Nick,
Yup this is pretty vexing 20 thou of taper is a lot. What is the lenght
of the piece the taper is over. Did you do the facing cut with the
compound screw or the cross slide screw?
Do you have a nice long piece of drill rod 1/2" x 8 or better? If so
chuck it in the 3 jaw and with a dial indicator mounted on the
carriage and touching the front side of the rod, does it turn close to
true? By resetting it in the chuck by slowly turning it while you
tighten the jaws you should be able to get it to less than .003" out of
round. Now slowly move the carriage to the tailstock end. Which
way does the dial indicator move and by how much? Now rotate the
chuck and how much out of round does it indicate?
I can see the taper being different depending on how you chuck
the stock, but all the same?????? When making the cut how did
you move the cutter? With the compound screw, the carriage
handwheel or use the power feed from lead screw?
Did you check the alignment of the centers by putting centers in
both head and tail stocks then move the tail stock up to the head
stock and then gently pich a piec of 5 thou feeler stock or similar
between the points of the centers. The shim should hang vertically
between the centers and be at right angles to the bed. Any twist or
lean indicates the centers aren't centered. A left lean is the tailstock
is high, a right lean is the tailstock is low. etc.
.
Bob
On 11 Dec 2002, at 9:54, Nick DeFeo wrote:
Roy:
The spindle shows fore/aft of .0005" difference. There is basically no runout of the face of the spindle when in motion. All gibs for the carriage, compound, and cross slide are adjusted with minimal play. I have not locked down the gibs on the compound/cross slide when taking these facing
cuts. Taking a face cut at the hs, shows no concave/convex, which leads me to believe the hs/compound alignment is true. This lathe cuts a .020" taper from the ts to the hs, no matter the method of securing the stock; 3 jaw, unsupported at ts, 3 jaw, live center at ts, dead center, live center at
ts. Pretty vexing situation. I have spent considerable effort and material in an attempt to get the lathe fairly accurate, and am convinced that it is time to swap this unit with a replacement. Perhaps there is something minor I am overlooking? Any thoughts would be greatly appreciated. Nick
"roylowenthal <roylowenthal@...>" <roylowenthal@...> wrote: What does a cross slide mounted indicator show when the front &
rear of the spindle are checked? It sounds like the HS is not
parallel to the ways, easiest measurement is spindle parallelism to
cross slide.
How much spindle run out is there?
Have you tried a test cut with the cross & compound gibs locked
down? Your chatter complaint makes me suspect one or both of them
may be moving during a cut.
Quick check for bed mounting distortion is to loosen the bolts &
try to rock the lathe; if it rocks, use feeler gauges or indicator to
determine the shim thickness for the non-contacting foot.
Roy
--- In 7x12minilathe@..., Nick DeFeo <ntdefeo@y...> wrote:
Good Morning Bob:
Here is what I have so far: Stock is 3/4" 12L14, HSS 3/8"
cutting tool - sharpened & honed, 3 jaw on hs and live center in ts.
With stock either chucked or supported by ts, I have indicated top
and rear of stock and corrected alignment using shims between the bed
and bench. Bolts are snug, but not tight to permit adjustment if
required. Whether the stock is held with just the 3 jaw, or supported
with the ts, the lathe still cuts a taper towards the hs in the
neighborhood of .02". I am using a Starret square base to level the
unit fore/aft and side to side. All readings using the level are dead
center, with no parallax error (all readings taken from top dead
looking down at the vial). Should I invest in a more precise level to
ensure these reading are true? I have checked for alignment at the
hs, center of the bed and ts areas. While it has been several years
since I have used a lathe, am I overlooking something minor here? All
carriage and compound gibs are properly adjusted and lubricated.
While cutting, I have used several fluids with the same results:
WD40, 10W oil with STP, and even kerosene. Are these lathes that far
out of alignment from the factory, or is this due to
shipping/handling? There was no damage to the carton or the lathe
when received, and I wonder if this unit should be returned for a new
one. While I am not opposed to making corrections/adjustments to get
acceptable results, this has been quite perplexing, to say the least.
Best regards, Nick
Bob Sunley <rosunley@s...> wrote:Check list time:
What are you cutting, type of metal/plastic, diameter and length.
How is it chucked, 3 jaw, 4jaw, between centers or combination.
Type of cutter, hss, carbide, a u-grind or factory insert.
Speed setting, power or manual feed.
Chattering and cutting tapers are two totally different problems.
Which do you want to fix first.
Cutting tapers can indicate a warped bed or tailstock not set
properly depending on how you are holding the workpiece.
which way is the taper?
Chattering can be any number of problems, wrong/no cutting lube,
wrong feed rate, tool height set wrong, wrong type of tool, too
fine a
cut, too agressive a cut, assorted gibs not adjusted properly, etc.
etc, etc.
Solidly mounting the lathe can cause tapered cuts as well if it
warps
the lathe bed
Need lots more info on exactly what you are doing.
Bob
On 9 Dec 2002, at 21:23, ntdefeo ntdefeo@y... wrote:
After setting and checking my Homier 7X12 lathe 9 ways to sunday,
I
am still turning tapers! As carriage is advancing towards the hs
assembly, the hs cutting tool starts to chatter, no matter what
adjustments are made. Is it possible that the bed it bowed/warped
in
such a manner that this machine should just be returned for a new
unit? I have never run up against such a perplexing problem. All
adjustments have been checked and rechecked for accuracy. Unit is
solidly mounted on a bench. Has anyone else run across this
problem?
Any comments? suggestions? short of heaving it into the trash?
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