Where to purchase and learn to use a lathe TEST BAR?

They make or used to make "lathe files" used to correct the taper on a shaft and or get the correct diameter size of a part.

I believe the block of wood that Nelson used to hold his test indicator was just something handy.
 
OK I know that i am posting to a 2 year old thread so i might not get a answer but here it goes anyway.I am sometimes slow with somethings I am wondering if the wood is not 100% concentric how can this be accurate? I guess im missing something.


J.B

Okay never mind I figured it out :whiteflag: I just had to think about it a min.
 
I got one from these folks,

Miller Machine and Fabrication
RR1 Box 108
Carrollton Il. 62016

Email absm@verizon.net

Phone 618 946 0793

This is from an advert I saw in Home Shop Machinist magazine.

frankie
 
Please correct me,i may be wrong.The method suggested for aligning the tail stock by turning two rings on a
bar mounted between centers,is exactly the same method for aligning the bed ways for warp.Now,if you want to
align the tailstock you must be sure that the bed ways are perfect and if you want to align the bed ways you must be sure that the tail stock is O.K. Both are unknowns for a new or a relocated lathe,so this is a chicken and egg
situation.So if you have a dependable test bar you can align the bed ways using a steady center and the bar, and
then align the tail stock.In my case,i have made a test bar using a Morse taper B22 chuck tail and a 12 mm guide
bar from a heavy dot printer.If there is some interest i will post, together with some photos,especially how i made
sure that the bar was straight an round. Please correct me.
Ariscats
 
There is no need to turn a test bar or to have one perfectly centered. Rollie's Dad's method will work to adjust the tailstock center.

For those who are not familiar with Rollie's Dad's method, it only requires a rigid test bar uniform roundness and, preferably, diameter. If a bar is mounted in a lathe chuck and the surface near the headstock is swept with a DTI, the average of the minimum and maximum readings will be the spindle axis position plus the radius. Runout is automatically compensated for. If the carriage is then moved to the far end of the bar and the process repeated the average of the two readings will be the same if the carriage ways are parallel to the spindle axis. This process is used to align the lathe bed to the spindle.

For adjusting the tailstock, a slightly different approach is taken. the test bar is mounted between centers. A lathe dog and face plate are used to turn the bar. The minimum and maximum readings are averaged at each of two positions. If the tailstock is properly aligned the two averages will be the same. Any runout is canceled out in the process so the center drills do not have to concentric with the bar diameter. The tailstock can to be moved correct any difference without having to go back to check the headstock readings although it would be wise to do a final verification.

If the headstock center is known to be true (no runout), the bar can be rotated by hand, no dog and face plate required.
 
You really only need the test bar when checking headstock alignment. (no tailstock) You can use just about anything to measure the tailstock alignment. Just turn it and measure it. I have the MT 5 test bar. It's a sweetheart.
 
There is no need to turn a test bar or to have one perfectly centered. Rollie's Dad's method will work to adjust the tailstock center.

For those who are not familiar with Rollie's Dad's method, it only requires a rigid test bar uniform roundness and, preferably, diameter. If a bar is mounted in a lathe chuck and the surface near the headstock is swept with a DTI, the average of the minimum and maximum readings will be the spindle axis position plus the radius. Runout is automatically compensated for. If the carriage is then moved to the far end of the bar and the process repeated the average of the two readings will be the same if the carriage ways are parallel to the spindle axis. This process is used to align the lathe bed to the spindle.

For adjusting the tailstock, a slightly different approach is taken. the test bar is mounted between centers. A lathe dog and face plate are used to turn the bar. The minimum and maximum readings are averaged at each of two positions. If the tailstock is properly aligned the two averages will be the same. Any runout is canceled out in the process so the center drills do not have to concentric with the bar diameter. The tailstock can to be moved correct any difference without having to go back to check the headstock readings although it would be wise to do a final verification.

If the headstock center is known to be true (no runout), the bar can be rotated by hand, no dog and face plate required.
Thanks even almost three years later. I know now.
Ariscats
 
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