What's new
What's new

MONARCH CK12 Cross Feed and Compound need help!

CHutchcroft

Plastic
Joined
Feb 25, 2020
Location
Florida, USA
So here’s the rub..

I’m going to make a new cross feed nut for my CK12. In fact I’m going to do both the cross slide and compound.

I disassembled both today to get some measurements and have a look at the shafts.

Cross Slide is 3/4-5 LH ACME
Compound is 1/2-10 RH ACME

Cross slide nut will be replaced by a new nut made from 954 Bronze.

I was able to order that and a correct tap from Mc Master.

Compound uses the Casting as the nut so I plan to drill and tap to 5/8-10 RH ACME.

I was able to get that tap also from Mac Master.

Now for the fun stuff!

The shaft for the compound and the cross need replacement.

I was able to order 3/4-5 LH ACME and 5/8-10 RH ACME precision ground rods 3’ long each.

So how should I splice this to the current shaft ends?

Drill and tap the existing shaft after parting off the old ACME and thread the ACME rods to engage with two cross drilled set screws?

I probably should just remake the entire shaft but with the trash slop I have the long ACME single point threading won’t end well.

Thoughts?
 
Last edited by a moderator:

johnoder

Diamond
Joined
Jul 16, 2004
Location
Houston, TX USA
Cross feed screw - if taper attach equipped - has a reduced diameter at the end near the operator to enable the telescoping business. Far end passes thru thrust block back near T/A and terminates with threads for a hex nut.
 

CHutchcroft

Plastic
Joined
Feb 25, 2020
Location
Florida, USA
Cross feed screw - if taper attach equipped - has a reduced diameter at the end near the operator to enable the telescoping business. Far end passes thru thrust block back near T/A and terminates with threads for a hex nut.

My machine has no taper attachment and the screw is the fixed type.
 

tommy1010

Hot Rolled
Joined
Apr 21, 2010
Location
northeastern Pa, USA
I would go to 1/2" for the 3/4 and 3/8 for the 5/8. Around 3/4 to 1" deep. Make them a press fit with 680 loctite. You can use the quick setting JB weld if you make them a little loose fitting. Both will work just fine.
 

Cole2534

Diamond
Joined
Sep 10, 2010
Location
Oklahoma City, OK
My 12ck is a 7/8-4LH thread.

Why on earth would you not make the shaft from solid? It's basic lathe work, and you done even need the shaft or nut in the machine to do it. I made my nut from Delrin, its works excellently.
 

CHutchcroft

Plastic
Joined
Feb 25, 2020
Location
Florida, USA
My 12ck is a 7/8-4LH thread.

Why on earth would you not make the shaft from solid? It's basic lathe work, and you done even need the shaft or nut in the machine to do it. I made my nut from Delrin, its works excellently.

Well 5 turns on my cross slide moves it 1” and it mics as .75 OD.

My machine is a 1935.

The ACME Stock is 4140. I was trying to get the least backlash possible and with the slop in both the compound and crossfeed I didn’t think single pointing the ACME would turn out as precise.
 

texasgeartrain

Titanium
Joined
Feb 23, 2016
Location
Houston, TX
You already bought stuff, so you're probably committed.

But an alternative to tapping larger on compound. You could drill out the old threads and bore slightly larger. Then buy 932 bronze round nuts and cut it down to press into the bored hole. They have left and rh btw. You can see them part way down on this page:
McMaster-Carr

Ive been toying with the idea of doing the same for crossfeed nuts. Bore out the old threads, and press one of these in.

I think you'll be ok with 954 bronze, but it is harder. I'd rather softer, and wear nut vs wear the screw. I like 932 here because its softer, plus the lead in it will help it survive longer with low or no lube.
 

Cole2534

Diamond
Joined
Sep 10, 2010
Location
Oklahoma City, OK
Well 5 turns on my cross slide moves it 1” and it mics as .75 OD.

My machine is a 1935.

The ACME Stock is 4140. I was trying to get the least backlash possible and with the slop in both the compound and crossfeed I didn’t think single pointing the ACME would turn out as precise.
Sounds like they gained weight with age, mine is a '43. Now I see why you'd choose that...becuase you have the option to do so. I didn't.

Shoukd you opt to make your own screw, don't forget to factor the helix angle into your tooling choices, coarse pitch and small diameter can make it pretty aggressive.

Programmed via Mazatrol
 

CHutchcroft

Plastic
Joined
Feb 25, 2020
Location
Florida, USA
You already bought stuff, so you're probably committed.

But an alternative to tapping larger on compound. You could drill out the old threads and bore slightly larger. Then buy 932 bronze round nuts and cut it down to press into the bored hole. They have left and rh btw. You can see them part way down on this page:
McMaster-Carr

Ive been toying with the idea of doing the same for crossfeed nuts. Bore out the old threads, and press one of these in.

I think you'll be ok with 954 bronze, but it is harder. I'd rather softer, and wear nut vs wear the screw. I like 932 here because its softer, plus the lead in it will help it survive longer with low or no lube.

I looked at the 932 AKA 660 but I could not get a 6” length that suited my need and price point.

The ACME stock is 4150 so much harder than the 954.

You have a good idea with the bore and bush method. It is SIGNIFICANTLY cheaper to do this.
 

CHutchcroft

Plastic
Joined
Feb 25, 2020
Location
Florida, USA
Well I pushed on and finished up both replacement shafts and nuts.

Went with the .0015 press fits and Loctite 680.

Ended up with around .001-.002 backlash down from around .035-.040. Let’s just say I’m happy!
 

Desmato

Plastic
Joined
Feb 25, 2018
CHutchcroft, mind sharing where you got the precision ground threaded rod from. I was searching all over for my 14-1/2" S.B. and struck out at every turn (unless I wanted to pay for custom ground) I needed 11/16 - 8 LH (ODD BALL SIZE !) but went with some precision rolled 5/8-8 and a 4G nut from a 13"

It's tight, but not what I had hoped for with all new stuff.
 

Desmato

Plastic
Joined
Feb 25, 2018
Welp, McMaster only sells the "precision" lead screw in a roll formed 2C class (.009"/ft accuracy)

I was looking for 4G class ground screw to replace the Orig 4G ground. The issue is this... If you order a new 4G class nut, as I did... It will NOT thread onto a 2C roll formed screw due to the rounded corners in the valley of the thread. this is a common and known issue with ACME thread and the commonly available options. I wound up using a .003"/ft roll formed screw from Thomson linear, and chased it on the lathe with the proper 4G threading tool. Like yours, I have .001-ish play but also like yours, the old one was trashed and unusable so way more better and less $$ than custom ground. As a comparison, my 10EE has .0003 lash in it's screw/nut

This was all for use on my 1956 S.B. 14-1/2" Crossfeed screw/nut. The Orig was 11/16-8 LH which is not made anywhere, so I downsized to the 5/8-8 screw and nut which is used on the 13"
 








 
Top