Automatic Threading Stop on SB Heavy 10

[MrWhoopee]

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.



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]

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]

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.

 

[BKahler]

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.

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.

 

[dullvinci]

It's less a reservoir than a sump. Having opened up the apron on mine, a little cast iron in that mix of chips and sludge will do no harm.

Like it or not, that is the natural course of events on these lathes.

 

[dullvinci]

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]

Not meaning to rain on this parade, but is a simultaneous pullout of the cross feed in your future plans?

Per your request....

 

[BKahler]

I'm speechless!

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

 

[MrWhoopee]

I'm speechless!

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

The Retractor

Some people (no one here) weren't satisfied with the automatic threading stop for my SB Heavy 10. They felt that the tool should also retract to avoid the necessity of a thread relief. I've always tried to fulfill people's unreasonable requests, so here goes. Please bear in mind that these...

www.hobby-machinist.com

 

[MrWhoopee]

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.

 

[dullvinci]

Per your request....

Great outside the box thinking. Keeping the slop out of that tool slide mechanism was probably tricky.

 

[MyLilMule]

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]

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.