Shop Floor Talk  

Go Back   Shop Floor Talk > Welding and Metalworking Forums > Machining

SFT Search:   
Reply
 
Thread Tools Display Modes
  #11  
Old 01-30-2021, 08:26 PM
ShawnR ShawnR is offline
Member
 
Join Date: Apr 2013
Location: Ontario, Canada
Posts: 60
Default Craftex B2227L

Quote:
Originally Posted by Scotts View Post
If there is a cover on the left I would open up and see if there is a key missing from the gear train on the lead screw or one of the other drive gears.

The lead screw should be timed to the chuck if you are using the same number on the thread dial and the threads are doing what you show in the pictures yo must have something slipping to cause this

Scott

What is make and model of lathe?


Sent from my iPhone using ShopFloorTalk mobile app
Craftex B2227L

I started looking into the gears yesterday to get started at cutting threads. I had all the gears off at sometime but am pretty sure they all went back on with keys in place cause they are all a pita to get installed...snug fit on shafts. I will check again tomorrow to try to ensure it all went back together correctly. I switched gears, for pitch, a few times today and double checked gears meshing correctly. The more time I spend in there, I am getting more comfortable. I have always avoided learning to use the machine for threading because of the gears but finally tackled it....so now don't know if it ever really worked well at it. I will go post the problem on the home shop machinist forum. I know that some members there have the same lathe because I have seen questions posted about it. The manual is attached

I have noted that the gear chart on the front of the machine is different than the one in the manual. Today I was going by the one on the machine but maybe it is wrong? I would have said that the chances are better that that would be the correct one. I will mess around more tomorrow.

Thanks for the input.
Attached Files
File Type: pdf B2227L.pdf (4.67 MB, 19 views)
Reply With Quote
  #12  
Old 01-30-2021, 08:55 PM
ShawnR ShawnR is offline
Member
 
Join Date: Apr 2013
Location: Ontario, Canada
Posts: 60
Default

Quote:
Originally Posted by camdigger View Post
So, forgive me, but are you cutting the same system pitch as your lead screw? Even if you can get the right pitch through gearing, an imperial (inch) lead screw will not reliably sync up with a metric thread using the threading dial ( and vice versa). This is due to the odd gearing needed for the pitch.

The job can still be done, but the lathe will have to be stopped at the end of the thread and reversed to clear the work far enough that all backlash will be taken up before the Tool starts to cut.

FWIW, some very competent machinists do the reverse thing routinely to prevent these exact issues. The multiple start has to be offset using the cross slide and compound.
Mmmmm..in my research today, I was reading about metric lead screws. I thought that since my lathe lists gears for imperial threads, this would not be an issue. I was running the carriage back well past the start of the threads before engaging the carriage to alleviate backlash issues but it did not seem to matter. Everything on the lathe is metric so it would make sense it is a metric lead screw. As mentioned earlier, I have two charts to use. I will try the gear selection from the other chart tomorrow. The gears to use are very different between the two charts.

Thanks for the input.
Reply With Quote
  #13  
Old 01-30-2021, 08:58 PM
ShawnR ShawnR is offline
Member
 
Join Date: Apr 2013
Location: Ontario, Canada
Posts: 60
Default

Quote:
Originally Posted by milomilo View Post
Try keeping your hand on the lead screw engagement lever and see if there is any pauses while running. Are you sure the thread dial gear is fully engaged on the lead screw? I had a gear is the quick change box I had to replace a few years ago. Caused the same issues you have.
I will try the hand on the lever tomorrow. Yes, the gear is fully engaged. All the gears seem ok .
Reply With Quote
  #14  
Old 01-30-2021, 09:05 PM
ShawnR ShawnR is offline
Member
 
Join Date: Apr 2013
Location: Ontario, Canada
Posts: 60
Default

I just thought of something. In my stack of gears, one had no keyway slot in it. Is this slot timed to the teeth like a timing gear in a vehicle? I cut (filed) a new slot last night but did not relate it to the teeth. I just the notch to match the other one (I had a second one, the same tooth)

So maybe I caused this? The more I think about it, that might be it....? For those of you that have cut gears, would this do it?

I will find a pitch tomorrow that does not use that gear and try again. That will be an easy resolve if that is the case!!



I will report back tomorrow.

Thanks
Shawn
Reply With Quote
  #15  
Old 01-30-2021, 09:41 PM
milomilo's Avatar
milomilo milomilo is offline
Auction Addict
 
Join Date: May 2010
Location: Wheatland, Wyoming
Posts: 17,198
Default

I think you may have found the problem.
__________________
Chris

The question isn't who is going to let me; it's who is going to stop me.
Reply With Quote
  #16  
Old 01-31-2021, 08:43 AM
ShawnR ShawnR is offline
Member
 
Join Date: Apr 2013
Location: Ontario, Canada
Posts: 60
Default

Quote:
milomilo I think you may have found the problem.
As much as that move is embarrassing, I rushed out to the shop to change the gear out, and it was sitting on the bench. I must have taken it out yesterday when trying different gears, so we continue the search.

I switched out all gears today. I went by the chart in the manual which should yield the same pitch but it made no difference either. I also noted the pitch is incorrect so I will just use the gear chart on the machine. Learned something already today...

I pulled the saddle off to check underneath. The only thing I can see is that there might be crud in the split nut (more of a half nut on this machine). If it is grabbing but not fully seating into the nut...

