measure doesn't go down that low. Hahaha
Gota make sure the little slidey bit at the end is in the correct position!
Nah, I always smack that rivet with a hammer to keep the tip from moving around on me!
dutchgray
Well-known member
Someone previously to my ownership penned "Radius" on the cross slide behind the dial on mine with marker, they likely had one of less common "diameter" reading dials on another machine, which would be really confusing.
I think everyone who uses a lathe has blown a dimension at some point by taking too many passes without measuring.
RoninB4
Well-known member
-It's less about the crime and more about the witnesses.
rlitman
Well-known member
On most cross feeds and compounds, yes. On many lathes with enlarged "micrometer" dials, 0.001" on the dial represents 0.0005" of feed, or 0.001" change in diameter (on the cross feed, or potentially much less than that if you're feeding the compound at an angle). That's what I've got on my South Bend.
slowtwitch73
Well-known member
I'm always amazed so many guys rely on dials.... I couldn't do it. I use indicators.
The dials on both my mill and lathe could vanish and I wouldn't care.
More power to you.
The dials on both my mill and lathe could vanish and I wouldn't care.
More power to you.
Most of my stuff +/- 1/8" is plenty fine.
niget2002
Well-known member
Mine was worse than that. Was finding the centerline of a part on the mill. Was a quick and dirty, so just used the drill bit to 'edge find'. Didn't pay attention and caught the flute of the drill bit on one edge and the valley of the drill bit on the other edge when I hit the '1/2' function. I don't remember the size of the drill bit, but it was big enough that the 'centerline' of the 2" part was off quite a bit. I caught it after drilling the first hole and looking at the location for the second on the opposite side of center going, "That looks too close to the edge".
Luckily this went on the bottom of the piece and the hole location didn't matter that much. I ended up just fudging the second hole using TLAR.
Luckily this went on the bottom of the piece and the hole location didn't matter that much. I ended up just fudging the second hole using TLAR.
Pro Tip I learned during this project.
When cutting the Id of a three jaw Chuck, or any interrupted cut you can measure your cut diameter by using the depth probe on your calipers from the tip of your boring bar to the opposite jaw.
When cutting the Id of a three jaw Chuck, or any interrupted cut you can measure your cut diameter by using the depth probe on your calipers from the tip of your boring bar to the opposite jaw.
I'm definitely in the TLAR camp.
Jim greengo
Well-known member
I was taught to always burn an inch , as my dear old dad called it.
lbhsbz
Well-known member
My Cadillac lathe crossfeed dial is marked such that if you dial in .020", it will reduce the diameter by .020"
See, it does kinda **** with one when using a different machine! I really want to put DROs on my lathes!
rlitman
Well-known member
And then you'd still have the same question. I've seen lathe DROs done both ways (radius / diameter reading). A good display might show both.
RoninB4
Well-known member
-Always a good habit to "zero off" the work and then take a minimal, "measured test cut on any machine you don't use on a regular basis. I've been machining for several decades and still do this. Test cut determines the cutting condition of the cutter and also verifies whether the dial is 1/2 or full movement reading without botching the target dimension. Just a suggestion.
goldtang
Well-known member
If I am not sure if the graduation on the dial on the cross feed is in diameter or radius, I place a magnetic base on the saddle of the lathe and place the the dial indicator on the tool post
poor mans DRO
poor mans DRO
txvwnut
Well-known member
When I bought my first machine I wanted to put a DRO on it but didn't have the budget for it as the only ones that were basically available were the high dollar ones. Now fast forward to current day and my mill and lathes both have DRO's on them. I rarely ever turn them on as I work off the dials more now than ever as I had a slide somehow go out of calibration and would lose measurement during the process. I'm reading I'm removing a hundred thou and in actuality I was removing one twenty or more. When I do flip the DRO's on I always zero the dials to compare my results.
oldmachinenut
Well-known member
You beat me to it, my South Bend also has the big direct read dials.
RoninB4
Well-known member
-I like having a DRO on a machine but there's always the chance that something has rendered it inaccurate.
The glass scale type are on the fragile side, a bit finicky to shim at installation, and when the seals allow liquid in they're shot. Cannot be shortened.
The magnetic scale type are on the bulky side and can be susceptible to metal chips (from reports) or a magnet. Can be shortened.
The electronic type (Spherosyn, Micro-Syn, etc) I have no long term experience to comment on.
There is no "best" because there's a mix of features, resolution, accuracy, and durability so your choice is about what you need and what machine it's mounted on. Any of them may also limit the travel range due to the physical space they occupy. The one thing that does seem to hold true is whether it's a reputable maker (Sony, Heidenhain, Newall, etc.) or not. The cheap unit from Chi-Wan are a **** shoot and should be considered disposable after a short time. A good DRO is expensive, that's why I only have one (Heidenhain) on the jig borer for close tolerance work. There is no "best" but there certainly are many contenders for "worst" on E(vil)-Bay so do some research beyond the advertising before plunking down your money.
For milling/turning/grinding I accept the potential error factor of wear in the lead screw and creep up on a target dimension while keeping track of progress with calipers/micrometers/indicators as tolerances dictate. Yes that's slow but I need accuracy over speed. JMO.
The glass scale type are on the fragile side, a bit finicky to shim at installation, and when the seals allow liquid in they're shot. Cannot be shortened.
The magnetic scale type are on the bulky side and can be susceptible to metal chips (from reports) or a magnet. Can be shortened.
The electronic type (Spherosyn, Micro-Syn, etc) I have no long term experience to comment on.
There is no "best" because there's a mix of features, resolution, accuracy, and durability so your choice is about what you need and what machine it's mounted on. Any of them may also limit the travel range due to the physical space they occupy. The one thing that does seem to hold true is whether it's a reputable maker (Sony, Heidenhain, Newall, etc.) or not. The cheap unit from Chi-Wan are a **** shoot and should be considered disposable after a short time. A good DRO is expensive, that's why I only have one (Heidenhain) on the jig borer for close tolerance work. There is no "best" but there certainly are many contenders for "worst" on E(vil)-Bay so do some research beyond the advertising before plunking down your money.
For milling/turning/grinding I accept the potential error factor of wear in the lead screw and creep up on a target dimension while keeping track of progress with calipers/micrometers/indicators as tolerances dictate. Yes that's slow but I need accuracy over speed. JMO.
Hohn
Well-known member
As screw ups go, that's fairly low-ranking. It's not like you forgot to take back one Kadam to honor the Hebrew God whose Ark it is.
Tim in Indiana
Well-known member
Yep, I've done it several times. A small diamond cutoff wheel on a dremel will easily cut the scale.
Or just a regular glass cutter to score and snap the glass.
Keep one in my box, think I got it at ACE for about $12.00.
RoninB4
Well-known member
-To correct myself, glass scales can be shortened. A problem may arise if the entire scale is used for a reference. Not having done this myself I was going with the reports from experienced machinists. Before attempting this it would be good to do some research regarding open/closed loop and analog signals. Not something I need to do but someone will. I appreciate those that posted to inform me.