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View Full Version : What Dial Indicator spec. is best for tramming ?



Mr-Mike
11-27-2015, 12:00 PM
Tossing the garbage Fowler X-Test and getting a Brown & Sharp. The question is what precision/range combination is "right" for mill tramming (can it be too sensitive).

B&S ranges go from .03 - .008 and accuracy/graduations from .001 - .0001 (0-4-0, 0-10-0, 0-15-0) The Fowler was .06 and .0005 (0-15-0) but it was such junk I don't really know if it was a good spec for tramming.

Waiting for comments with the following in my 'cart':

Brown & Sharpe p/n 599-7023-6
0.008 Inch Range, 0.0001 Inch Dial Graduation, Horizontal Dial Test Indicator 1-1/2 Inch White Dial, 0-4-0 Dial Reading, Accurate to 0.0001 Inch



Thank guys!

JoeLee
11-27-2015, 12:34 PM
Well first off it depends on how fussy you want to get. If you start out with a dial that reads in tenths you'll most likely drive your self nuts, it's too sensitive. So I always start out with a dial that reads in thous. once I get it as close as I can with the .001 dial then I'll move up to the .0001.
That still can be tricky because just tightening down the bolts will change your indicator reading, you have to see what's happening and then compensate. The length of the arm your dial is mounted on will also make a difference. Mine is about 10" long so I swing about a 20" dia. circle over the table. OK left and right but front to back I have to move the table as it's only 9" front to back.
Also........... I don't sweep the table top, I always lay down a parallel and indicate off of it. This way you don't have to worry about the table slots or any peck marks in the table. Just lightly stone the table first to knock off any highs from nicks.
One of these days I'm going to grind a 12" dia. ring for this purpose, maybe a brake rotor will be a good start for this project.

JL...................

rklopp
11-27-2015, 12:43 PM
Your chosen 0.0001 graduation indicator is too sensitive for tramming unless you are fixing jig borers. The short range will drive you nuts. Get an indicator that has at least 0.030 travel each direction and at most 0.0005 graduations. I recommend Compac, Interapid, and Mitutoyo, in that order. I have those, plus a 0.0001" B&S. The latter only gets used occasionally for checking spindle runouts and for surface plate gauge block work.

Mcgyver
11-27-2015, 01:20 PM
I've sort of gotten used to tenths indicator for the completely illogical reasons thats the indicator i got used grabbing lol. I agree its easier with .001 and there is just no point in trying to tram say 1/2 a foot out to a tenth. lean on the head and it'll change.

I recently got a .0005" interapid and its a nice in-between. you could interpolate between lines to get close to a tenth but its not as fussy. If you're going to have one, it might be a good choice. Interapid, best there is imo.

lakeside53
11-27-2015, 01:24 PM
I use a 15-0-15, either Interapid or Mitutoyo (I have both, and more) . Easy to see "10ths" of movement but 5 of them is good enough for most of what do.

Forrest Addy
11-27-2015, 02:14 PM
My personal preference: I use the Mitutoyo 513-412 DTI I have in the Indicol to tram the import turret mill I bought in 1981. It's my go-to indicator for anything requiring a DTI. I like it because of the smooth predictable action, the large easy to read face, its mechanical ruggedness, and the 1.3" length contact. It has 15 - 0 -15 graduations sub-divided into half thousandths making it possible to eyeball 0.0001" to some degree of accuracy. Its downside is that its a bit bulky but I have a Starrett "Last Word" DTI I can use for those tight quarters jobs like scanning a shoulder deep in a bore - and - the long contact is subject to breakage so I keep a couple spares ($45 each!! Gasp!!) . I have had several DTI's come to me over the years and while I've experimented I seem to gravitate to the Mitutoyo 513-412. But that's my preference in indicator equipment for tramming my turret mill not a real response to the OP.

Rant: If I want greater accuracy in my tram, I enlarge the sweep but you have to be practical when tramming the average turret mill. 0.0005" on a 10" sweep circle corresponds to 10 arc seconds which is the practical limit of a good manual machine tool's coordinate system. Some classes of work demand greater care in geometry control. Achieving the desired accuracy in these cases falls to the skill of the man on the handles and his ability to check and producing better part geometry better than the machine registers in it's annual survey. If you know the machine's behavior, you can compensate for it.

In any case don't sweat tramming. You don't really need fancy uni-tasking tramming gadgets. Tramming imposes no great challenge on a dial indicator or the operator. The challenge lies in the condition of the machine and how to get the best from it.

