Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Default Turning a taper between offset centers

After much adieu over nothing I suppose (since at the moment I only have
one to do) I decided to turn a tapered mandrel between centers. The
first one turned out pretty good except I screwed up the finish pass(es)
and came in under sized. No I can't just shorten it up. So I still
have just one to do. LOL.

I picked up one of those little offsettable centers and it worked well
enough, except the tip melted. I kept it lubricated, but it might have
just been to high of an rpm for the method. I can turn it slower, but
if I get to do more of these I sure don't want to go slower.

I have two thoughts:

I can offset the tail stock and use a ball bearing center.

I can machine off the melted center, center drill it, and insert a ball
bearing between it and the center drill on that end of the stock. The
ball bearing certainly won't melt, and it will more evenly distribute
the load from the stock to the center. It would also have more contact
with the drilled out center. It would also allow me to have a small
reservoir of grease behind the bearing.

I really don't have a strong feeling for which approach will work out
better other than I dislike the time spent adjusting my tailstock back
in. I can leave the offset center setup for this taper indefinitely.
Ok, maybe I hope the ball bearing method will work out atleast as well.

The taper is pretty shallow. .157 over 10 inches.



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Default Turning a taper between offset centers

On Sun, 7 Jan 2018 12:25:04 -0700, Bob La Londe
wrote:

After much adieu over nothing I suppose (since at the moment I only have
one to do) I decided to turn a tapered mandrel between centers. The
first one turned out pretty good except I screwed up the finish pass(es)
and came in under sized. No I can't just shorten it up. So I still
have just one to do. LOL.

I picked up one of those little offsettable centers and it worked well
enough, except the tip melted. I kept it lubricated, but it might have
just been to high of an rpm for the method. I can turn it slower, but
if I get to do more of these I sure don't want to go slower.

I have two thoughts:

I can offset the tail stock and use a ball bearing center.

I can machine off the melted center, center drill it, and insert a ball
bearing between it and the center drill on that end of the stock. The
ball bearing certainly won't melt, and it will more evenly distribute
the load from the stock to the center. It would also have more contact
with the drilled out center. It would also allow me to have a small
reservoir of grease behind the bearing.

I really don't have a strong feeling for which approach will work out
better other than I dislike the time spent adjusting my tailstock back
in. I can leave the offset center setup for this taper indefinitely.
Ok, maybe I hope the ball bearing method will work out atleast as well.

The taper is pretty shallow. .157 over 10 inches.


Ball bearings have been used that way for a century or more.

You probably don't have any white lead. That's the traditional
lubricant for dead centers. I still have an ounce or so, and I use it.

HOWEVER, it's no damend good at high speeds. It was the standard
lubricant for centers when speeds were much lower.

--
Ed Huntress
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Default Turning a taper between offset centers


On 1/7/2018 12:44 PM, Ed Huntress wrote:
On Sun, 7 Jan 2018 12:25:04 -0700, Bob La Londe
wrote:

After much adieu over nothing I suppose (since at the moment I only have
one to do) I decided to turn a tapered mandrel between centers. The
first one turned out pretty good except I screwed up the finish pass(es)
and came in under sized. No I can't just shorten it up. So I still
have just one to do. LOL.

I picked up one of those little offsettable centers and it worked well
enough, except the tip melted. I kept it lubricated, but it might have
just been to high of an rpm for the method. I can turn it slower, but
if I get to do more of these I sure don't want to go slower.

I have two thoughts:

I can offset the tail stock and use a ball bearing center.

I can machine off the melted center, center drill it, and insert a ball
bearing between it and the center drill on that end of the stock. The
ball bearing certainly won't melt, and it will more evenly distribute
the load from the stock to the center. It would also have more contact
with the drilled out center. It would also allow me to have a small
reservoir of grease behind the bearing.

I really don't have a strong feeling for which approach will work out
better other than I dislike the time spent adjusting my tailstock back
in. I can leave the offset center setup for this taper indefinitely.
Ok, maybe I hope the ball bearing method will work out atleast as well.

The taper is pretty shallow. .157 over 10 inches.


Ball bearings have been used that way for a century or more.

You probably don't have any white lead. That's the traditional
lubricant for dead centers. I still have an ounce or so, and I use it.

HOWEVER, it's no damend good at high speeds. It was the standard
lubricant for centers when speeds were much lower.


