Thursday, 24 December 2015

Re: [7x12minilathe] Re: MT2 Test Bar

 

The test bar in my case needed no "hacking" off the MT end to fit the tailstock.
If you put in a set screw 3/8" x 16 or 10 mm in the threaded hole for the knock out (retraction) 
you should be OK.
The only issues with any # 2 MT´s in a 7 x · lathe is if the tool has a knock out tang.

I have never seen or used a "test bar" with a tang as this is a "metrology" tool not used
for machining and or taking a radial load.

John


On Thursday, December 24, 2015 7:32 AM, "Bill Vance mlt@xpresso.seaslug.org [7x12minilathe]" <7x12minilathe@yahoogroups.com> wrote:


 


Thanks guys, those silutions will definitely do the trick.

Bill


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Wednesday, 23 December 2015

Re: [7x12minilathe] Re: MT2 Test Bar

 



Thanks guys, those silutions will definitely do the trick.

Bill

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[7x12minilathe] Re: MT2 Test Bar

 

The easy way is with the graduations on the TS ram. Seat the bar with the ram fully extended, retract it until the bar starts to eject - the reading on the ram is the amount to cut off. That still leaves a little safety margin because the ram retracts beyond the 0 graduation.


Roy

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Re: [7x12minilathe] MT2 Test Bar

 

Bill, I'll admit to not knowing the answer in numbers, but I had to do one and this is what I did....

I cleaned off the shaft and put a working MT2 in the tailstock so it seated (I think it was one of my drill chucks) and shot it with a little Dychem.  I popped that out and measured it.  Mess was all cleaned up with Dychem solvent and I had the answer.

Warren L

On 12/23/2015 1:10 PM, Bill Vance mlt@xpresso.seaslug.org [7x12minilathe] wrote:
 



I've seen it often enough, but now can't seem to find it.
Assuming I start with an MT2 test bar, how much would I
need to saw off the taper to make it compatable with a
7x* minilathe?

Bill


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[7x12minilathe] MT2 Test Bar

 



I've seen it often enough, but now can't seem to find it.
Assuming I start with an MT2 test bar, how much would I
need to saw off the taper to make it compatable with a
7x* minilathe?

Bill

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Monday, 21 December 2015

Re: [7x12minilathe] MT3 Test Bar from Ebay.

 

Hi Ian,

When the runout of a straight, constant diameter bar is nil at all points along that bar then the bar is perfectly aligned with the spindle's axis of rotation.  This will perform the same as a test bar which is fitted in the lathe's spindle taper. The part of the bar which the indicator will touch has the same relation to the spindle in either case; it's centered on the spindle's rotation axis - just held differently.

It does take some fiddling to get the arbitrary bar aligned but it's much cheaper than a test bar and a Thomsen bar has equivalent or better specs for roundness, diameter, straightness and surface finish. Since most owners align a lathe infrequently, often only once, the time vs cost tradeoff may be reasonable.

In either case, if the spindle axis is not aligned with the ways then as an indicator mounted on the carriage and zeroed at the headstock end of the bar is traversed along the bar it will read the change in distance between the ways and the spindle axis, i.e. the alignment error.  Depending on whether the indicator finger touches the top or front of the bar it will read the vertical or horizontal error.  Note that if you stop at any point and rotate the spindle there should be no runout if the real test bar or the arbitrary bar held in the chuck is perfectly straight, constant diameter, and perfectly aligned with the spindle axis.   In the real world, where things are seldom perfect,  one can use RDM to reduce the error due to imperfections, but limited by the resolution and accuracy of the readings, of course.

John




---In 7x12minilathe@yahoogroups.com, <ian_new@yahoo.com> wrote :

Hi John,

OK - I'll bite:

The point of using the test bar is to check the alignment of the system.

The process you describe in your post outlines a possible way to get a test bar aligned in a 'less than perfect' three or four jaw chuck.  Doesn't this method assume the axis is already in perfect alignment?

All the best,
Ian


On 21 Dec 2015, at 16:55, "John@GadgetBuilder.com [7x12minilathe]" <7x12minilathe@yahoogroups.com> wrote:

 

It is fair to point out that unless you're concerned with alignment of the spindle's MT taper to the spindle axis, an accurately ground bar (e.g. 3/4" Thomsen case hardened linear shaft, $12 at ENCO) can provide the same measurements as a more expensive test bar. 

Or if you have an accurately ground bar you can make acceptably accurate measurements for alignment of a 7x12 with that. If you're willing to work at it you can lap a straight 1" round steel bar (preferably a tube), use a 4 jaw and set the runout near the chuck to nil, then set the runout at the far end to 4/10 or less by tapping it in the right direction as you incrementally tighten the jaws. It takes a few minutes to do this but at that point you have the test bar aligned exactly on the spindle axis. This should perform just like a commercial test bar. Of course, you should use RDM to correct for any minor runout remaining, just like when using a real test bar. Or, you could chuck the lapped bar in a 3 jaw, accept a thou or so runout, push the high side on the far end as you tighten the chuck incrementally and get runout to a thou or so, then use RDM - my guess is there will be little difference in results.

