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Thread: Test Bar Suggestions
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20th January 2015, 09:37 PM #16SENIOR MEMBER
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Just how much do you feel you can stuff a dial test indicator up a #2MT socket. Critical measurement over 5/8" - 16mm. About the lenght of the stylus. Thats going to show you the lay of the land. Good luck with that.
Please feel free to argue with yourself.
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20th January 2015 09:37 PM # ADSGoogle Adsense Advertisement
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20th January 2015, 11:06 PM #17Cba
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It depends what you are about to do. If this is about testing to Schlesinger standards a new lathe (or reconditionong an old one) I perfectly agree with you. If it is just about looking at the lay of land, say to see if it is bad enough to warrant doing something about, my method actually works good enough. Not everybody can afford the expense of a real MT2 test bar. And using a centerless ground silver steel bar held in a chuck is FAR less accurate than the DTI method I described. It is not always necessary to chase microns, it really depends what the op wants to do.
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20th January 2015, 11:33 PM #18Member
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I contacted the seller some time ago, because I had the idea to use as a test bar. They seemed to think the ends could be drilled without to much hassle as the surface is hardened not the ends.
I ended up purchasing a precision MT3 test bar. However for $20-$30 its probably worth a shot.
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21st January 2015, 01:11 AM #19.
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Hi Phil and Richard.
Alan's test bar is a Rimet. I thought I'd better run a minty 0.002mm indicator along the bar and the results are less glowing than those achieved with the vintage Mitutoyo DTI. My investigation continues.
The parallel ground bar was not specifically for this problem. I need something to facilitate tramming the mill's vertical head and for checking alignment of the little Hercus dividing head. A bit of bar would prove handy.
Bob.
008 (Large).JPG 015 (Large).JPG
PS Max, I will buy a couple of bits of steel from your linked seller. At least I'll find out how knackered my drill chucks actually are.
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21st January 2015, 08:10 AM #20SENIOR MEMBER
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Haven't looked at the link to the bar, but IME hard chromed induction hardened rod as used in hydraulic rams machines very nicely once you get under the hard skin, which isn't a problem with TCT tooling. I've used a fair bit of it for projects over the years.
I have a Hercus TS casting here - top part only I think - that I don't actually need or want. Ditto for the HS casting.
One of these days I'll need to make/acquire a MT4.5 taper test bar to check out my Chipmaster. I'm thinking to myself 'good luck with that', probably easier to make one oversize and take it to a local outfit with a really good grinder.
PDW
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21st January 2015, 01:10 PM #21Philomath in training
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I have - that's why I buy second hand. To date I think I've bought 4 (maybe 5). I've found that the chucks are normally pretty good. Even in a heavily abused one that I bought, the chuck was basically good with respect to wobble and the main problem was the arbor it was mounted to (I still had to replace some parts internally though). I have something of dubious origins coming in shortly. I might have to do another of my "what's inside" threads so people can see what is in these chucks and how to take them apart. It's a 13 - would you like to swap it for your 10 Bob?
Schlesinger suggests that a drill chuck should only have 0.03mm run out at 300mm. Not sure I have a bar that I trust that much. (that's roughly a tenth per foot - the PG bar specs I've seen are 3 thou per foot, so yes, they are not going to be good enough)
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21st January 2015, 01:24 PM #22Intermediate Member
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Bob,
You may be chasing your tail tramming a round bar without an 'elephant's foot" tip on a clock. Any wear in the saddle ways, either vertical or horizontal, (or both) will register with a ball-end tip.
Peter
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21st January 2015, 03:31 PM #23.
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Hello Peter,
It is good to hear from you.
When Alan dropped the bar off on Friday I fitted a flat foot to the Baty indicator I used for some initial tests. In an email exchange a short while ago, PeteF made the same comment in relation to the 0.002 Compac's stylus.
I know I am pissing in the wind using a ball end. I'll turn up a foot to suit the Swiss.