I don't know what white lead is. I've got 99.5% pure (used for testing
molds before I ship them) and some hard alloy I mix in from time to time
for special applications.
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Default Turning a taper between offset centers

On Sun, 7 Jan 2018 13:36:26 -0700, Bob La Londe
wrote:


On 1/7/2018 12:44 PM, Ed Huntress wrote:
On Sun, 7 Jan 2018 12:25:04 -0700, Bob La Londe
wrote:

After much adieu over nothing I suppose (since at the moment I only have
one to do) I decided to turn a tapered mandrel between centers. The
first one turned out pretty good except I screwed up the finish pass(es)
and came in under sized. No I can't just shorten it up. So I still
have just one to do. LOL.

I picked up one of those little offsettable centers and it worked well
enough, except the tip melted. I kept it lubricated, but it might have
just been to high of an rpm for the method. I can turn it slower, but
if I get to do more of these I sure don't want to go slower.

I have two thoughts:

I can offset the tail stock and use a ball bearing center.

I can machine off the melted center, center drill it, and insert a ball
bearing between it and the center drill on that end of the stock. The
ball bearing certainly won't melt, and it will more evenly distribute
the load from the stock to the center. It would also have more contact
with the drilled out center. It would also allow me to have a small
reservoir of grease behind the bearing.

I really don't have a strong feeling for which approach will work out
better other than I dislike the time spent adjusting my tailstock back
in. I can leave the offset center setup for this taper indefinitely.
Ok, maybe I hope the ball bearing method will work out atleast as well.

The taper is pretty shallow. .157 over 10 inches.


Ball bearings have been used that way for a century or more.

You probably don't have any white lead. That's the traditional
lubricant for dead centers. I still have an ounce or so, and I use it.

HOWEVER, it's no damend good at high speeds. It was the standard
lubricant for centers when speeds were much lower.


I don't know what white lead is. I've got 99.5% pure (used for testing
molds before I ship them) and some hard alloy I mix in from time to time
for special applications.


It's lead carbonate. It's white powder. Red lead is lead oxide. Both
were used in paints before 1978. Both forms are highly toxic.

White lead mixed with litharge (metallic soap) or oil forms an
extreme-pressure lubricant. There are higher EP lubricants available
today, but the pasty version of white lead, sold for such uses as
lubricating tailstocks, will resist an extraordinary amount of
pressure without puncturing the lubricating film.

Not recommended today, because of the toxicity. Clowns used it for a
makeup base. They lost their minds and some died from it.

--
Ed Huntress


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Default Turning a taper between offset centers

On Sun, 7 Jan 2018 13:36:26 -0700, Bob La Londe
wrote:

snip

I don't know what white lead is. I've got 99.5% pure (used for testing
molds before I ship them) and some hard alloy I mix in from time to time
for special applications.


BTW, is you have a really old lathe, like my 1945 South Bend, you'll
have a little tapered brass plug that fits loosely into a hole in the
tailstock. There is a little pocket under the plug. That's for white
lead. The plug is a dauber to spread a dab of white lead on your dead
center.

--
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Default Turning a taper between offset centers

On 07/01/18 19:25, Bob La Londe wrote:
After much adieu over nothing I suppose (since at the moment I only
have one to do) I decided to turn a tapered mandrel between centers.
The first one turned out pretty good except I screwed up the finish
pass(es) and came in under sized.Â* No I can't just shorten it up.Â* So
I still have just one to do.Â* LOL.

I picked up one of those little offsettable centers and it worked well
enough, except the tip melted.Â* I kept it lubricated, but it might
have just been to high of an rpm for the method.Â* I can turn it
slower, but if I get to do more of these I sure don't want to go slower.

I have two thoughts:

I can offset the tail stock and use a ball bearing center.

I can machine off the melted center, center drill it, and insert a
ball bearing between it and the center drill on that end of the
stock.Â* The ball bearing certainly won't melt, and it will more evenly
distribute the load from the stock to the center.Â* It would also have
more contact with the drilled out center.Â* It would also allow me to
have a small reservoir of grease behind the bearing.

I really don't have a strong feeling for which approach will work out
better other than I dislike the time spent adjusting my tailstock back
in.Â* I can leave the offset center setup for this taper indefinitely.
Ok, maybe I hope the ball bearing method will work out atleast as well.

