13" Leblond

1. Plastic
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## 13" Leblond

Going to make a backing plate for a 10" chuck, I need to thread it to 2 1/8" x 5 tpi. There are 3 different 5 tpi on my gear change box, number plates is very worn and I can't read why there are 3 different 5 tpi. Not sure which one to set it on to cut my threads. Guess i can try on a piece of scrap and see if there's a difference, but any help would be appreciated.

Thanks, Joe

2. Find the one that moves the carriage along the bed exactly .200" each time you turn the chuck by hand exactly one turn - and do be sure you are using the half nut lever and not the the longitudinal feed

3. Plastic
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Just tried it, the first 5 tpi is the one, chuck rotates further on the other 2 "5 tpi's" Thanks You very much !!!

Joe

RECIPROCAL - its the 1/X button on my old HP 11C calculator

Like 13 TPI is 0.076923077"

5. Cast Iron
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Originally Posted by johnoder

RECIPROCAL - its the 1/X button on my old HP 11C calculator

Like 13 TPI is 0.076923077"
Still have my 11C from college

6. Diamond
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I can't resist saying this: I still have my SLIDE RULE from HS and engineering school. That was a calculator which never needed sunlight to charge up, nor did it require plugging in to recharge its battery as the 1st generation SR 50's did.

Formula for pitch of any thread is: p = 1/n where n = number of threads per inch. I've got a 13" LeBlond Roundhead Regal lathe and there is only one (1) position for 5 threads/inch on the quick change gearbox data plate. However, there are two (2) positions given for the "feed compound" lever: fine & coarse. There are three (3) positions for the lever underneath the quick change gear box: left-middle-right.

To cut 5 threads per inch on a 13" LeBlond Roundhead Regal lathe: slide the tumbler lever (the lever with the spring-loaded handle that slides along the row of holes) so it lines up and locks into position under the "5" threads/inch. Put the "feed compound" lever in Coarse position, and shift the lever underneath the quick change gearbox to the Left.

My LeBlond Regal lathe has the 5 thds/inch spindle nose. It was built in July of 1943, and the chart on the quick change gearbox is clear as to how to position the levers and tumbler lever to get the different pitches/feeds. The only way there could be "three" positions for 5 thds/inch would be if the position of the lever underneath the quick change gearbox was not given on the chart plate.

7. I have the 15" version of that machine circa 1942.. This is the second one I have owned, consecutive serial number with the first (surplus from Louisiana State University) and it also has 2 1/8 - 5 spindle.. I made ALL of my chuck back plates with no problem what so ever...Mine only has one position for 5tpi...Ramsay 1

8. Plastic
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I love my 13 in leblond. Hope you have a great time with yours also

9. Plastic
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OK, I made a male test piece that matches spindle. I threaded my backing plate and checked with test piece, it went in fine. I took the chuck off with plate still in jaws, turned it around and screwed it on spindle, it only went on about 2 to 3 threads and got tight. But now I moved my threading setup and I need to remove maybe another 2 thousands....how do I set it back up to do this? after I moved everything. Very frustrating..so close !!!! I was able to reset up once before but that was external threads and it was fine, internal is another challenge.

Thanks, Joe

10. Plastic
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Originally Posted by Joe Michaels
I can't resist saying this: I still have my SLIDE RULE from HS and engineering school. That was a calculator which never needed sunlight to charge up, nor did it require plugging in to recharge its battery as the 1st generation SR 50's did.

Formula for pitch of any thread is: p = 1/n where n = number of threads per inch. I've got a 13" LeBlond Roundhead Regal lathe and there is only one (1) position for 5 threads/inch on the quick change gearbox data plate. However, there are two (2) positions given for the "feed compound" lever: fine & coarse. There are three (3) positions for the lever underneath the quick change gear box: left-middle-right.

