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View Full Version : i need ideas for an E-Z threading dial - and THANKS to Ringer!!!!



andy_b
12-29-2008, 10:44 AM
i know what a threading dial DOES, but until i watched Ringer's video, i had no idea how it OPERATED. believe it or not, i thought it kept spinning once the leadscrew was engaged. of course, once you think about it, since it's traveling with the carriage, it should stop turning once the carriage is moving. i don't own a threading dial and never saw one in operation (in person or in a video).

---well, technically there is a threading dial on my OLD LeBlond lathe, but there is an issue with the half-nuts and i haven't been using the lathe because my slightly newer SouthBend does everything i've asked of it so far---

anyway, i don't own a threading dial for the SouthBend, and it's a 11" lathe so very few accessories are ever available for it, let alone a threading dial. i remember some posts a few years ago regarding how to cut the gear for the dial, but i believe it involved using a piece of leadscrew to make the cutter. since cutting a thread of the same pitch as the leadscrew should be ALMOST foolproof, if i was to make such a piece of "leadscrew" out of some CRS i have laying around, do you think it would be suitable to cut one brass gear for the threading dial? any other ideas on how to go about making a simple threading dial? there are about 20 projects i have that are at stopping points because i don't have a threading dial. these are all just tinkering projects, so they were never a high enough priority for me to worry about, but i am really getting the itch to work on several of them.

yes, i know the tips of stopping the lathe and running it in reverse and so on, but the only way i have to "reverse" the motor on my lathe is to turn it by hand. that would be fine for maybe one project (like making a fake "leadscrew"), but i have no desire to run the thing in reverse by hand for 20,000 rotations. :)

andy b.

Oldbrock
12-29-2008, 03:01 PM
crs 1020 won't cut it. You need some 1045 turned and ground or some alloy steel. But 1045 would be the easiest to thread and harden and temper. you need some bronze for the gear and you have to gash it to 16 teeth before you use the hob you are going to make. If you need more info you can send me a private message and I can fill you in on all the details. Peter

Mcruff
12-29-2008, 04:07 PM
Here's a suggestion:
Rather than making the gear, find out what your lead screw measures, diameter and thread pitch. I bet its the same as the heavy 10 or 13", buy the gear and build the rest. I bought the gear for a 9" Workshop for $50. Heck the thread dial for the Heavy 10 or the 13" machine may actually fit your machine.

If you go to the South bend section of the Practical Machinist forum, someone over there can probably tell you what fits or maybe has spare parts or a drawing.

garyphansen
12-29-2008, 07:51 PM
Go to the South bend section of the Practical Machinist forum and look for the thread called "Thread Dial Kits; any interest!" In that thread you will find all the information you will need to make a thread dial for your lathe. A hob made fron CRS wil not hold up to even cut one gear. I made one out of tool steel but did not harden it. If I remember right five or six gears would ware out the section of hob I was using. Using and Acme tap of the right TPI as a hob is a lot easier. Gary P. Hansen

garyphansen
12-29-2008, 10:21 PM
I bumped the thread dial thread on PM so you could find it. Gary P. Hansen

isaac338
12-29-2008, 10:44 PM
Where can one find this ringer video?

dp
12-29-2008, 10:47 PM
Where can one find this ringer video?

http://au.youtube.com/watch?v=m4iquaxrO6Q

oldtiffie
12-30-2008, 07:01 AM
Start from here on PM:
http://www.practicalmachinist.com/vb/search.php?searchid=1137719

There is a lot of "over-kill" as regards thread chaser dial "gears" or "worms".

As they are driving next to no load and as accuracy is not a real requirement other than it turns "one tooth" for every revolution of the lead-screw, there is no real need for accuracy at all.

All they need to be is a thin disk with the required number of "teeth" supported by flanges (just like a grinder wheel or a wood-worker's circular saw) and a key or clamping nut on the shaft/spindle to stop "slip".

