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Chasing Metric Threads with Metradial

Tex-VA

Cast Iron
Joined
Jan 16, 2008
Location
Northern VA - USA
I have cut metric threads on an inch lathe before and posted the process I used a while back. http://www.practicalmachinist.com/vb/south-bend-lathes/cutting-metric-threads-156039/ I needed to cut some more metric threads and see this as a chance to use the Metradial.
I'm converting a Sieg X-3 mill to a CNC mill. I, also, want to change the spindle to a belt drive and do away with the quill. There's not much room for a pulley on the spindle after I remove the spline but my friend Steve Stallings had a good idea he shared with me. The spindle has about three quarters inch of threads that have the nut for loading up the bearings and a jam nut to keep the first nut from losing. I plan to replace the first nut with a pulley then lock it in place with the second nut.

TEX01.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2182.jpg

TEX02.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2181.jpg

The threads are 1.5 mm pitch with a diameter of 1.050 inch, 26.670 mm (weird size) and I plan to cut them on a South Bend 10L. I have the transpose gears and a Metradial I bought from Rose when she worked with Ted (SouthBendLatheMan).

Photo of Metradial and a inch/metric feed screw mic I haven't installed:

TEX03.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2149-1.jpg

The first thing I needed to do was make some kind of mount for the Metradial:

TEX04.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2153.jpg

TEX05.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2154-1.jpg
 
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Chasing Metric Threads with Metradial #2

I was unhappy with the size (thickness) of the gears that connect the Metradial to the leadscrew of the lathe. The slot on the leadscrew that drives the power feeds is 3/16" .1875 and the gears were 5/16" .3125 thick. I was concerned that the gear might get caught in the in leadscrew slot. The gears were probably made for a lathe with a separate shaft for driving the cross feed.

TEX06.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2151-1.jpg

Awhile back I made some gears for the dial that were 1/2" .500 thick, like the ones that come with the South Bend thread dial.

TEX07.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2152-1.jpg

Here it is on the lathe:

TEX08.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2154-1.jpg
 
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Chasing Metric Threads with Metradial #3

Here is the drawing of what I made:

PullyJig.jpg


And here are the bits that I needed to thread:

TEX09.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2158-1.jpg

One is for the mandrel I'll need for making the gear, the blank for the gear, and the jam nut. I didn't show making these parts, just a basic lathe turning Job.

This photo is of the the mandrel mounted in the lathe ready to thread:

TEX10.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2160-1.jpg

This is the set up for the metric transpose gears mounted on the lathe:

TEX11.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2157.jpg
 
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Chasing Metric Threads with Metradial #3

Here, I'm cutting the 1.5 mm thread:

TEX12.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2162.jpg

I found the Metradial to be a bit of a pain to use. It took a very long time for the dial to come around the line to engage the half nuts ( I found this a problem the last time I cut metric threads on my other post) and a new problem here that the nuts could be engaged just a half a line from the witness mart. This was very difficult to do on the fly so I just gave up and did it the usual way of stopping the lathe and withdrawing the tool bit then reversing the spindle and running it back to the beginning of the cut.

TEX13.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2161.jpg

I did find the Metradial handy for moving the carriage out of the way for testing the threads with the jam nut then bringing it back to take another cut.

TEX14.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2164-1.jpg

The threads here a looking good so now I can start the internal threads.
 
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Chasing Metric Threads with Metradial #4

I chucked the gear blank in the "Adjust-True type" chuck and removed the run out.

TEX15.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/dscn2166.jpg

Now I cutting the internal threads.

TEX16.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2169.jpg

I'm using the mandrel to test the threads.

TEX17.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2170.jpg

Here are the mandrel and the blank with the metric threads cut.

TEX18.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2175.jpg

TEX19.jpg


http://i260.photobucket.com/albums/ii1/Tex-VA/X3 Mill Spindle Pulley/DSCN2177.jpg
 
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Chasing Metric Threads with Metradial #6

To finish up, the Metradiad was really not needed to do this job. It did help and save a little time when testing the thread but all in all I don't thinks it was worth the effort. I'm still glad I got it and it's a neat tool to have, also, it might work better with another metric pitch. I will try it again sometime. Thanks for looking, Tex
 
Metradial?

Nice job Tex, is the metradial something you bought? from who?
Hey Alan, -- The Metradial, made by Crawford Collets in the UK, was listed on ebay a few years back by "South Bend Rose" who was working with Ted Pflugner (SBLatheman here), in a company called "Parts Works". I thought it was the coolest thing and I was happy to get it. Some where on here on PM, Ted did a great write up on the lathes South Bend was selling back when it looked like we were going metric in the USA. It was quite informative and I wish I had booked marked it. I searched around a little but I didn't find it. May be Ted or someone can point to it. The Metradial basically turns the lathe into "Babbage Engine" or the mechanical computers on WW-2 battleship gun firing mechanisms. The 127/100 tooth gear and the pick off gears in the gear train lets you cut the metric threads, most of use know this. The neat thing was the Metradial, which has a gear box built in (I did take it apart, I had to look. I took some photos and drew it up if anyone is interested.), lets you open the half nuts while cutting metric threads. Like I wrote earlier there are things I did find helpful, like the slow speed or revolution of the dial and the difficulty of hitting the witness line. Tex

Here's a link:metradial
 
That's the coolest thing- never seen one before. Nice work on your part too. It's probably too basic for the level you're at, but I just put up a page on metric threading here that people might find interesting/useful.