More thoughts on 7x12 alignment here:  MiniLathe Alignment   There's more to it than a test bar, a precision level may also be helpful, upping the cost for alignment tools.

 

John

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Re: [7x12minilathe] MT3 Test Bar from Ebay.

 

Hi John,

OK - I'll bite:

The point of using the test bar is to check the alignment of the system.

The process you describe in your post outlines a possible way to get a test bar aligned in a 'less than perfect' three or four jaw chuck.  Doesn't this method assume the axis is already in perfect alignment?

All the best,
Ian


On 21 Dec 2015, at 16:55, "John@GadgetBuilder.com [7x12minilathe]" <7x12minilathe@yahoogroups.com> wrote:

 

It is fair to point out that unless you're concerned with alignment of the spindle's MT taper to the spindle axis, an accurately ground bar (e.g. 3/4" Thomsen case hardened linear shaft, $12 at ENCO) can provide the same measurements as a more expensive test bar. 

Or if you have an accurately ground bar you can make acceptably accurate measurements for alignment of a 7x12 with that. If you're willing to work at it you can lap a straight 1" round steel bar (preferably a tube), use a 4 jaw and set the runout near the chuck to nil, then set the runout at the far end to 4/10 or less by tapping it in the right direction as you incrementally tighten the jaws. It takes a few minutes to do this but at that point you have the test bar aligned exactly on the spindle axis. This should perform just like a commercial test bar. Of course, you should use RDM to correct for any minor runout remaining, just like when using a real test bar. Or, you could chuck the lapped bar in a 3 jaw, accept a thou or so runout, push the high side on the far end as you tighten the chuck incrementally and get runout to a thou or so, then use RDM - my guess is there will be little difference in results.

More thoughts on 7x12 alignment here:  MiniLathe Alignment   There's more to it than a test bar, a precision level may also be helpful, upping the cost for alignment tools.

 

John

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Re: [7x12minilathe] MT3 Test Bar from Ebay.

 

It is fair to point out that unless you're concerned with alignment of the spindle's MT taper to the spindle axis, an accurately ground bar (e.g. 3/4" Thomsen case hardened linear shaft, $12 at ENCO) can provide the same measurements as a more expensive test bar. 

Or if you have an accurately ground bar you can make acceptably accurate measurements for alignment of a 7x12 with that. If you're willing to work at it you can lap a straight 1" round steel bar (preferably a tube), use a 4 jaw and set the runout near the chuck to nil, then set the runout at the far end to 4/10 or less by tapping it in the right direction as you incrementally tighten the jaws. It takes a few minutes to do this but at that point you have the test bar aligned exactly on the spindle axis. This should perform just like a commercial test bar. Of course, you should use RDM to correct for any minor runout remaining, just like when using a real test bar. Or, you could chuck the lapped bar in a 3 jaw, accept a thou or so runout, push the high side on the far end as you tighten the chuck incrementally and get runout to a thou or so, then use RDM - my guess is there will be little difference in results.

More thoughts on 7x12 alignment here:  MiniLathe Alignment   There's more to it than a test bar, a precision level may also be helpful, upping the cost for alignment tools.

 

John

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Sunday, 20 December 2015

Re: [7x12minilathe] MT3 Test Bar from Ebay.

 

So glad to read the topic of Test bar procurement is becoming popular issue.
3 years ago I mentioned the use of this IMHO invaluable tool.
I thought I was pushing string uphill, as when I posted the use of this tool,it always seemed to be a non starter.
Oh well drips of water erode stone,and I can´t understand why the US are so far behind on this issue,very popular tool
in any of the European workshops.

I still think #2 with a reducer gives flexibility,and for resetting the tailstock for height/spindle axis and angular alignment it´s very easy to do.
Of course that´s if you have a lathe longer than the 10" bed.
The purchased reducer naturally needs to be accurate and not a cheap type they use for drill press tooling.
But anyway,Test bars are currently topical,which is good for us all.

John
Spain.


On Sunday, December 20, 2015 4:32 PM, "Bill Williams BWMSBLDR1@Gmail.com [7x12minilathe]" <7x12minilathe@yahoogroups.com> wrote:


 
A well reasoned argument! I am considering a test bar(s) and a
MT-3 would be my starting point both for my 7X12 and my 12x36. Then I
would think about my 618! The AA-109 is way down the road! And I agree;
this list is a great resource! Bill in Boulder

On 12/20/2015 6:21 AM, WAM ajawam2@comcast.net [7x12minilathe] wrote:
> I do 99% chucking work, mainly dayjob stuff. Lots of boring. I use the
> tailstock for drilling but that's about it. The work I use it for is no
> where near as critical as what you guys do, the modeling stuff I see
> posted by the users like you guys blows my mind.... even with a nuts
> dead on lathe I doubt I could even come close.
>
> I did try and test the tailstock alignment with it - I typically use a
> coax to align the TS.
>
> They center both ends of the test bar... with the indicator still at the
> far end of the testbar, I checked to see how far the indicator moved
> when I cranked a center into the predrilled center hole of the
> testbar. With the center fully seated into the predrilled testbar
> center hole it barely registered any deflection. So i guess the coax
> method I use is OK for what I need.
>
> Happy holidays to all on the list. I can't think of a better resource
> for any machine tool than the forum here. Learned a lot.