More rant: My turret mill while 30+ years old has been babied so it's still quite accurate. The table has sagged 0.003" so the "lamb effect" on features widely separate may have to be taken into account - for example if I was ever asked to make a die set. Most small scale work (parts you can carry in one hand) don't require heroic deeds in accuracy so an every day 0.001" in 8" sweep circle is plenty good enough.

If you really want to make your tramming session simple and painless, learn the "nod ratio" of your particular machine and use it the mathematically calculate the correction to nod in thousandths from the error noted in the initial sweep circle. Work that number and you can tram out the nod error in two corrections, possibly three. Don't ask me to elaborate. Go to your machine and examine the geometry of the nod pivot and its relationship to the nod circle. Apply high school geometry and ratio and proportion.

Report back and brag your successes or lament failures accordingly.

Actual response: Chances are you have a suitable indicator already in your inventory though it may not be your preference.
Pick what dial indicator suits you, your budget, and your application and go with that.

JoeLee
11-27-2015, 04:20 PM
I've sort of gotten used to tenths indicator for the completely illogical reasons thats the indicator i got used grabbing lol. I agree its easier with .001 and there is just no point in trying to tram say 1/2 a foot out to a tenth. lean on the head and it'll change.

I recently got a .0005" interapid and its a nice in-between. you could interpolate between lines to get close to a tenth but its not as fussy. If you're going to have one, it might be a good choice. Interapid, best there is imo. Well yes there is............ if your trying to fly cut it'll make a difference.
You'll either cut slightly concave or convex, same goes for boring or drilling deep. So the closer you get it the better results you will get.
Agreed that if you lean on the head you'll see deflection.

JL...............

Mcgyver
11-27-2015, 04:28 PM
Well yes there is............ if your trying to fly cut it'll make a difference.
You'll either cut slightly concave or convex, same goes for boring or drilling deep. So the closer you get it the better results you will get.
Agreed that if you lean on the head you'll see deflection.

JL...............

if you're milling to a tenth over a 6" span, you're a better man than I.

JoeLee
11-27-2015, 05:30 PM
if you're milling to a tenth over a 6" span, you're a better man than I. I doubt I'm a better man than anyone else here is but, I recently fly cut a machine fixture base that measured about 7" long x about 5" wide. It looked beautiful, in fact it looked perfect until I put it on my surface plate and found out how nice and freely I could spin it around. It was slightly crowned. My mill is trammed within about .0002 best I could tell but it still cut convex. I had to stone it flat after several repeat attempts.

JL.............

Mcgyver
11-27-2015, 05:37 PM
we're actually pretty much the same there, using a tenths indicator its not much more trouble to get it to .0002 than .001 and no harm is done....even with .0005 its pretty easy to get the needle close to a line. I didn't want to extend my own fussiness to someone poor newbie thinking the world would crash if he wasn't tramming to a tenth. We're really not milling to tenths no much how we delude yourself...but no harm in a spot on tram

Convex? no matter what direction it was out of tram, wouldn't the shape be concave? On reflection, I let the cutting all the way across....if high on the leading side, i see how it could cut convex if stopped before the back arc cuts.

one last comment....flat to surface plate tolerances is a lot to ask of milling. to much imo. might be better to let it go all the away across and have it slight concave.

10KPete
11-27-2015, 06:07 PM
I was gonna say that milling to granite flatness is nigh on to impossible!! That's grinder territory!

Pete

Mr-Mike
11-27-2015, 07:45 PM
I am grateful for your comments. I almost erred again... Following the recommendations I am just stuck between the Interapid - [.06 & .0005 | 0-15-0] and the B&S [.03 & .0005 | 0-15-0]. Price-wise it's a wash. I am leaning toward the B&S - I understand B&S and Interapid are made by the same Swiss company but the B&S has a constant clockwise operation which for no valid reason, appeals to me. Is it simply a matter preference or is one "better" than the other.

Thank you all so much!

By the way, the discussion on milling a perfectly flat surface is a bonus for me as I have struggled with fly-cutting such a surface myself. It's helpful hear it is beyond my mini-mill's capability and not just me (though I would have preferred it be just me).

Edit: The only source I found for the Compaq (which also appeals to me) is $80 more than the other two at Enco).

boslab
11-28-2015, 12:47 AM
+1 on Mcgyvers comment, I've never milled convex yet, I've ended up convex a couple of times due to the plate distorting either by removing the material that was keeping it flat or actually distorting it accidentally with clamping, I tram to a thou or two, more than that is witchcraft
Mitutoyo plunger clock btw
Mark

Charles Spencer
11-28-2015, 04:20 AM
I haven't actually made my tramming head yet, but I did buy the dial indicators. I bought two metric ones on sale. So I guess that would be @ .0004"

I'm not really that fussy.

