|
Posted by on May 10, 2006, 5:08 pm
Please log in for more thread options
Hello,
First of all, I have an Acra (now Enco?) 9x20 Chinese bench lathe. This
lathe was given to me by a friend a few weeks ago and it didn't get
much use at all from him.
For some reason the thread cutting system seems way off. When I cut one
pass (say 16tpi) and measure the light cut with my thread guage, I'm
getting closer to a 17tpi cut. When I try to do a 26 tpi pass I get
closer to a 28tpi cut. I've checked and rechecked all of the gear
combinations listed on the chart and the are correct.
Additionally, when I try to use the thread chasing dial, I can never
get the same cutting pass. For example, I'll use strictly the number 1
on the dial and my second cutting pass will be right in between the
first cutting pass. I'll try it for a third pass and I'll get a whole
different cutting pass.
This is really frusterating! Has anybody ever heard of this before? I
was actually impressed with the quality of this Chinese manufacturing,
but now I'm beginning to wonder...
If pictures would help at all I'd be glad to take a few and post them.
Thank you very much,
Carter
|
|
Posted by Randy Replogle on May 10, 2006, 5:48 pm
Please log in for more thread options
CarterJC12@gmail.com wrote:
> Hello,
>
> First of all, I have an Acra (now Enco?) 9x20 Chinese bench lathe. This
> lathe was given to me by a friend a few weeks ago and it didn't get
> much use at all from him.
>
> For some reason the thread cutting system seems way off. When I cut one
> pass (say 16tpi) and measure the light cut with my thread guage, I'm
> getting closer to a 17tpi cut. When I try to do a 26 tpi pass I get
> closer to a 28tpi cut. I've checked and rechecked all of the gear
> combinations listed on the chart and the are correct.
>
> Additionally, when I try to use the thread chasing dial, I can never
> get the same cutting pass. For example, I'll use strictly the number 1
> on the dial and my second cutting pass will be right in between the
> first cutting pass. I'll try it for a third pass and I'll get a whole
> different cutting pass.
>
> This is really frusterating! Has anybody ever heard of this before? I
> was actually impressed with the quality of this Chinese manufacturing,
> but now I'm beginning to wonder...
>
> If pictures would help at all I'd be glad to take a few and post them.
>
> Thank you very much,
> Carter
>
Are you counting the "first" thread as one instead of zero? That would
give you one too many threads.
Randy
|
|
Posted by d.dixson on May 10, 2006, 6:46 pm
Please log in for more thread options
CarterJC12@gmail.com wrote:
> Hello,
>
> First of all, I have an Acra (now Enco?) 9x20 Chinese bench lathe. This
> lathe was given to me by a friend a few weeks ago and it didn't get
> much use at all from him.
>
> For some reason the thread cutting system seems way off. When I cut one
> pass (say 16tpi) and measure the light cut with my thread guage, I'm
> getting closer to a 17tpi cut. When I try to do a 26 tpi pass I get
> closer to a 28tpi cut. I've checked and rechecked all of the gear
> combinations listed on the chart and the are correct.
>
> Additionally, when I try to use the thread chasing dial, I can never
> get the same cutting pass. For example, I'll use strictly the number 1
> on the dial and my second cutting pass will be right in between the
> first cutting pass. I'll try it for a third pass and I'll get a whole
> different cutting pass.
>
> This is really frusterating! Has anybody ever heard of this before? I
> was actually impressed with the quality of this Chinese manufacturing,
> but now I'm beginning to wonder...
>
> If pictures would help at all I'd be glad to take a few and post them.
>
> Thank you very much,
> Carter
I wonder if you have a metric cut lead screw. I would recommend that
you measure the pitch to see if it is cut in inches or millimeters.
That would explain why you cannot pick up the lead on your second cut
using the chasing dial. It may also explain why your threads are off in
that the gearing/lead screw combination may only allow an approximation
of the desired thread. HTH
|
|
Posted by Ken Davey on May 10, 2006, 7:49 pm
Please log in for more thread options d.dixson wrote:
> CarterJC12@gmail.com wrote:
>> Hello,
>>
>> First of all, I have an Acra (now Enco?) 9x20 Chinese bench lathe.
>> This lathe was given to me by a friend a few weeks ago and it didn't
>> get much use at all from him.
>>
>> For some reason the thread cutting system seems way off. When I cut
>> one pass (say 16tpi) and measure the light cut with my thread guage,
>> I'm getting closer to a 17tpi cut. When I try to do a 26 tpi pass I
>> get closer to a 28tpi cut. I've checked and rechecked all of the gear
>> combinations listed on the chart and the are correct.
>>
>> Additionally, when I try to use the thread chasing dial, I can never
>> get the same cutting pass. For example, I'll use strictly the number
>> 1 on the dial and my second cutting pass will be right in between the
>> first cutting pass. I'll try it for a third pass and I'll get a whole
>> different cutting pass.
