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Automatic Threading Stop on SB Heavy 10

MrWhoopee

Hot Rolled
Joined
Nov 8, 2017
Good point. Oil is constantly being supplied up high and it slowly flushes down into the sump.

It sounds like you have played with different spring tensions, any chance of providing a source/part number for the spring you ended up using on the retractor arm?
A little crude testing with a 50 lb. scale indicated I needed about 20 lbs. of pull while exerting pressure against the half-nut with the handwheel. I found my spring at True Value, but this is the same.

1655134443936.png

So far, I've only tested up to 3/4-10. At coarser pitches, the pressure against the half-nut increases, both due to the greater travel per rev and the larger face contact (=chip load) nearing the finish. Planning to try 1-8, which is as coarse as my threading inserts go.
 

BKahler

Aluminum
Joined
Jul 2, 2006
Location
Richmond, Kentucky USA
A little crude testing with a 50 lb. scale indicated I needed about 20 lbs. of pull while exerting pressure against the half-nut with the handwheel. I found my spring at True Value, but this is the same.

View attachment 366732

So far, I've only tested up to 3/4-10. At coarser pitches, the pressure against the half-nut increases, both due to the greater travel per rev and the larger face contact (=chip load) nearing the finish. Planning to try 1-8, which is as coarse as my threading inserts go.

Thanks for the spring info.

Later this year I have to turn a 4 tpi acme thread. I wonder what kind of pressure this will generate on the half nuts. Probably considerable.
 

MrWhoopee

Hot Rolled
Joined
Nov 8, 2017
Thanks for the spring info.

Later this year I have to turn a 4 tpi acme thread. I wonder what kind of pressure this will generate on the half nuts. Probably considerable.
Yes, but it can be reduced substantially by reducing the DOC on each pass. I would definitely be using the compound and not trying to feed straight in.
 

dullvinci

Cast Iron
Joined
Aug 26, 2004
Location
Fla
Very true. I am also considering roughing in the thread with a V tool to remove most of the metal before switching to the acme tool bit.
I have roughed Acmes using a stubby straight tool, ground with clearances to suit. Worked out well.
 

MrWhoopee

Hot Rolled
Joined
Nov 8, 2017
I'm speechless!

Needless to say I would really like to see the parts details for that pullout device :)
 

MrWhoopee

Hot Rolled
Joined
Nov 8, 2017
The retractor got some detailing this week. The reset lever was moved to the top, a new trip lever was mounted on the bottom and it got it's own dovetail to reduce overhang and free up the tool holder. As an added bonus, the height adjusting screw is perfectly postioned as a reset stop.

20220624_111230 small.jpg
 

MyLilMule

Cast Iron
Joined
Jan 5, 2021
Location
Ohio, USA
The retractor got some detailing this week. The reset lever was moved to the top, a new trip lever was mounted on the bottom and it got it's own dovetail to reduce overhang and free up the tool holder. As an added bonus, the height adjusting screw is perfectly postioned as a reset stop.

View attachment 367458
Awesome job on this widget. I love it. I think I love it as much for it's usefulness as it's "I'll show you!" factor. LOL!
 

MrWhoopee

Hot Rolled
Joined
Nov 8, 2017
Great outside the box thinking. Keeping the slop out of that tool slide mechanism was probably tricky.
Yes, I was able to mill the slots, but lacking a surface grinder, I did a lot of lapping on the tool shank with 320 wet-or-dry. I checked the assembly and get .001" side to side movement.
 








 
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