LKeithR
11-28-2015, 05:06 AM
I was gonna say that milling to granite flatness is nigh on to impossible!! That's grinder territory!

And completely unnecessary for 99 per cent of the work performed on the average mill. I guess if you're a hobbyist with nothing better to do it's OK but in a working job shop shop you'd be wasting time and money trying to achieve those kinds of tolerances on a regular basis. For a lot of repair and maintenance type jobs a couple thou is often as close as you ever need to be. I'm not saying you shouldn't know how to hit the numbers when it's necessary, but working to really tight tolerances when it's not required is a recipe for losing money...

rklopp
11-28-2015, 12:57 PM
The Interapids have a built in swivel stem which is very useful for grabbing in a drill chuck to sweep in a hole, straddle the center of a piece of stock, and other relatively short-sweep tasks. Note that the swivel stem on the Interapid "vertical" model does not swivel far enough to be able to sweep small holes. The "normal" model, with the dial on the skinny side like most DTIs, does not suffer this drawback. It can sweep a hole as small as the diameter of the probe tip. I agree that a constant-direction dial is useful, but the swivel stem wins IMHO. I use it almost every time I use a DTI.

Mr-Mike
11-28-2015, 02:13 PM
The Interapids have a built in swivel stem which is very useful for grabbing in a drill chuck to sweep in a hole, straddle the center of a piece of stock, and other relatively short-sweep tasks. Note that the swivel stem on the Interapid "vertical" model does not swivel far enough to be able to sweep small holes. The "normal" model, with the dial on the skinny side like most DTIs, does not suffer this drawback. It can sweep a hole as small as the diameter of the probe tip. I agree that a constant-direction dial is useful, but the swivel stem wins IMHO. I use it almost every time I use a DTI.

Thanks for the great comment - an important consideration. I am thinking the B&S PLUS a swivel support (dovetail - 3/8" pivoting shaft) will be perfect. Any flaws with that approach?

rklopp
11-28-2015, 08:48 PM
Thanks for the great comment - an important consideration. I am thinking the B&S PLUS a swivel support (dovetail - 3/8" pivoting shaft) will be perfect. Any flaws with that approach?
No flaws other than two pieces to keep track of, rather than one, and twice the range on the Interapid. It's not that I'd use all that range to make a measurement, but the smaller range means you need to be closer to concentric before applying the DTI when dialing something in.

Mr-Mike
11-29-2015, 12:09 AM
Alrighty then. I am set. Thanks for following up 'rk'.

All, thanks for your time gentlemen. As always, much appreciated!

philbur
11-29-2015, 12:01 PM
I doubt I'm a better man than anyone else here is but, I recently fly cut a machine fixture base that measured about 7" long x about 5" wide. It looked beautiful, in fact it looked perfect until I put it on my surface plate and found out how nice and freely I could spin it around. It was slightly crowned. My mill is trammed within about .0002 best I could tell but it still cut convex. I had to stone it flat after several repeat attempts.

JL.............

Is your table flat and perpendicular to the spindle axis to a tenth over a 7" x 5" area? Did you check if the fixture base was deformed under the clamping load? If you are hoping to work to tenths on a mill then you need to compensate for phases of the moon.:rolleyes: I think the only way to ensure a large milled surface will sit well on a known flat surface is to mill it slightly concave. I thought this was kinda standard practice.

Phil:)

JoeLee
11-29-2015, 12:49 PM
Is your table flat and perpendicular to the spindle axis to a tenth over a 7" x 5" area? Did you check if the fixture base was deformed under the clamping load? If you are hoping to work to tenths on a mill then you need to compensate for phases of the moon.:rolleyes: I think the only way to ensure a large milled surface will sit well on a known flat surface is to mill it slightly concave. I thought this was kinda standard practice.

Phil:)Maybe .0002 over that area.
What I thought may have been the cause was the base that I was fly cutting had a 1/2" wide slot down the (almost center) It was my conclusion that every time the insert jumped the slot it caused a little vibrtation resulting in a slight high spot in that general area. Coming into the edge of the part also would have caused some vibration. On the final pass I took .001 off with a new dead sharp insert and ended up with the same result.
If I can find some pics of this I'll post them, thought I took some!!

JL............