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Re: [7x12minilathe] MT3 Test Bar from Ebay.

 

A well reasoned argument! I am considering a test bar(s) and a
MT-3 would be my starting point both for my 7X12 and my 12x36. Then I
would think about my 618! The AA-109 is way down the road! And I agree;
this list is a great resource! Bill in Boulder

On 12/20/2015 6:21 AM, WAM ajawam2@comcast.net [7x12minilathe] wrote:
> I do 99% chucking work, mainly dayjob stuff. Lots of boring. I use the
> tailstock for drilling but that's about it. The work I use it for is no
> where near as critical as what you guys do, the modeling stuff I see
> posted by the users like you guys blows my mind.... even with a nuts
> dead on lathe I doubt I could even come close.
>
> I did try and test the tailstock alignment with it - I typically use a
> coax to align the TS.
>
> They center both ends of the test bar... with the indicator still at the
> far end of the testbar, I checked to see how far the indicator moved
> when I cranked a center into the predrilled center hole of the
> testbar. With the center fully seated into the predrilled testbar
> center hole it barely registered any deflection. So i guess the coax
> method I use is OK for what I need.
>
> Happy holidays to all on the list. I can't think of a better resource
> for any machine tool than the forum here. Learned a lot.

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Re: [7x12minilathe] MT3 Test Bar from Ebay.

 

I do 99% chucking work, mainly dayjob stuff. Lots of boring. I use the
tailstock for drilling but that's about it. The work I use it for is no
where near as critical as what you guys do, the modeling stuff I see
posted by the users like you guys blows my mind.... even with a nuts
dead on lathe I doubt I could even come close.

I did try and test the tailstock alignment with it - I typically use a
coax to align the TS.

They center both ends of the test bar... with the indicator still at the
far end of the testbar, I checked to see how far the indicator moved
when I cranked a center into the predrilled center hole of the
testbar. With the center fully seated into the predrilled testbar
center hole it barely registered any deflection. So i guess the coax
method I use is OK for what I need.

Happy holidays to all on the list. I can't think of a better resource
for any machine tool than the forum here. Learned a lot.

Ian Newman ian_new@yahoo.com [7x12minilathe] wrote:

>Hi John,
>I would guess that Wam has taken the very sensible attitude that if you are making tests using a master test bar you would avoid adding unnecessary errors.
>If you put the test bar in a reducing sleeve you are adding the errors that must exist in the sleeve to the test measurements that you take.
>All the best,Ian
>
>
>
> From: "John Lindo bechetboat@yahoo.com [7x12minilathe]" <7x12minilathe@yahoogroups.com>
> To: "7x12minilathe@yahoogroups.com" <7x12minilathe@yahoogroups.com>
> Sent: Sunday, 20 December 2015, 3:36
> Subject: Re: [7x12minilathe] MT3 Test Bar from Ebay.
>
> Hi Wam, glad you like test bar.Just a question on why you chose the #3 MT bar as opposed to a # 2 MT with a #3-#2 reducer.A # 2 MT would allow you confirm any T/S misalignment issues as well as checking the H/S.Hoping you are keeping well,have a festive season and happy new year.
>JohnSpain
>
>
> On Saturday, December 19, 2015 10:08 PM, "WAM ajawam2@comcast.net [7x12minilathe]" <7x12minilathe@yahoogroups.com> wrote:
>
>
>
> Just got my 3MT testbar from the aussies on Ebay. The one that comes in
>the wooden box. It came in a UPS bag, with a Toll (AU's carrier) bag
>inside. Needless to say the wooden box suffered a bit of damage, tho
>just the ends. The wooden box was bubble wrapped fairly tightly so I
>don't think the bar was damaged; at least no obvious indication of trama...
>
>A few years back, I did a Rollie's Dad's Method with an old injet
>carriage bar i had lying around. The new test bar agreed that I was
>off about 1mil of headstock alignment. I'd checked the ways previous to
>this and I got lucky, everything was within a mil...
>
>You may still want to use RDM with a testbar - I still see about mil
>variance at the far end when it rotates; at the headstock I can't even
>see my indicator move, so the 3MT taper is damn close to the bar section.
>Got the headstock about as good as a 7x can get...
>
>TSE Ming-wai mwtse@netvigator.com [7x12minilathe] wrote:
>
>
>
>>Many thanks, have ordered from ebay.
>>
>>
>>------------------------------------
>>Posted by: TSE Ming-wai <mwtse@netvigator.com>
>>------------------------------------
>>
>>
>>------------------------------------
>>
>>Yahoo Groups Links
>>
>>
>>
>>
>>
>>
>>
>>
>
>
>
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>
>
>

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