The taper is pretty shallow.Â* .157 over 10 inches.



Bob,

I think it was me that suggested those offsettable centres so shame the
centre melted. I think if it was me I would try and modify it to have a
rotating centre. Maybe you can fit a housing to the movable part to
support the outer races of a couple of ball races back to back and fit a
centre into those so you'll have a well supported rotating centre. I've
done similar before but not for a centre application but the application
is still going well, it was actually the rotating mass bearings for a
vibratory table, the housing was fixed to the vibrating table and the
centre shaft connected to the motor via a bit of flexible hose.

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Default Turning a taper between offset centers

On 1/7/2018 12:25 PM, Bob La Londe wrote:
After much adieu over nothing I suppose (since at the moment I only have
one to do) I decided to turn a tapered mandrel between centers.Â* The
first one turned out pretty good except I screwed up the finish pass(es)
and came in under sized.Â* No I can't just shorten it up.Â* So I still
have just one to do.Â* LOL.

I picked up one of those little offsettable centers and it worked well
enough, except the tip melted.Â* I kept it lubricated, but it might have
just been to high of an rpm for the method.Â* I can turn it slower, but
if I get to do more of these I sure don't want to go slower.

I have two thoughts:

I can offset the tail stock and use a ball bearing center.

I can machine off the melted center, center drill it, and insert a ball
bearing between it and the center drill on that end of the stock.Â* The
ball bearing certainly won't melt, and it will more evenly distribute
the load from the stock to the center.Â* It would also have more contact
with the drilled out center.Â* It would also allow me to have a small
reservoir of grease behind the bearing.

I really don't have a strong feeling for which approach will work out
better other than I dislike the time spent adjusting my tailstock back
in.Â* I can leave the offset center setup for this taper indefinitely.
Ok, maybe I hope the ball bearing method will work out atleast as well.

The taper is pretty shallow.Â* .157 over 10 inches.




So how much RPM do you think a ball bearing can take?