To cut 5 threads per inch on a 13" LeBlond Roundhead Regal lathe: slide the tumbler lever (the lever with the spring-loaded handle that slides along the row of holes) so it lines up and locks into position under the "5" threads/inch. Put the "feed compound" lever in Coarse position, and shift the lever underneath the quick change gearbox to the Left.

My LeBlond Regal lathe has the 5 thds/inch spindle nose. It was built in July of 1943, and the chart on the quick change gearbox is clear as to how to position the levers and tumbler lever to get the different pitches/feeds. The only way there could be "three" positions for 5 thds/inch would be if the position of the lever underneath the quick change gearbox was not given on the chart plate.
I know about the 3 positions for lower handle and the position for each TPI, but mine shows 3 different 5 TPI 4/ 4/ 5/ 5 /5 /6 /6/ 7 in fact there are 2- 4tpi and 2- 6 tpi

11. Hot Rolled
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Originally Posted by jstef
I know about the 3 positions for lower handle and the position for each TPI, but mine shows 3 different 5 TPI 4/ 4/ 5/ 5 /5 /6 /6/ 7 in fact there are 2- 4tpi and 2- 6 tpi
I have a reed prentice and a hendey and each of hem has duplicate positions for certain thread pitches. I always assumed it was because certain combinations of gearing resulted in duplicate pitches.

But solving this riddle does nothing to help with your face plate problem. If it were me, i would get the chuck back on without removing the work. get it centered up relative to the spindle center. I would then remove my boring bar without moving the boring bar holder relative to the compound. I would then engage the half nuts and advance the tool holder close to the work. Leaving the half nuts engaged, i would then try to get the boring bar and cutting tool back into the boring bar holder and adjust the tool position until it just touches the start of the thread. Be sure to remove all the backlash between the lead screw and half nuts. The idea here is to restore the position of the cutting tool relative to the work to what it was before you removed the work. Keep in mind, i've never done this so it's all theory. I'm sure you would run into some unforseen problem so tread carefully.

Hopefully someone with more experience than i will weigh in to help you.

12. Plastic
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Yes, thats exactly what i did for an external thread once and it worked, but it so hard to see on internal threads, i set it up just like you mentioned, ready to try, but will wait till morning. I never took work out of chuck, removed everything as a unit to try on spindle.
Yeah, i am curious about the multiple tpi's. Its only on those , the higher ones up to 224 are single.

13. Diamond
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A method I've used to "catch" a threading tool once the setup and all else has been moved or disturbed is:

1. Clean the internal threads well, wash with solvent to remove oil. Paint the internal threads with Layout Dye (aka "Dykem Blue" or similar). When the layout dye is dry, follow Marka's instructions about centering the job when you set it back up in the lathe.

2. Set out quick change gear box to cut 5 threads/inch.

3. Setup your boring bar with the internal threading tool bit as you had it when you were threading the hub of the chuck plate previously. I leave the boring bar holder loose in the tool holder, and this is where my method my vary a bit from the accepted methods. Crank out the cross feed to there is no way the tool bit can touch the work.

4. Start the lathe in slowest spindle speed, engage the half nuts using the threading dial (aka "Thread chasing dial"). For odd threads, I believe the nameplate will state : "engage on any whole number". Engage the half nuts and let the carriage feed the boring bar so the tool bit is inside the female thread you want to "open up".

5. Stop the lathe without disengaging the half nuts. Carefully move the cross slide out until the boring bar/threading tool bit are sort of entering the threads. I zero the cross feed micrometer collar before running the tool bit clear of the work, and note how many turns it takes to clear the work. At this point, I move the boring bar so it is fairly close to entering the threads. If you move the compound rest, make sure it is in the direction of travel you will be using to feed in to cut the thread.