I will clean and reassemble and report back.
Attached Thumbnails
Click image for larger version

Name:	Double cut new gears.jpg
Views:	37
Size:	193.7 KB
ID:	159388   Click image for larger version

Name:	Half nut.jpg
Views:	36
Size:	77.8 KB
ID:	159389  
Reply With Quote
  #17  
Old 01-31-2021, 09:58 AM
Ironman's Avatar
Ironman Ironman is offline
Iron Modification Investigator
 
Join Date: Feb 2008
Location: Warburg, Alberta, Canada
Posts: 15,381
Default

I bought the 12 x 40 version in 1985 when it was called Dai Fong.
Never had threading problems.
I was thinking that as these things get assembled without a QAQC program, someone may have grabbed a threading indicator from a metric machine and slapped it on there just to finish it off in the assembly line.

There is also a shear pin where the quick change box output shaft joins the acme screw. If it has failed that would explain everything. As I recall, the pin was steel, sort of rolled up tin, and when it crapped the machine would fail to feed under a heavy cut. I punched out the hole to 1/4" and put in a soft aluminum pin.
__________________
Gerry
You got freedom of speech, if you don't say too much.
Aaron Neville.

The virtue is always a cover for the sin. That's the key to understanding the modern left. Whatever they're accusing you of doing, they are doing themselves but more enthusiastically. And that's definitely the story of Justin Trudeau. Tucker Carlson
Reply With Quote
  #18  
Old 01-31-2021, 11:54 AM
GWIZ's Avatar
GWIZ GWIZ is offline
SFT Historian
 
Join Date: Feb 2006
Location: USA
Posts: 7,186
Default

from the pictures it appears you are threading towards the tail-stock or back in forth.
before you go too far confirm direction right to left or what ?
__________________
*
*
The factory of the future will have only two employees, a man and a dog. The man will be there to feed the dog. The dog will be there to keep the man from touching the equipment. ~Warren G. Bennis
Reply With Quote
  #19  
Old 01-31-2021, 12:34 PM
ShawnR ShawnR is offline
Member
 
Join Date: Apr 2013
Location: Ontario, Canada
Posts: 60
Default

[QUOTE=Ironman;767282.
I was thinking that as these things get assembled without a QAQC program, someone may have grabbed a threading indicator from a metric machine and slapped it on there just to finish it off in the assembly line.

There is also a shear pin where the quick change box output shaft joins the acme screw. If it has failed that would explain everything. As I recall, the pin was steel, sort of rolled up tin, and when it crapped the machine would fail to feed under a heavy cut. I punched out the hole to 1/4" and put in a soft aluminum pin.[/QUOTE]

But even if it is a wrong gear, should it not at least line up with the last cut? I quit worrying too much about actual pitch. I just want it to start at the same spot and follow that last scratch. I took the saddle off and disassembled, cleaned, and reassembled. I could not find any faults other than chips here and there. It all feels much nicer to use now, but no difference. I also adjusted the nuts on the leadscrew that, I believe, are for taking up backlash (not that I could detect any before ) and still the same. I actually had 3 separate scratches today.

Maybe my technique is wrong?

Here is what I am doing...
1 set tool bit using gauge so it is square to stock
2 set compound slide at 30 degrees (or 29.5) and zero it
3 adjust cross slide to just scratch stock, then zero cross slide dial
4 pick a threading number to use
5 with cutter at right of start of thread, engage carriage feed when your number comes up
6 make first scratch (or cut) till end of thread
7 release carriage feed,retract cross slide to clear stock, and run carriage back to position for start of thread
8 put cross slide back to zero
9 advance compound a little (not doing this today cause just scratching)
10 when your number comes around, engage carriage feed
11 goto 6
12 repeat till thread is cut or stock is ruined, which ever comes first...

Have I gotten it wrong? Currently, I am barely moving compound cause the multiple scratches are more illustrative of the process. Not much point in making cuts, I don't think.

GWIZ--> only cutting right to left

I know an option is to not disengage the carriage but hoping to find a fault here and not have to do that/learn that.

Back to shop, will check in later.

Thanks guys! Nice to have a group to bounce these ideas and questions off of.

Cheers,
Shawn
Reply With Quote
  #20  
Old 01-31-2021, 12:50 PM
Ironman's Avatar
Ironman Ironman is offline
Iron Modification Investigator
 
Join Date: Feb 2008
Location: Warburg, Alberta, Canada
Posts: 15,381
Default

I can't see anything odd with your process. Maybe try to start on the same number on the dial each time. You shouldn't have to, but it eliminates one thing that way.

You are certain the shear pin is intact? A visual inspection won't do. You should be able to tap it out with a pin punch. If it won't drive out, it has been sheared and rotated.

reversing and not disengaging the half nut will probably break the insert as it won't follow the cut, in my opinion.
__________________
Gerry
You got freedom of speech, if you don't say too much.
Aaron Neville.

The virtue is always a cover for the sin. That's the key to understanding the modern left. Whatever they're accusing you of doing, they are doing themselves but more enthusiastically. And that's definitely the story of Justin Trudeau. Tucker Carlson

Last edited by Ironman; 01-31-2021 at 01:00 PM.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Web Search:

All times are GMT -5. The time now is 05:44 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.