I thought I was turning at 300 RPM the first time, but it turns out I
was actually turning at 460. Oops. The only ball bearing I have that I
know is hard is one of the little bearings out of the ACBs I pulled out
of the Hurco mill. Its only about .20 so I know it doesn't have enough
mass to sink much heat.

~~~ time lapsed ~~~

I finished it at 115 RPM. Wow. Talk about slow. On the other hand it
looks really nice after three passes with the vertical shear and then
hand finishing with fine grit.

I did have the grease around the bearing start to smoke once so I let it
cool for a while and then used another bearing with fresh grease. In my
mind a larger bearing would have worked better, and taken longer to
overheat.

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Default Turning a taper between offset centers

On Sun, 7 Jan 2018 12:25:04 -0700, Bob La Londe
wrote:

After much adieu over nothing I suppose (since at the moment I only have
one to do) I decided to turn a tapered mandrel between centers. The
first one turned out pretty good except I screwed up the finish pass(es)
and came in under sized. No I can't just shorten it up. So I still
have just one to do. LOL.

I picked up one of those little offsettable centers and it worked well
enough, except the tip melted. I kept it lubricated, but it might have
just been to high of an rpm for the method. I can turn it slower, but
if I get to do more of these I sure don't want to go slower.

I have two thoughts:

I can offset the tail stock and use a ball bearing center.

I can machine off the melted center, center drill it, and insert a ball
bearing between it and the center drill on that end of the stock. The
ball bearing certainly won't melt, and it will more evenly distribute
the load from the stock to the center. It would also have more contact
with the drilled out center. It would also allow me to have a small
reservoir of grease behind the bearing.

I really don't have a strong feeling for which approach will work out
better other than I dislike the time spent adjusting my tailstock back
in. I can leave the offset center setup for this taper indefinitely.
Ok, maybe I hope the ball bearing method will work out atleast as well.

The taper is pretty shallow. .157 over 10 inches.


What grease are you using? White lithium isnt going to cut it on this
sort of job...just saying...

Red Lead or a really good axle grease...


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Default Turning a taper between offset centers

On 2018-01-07, David Billington wrote:
On 07/01/18 19:25, Bob La Londe wrote:
After much adieu over nothing I suppose (since at the moment I only
have one to do) I decided to turn a tapered mandrel between centers.
The first one turned out pretty good except I screwed up the finish
pass(es) and came in under sized.* No I can't just shorten it up.* So
I still have just one to do.* LOL.

I picked up one of those little offsettable centers and it worked well
enough, except the tip melted.* I kept it lubricated, but it might
have just been to high of an rpm for the method.* I can turn it
slower, but if I get to do more of these I sure don't want to go slower.


Bob,

I think it was me that suggested those offsettable centres so shame the
centre melted. I think if it was me I would try and modify it to have a
rotating centre. Maybe you can fit a housing to the movable part to
support the outer races of a couple of ball races back to back and fit a
centre into those so you'll have a well supported rotating centre. I've
done similar before but not for a centre application but the application
is still going well, it was actually the rotating mass bearings for a
vibratory table, the housing was fixed to the vibrating table and the
centre shaft connected to the motor via a bit of flexible hose.


If you make a set of ball races in a cup for the offsetable
center, I would suggest that you also make it tiltable towards the
center line too. You want the axis of rotation for the workpiece to be
parallel to the axis of rotation of the center. Otherwise, you get lots
of friction as the angle of the center changes in the drilled center in
the workpiece. And if the workpiece is a soft alumin(i)um, you will
wallow the center hole out as you work unless the axis of rotation of
the tailstock center matches that of the workpiece.

I think that the amount of angle change at the headstock center
would still be a problem, so inlay a ball in that center so it has
maximum contact with the drilled center in the workpiece. (The same
problem exists with the offset tailstock, too.) Even worse was the way
the Unimat SL-1000 (and DB-200) did it, where the headstock was pivoted,
so the angle of contact of the headstock center with the drilled center
hole was worse, since the headstock and the workpiece axes were in
opposite directions.

Good Luck,
DoN.

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Default Turning a taper between offset centers

On 1/7/2018 5:11 PM, Bob La Londe wrote:
On 1/7/2018 12:25 PM, Bob La Londe wrote:
After much adieu over nothing I suppose (since at the moment I only
have one to do) I decided to turn a tapered mandrel between centers.
The first one turned out pretty good except I screwed up the finish
pass(es) and came in under sized.Â* No I can't just shorten it up.Â* So
I still have just one to do.Â* LOL.

I picked up one of those little offsettable centers and it worked well
enough, except the tip melted.Â* I kept it lubricated, but it might
have just been to high of an rpm for the method.Â* I can turn it
slower, but if I get to do more of these I sure don't want to go slower.

I have two thoughts:

I can offset the tail stock and use a ball bearing center.

I can machine off the melted center, center drill it, and insert a
ball bearing between it and the center drill on that end of the
stock.Â* The ball bearing certainly won't melt, and it will more evenly
distribute the load from the stock to the center.Â* It would also have
more contact with the drilled out center.Â* It would also allow me to
have a small reservoir of grease behind the bearing.

I really don't have a strong feeling for which approach will work out
better other than I dislike the time spent adjusting my tailstock back
in.Â* I can leave the offset center setup for this taper indefinitely.
Ok, maybe I hope the ball bearing method will work out atleast as well.

The taper is pretty shallow.Â* .157 over 10 inches.




So how much RPM do you think a ball bearing can take?

I thought I was turning at 300 RPM the first time, but it turns out I
was actually turning at 460.Â* Oops.Â* The only ball bearing I have that I
know is hard is one of the little bearings out of the ACBs I pulled out
of the Hurco mill.Â* Its only about .20 so I know it doesn't have enough
mass to sink much heat.

~~~ time lapsed ~~~

I finished it at 115 RPM.Â* Wow.Â* Talk about slow.Â* On the other hand it
looks really nice after three passes with the vertical shear and then
hand finishing with fine grit.

I did have the grease around the bearing start to smoke once so I let it
cool for a while and then used another bearing with fresh grease.Â* In my
mind a larger bearing would have worked better, and taken longer to
overheat.


I used plane old waterproof wheel bearing grease, and it worked fine.
Not great, but fine for high pressure low RPM. I was going to try some
MolyKote BG-20, but I couldn't find my tube of the stuff. Of course
this morning when I walked into the shop... there it was on my desk.
Right where I thought it as. LOL.

I may buy a few carbide balls to keep in my lathe tool cart for future
projects, but like I said before. If find myself needing to do a bunch
of these I'm going with to make a linear rod taper attachment.

