Re: Head stock alignment


Steve Wells
 


the geometry tests would be checking the saddle to bed alignment, then the spindle alignment
is checked using the saddle as a base. I've heard that somewhere before Ted...lol
then the tailstock is aligned to center with spindle. The saddle can wear quite a bit more than the
ways, very common. The temperature in the shop can effect the twist of the bed.
I would run an indicator on the saddle with the compound removed checking the outside ways in the
area you mentioned Mark and map the drop on the side of the lower V so you can see if it is indeed
low from wear. You can compensate some of this by twisting. Using a larger bar for test cuts is for
reduced movement from tool pressure as is a lighter cut. headstock bearing wear can also effect movement
of the test bar.
With an indicator on the good test bar in a four jaw with the piece dialed in, run the indicator down the
bar with the saddle with the headstock bolts just barely snug. tighten each clamp evenly watching the test indicator
and adjust the bolts for the best indicator reading as you tighten. do this before twisting the bed. Twist the bed by
test cuts. remember the bed may still move more after twisting depending on temperature, the next day you might have to back it off a bit.
Steve Wells  

----- Original Message -----
From: Latheman
Sent: Tuesday, March 11, 2014 3:46 PM
Subject: Re: [SOUTHBENDLATHE] Head stock alignment

 


"PS He more or less managed to twist the bed in a way that would practically eliminate the taper. Therefore, the lathe could have passed inspection that way."

NO WAY !
The first thing the tester did was level the bed, then perform the geometry tests. The cutting tests were next(chatter test and 2 collar test)

Ted

On Mar 11, 2014, at 2:57 PM, Paolo Amedeo <machineshop@...> wrote:

 

It is more likely that, instead of cutting a nice taper you'd end up more or less with a two diameters piece, with an abrupt change in diameter when the carbide tool starts to bite into the piece (cutting from tailstock to headstock) or starts gliding over the surface (cutting the opposite way).
I don't think Mark has mentioned anywhere that he has used a carbide tool.
Anyhow, hopefully we haven't been very successful in scaring Mark away and I hope that he will intervene in the discussion by filling in with missing details.

Paolo

PS He more or less managed to twist the bed in a way that would practically eliminate the taper. Therefore, the lathe could have passed inspection that way.
 

On 03/11/2014 02:48 PM, Jim B. wrote:
 

I do know that, (from my sad experience) trying to cut an unsupported 6”, or even a 4” length, with a carbide tool, using a light cut will result in a taper.

Carbide, unless you take the time to hone/polish it, should not be used for light cuts. It just skims over the surface.

A nice sharp, polished HSS tool, with a rounded point might be OK.

Jim B.


From

 

Jim,
I agree that we miss a few details (e.g. material of the bar, etc.), but by the overall description that Mark gave in his original post, I have the impression that he knows at least the basics (light cuts, not a really skinny test piece, etc.).
Moreover, at least for me it would be quite challenging to be able to remove such a strong taper and cutting true the whole 5-6" if the taper were mostly caused by a lousy cutting setup.


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