Best,
Conrad
 
Metric Threads

That's the coolest thing- never seen one before. Nice work on your part too. It's probably too basic for the level you're at, but I just put up a page on metric threading here that people might find interesting/useful.
Best,
Conrad
Hi Conrad - Not too basic for me. I'm still learning and I often find myself on a tightrope, with no net, when I try something new. I was a song writer and I find I use the same creative part of my brain when I do something new in the shop and I don't have to perform it for someone to see if it's any good. I haven't found a micrometer for a song yet?? I do like to share my work here and at my club meetings, but at least I know what I've got before I "show it off". Tex
 
Tex

The Metradial is designed to be used with the Ainjest high speed threading attachments once popular on Colchester, Harrison and similar lathes. For practical purposes these are a fly off trigger on the half-nut giving an inelegant approximation to the capabilities of the single tooth dog clutch drive used in by Holbrook, Pratt & Whitney and some other makes. When used with an Ainjest the high screw speed makes the wait between for the engagement points bearable but at normal, manual, speeds it seems like forever. The gearbox makes the system a pretty close analogue of the glacier slow "put a return stop on the bed and wait for the marks on the chuck and lead screw to coincide" system, fortunately with some speed up improvements.
Frankly a Metradial can never be fast, on reflection slower is better in its design application. You'd be better off making a proper metric dial and stack of drive gears, I think a careful read of the book Screw-cutting in the Lathe by Martin Cleeve will give you enough information to calculate what gears you need. That said I've been driving a full metric lathe for the last 18 months and have yet to bother with the threading dial.

Clive
 
what does a metradial cost? whats the cost to make the parts to fit the metradial to a south bend lathe? does anyone in the US have one for sale?
If you increased your threading speed would the wait time be quicker, and would hitting the witness mark be any easier?
my 1984 10k lathe came with a original Metric threading chart stamped to the back of the gearbox cover, i can buy transposing metric gears and maybe a metradial, and maybe Ted's 10k headstock with the Timken tapered roller bearings:drool5:

Hey Alan, -- The Metradial, made by Crawford Collets in the UK, was listed on ebay a few years back by "South Bend Rose" who was working with Ted Pflugner (SBLatheman here), in a company called "Parts Works". I thought it was the coolest thing and I was happy to get it. Some where on here on PM, Ted did a great write up on the lathes South Bend was selling back when it looked like we were going metric in the USA. It was quite informative and I wish I had booked marked it. I searched around a little but I didn't find it. May be Ted or someone can point to it. The Metradial basically turns the lathe into "Babbage Engine" or the mechanical computers on WW-2 battleship gun firing mechanisms. The 127/100 tooth gear and the pick off gears in the gear train lets you cut the metric threads, most of use know this. The neat thing was the Metradial, which has a gear box built in (I did take it apart, I had to look. I took some photos and drew it up if anyone is interested.), lets you open the half nuts while cutting metric threads. Like I wrote earlier there are things I did find helpful, like the slow speed or revolution of the dial and the difficulty of hitting the witness line. Tex

Here's a link:metradial
 
That's the coolest thing- never seen one before. Nice work on your part too. It's probably too basic for the level you're at, but I just put up a page on metric threading here that people might find interesting/useful.

Best,
Conrad

Good article Conrad.

Just a thought - no mention of threading stops?
They are not essential, but do away with the necessity of keeping track of the cross feed zero position, especially when your thread depth is more than a single turn of the handle (or you have nearly a turn of backlash to deal with before the tool starts to back out).
You can use it for internal and external threads, for one you stop against the screw head, the other against the cross slide.

Adding one to my 13" has definitely speeded up my threading - I haven't lost track of the cross slide since :)

Jim
 
Hey Jim, that's an excellent idea. About the only threads I ever screw up (no pun intended) are the ones where I simply forget the settings. I don't have easily adjustable dials on my Logan so I can't set zero. Yes, there's a small slotted set screw to loosen the dials, but who bothers with that?

edit- OK, made some changes to my write up. Feel free to contribute some text if what I've got is BS!

Best,
Conrad
 
Thread Stop

Hey Jim, I didn't go into all the details of the threading operation, I did much more of that on my earlier posts on metric threading (http://www.practicalmachinist.com/vb/south-bend-lathes/cutting-metric-threads-156039/) and this posting was suppose to be about the Metradial. If you take a look a this photo, you can see I did use a threading stop. I find it to be quite helpful when chasing threads.


DSCN2165.jpg



Also, I placed a spacer on my cross feed assembly to give me a little more cross slide travel, 3/4" .750. I hope to make a new unit with a larger micrometer dial and I was thinking of making it longer and I wanted to see if it would interfere with the other stuff on the apron. So far so good but I'm still not sure. I write it up if I can get it done. Tex
 








 
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