I've got some other tapers I want to make for myself down the road anyway.




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Default Turning a taper between offset centers

On Sun, 7 Jan 2018 17:11:03 -0700, Bob La Londe
wrote:

On 1/7/2018 12:25 PM, Bob La Londe wrote:
After much adieu over nothing I suppose (since at the moment I only have
one to do) I decided to turn a tapered mandrel between centers.* The
first one turned out pretty good except I screwed up the finish pass(es)
and came in under sized.* No I can't just shorten it up.* So I still
have just one to do.* LOL.

I picked up one of those little offsettable centers and it worked well
enough, except the tip melted.* I kept it lubricated, but it might have
just been to high of an rpm for the method.* I can turn it slower, but
if I get to do more of these I sure don't want to go slower.

I have two thoughts:

I can offset the tail stock and use a ball bearing center.

I can machine off the melted center, center drill it, and insert a ball
bearing between it and the center drill on that end of the stock.* The
ball bearing certainly won't melt, and it will more evenly distribute
the load from the stock to the center.* It would also have more contact
with the drilled out center.* It would also allow me to have a small
reservoir of grease behind the bearing.

I really don't have a strong feeling for which approach will work out
better other than I dislike the time spent adjusting my tailstock back
in.* I can leave the offset center setup for this taper indefinitely.
Ok, maybe I hope the ball bearing method will work out atleast as well.

The taper is pretty shallow.* .157 over 10 inches.




So how much RPM do you think a ball bearing can take?

