LeBlond 15c Threading
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  1. #1
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    Default LeBlond 15c Threading

    Hey guys,
    I am new to machining and need help interpreting the threads and feeds chart on my LeBlond 15c lathe. I am trying to cut 3/4 x 10 threads and the closest pitch on the lathe is 0.104. Also I have looked at a few thread pitch charts online and compared the to the chart on this lathe. Needless to say very few of them match up. Am I missing something? Thanks for the help. I’ll post a picture of the lathe and chart when I get back to my laptop.

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    You are looking at the feed side of the chart. There is a thread side of the chart that used whole numbers you need for threading. Post a good picture of the chart and an overall shot of the controls and we can tell you how to set your lathe.

    There is a possibility you have a manufacturing lathe without a lead screw. The pictures will confirm/deny that possibility.

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    Perfectly dreadful copy but here is a page and the link to the whole thing

    http://vintagemachinery.org/pubs/2102/3414.pdf
    Attached Thumbnails Attached Thumbnails leblond-manual-page.jpg  

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    img_4455.jpgimg_4457.jpgimg_4456.jpg
    Here you go.

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    Can't see the levers well, but if you set the box lever to 'B', the head lever to 'E' and the slider to the slot with the '10', then you get 10tpi. Also, you must use the half-nuts and not the longitudinal feed. Selecting one should lock out the other. (You typically 'select' half nut operations by putting the carriage/crosslide feed selector lever in neutral, then the half-nuts will engage.)

    If the markings for the head and/or box levers are missing or unreadable, you'll have to get another user to tell you what they are.
    Last edited by Gordon Heaton; 01-16-2020 at 10:46 PM.

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    So I turned the threads in the middle picture which are really close if not dead on M1.5 on setting box lever A, Head lever on E, and knob in first slot which has the number 7 and .059 in it. M1.5 is almost 17 TPI (16.93 to be exact) which make no since with the numbers on the lathe.

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    I have the original manual for it and have read it from cover to cover. it is more about maintenance and parts ordering then operation.

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    Your photos are a help - show us the gears under left end cover

    But first tell us WHAT apron control you are using to "cut threads"

    As Gordon said if you are using the longitudinal FEED control, it will not cut threads, it will just feed along at the .059 - DID YOU KNOW THE .059 is very very close to 1.5 mm?

    To thread, forget the feed control on the apron and use the HALF NUT LEVER

    Thumbnail shows you that lever
    Attached Thumbnails Attached Thumbnails img_4456.jpg  

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    Quote Originally Posted by Gordon Heaton View Post
    Can't see the levers well, but if you set the box lever to 'B', the head lever to 'E' and the slider to the slot with the '10', then you get 10tpi. Also, you must use the half-nuts and not the longitudinal feed. Selecting one should lock out the other. (You typically 'select' half nut operations by putting the carriage/crosslide feed selector lever in neutral, then the half-nuts will engage.

    If the markings for the head and/or box levers are missing or unreadable, you'll have to get another user to tell you what they are.
    Seems that is the way to go B E in the 10 slot and using the half nut

    The 10-TPI slot is three places back from the far right.
    Your Photo looks like the gear change lever is way over to the far left side.(the wrong side according to your chat.)

    Good to put a 10 thread screw in the chuck /collet and just follow it with looking with your loop so not wasting the time to cut a thread for test. just eyeball follow your bit in the thread.

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    Your lathe is not set up to cut metric threads.Why are you using a metric thread pitch gauge?
    The large numbers above the decimal no's are the threads,the lower are the feeds.When you select "E" instead "F" you will be cutting coarse threads.Switch back to "F" for all other cutting and fine threads .Do not go over 300rpm in "E".

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    John, Thanks a million about the half nut lever. I was cutting with the feed speed and not the half nut engaged. I only scraped on part that I have plenty of stock to replace. This forum is AWESOME!!!!

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    Quote Originally Posted by jmoore2784 View Post
    John, Thanks a million about the half nut lever. I was cutting with the feed speed and not the half nut engaged. I only scraped on part that I have plenty of stock to replace. This forum is AWESOME!!!!

    You are certainly welcome

    I am new to machining
    Old but really great generic how to info

    http://vintagemachinery.org/pubs/1617/5795.pdf

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    Also know there is a sliding sleeve on the left end of the lead screw, at least on older machines. When slid to the right, it disengages the lead screw.

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    Also with a new to you lathe it is a good idea to clean the lead screw before cutting threads.
    They accumulate a lot of crud if not used for a while and won't do your half nuts any good with swarf embedded in them.

    The half nuts and feed levers are interlocked so you can only engage one or the other,however I have seen a few cases where it didn't work and something will break.So it may be a good idea to check that it works since you don't know its history and you are just starting threading.
    Those are really good lathes.We bought one 20 years ago that was well used and have used it daily since.


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