>>
>> This is really frusterating! Has anybody ever heard of this before? I
>> was actually impressed with the quality of this Chinese
>> manufacturing, but now I'm beginning to wonder...
>>
>> If pictures would help at all I'd be glad to take a few and post
>> them.
>>
>> Thank you very much,
>> Carter
>
Are you driving through the half-nuts or incorrectly using the longditudinal
clutch?
--
Volunteer your idle computer time for cancer research
http//www.grid.org/download/gold/download.htm
Return address courtesy of Spammotel http://www.spammotel.com/
|
|
Posted by Eric R Snow on May 10, 2006, 8:02 pm
Please log in for more thread options On 10 May 2006 14:08:37 -0700, CarterJC12@gmail.com wrote:
>Hello,
>
>First of all, I have an Acra (now Enco?) 9x20 Chinese bench lathe. This
>lathe was given to me by a friend a few weeks ago and it didn't get
>much use at all from him.
>
>For some reason the thread cutting system seems way off. When I cut one
>pass (say 16tpi) and measure the light cut with my thread guage, I'm
>getting closer to a 17tpi cut. When I try to do a 26 tpi pass I get
>closer to a 28tpi cut. I've checked and rechecked all of the gear
>combinations listed on the chart and the are correct.
>
>Additionally, when I try to use the thread chasing dial, I can never
>get the same cutting pass. For example, I'll use strictly the number 1
>on the dial and my second cutting pass will be right in between the
>first cutting pass. I'll try it for a third pass and I'll get a whole
>different cutting pass.
>
>This is really frusterating! Has anybody ever heard of this before? I
>was actually impressed with the quality of this Chinese manufacturing,
>but now I'm beginning to wonder...
>
>If pictures would help at all I'd be glad to take a few and post them.
>
>Thank you very much,
>Carter
Greetings Carter,
It sounds like it may have a metric leadscrew. Another thing to check
when looking at the gears is to see if paired gears are used and if so
maybe one of the gears is on the shaft the wrong way. What I mean is
this: the lathe may have a 120 tooth gear paired with a 127 tooth
gear. These gears will be on the same shaft and both gears will be
keyed to the shaft so they rotate together. There should be a gear
driving the 120 tooth gear and the 120 tooth gear should drive another
in turn. So the 120 tooth gear is acting as an idler. OR, it could be
the 127 tooth gear that is acting as the idler. But if the lathe has
an inch leadscrew and you want to cut metric threads then one gear
will drive the 127 tooth gear, which spins the 120 tooth gear, which
drives another gear. This is how the metric conversion is done. Also,
when cutting metric threads using this method you must keep the half
nut closed until all threading passes have been made. This means that
at the end of the cut you must withdraw the tool and stop the lathe at
the same time. Then with the tool clear of the part, reverse the
spindle to back the tool up, then so on and so forth. If your machine
is equipped with a metric leadscrew and the gears are set up for
cutting inch threads then the same thing happens. By the way, when you
figure out what is really going on please let us know.
Eric
|
| Similar Threads | Posted | | Cutting oil v. thread cutting oil - difference? | July 4, 2008, 8:45 pm |
| Re: Cutting oil v. thread cutting oil - difference? | July 9, 2008, 9:05 pm |
| Cutting 1"-8 thread | November 10, 2008, 9:36 pm |
| Lathe Thread Cutting Question | June 22, 2007, 2:33 am |
| Thread cutting on a reversible lathe | July 10, 2008, 10:44 am |
| Buying thread cutting taps dies and best type of tool steel to use???? | February 20, 2008, 4:29 pm |
| Re: Another 4-start thread question - 1/4" internal thread | April 2, 2006, 5:25 pm |
| class of thread fit on studs and all-thread | January 23, 2007, 10:18 am |
| Thread help | September 29, 2006, 10:20 am |
| What Thread...THANKS | November 7, 2006, 4:48 am |
|
|
Yahoo! 
Google 
Windows Live 
del.icio.us 
digg 
Netscape 
XML Sitemap
>
> First of all, I have an Acra (now Enco?) 9x20 Chinese bench lathe. This
> lathe was given to me by a friend a few weeks ago and it didn't get
> much use at all from him.
>
> For some reason the thread cutting system seems way off. When I cut one
> pass (say 16tpi) and measure the light cut with my thread guage, I'm
> getting closer to a 17tpi cut. When I try to do a 26 tpi pass I get
> closer to a 28tpi cut. I've checked and rechecked all of the gear
> combinations listed on the chart and the are correct.
>
> Additionally, when I try to use the thread chasing dial, I can never
> get the same cutting pass. For example, I'll use strictly the number 1
> on the dial and my second cutting pass will be right in between the
> first cutting pass. I'll try it for a third pass and I'll get a whole
> different cutting pass.
>
> This is really frusterating! Has anybody ever heard of this before? I
> was actually impressed with the quality of this Chinese manufacturing,
> but now I'm beginning to wonder...
>
> If pictures would help at all I'd be glad to take a few and post them.
>
> Thank you very much,
> Carter
>