I thought I was turning at 300 RPM the first time, but it turns out I
was actually turning at 460. Oops. The only ball bearing I have that I
know is hard is one of the little bearings out of the ACBs I pulled out
of the Hurco mill. Its only about .20 so I know it doesn't have enough
mass to sink much heat.

~~~ time lapsed ~~~

I finished it at 115 RPM. Wow. Talk about slow. On the other hand it
looks really nice after three passes with the vertical shear and then
hand finishing with fine grit.

I did have the grease around the bearing start to smoke once so I let it
cool for a while and then used another bearing with fresh grease. In my
mind a larger bearing would have worked better, and taken longer to
overheat.

I'm glad you got it done Bob. I used to do lots of between centers
work. Dead centers for some of it. Ball centers too. When I used a
ball center I would usually first use a same size ball and a hammer to
form a depression in the drilled center to fit the ball. This results
in more surface area for the lube and lowers the pressure per area. So
less heat is generated. When needing to turn the work at relatively
high rpm with dead centers I would lube the center and leave it a
little loose. Then spin up the lathe and let the part warm up. And
check the tightness of the center in the part during the warm up. And
once machining commences the center tightness needs to be checked on a
regular basis. This all done by feel but it doesn't take too long to
learn. I tried all sorts of high pressure lubes and mixed some of my
own.
Eric
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Default Turning a taper between offset centers

On 1/7/2018 2:47 PM, David Billington wrote:
On 07/01/18 19:25, Bob La Londe wrote:
After much adieu over nothing I suppose (since at the moment I only
have one to do) I decided to turn a tapered mandrel between centers.
The first one turned out pretty good except I screwed up the finish
pass(es) and came in under sized. No I can't just shorten it up. So
I still have just one to do. LOL.

I picked up one of those little offsettable centers and it worked well
enough, except the tip melted. I kept it lubricated, but it might
have just been to high of an rpm for the method. I can turn it
slower, but if I get to do more of these I sure don't want to go slower.

I have two thoughts:

I can offset the tail stock and use a ball bearing center.

I can machine off the melted center, center drill it, and insert a
ball bearing between it and the center drill on that end of the
stock. The ball bearing certainly won't melt, and it will more evenly
distribute the load from the stock to the center. It would also have
more contact with the drilled out center. It would also allow me to
have a small reservoir of grease behind the bearing.

I really don't have a strong feeling for which approach will work out
better other than I dislike the time spent adjusting my tailstock back
in. I can leave the offset center setup for this taper indefinitely.
Ok, maybe I hope the ball bearing method will work out atleast as well.

The taper is pretty shallow. .157 over 10 inches.



Bob,

I think it was me that suggested those offsettable centres so shame the
centre melted. I think if it was me I would try and modify it to have a
rotating centre. Maybe you can fit a housing to the movable part to
support the outer races of a couple of ball races back to back and fit a
centre into those so you'll have a well supported rotating centre. I've
done similar before but not for a centre application but the application
is still going well, it was actually the rotating mass bearings for a
vibratory table, the housing was fixed to the vibrating table and the
centre shaft connected to the motor via a bit of flexible hose.


Its ok. They atleast paid lip service to it needing to be hard. Based
on how it machines it was case hardened. Very hard start, and then
right through for a pretty face. Its a neat idea, but the boring head
might have been better. The offset center tool is really wide for what
it is and you have to use longer than ideal tool stick out from the tool
post. I have no hard feelings about it. I learned quite a bit in a
very short time by using it.

I socketed the center for a ball bearing and got the job done using some
waterproof wheel bearing grease. I may never use it again, but then...
I might. LOL. I've mentioned two or three times now. If I have to
turn a lot of tapers I'm going to invest a day into making a proper
linear rod taper attachment.

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Default Turning a taper between offset centers


On 1/7/2018 9:09 PM, Gunner Asch wrote:
On Sun, 7 Jan 2018 12:25:04 -0700, Bob La Londe
wrote:

After much adieu over nothing I suppose (since at the moment I only have
one to do) I decided to turn a tapered mandrel between centers. The
first one turned out pretty good except I screwed up the finish pass(es)
and came in under sized. No I can't just shorten it up. So I still
have just one to do. LOL.

I picked up one of those little offsettable centers and it worked well
enough, except the tip melted. I kept it lubricated, but it might have
just been to high of an rpm for the method. I can turn it slower, but
if I get to do more of these I sure don't want to go slower.

I have two thoughts:

I can offset the tail stock and use a ball bearing center.

I can machine off the melted center, center drill it, and insert a ball
bearing between it and the center drill on that end of the stock. The
ball bearing certainly won't melt, and it will more evenly distribute
the load from the stock to the center. It would also have more contact
with the drilled out center. It would also allow me to have a small
reservoir of grease behind the bearing.

I really don't have a strong feeling for which approach will work out
better other than I dislike the time spent adjusting my tailstock back
in. I can leave the offset center setup for this taper indefinitely.
Ok, maybe I hope the ball bearing method will work out atleast as well.

The taper is pretty shallow. .157 over 10 inches.


What grease are you using? White lithium isnt going to cut it on this
sort of job...just saying...

Red Lead or a really good axle grease...


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At 115 RPM plane old waterproof wheel bearing grease worked ok. The job
took a couple hours at that speed, but the bearing didn't start to get
really hot until about 3/4 of the way through the job. I replaced the
bearing and the grease and finished the job. It was pretty frustrating
to go so slow. This was a 416 stainless shaft, and it will actually
machine much faster.

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Default Turning a taper between offset centers

On 2018-01-08, Bob La Londe wrote:

On 1/7/2018 9:09 PM, Gunner Asch wrote:
On Sun, 7 Jan 2018 12:25:04 -0700, Bob La Londe
wrote:

After much adieu over nothing I suppose (since at the moment I only have
one to do) I decided to turn a tapered mandrel between centers. The
first one turned out pretty good except I screwed up the finish pass(es)
and came in under sized. No I can't just shorten it up. So I still
have just one to do. LOL.


[ ... ]

The taper is pretty shallow. .157 over 10 inches.


What grease are you using? White lithium isnt going to cut it on this
sort of job...just saying...

Red Lead or a really good axle grease...


[ ... ]

At 115 RPM plane old waterproof wheel bearing grease worked ok. The job
took a couple hours at that speed, but the bearing didn't start to get
really hot until about 3/4 of the way through the job. I replaced the
bearing and the grease and finished the job. It was pretty frustrating
to go so slow. This was a 416 stainless shaft, and it will actually
machine much faster.


One problem with turning between centers is that the workpiece
length increases as it heats up. A setting which is right at the start
of the job can be too tight part way along.

If you can make the center both a ball bearing mounted center,
and spring loaded to keep about the same pressure throughout the job,
you probably won't get the overheating you've observed, and maybe can
run faster, too.

Such centers are made for cylindrical grinding (where the
workpiece is more likely to heat up and seize if the spring loading is
not provided. Of course, these centers are likely not made for offset
turning -- though there may be some for grinding tapers like Morse Taper
shanks.

Enjoy,
DoN.

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