[4]

Trouble Parting On CM 9x20 Lathe?

[3]
[10] Like what you see?
Click here to donate to this forum and upgrade your account!

vocatexas

Active Member
Registered
Joined
May 8, 2017
Messages
121
Likes
124
#1
If you have one of the 9x20 lathes sold by Central Machinery, Grizzly, etc. and have trouble parting, do yourself a HUGE favor and make the four bolt compound base as a project. You can download the plans here: http://bedair.org/clamp/9x20clamp.html

I was getting VERY frustrated at parting. Maybe one in five attempts resulted in an acceptable job without breaking a blade or bending the work piece. I made the compound base on the lathe and installed it and the difference is night and day. I can part one inch cold roll into paper-thin wafers now, and that is using a parting blade straight from the package; no grinding or honing. The new base really makes the compound MUCH more rigid. Not only does this help in parting, it also helps on interrupted cuts and enables you to take more depth of cut on stock.

This project is well worth taking the time to do, and, if you are new to machining like me, you will learn several new skills along the way.
 

dlane

Active User
H-M Supporter - Gold Member ($25)
Joined
Sep 27, 2014
Messages
3,001
Likes
1,415
#2
Got to tweet things nowadays to make them work .<>!
 

Fabrickator

Active User
Registered
Joined
Jan 22, 2014
Messages
577
Likes
479
#3
+1 for the 4-bolt mod, first thing I did on my Grizzly.

Also, set-up for parting properly. Set cutting tool height, Set compound so it's all the way under the QCTP (not @ 30*) so they both ride on the center of carriage for maximum support. Use the proper speed for the size that your cutting. Use proper lubrication for the material that your cutting.
 

The_Apprentice

H-M Supporter - Gold Member
Staff member
H-M Supporter - Gold Member ($25)
Joined
Jun 14, 2017
Messages
248
Likes
125
#4
After doing so much reading... I have decided to always stay the safe route for now and part off only with a hack-saw... Of course, NOT when the lathe is still turning!
 

C-Bag

Ned Ludd's bro
H-M Supporter - Gold Member ($25)
Joined
Feb 9, 2017
Messages
476
Likes
327
#5
Mine came with the 4 bolt mod but was still squirrley trying to part. As I got more experience I found the top slide of the compound was so messed up from the OO drilling the mount for the AXA qctp unsquare (!) which made it almost impossible to tighten the qctp down so it wouldn't move. This also made to mount bolt head start pulling through the top slide because of over torquing and making a rise under the qctp further causing problems and warping the topslide! This made it impossible to adjust the gibs properly, talk about a cluster!

So bless Grizzly's heart and all their vital organs that they stock parts for the 9x20 and I got a new topslide and what a difference. I can adjust the gib properly. I also don't use parting blades and use a HSS tool ground down fairly thin with some side relief. Parting is no big deal now. My next project is to make the 4bolt mount where it covers up that silly degree indicator(which isn't accurate) so those bolts are out from under the compound like the back ones and will be easier to pull off or move.
 

MSD0

Active Member
Registered
Joined
Apr 22, 2015
Messages
291
Likes
85
#6
I was thinking about doing the 4 bolt mod on my PM-1127, but ended up replacing the entire compound with a solid toolpost riser since I rarely use the compound. No more issues with parting or chatter.
 

gzoerner

Active Member
Registered
Joined
Apr 20, 2016
Messages
48
Likes
62
#7
When parting on my G4000 I found that being more aggressive with the cross-slide results in much smoother performance. Once the parting tool bites in, just keep pushing. You'll know if you are pushing too hard. A sharp tool is mandatory. Parting needs to be pretty close to the chuck.
 
[6]
[5] [7]
Top