Have you built your shed yet?
Bob.
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21st January 2015, 05:40 PM #24Intermediate Member
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The shed is built, 3 metre stud height,25 degrees gable roof and 150mm concrete floor 6x7metres. My container should be leaving Perth in a few days so there will be a bit of action in the offing.
Peter
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21st January 2015, 06:16 PM #25.
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21st January 2015, 10:31 PM #26Intermediate Member
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Yes Bob, the Russian (Maho 600 clone) could sure hog metal. I could only bring one container over so the other machines all went to good homes. I am just hoping that my lathes have not deteriorated too much after 14 months in the container! Plenty of preserving oil should have done its work, fingers crossed.
Peter
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21st January 2015, 10:56 PM #27GOLD MEMBER
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You don't mention the diameter of the bar or the error BT, but I'd be surprised if error on one plane is adding much to your error in the other. (unless its REALLY BAD! and by that stage you wouldn't care). Not sure about a dial indicator on that stand(though I would expect it to read low rather than high)
I think part of your problem is you seem to trying to measure an unknown from an unknown with an unknown.
To test the axis alignment of the MT2 and the TS quill, how about this.
Set the quill up in the 4 jaw with as much over hang as you can get, allowing you to check runout in two positions as far apart as possible. once you have it dead on, fit your test bar(you can check your test bar first if you like). measure the runout. TIR should be the same at both ends of the bar. Nothing can effect that........ right?
I'm tempted to start talking about Marcels and steel wire.
Stuart
p.s. TIR should be 0 both ends and on the taper.Last edited by Stustoys; 22nd January 2015 at 12:20 AM. Reason: p.s.
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22nd January 2015, 11:46 AM #28Pink 10EE owner
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Not wanting to dob Alan in.. But doesn't he have a cylindrical grinder
If you make it out of rod held in a four jaw chuck in the lathe, I have read in the model engineering type books you will have to cut the centres with a tool bit.. A centre drill will not get it centre enough...
Of course if there is twist in the ways or worn ways or whatever it makes the measuring even worse as you run the saddle up and down and it is moving all over the place...
But then there is Rollies Dad...Light red, the colour of choice for the discerning man.
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26th January 2015, 01:41 PM #29.
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Not up to Georg's standards!
Michael,
I haven't been ignoring your suggestion of a swap, in fact I picked up a 500 gram Parcel Post bag on Wednesday to facilitate the exchange. I thought I had better see how good or bad the chuck was before I sent it off. It's bad and it's only a 0 - 6.5mm, not the 10 I thought it was.
To obtain some idea of the condition of the Albrecht and my other chucks, I turned a parallel spigot on the end of a length of 4140 and mounted the chucks jaws first. I then measured the run out on their arbors or inside their Jacobs tapers. The Albrecht is pretty much landfill with 0.013" TIR at the outboard end of the arbor if the arbor isn't bent. I measured run out along the body of the chuck before the arbor and it was progressively greater further from the jaws suggesting a jaw problem.
My 1/2 "Jacobs ball bearing chucks faired better with about 0.005" TIR at the extreme end of their arbors. The 1/2" Rohm Supra was about the same but could be improved by repositioning the jaws and retightening.
I have a good looking, conditionwise, Jacobs 8 1/2N (1/4") and an 11N (3/8") . Both chucks have been rebuilt by me with new jaws and bearings. There was about 0.003" TIR inside the taper socket of each chuck.
The best performing chuck I have is a beater 1/4" Rohm Supra. It has 3 thou runout but it remains consistent along the length of its arbor.
Looks like I'll stick with my habit of boring holes of importance.
Let me know if you want the Albrecht. No exchange involved.
Bob.
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26th January 2015, 02:34 PM #30GOLD MEMBER
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I would have thought it possible to mount a tool post grinder, and regrind the ones that are out of tolerance. Theoretically that should make them perfect????
Is it the way that the 2 tapers fit together that causes them to be out?
Kryn
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