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CJ0618 lead screw

 

When I purchased my mini lathe (about 5yrs ago) it was advertised as having a 16tpi lead screw. I recently decided to check and noticed that is not the case. It is actually the 1.5mm pitch leadscrew instead. 
 
I am considering purchasing a 16tpi replacement along with new half nuts. I found the items on Arc Eurotrade. However, the shipping to the US is a bit expensive. I haven't been able to find these items on Amazon. eBay and AliExpress have the metric version but I cannot find imperial versions. Little Machine Shop has lead screws for Sieg 7x14 lathes, but I believe there are some differences that may cause problems.
 
Has anyone else made this swap or have suggestions as to where I should look for these items.
 
Thanks in advance. 
 

The CJ0618 is a Real bull lathe. If I remember right (don't quote me 100%) the Grizzly 7X mini is also. Take a look there. It's easy enough to tell a Sieg from a RB by the cross slide. The RB has the solid rectangular slide and the Seig has the "H" shaped one. Shipping from Arc is a bit expensive across the pond but in my experience they are very good to deal with so there's that. 
On Oct 17, 2024 at 5:36 PM -0400, thomasfkeefe@... <thomasfkeefe@...>, wrote:

When I purchased my mini lathe (about 5yrs ago) it was advertised as having a 16tpi lead screw. I recently decided to check and noticed that is not the case. It is actually the 1.5mm pitch leadscrew instead. 
 
I am considering purchasing a 16tpi replacement along with new half nuts. I found the items on Arc Eurotrade. However, the shipping to the US is a bit expensive. I haven't been able to find these items on Amazon. eBay and AliExpress have the metric version but I cannot find imperial versions. Little Machine Shop has lead screws for Sieg 7x14 lathes, but I believe there are some differences that may cause problems.
 
Has anyone else made this swap or have suggestions as to where I should look for these items.
 
Thanks in advance. 
 

Why are you considering replacing the lead screw?
 
There are numerous sites that provide comprehensive threading charts for either flavor lead screw; with 3-D printing, additional change gears are easily obtainable.  Actually, if you had access to an engine lathe, you could even make your own leadscrew ;-)
 
Roy
 

My Real Bull came fitted with a metric leadscrew, and for some reason had the imperial one as well.

 

I’ve never had to use the imperial one, but shipping (I’m in Oz) would be a bit steep.

 

Tony

 

 

From: 7x12MiniLathe@groups.io <7x12MiniLathe@groups.io> On Behalf Of Ryan H via groups.io
Sent: Friday, 18 October 2024 11:34 AM
To: 7x12minilathe@groups.io
Subject: Re: [7x12MiniLathe] CJ0618 lead screw

 

The CJ0618 is a Real bull lathe. If I remember right (don't quote me 100%) the Grizzly 7X mini is also. Take a look there. It's easy enough to tell a Sieg from a RB by the cross slide. The RB has the solid rectangular slide and the Seig has the "H" shaped one. Shipping from Arc is a bit expensive across the pond but in my experience they are very good to deal with so there's that. 

On Oct 17, 2024 at 5:36 PM -0400, thomasfkeefe@... <thomasfkeefe@...>, wrote:

When I purchased my mini lathe (about 5yrs ago) it was advertised as having a 16tpi lead screw. I recently decided to check and noticed that is not the case. It is actually the 1.5mm pitch leadscrew instead. 

 

I am considering purchasing a 16tpi replacement along with new half nuts. I found the items on Arc Eurotrade. However, the shipping to the US is a bit expensive. I haven't been able to find these items on Amazon. eBay and AliExpress have the metric version but I cannot find imperial versions. Little Machine Shop has lead screws for Sieg 7x14 lathes, but I believe there are some differences that may cause problems.

 

Has anyone else made this swap or have suggestions as to where I should look for these items.

 

Thanks in advance. 
 

Hi Thomas,

If you want to replace a metric lead screw by an imperial one, the pinion sets, as per the threading table of your lathe, will need to be modified. This is mandatory because there are no common divider in between millimeters and inches. So,

- either you recompute each pinion set for each pitch with the existing pinions, making the compromise to have some close approximations,
- or you'll have to buy pinions compatible with the imperial pitches you intend to make. In your case, the existing pinions are more likely metric in diameter and module. Imperial pinions are imperial (!), their teeth are measured in inches, and the metric 'module' is expressed in terms of 'diametral pitch' that is a different unit. The module is equal to the primitive diameter in mm divided by the number of teeth hence a module of 1 corresponds to a tooth-to-tooth distance of 3.14mm measured on the primitive diameter. The diametral pitch is equal to the number of teeth divided by the primitive diameter in inches. Both Module and Diametral Pitch have no unit.

Equivalence table (the circular pitch corresponds to the distance between 2 teeth, measured on the primitive diameter, here in mm. No practical use, just an indication) :

Of course, metric gears are not compatible with imperial pinions, even with the same tooth number or same diameter.

In addition, make sure  before ordering that you have room to mount the pinions on the existing bracket.

Just a remark: It seems that you didn't make threading for 5 years, otherwise you had already discovered the issue, do you absolutely need to make the transition to imperial ? The character of this transition does only apply to threading, unless you have specific accessories TBD on your lathe. In consequence, if you don't thread on the lathe and if the lead screw and/or half nuts aren't damaged, keep the current configuration !

Regards


On 17.10.24 23:36, thomasfkeefe via groups.io wrote:

When I purchased my mini lathe (about 5yrs ago) it was advertised as having a 16tpi lead screw. I recently decided to check and noticed that is not the case. It is actually the 1.5mm pitch leadscrew instead. 
 
