Carriage stop rod Lufkin micrometer question

bll230 · Aug 26, 2019

My micrometer head is old and wobbly so I bought a very nice Lufkin 680 set off ebay, but I found out that there are obviously two versions of the Lufkin 680 head. The bottom one is off my lathe, the top one is the new one. It is obviously smaller, which I don't care about, but the threads are different, so it won't screw into my stop rod.

They both have "Lufkin 680" engraved on them. Is there some other identifying characteristic so I don't buy another wrong one off Ebay?

Anybody want a very nice Lufkin 680 inside micrometer set?

John

Matt_Maguire · Aug 26, 2019

Make a new stop rod for the new mic head???

I dunno if the Lufkin small inside mic head will adjust for wear but my small Starretts & Lufin 4-40" mics will.

Good luck,
Matt

bll230 · Aug 26, 2019

Upon further investigation, I do think the threads are the same, the problem is the previous owner boogered up the interior threads in the stop rod, like he did to everything else on the lathe. This little micrometer head is very nice, the threads on the inside are adjustable with a little collet on the inside of the body. Lufkin did a fine job.

old_dave · Aug 27, 2019

The Starrett No. 823 tubular inside micrometer head will also fit, is still available new, and you may be able to buy the head alone. I believe the thread is 5/16-48 per my B&S leaf type thread pitch gage. (Maybe someone else can confirm this). A quick google search shows this NS tap is readily available so maybe could be used to chase out your boogered-up threads.

David

bll230 · Aug 28, 2019

David, thanks for the info. I had assumed 50 tpi from measuring the change with rotation. I'll get a proper tap and go from there.

John

rke[pler · Aug 31, 2019

I recall that Victor Machinery has the tap. If I recall the Lufkin, Starrett, Central and Mitutoyo inside mic heads all use that size.

Also, there are some 5/16-56 heads from Tumico - I grabbed a bunch of them as the fittings for the 4 position stop and the cross slide stops all use little fittings that the mic head screws into and since I needed to make them it didn't make any difference what thread I used. For a few bucks apiece I liked the Tumico.

donie · Aug 31, 2019

For those who are new, or are curious, "the stop rod" is mounted on the front side of the headstock down low at the level of the carriage top.
On the top left of the carriage a solid stop can be placed, but better, a tenth reading indicator.
Another pretty cool Monarch gizmo! The stop rod is accurately notched every 1/2" inch, so to quickly adjust it, the rod is simply rotated, moved, then snapped in to the desired slot. So, the 1/2" travel inside tubular micrometer head "along with extensions" can be used for carriage travel stop to .001", but using a dial indicator is just nicer, and much more accurate.
Of course, the fine controls of the EE play a big part there.

I found using this feature, I never really needed a DRO

hanermo · Aug 31, 2019

On a monarch you can easily thread drill rod or a hardened 12.x bolt to the thread desired, cut some slots for relief, even dremel or angle grinder will work, and make a custom tap in 15 minutes.

bll230 said:
Upon further investigation, I do think the threads are the same, the problem is the previous owner boogered up the interior threads in the stop rod, like he did to everything else on the lathe. This little micrometer head is very nice, the threads on the inside are adjustable with a little collet on the inside of the body. Lufkin did a fine job.

old_dave · Sep 1, 2019

It turns out I have both a 5/16-48 tap and a 5/16-48 die. The tap is a no-name made in China; it came from KBC tools. The die is TMX brand, made in Poland; it probably came from KBC too. The die produces a thread that screws in to the "stop rod". The tap produces a thread in to which both the Starrett No. 823 and the the micrometer head that came with my 10EE will screw. The micrometer head that came with my 10EE is not marked with a maker's name or model number. It looks a bit different from the Lufkins shown at the beginning of this thread. My 10EE was built in 1977, I got it in 2002. This "no-name" micrometer head may or may not be original.

David

Cal Haines · Sep 1, 2019

To add to what donie posted: the stop rod, when used without an indicator, it strictly a manual feed aid. It DOES NOT automatically stop the carriage, so if you run the carriage into it using power feed or with the half nuts engaged, you're going to break something. On a round-dial, it will blow up the little casting that holds the spring-loaded stop. On a square-dial it will probably do even more damage.

Cal

donie · Sep 2, 2019

The only way damage can happen is by using the half nuts and leadscrew.

Often the apron clutches get sticky, and seem to be either on or off.
To completely oil the apron feed clutches, both clutches can be engaged, then the carriage moved back and forth a time or two.

With the clutches oiled as above, hold the carriage handwheel, then very lightly begin to engage the the apron clutch. At first the tension on the handwheel will feel uneven and jerk a bit, then the friction will smooth out, at that point the clutches are fully lubed, and will release instantly, and can be applied lightly to slip when the carriage stop is contacted. The old lufkin on my 1951 machine has some how held up to it.
I think using the inside tubular type micrometer head in combination with an indicator is much better, and using clutch to stop....now that the clutches are lubed up.

Cal Haines · Sep 2, 2019

I have no doubt that someone with your skill can get away with power-feeding into the stop bar, but personally, I wouldn't attempt it. I like using an indicator, as you suggest. One way to safely use the hard stop is to start with the carriage against the stop, then power feed to the right, away from the stop.

Cal

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