The pitch circle circumference must be a multiple of the lead-screw pitch on your lathe. The pitch circle diameter is just the pitch circle circumference divided by "pi" (22/7 or 3.142 is close enough).

The depth of cut/tooth is "just a whisker" more than the depth of the thread on your lead-screw - a little less than half of it above your pitch circle diameter and the rest (just a bit more than half) below it.

The outside diameter is the pitch circle diameter plus twice the ("little less than half") of the tooth depth.

Make the tooth "shape" a bit "too wide" and approximating an involute shape (like a spur gear of the same size) - a "good guess" is good enough.

To "test" your "gear" just grip it between your thumb and a finger or put it on a "near enough" shaft/spindle and "roll" it along the lead screw. If it "works" its OK. If it doesn't, just re-mount it in your rotary table, "adjust" the ("fly") cutter to suit and have at it. Repeat until satisfied and you are set to go.

Post the lead-screw pitch/lead (I assume it is "acme") and the number of "teeth" you want on your "gear" and I will do and post my "calculations".

"Near enough" is good enough here - so long as it works. Its only a light non-important/accurate requirement. Its not as if its indexing a rotary table for accuracy or load.

On thinking back, there is no reason why the "cheek-plate" and "thin disk" can't be all in one piece - as long as the part with the "teeth" in it is "thin" it will do the job.

I suspect that this will cause a bit of heart-burn with some of the "purists" and "readers of books" (bibles?, gospels?).

I am not in the habit of making work harder than it needs to be.

garyphansen
12-30-2008, 12:24 PM
oldtiffie: What you said about a thin disk gear would not work if the lead screw has a keyway. The thread dial gear needs to be wide enough to span the keyway. Gary P. Hansen

oldtiffie
12-30-2008, 12:34 PM
That's true Gary - if there is a key-way - otherwise the single disk will do.

If there is key-way, two or more disks pinned together and at least the width of the key-way apart will do the job. Two will do it but three is better.

It is quite feasible to make a stack of disks and then "spread" them out to emulate a gear and then pin them and it will "work".

bytewise
12-30-2008, 01:06 PM
I made a threading dial for our Hendey lathe. It had a 6 thd/in lead screw.
I am not able to post an attached drawing.
I made a spool of aluminum and drilled 12 equally spaced holes using a rotary table. The diameter of the hole circle was such as to give a circumference of 2 inches. I used 1/16 in. dia. piano wire for the teeth. You would have to change the number of teeth for a different lead screw pitch. The pitch dia. chosen gave a 2 inch circumference and thus two index marks on the dial.
Many lead screws are 8 thd/in and a convenient gear would have 16 teeth on a larger dia. circle.
If you would like drawings of my indicator, send me a PM with an email address.
Hugh

dp
12-30-2008, 01:29 PM
Bytewise - I love your solution to the gear construction problem. So simple as to be elegant.

andy_b
12-31-2008, 01:47 AM
hmm, a bunch of excellent ideas here.
first, i found out the leadscrew is the same on the 9", 10" and 11" South Bend lathes, so any threading dial from one will work on the others, provided you come up with a suitable mount. the leadscrew is 8tpi, and it looks like the factory SB dials use a 32-tooth gear.

bytewise's idea is a great one. i was looking at the threading dials on fleabay, and it appears the threads are just angled splines cut in a bronze disk. i have a dividing head and i think i may have a suitable cutter for my horizontal mill, or i could even do it on the shaper. or cutting teeth in several thin disks and stacking them with a spiral offset may even be easier. i think this might be a doable project.

in the mean time, i did some rewiring and installed a switch on my lathe motor control and i now have reverse. it is kind of a pain to be stopping the lathe and running it in reverse half the time, but i did manage to cut some 1/2"x36 external, and INTERNAL threads this afternoon. the two pieces actually thread together nicely, and they fit on what they were supposed to fit. i need to practice some more on grinding my threading tool to the correct profile, but at least i seem to have the general concept down. :)

andy b.