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Metric threads on clausing 100

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Mwmx54

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Hi all, sorry the only time I post is when I need help, I have an old clausing 100, built sometime during the war according to the war order sticker, with the quick change gear box.
My question is while I was searching the best way to turn a metric thread, an old manual for this lathe popped up, and said it can cut “near perfect metric threads” with just a 17 or 23 tooth gear on the stud, unfortunately I cant find any other info about this, has anyone turned a metric thread this way? If so and it worked, I’ll be making a couple of new small gears, which will be much easier than making 100 and 127 tooth gears . Here’s a photo from the manual that I got from vintagemachinery.com
 

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Rootpass

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Read through this and see if it helps at all.

 

mickri

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There are several threads on cutting metric threads through a QCGB on craftsman/atlas lathes. I have converted my craftsman 12x36 to be able to cut metric threads through the QCGB and have successfully cut metric threads. What you are basically doing is converting the lead screw to a metric lead screw. There is also a video by Halligan142 on You Tube about cutting metric threads on a Southbend lathe. He goes through all of the math.

I don't know if this will be true for your lathe or not but on the craftsman/atlas lathes you can't use the threading dial and have to leave the half nuts engaged. You start by engaging the half nuts. When you get to the end of the thread instead of disengaging the half nuts you stop the lathe. Back out the cross slide and reverse the motor to get the carriage back to the start of the threads. Move the cross slide in and increase the depth of cut on the compound. Start the motor in forward and take another cut. Keep repeating this process until you have cut the thread. Never disengaging the half nuts.

Having said that there is a way that you can use the half nuts. It is more complex with more to keep track of. For me I found that it was way easier to just keep the half nuts engaged.
 

benmychree

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Could you copy that catalog page at a larger size so that it can be read?
 

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wa5cab

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That copy is now in Downloads. I had it local and don't know how I missed it. Resolution and general cleanliness is better than the other copy that was already there.

Does anyone have a good scan of the threading chart for the Clausing 100 QCGB?

Someone earlier mentioned the QCGB equipped Atlas 10 and 12's in conjunction with cutting metric threads. One version on those machines requires a 44T and a 52T transposing gear set driving one of the 48T gears driving the gear box (the other one is removed). Switching from Imperial to Metric requires only moving the sliding gear from OUT to IN and positioning the selector levers to the proper positions. In order to do this, you give up the ability to cut 4 TPI to 7,5 TPI without changing the setup back to stock. Whether or not this approach would somehow work on the 100 I don't know and don't have enough information to find out.

One thing to keep in mind with any scheme to cut metric threads on a lathe with an Imperial lead screw is that it will not be good enough to be able to make a metric lead screw. Those errors in the third and fourth decimal place aren't significant for nuts and short screws. But if one is trying to cut a long screw, they add up.
 

Downunder Bob

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Hi all, sorry the only time I post is when I need help, I have an old clausing 100, built sometime during the war according to the war order sticker, with the quick change gear box.
My question is while I was searching the best way to turn a metric thread, an old manual for this lathe popped up, and said it can cut “near perfect metric threads” with just a 17 or 23 tooth gear on the stud, unfortunately I cant find any other info about this, has anyone turned a metric thread this way? If so and it worked, I’ll be making a couple of new small gears, which will be much easier than making 100 and 127 tooth gears . Here’s a photo from the manual that I got from vintagemachinery.com

Hi, The Most accurate way to cut metric threads on an imperial lathe is to use the 127 x 120 tooth gear set. This works very well as 127 is half of 254, so 25.4 mm to the inch exactly, and you can get pretty much all the common metric threads from your norton thread box.

The 127 x 120 tooth gears will fit moist medium and larger lathes, but many smaller lathes have to use an approximation set of gears commonly 63 x 60, and there are others. While the threads produced by these approximation methods are accurate enough for short bolts and nuts, they will produce small errors that add up in longer threads. They are not suitable for making a lead screw for instance.

There are a number of charts available on the web and some here on HM that will help you. Good luck.
 

Mwmx54

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Thanks everyone for the help, I haven’t had a chance to get back in the garage to work on this, I have a small dividing head, and an el cheapo set of the correct gear cutters for my lathe, so I will make the 17/23t gears and see how that goes. It looks like even with those gears, I think it was the 1.75 or 1.50 that it still couldn’t do, but I don’t need that pitch at the moment, maybe later on I will try making the large transposing gear set, should only take about 2 maybe 3 years to get through cutting all those teeth (-;
I’ll post back my results when I get back on this maybe this weekend or next week. Just wanted to say thanks for the answers and help. Here is a pic of the gearbox plate I made with ferric chloride and the blue sheet stuff. It took a couple try’s to get the toner to transfer, but it turned out great.
 

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francist

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That's a great looking plaque! Nicely done :encourage:

-frank
 

Mwmx54

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thanks, the plaque turned out better than I expected, I didn’t quite get the size right though, and I wasn’t computer savvy enough to design spots for the screws to go, and on top of it all I snapped a tap off in one of the existing pin holes, cause I thought it would be a good idea to use little screws instead of the drive pins, so I had to move the one hole slightly. I’ll see if I can find the file I made, maybe it will be useful to someone. I tried using one from this forum but I think it was the type of file that made it so I couldn’t use it(again, not computer savvy), but I still used it for the layout. As my plaque was completely missing when I got the lathe.
 

GrayTech

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Hi, The Most accurate way to cut metric threads on an imperial lathe is to use the 127 x 120 tooth gear set. This works very well as 127 is half of 254, so 25.4 mm to the inch exactly, and you can get pretty much all the common metric threads from your norton thread box.

The 127 x 120 tooth gears will fit moist medium and larger lathes, but many smaller lathes have to use an approximation set of gears commonly 63 x 60, and there are others. While the threads produced by these approximation methods are accurate enough for short bolts and nuts, they will produce small errors that add up in longer threads. They are not suitable for making a lead screw for instance.

There are a number of charts available on the web and some here on HM that will help you. Good luck.
Bob are you sure about the 127/120 combination? I was under the impression it was 127/100. I have a 127 tooth to fit my lathe and am looking around for a 100 tooth gear, but they are spendy. 127/100 combo is a close enough approximation to work on any imperial lead screw but the lesser tooth combinations seem to work out only for certain imperial leadscrew TPIs and are limited to the number of metric pitches they can cut. My Lathe does not have a QC gearbox, only change gears. A QC gearbox may open up more possibilities than I'm aware of.
 

Downunder Bob

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Bob are you sure about the 127/120 combination? I was under the impression it was 127/100. I have a 127 tooth to fit my lathe and am looking around for a 100 tooth gear, but they are spendy. 127/100 combo is a close enough approximation to work on any imperial lead screw but the lesser tooth combinations seem to work out only for certain imperial leadscrew TPIs and are limited to the number of metric pitches they can cut. My Lathe does not have a QC gearbox, only change gears. A QC gearbox may open up more possibilities than I'm aware of.
The 127 x 120 gear set is what came with my lathe, so perhaps it varies depending on other gears in teh train. If you don't have a QCGB then you will have to calculate the full gear chain for each thread pitch that you want, unless you can find a chart for your lathe.

Whatever you use it's 127 gear that does the magic for metric threads. Yes the QCGB does make it easy I can get all the standard metric threads on mine, but as I bought mine new I was able to order it for a specific purpose.
 
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