I am considering purchasing a 16tpi replacement along with new half nuts. I found the items on Arc Eurotrade. However, the shipping to the US is a bit expensive. I haven't been able to find these items on Amazon. eBay and AliExpress have the metric version but I cannot find imperial versions. Little Machine Shop has lead screws for Sieg 7x14 lathes, but I believe there are some differences that may cause problems.
 

Grizzly has them for their 7x14 which is like the Real Bull. The part number is P0765129 and lists for $53.50. You would also need to change the half nuts. The part number is P0765075 and lists for $33.90 for the pair. I would check with them to make sure they fit your brand of lathe. Paul M
 

Roy, I am still considering my options and may decide it's not worth switching.
 
Tom
 

Tony Smith, I suspect you are right about shipping. But I will keep that in mind. Thanks.
 
Tom
 

Wasn't thinking about that but st a minimum I'm pretty sure you're going to have to swap the half nut actuator shaft and maybe the apron. The nuts use a different engagement to the shaft and I don't know if the shaft will fit the Seig apron. 

I went with a electric lead screw a couple years ago. Back then it cost me a bit over 500 dollars for everything but has been great. I push buttons and can change from imperial threading to metric in seconds and also do feed in both. 

For me it was worth every penny as I do quite a bit of both imperial and metric single point threading. 
On Oct 18, 2024 at 12:44 PM -0400, thomasfkeefe@... <thomasfkeefe@...>, wrote:

Tony Smith, I suspect you are right about shipping. But I will keep that in mind. Thanks.
 
Tom
 

With my metric lathe I got the imperial 16 TPI leadscrew and half nuts, I don’t recall getting a spare apron so I don’t think that’s a problem.

 

I’ve only had to cut a few imperial threads, nothing exotic just ¼” or ½” or whatever, and used the LMS calculator: https://www.littlemachineshop.com/Reference/change_gears.php to set up the gears.  Came out close enough for my needs.

 

IIRC cutting metric on an imperial lathe is harder.

 

Of course with computer control the problem just goes away no matter what you have.

 

Tony

 

 

From: 7x12MiniLathe@groups.io <7x12MiniLathe@groups.io> On Behalf Of Ryan H via groups.io
Sent: Saturday, 19 October 2024 4:07 AM
To: 7x12minilathe@groups.io
Subject: Re: [7x12MiniLathe] CJ0618 lead screw

 

Wasn't thinking about that but st a minimum I'm pretty sure you're going to have to swap the half nut actuator shaft and maybe the apron. The nuts use a different engagement to the shaft and I don't know if the shaft will fit the Seig apron. 

I went with a electric lead screw a couple years ago. Back then it cost me a bit over 500 dollars for everything but has been great. I push buttons and can change from imperial threading to metric in seconds and also do feed in both. 

For me it was worth every penny as I do quite a bit of both imperial and metric single point threading. 

On Oct 18, 2024 at 12:44 PM -0400, thomasfkeefe@... <thomasfkeefe@...>, wrote:

Tony Smith, I suspect you are right about shipping. But I will keep that in mind. Thanks.

 

Tom
 

Pierre, I believe both versions of the lathe use module 1 gears. And I think they are sold with same set of nylon gears. But I could be wrong about that. 
 
I have done some single point threading on the lathe. As the difference in pitch between 16tpi and 1.5 mm is pretty small, I never really noticed. Many times I threaded things I didn't have a tap or die for. So I would end up doing both sides. But I am kind of embarrassed to discover it after such a long time.
 
Tom
 

I still have my 20-year-old mini lathe and it is just fine the way it came.
Regards,
John Mattis (retired mechanical engineer)

On Fri, Oct 18, 2024 at 9:35 AM thomasfkeefe via groups.io <thomasfkeefe=gmail.com@groups.io> wrote:
Roy, I am still considering my options and may decide it's not worth switching.
 
Tom
 

The problem with cutting threads of a system different from the lead screw is that the gears can't be disengaged & re-engaged in the same position. You have to keep them engaged the whole time and retract the tool when returning the carriage for another cutting pass. With a hand crank for more low speed torque, a power return can be a little exciting ;-)
 
Roy
 

I have a handwheel not a crank so it no problem with power reverse. 
I have cut many threads this way. 

On Fri, Oct 18, 2024 at 4:49 PM Roy via groups.io <roylowenthal=yahoo.com@groups.io> wrote:
The problem with cutting threads of a system different from the lead screw is that the gears can't be disengaged & re-engaged in the same position. You have to keep them engaged the whole time and retract the tool when returning the carriage for another cutting pass. With a hand crank for more low speed torque, a power return can be a little exciting ;-)
 
Roy
 

Contact LittleMachineShop and see what they say instead of relying on just the website.  They do know a thing or two.
 
 

The I purchased last came with metric lead screw 2.00mm 
 
I do most time both inch and metric with dies. 
 
If doing projects that needs both inside and outside threads I just 2.00, 1.00 or 0.50 mm pictures.  I do not use a thread dial. 
 
It is easier to metric pitch 
When I was doing machine work I did not have choice 
 
Dave 
 
On Fri, Oct 18, 2024 at 09:35 AM, @ThomasKeefe wrote:

Roy, I am still considering my options and may decide it's not worth switching.
 
Tom
 

I decided to go ahead and get an imperial lead screw for my lathe.
I looked around and could not find the imperial leadscrew for a cj0618 on AliExpress or Ebay.
Only the 1.5mm screw was available. However, I did find the 16TPI screw and half nuts on Grizzly's 
site. The price was pretty good (about $86 US) and it shipped for free. I will be getting that in
a few days. 
 
Thank you all for your suggestions and comments.
 
Tom

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