6. When you have the boring bar fairly well position, snug the toolpost lightly. Back the cross slide so the boring bar/toolbit clear the threads and disengage the half nuts. Run the carriage to a convenient location so you can use your center gauge (aka "fish") to make sure the tool bit is properly lined up for threading (I sometimes wind up putting a parallel or similar against the end of a job with a bored hole and hold the center gauge against it so I have something to check tool bit position against). Bump the boring bar as needed to bring the tool bit into correct position with the center gauge. Then, lock the tool post and tool holder solidly.

7. Start the lathe and engage the half nuts using the chasing dial. Let the carriage feed the boring bar/tool bit inside the work and then stop the lathe without disengaging the half nuts.

9. Run the cross slide in so the tool bit clears the threads, disengage the half nuts and run the carriage out.

10. Set the lathe to a fairly slow spindle speed, as 5 tpi will have the carriage moving along quite rapidly. Run the cross slide back out to your zero point, start the lathe and engage the half nuts on the appropriate line. Let the carriage feed in and make a pass without changing anything on the cross slide and compound.
When you have made this pass, run the cross slide in so the tool bit will clear the threads, disengage the half nuts and run the carriage out.

11. Inspect the threads with your mirror and light to see if any of the Layout Blue was removed. Chances are you will see a faint bit of bright steel where the tool bit cut thru the layout blue on the flank of the thread in the direction the toolbit is feeding in. Back the compound out about 0.025"-0.050", then run it in to your zero plus 0.001". I call this "sneaking up on a cut". The reason I do this is there is "stick slip friction" in the sliding parts of machine tools. If you tried to crank in an additional 0.001" frm your zero point, you might not get it due to this stick slip friction. By having the backlash removed and the compound moving freely (having moved past the stick-slip friction to break things loose), I find I can get a cut of 0.001".

12. Take a threading cut with this 0.001" cut set on your compound. Check the bluing afterwards. If you have a male plug gauge (dummy spindle) made, try it. If not, you can take a chance and take a "spring cut"- letting the "spring" or deflection of the boring bar force the toolbit in for another very fine cut.

13. Take a "spring cut", a cut without changing any settings on your cross slide or compound. The "spring cut" will remove something less than 0.001". Inspect the blue on the threads and see how the toolbit is cutting. Chances are you will see the bluing is removed from one flank of the thread.

14. With the carriage run out, zero the compound rest micrometer collar and run the compound rest in about 0.025-0.050" to take out backlash. Crank the compound rest back out heading towards your zero, and stop an additional 0.001" beyond your zero. This will set the tool up to cut the other flank of the thread.

15. Follow the usual steps with the cross slide and half nuts to take another pass on the threads. This time, the tool should be skimming the flanks of the threads on the side "away" from the direction of feed.

This will ease off the threads with a cut on both flanks. I like to use the layout dye for work like this as it lets me see when the tool bit starts to contact the work and where it is "hitting" and cutting. It is very easy to overdo things when "easing off" a thread in the lathe. At the point you are at, even a spring cut can loosen the fit of threads a bit more than is needed. I tend to think that some spring of the boring bar is what bit you: namely, the boring bar deflected a bit more as the lathe advanced it into the work. Another thing that can bite you on this sort of job is the fact that the forces applied to the toolbit act on the boring bar, using it as a lever and can actually turn the toolpost very slightly if things are not really made up tight and clean. Burrs on surfaces of the compound rest and toolpost can result in less than good bearing contact between them, and under load, a tool post can turn. I stone these surfaces off from time to time, and wipe them well before making things up. A boring bar is an excellent lever, and the forces acting on it produce a "turning moment" about the center screw in your tool post or boring bar holder. Keeping things as close and rigid as possible is another key to this kind of work.

Before you make up your toolpost and boring bar for this go-round, take an oil stone and stone off the top surface of your lathe's compound (the top of the tee slot), and the bottom of your tool post or boring bar holder. When you do make things up, do not be bashful about pulling on the wrenches.

