Single Point Threading

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  • #48722
    david pierce
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    • Topics Started: 90
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    Single point threading on a lathe is an operation that generally requires a strong powerful machine (due to the cutting forces) and slow RPMs, but, does not require extreme precision. These requirements are juxtaposed to the features offered by a watchmaker lathe. The operation also requires a lot of mechanical mechanisms that would get in the way and do not have a lot of meaning on a lathe designed to operate with a sense of feel from the operator. The mechanisms would include the gear train, a three axis compound rest with the top axis able to adjust to different angles, a lead screw, threading dial and half nuts to engage and disengage the carrage during the threading operation. In short, this is a job that is best acomplished with an engine lathe. I have ocasionally come across single point threading kits for Lorch and Boley lathes but they are extremely rare. In truth trying to turn a watchmaker lathe into an engine lathe lathe will not result in the best of both worlds.
    david

    #54320
    tmac1956
    Participant
    • Topics Started: 171
    • Total Posts: 1259

    David:

    As far as the non-professional (wanna-be) machinist like myself, would this lathe serve for the purposes of general machining?

    http://www.grizzly.com/products/10-x-22-Variable-Speed-Lathe/G0752

    Thanks!
    Tom

    #54321
    david pierce
    Participant
    • Topics Started: 90
    • Total Posts: 1360

    Tom,
    Long time, no see. Yes it would. Mine has a 9″ swing and weighs about 250 pounds. As you can see going to a 10″ swing increases the weight to about 450 pounds. Considering this it would probably be a good idea to get the metal stand as well. I made a bench for mine out of 4 x 4s for the legs, 2 x 4s, for the cross bracing and two sheets of 3/4 inch plywood glued and screwed together for the top. This would probably not be stable enough for a 450+ pound machine. One nice aspect of a lathe like this is with the large MT spindle hole you can use large ER collets. I owned both a 6″ and 12″ ATLAS back in the early 1970s and was not happy with either one and sold them. The Central Machinery style lathes have a much better bed design than the ATLAS lathes had. If you get one of these, get the largest size you can deal with. The bigger they are the more stability they have but the 10″ will work out very nicely. Mine works fine but the size I really wanted was a 15″ swing. With a home shop this was not feasible due to the weight and power requirements.
    david

    #54322
    tmac1956
    Participant
    • Topics Started: 171
    • Total Posts: 1259

    Daivd:

    Thanks my friend. I’m still haunting the forum!

    Later,
    Tom

    #54323
    Bob Tascione
    Moderator
    • Topics Started: 38
    • Total Posts: 1559

    Hi Tom and David,
    I have the same machine here. Mine is the 12×36 and is pretty hefty. It’s a decent machine for all around general machining but I won’t be making any watch parts with it! lol
    This lathe was given to me so I couldn’t pass it up!
    Here’s a pic of it.

    Bob

    #54324
    david pierce
    Participant
    • Topics Started: 90
    • Total Posts: 1360

    Bob,
    Now that is a lathe. Grizzly has it listed for $2795.00 + $375.95 for the stand and it weighs over 1000 pounds. Is your friends name Santa Clause?
    david

    #54325
    Bob Tascione
    Moderator
    • Topics Started: 38
    • Total Posts: 1559

    :D
    That’s the lathe I had told you about in a phone conversation a while back. I had replaced this lathe with the ROMI for the company in Santa Barbara when I retooled their shop. If I removed it then it was mine to keep! They just wanted it out of there. Two trips in a small Toyota pickup did the trick but it wasn’t easy. It’s about as large as I would want to go without moving up to 3 phase. Ideal for small shop or big garage though. It was only used a few times so like new.

    Bob

    #54326
    tmac1956
    Participant
    • Topics Started: 171
    • Total Posts: 1259

    Bob:

    I hope you have something thicker than a 4″ slab under that thing. What a beast! (I wish I had one).

    Later,
    Tom

    #54327
    willofiam
    Moderator
    • Topics Started: 75
    • Total Posts: 1437

    Hey Bob that looks like a nice setup, and I thought I was getting the good deals. Hey guys, what do you mean to single point thread? William

    #54328
    david pierce
    Participant
    • Topics Started: 90
    • Total Posts: 1360

    William,
    Single point threading implies that the thread is cut with the point of only one cutter. When you tap a steel rod with a die the thread that is built into the die determines the path of the cutters. To cut a thread with only one point the movement of the cutter is controlled with the revolution of the shaft being cut in relation to the movement of the cutter. With a manual lathe this is usually done with a gear train connected from the back of the spindle to a threaded rod on the lathe called a lead screw. If the part and the leadscrew are turning at the same RPM, the thread of the leadscrew is directly transferred to the part being threaded. By changing the gear ratios in the gear train different speeds can be obtained between the part being threaded and the actual thread on the leadscrew. The advantage to this system is the ability to control the quality of the thread, the type of thread and the lead of the thread. In other words it is more versitale and accurate.
    david

    #54329
    tmac1956
    Participant
    • Topics Started: 171
    • Total Posts: 1259

    Here’s a helpful video on the subject. At least it was for me. If you already know about the different types of threads then you can just skip to around 4:00 to get at the thread cutting part.

    http://www.youtube.com/watch?v=1IqN0sHupQE

    Thanks!
    Tom

    #54330
    Bob Tascione
    Moderator
    • Topics Started: 38
    • Total Posts: 1559

    I love Tubalcains videos. I’ll bet every kid that took his shop class in school has fond memories of those days. He’s sure a natural teacher and it’s obvious he loves machining and helping all of us!
    Bob

    #54331
    tmac1956
    Participant
    • Topics Started: 171
    • Total Posts: 1259

    @willofiam wrote:

    Hey Bob that looks like a nice setup, and I thought I was getting the good deals. Hey guys, what do you mean to single point thread? William

    William:

    What in the world is that around you neck in your avatar? It looks like a “watch tool” necklace. There might be a market for that on ebay!

    Very kool!
    Tom

    #54332
    willofiam
    Moderator
    • Topics Started: 75
    • Total Posts: 1437

    Hey Tom, your exactly right, the only necklace I had to go with the pocket watch earrings, I must have been going bonkers when I took this pic. maybe it was the graver cigar I was smoking, gotta have some fun dont yah think, William P.S. I really dont dress like that everyday.

    #54333
    tmac1956
    Participant
    • Topics Started: 171
    • Total Posts: 1259

    @willofiam wrote:

    Hey Tom, your exactly right, the only necklace I had to go with the pocket watch earrings, I must have been going bonkers when I took this pic. maybe it was the graver cigar I was smoking, gotta have some fun dont yah think, William P.S. I really dont dress like that everyday.

    William:

    I didn’t notice the earrings. Nothing like appropriate accessorising. :)

    Later,
    Tom

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david pierceSingle Point Threading