A lot of little factors can add up to bite a person when doing machine work. Getting a tool bit restarted to "pick up" an internal thread is a good skill to have in your hip pocket. Being able to pick up a thread and just skim off a thousandth or two is really a fine skill to have, and you have jumped into the deep end pool with this job, for sure. Take it slow, use the layout dye trick and pull the lathe over by hand to be sure the toolbit is where it needs to be before you take cuts under power. Slow and careful is the way, as it is all too easy to mess up hours of work and screw up expensive material.

14. Plastic
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Wow Joe, thanks so much for the detailed instructions. I did about %90 of what you said, good idea leaving cutting tool loose, i only have 1 shot at this and i dont want to screw it up... ha ha...

Joe

15. "for the next time" - when you make a copy of your spindle nose for a tester, measure the thread over wires on the spindle and on your workpiece. (Search "measure threads 3 wire method")

This site will let you calculate to a known wire diameter, assuming you don't have a set of thread wires.

16. Plastic
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Well, it took me some time in between work and life, but I got it. Was able to chase the thread and take off another three thousands. I then turned the recess, beautiful fit, then drilled and tapped the 5/8-11 bolt holes on milling machine. But holy crap is this thing heavy !!!!! has to weigh 80+ lbs. Not easy to get onto spindle. Thanks for all your help. Not sure how often I will need it, but if I do , I now have a 10" chuck.

Thanks, Joe

17. Diamond
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Joe:

I am glad to read that your backplate and chuck mounting all worked out for you. A word to the wise: chucks are heavy enough to cause a person to throw out their back, and can smash fingers when trying to get the chuck started on the spindle threads (or more often, when removing it from the spindle). No sense being a hero, so here are a few hints to "work smart" when mounting/dismounting heavy chucks from a lathe spindle.

1. Make a cradle block for the chuck. A cradle block is a piece of wood (hardwood being preferable) which is cut to the approximate radius of the chuck's body, and cut to fit on the vee and flat ways of the lathe. The cradle block is sized so it supports the chuck close to height to screw onto the spindle. I make my own cradle blocks about 1/8" low so as not to wedge or jam the chuck. If you are strapped for a piece of heavy enough hardwood, the side members of a wood pallet can be salvaged for this purpose. If you have to join and glue up a couple of pieces of hardwood, it will not matter. Cutting the radius and cuts for the lathe ways is best done on a bandsaw, but a hand-saw for the vee cuts and a "Sawzall" for cutting the radius will work.

2. Consider some lifting device. Some heavy chucks have a tapping in the body of the chuck for a lifting eye. Other people have made lifting fixtures for their lathe chucks. These are fabricated from round bar stock (maybe 1 1/2" or 2" stock) welded or screwed to a steel lifting bracket. The lifting bracket has a lifting eye or hole for a shackle approximately centered over the body of the chuck.

Having a light chain hoist hung from the overhead (a piece of 2" x 2" steel angle lagged across two joists about your lathe will work to hang a light chainfall) is the simplest method. Some people have "done it right" and built jib cranes which can swing over the lathe bed and away from the bed to land the chuck on the floor behind the lathe. The jib cranes are made of pipe or box tube, and can be mounted to a stout wall, or on a post that is anchored into the floor.

Trust me on this: picking up 85 or 100 pounds is not a bad proposition for most people, but wrassling it in the form of a lathe chuck while worrying about dropping it on the bedways of the lathe and trying to catch the spindle threads is a whole 'nother matter. I have a strong back and good core muscle strength, but a recent physical disclosed I have a very small ingenual hernia. The doctor said it's too small to worry about or need surgery- yet. She also said I have to take it easy with lifting and heavy work. Too much fabrication work and similar heavier work out in the field, I guess.

It's easy enough to mess up our bodies if something like a lathe chuck gets away when we are trying to get it on or off the spindle. In the least, I'd recommend making cradle blocks for your chucks. Some people also keep the chucks on a cart with casters on the legs. In that way, they can roll the cart with the chuck right up close to the lathe and minimize the actual lifting and carrying.