Thread dial indicator for Lathes

[Jors]

I am the owner of a Quantum 210 X 400 mm Metric lathe.

The Leadscrew is 2.0 mm metric pith and I can cut a wide range of both metric and imperial threads.

The lathe is designed to cut an reverse, forward (cut) and reverse. There is no Thread dial.

I would like to make a thread dial, but I have now idea how it works. I am referring to the marks on the top of the dial and how many teeth the gear must have that runs on the lead screw.

I have seen some thread dials with 4 marks and even one with 12 marks (numbered 1 - 12).

Where can I get the info how to make one or the theory behind it for me to work from.

I also see that the thread dial is normally situated on the right side of the saddle. My one has got 3 screws standing out on this place, but they are meant for the gib of the half nut. However I am sure I will be able to make use of them without having to influence the grip on the gib.

I will really appreciate any help.

[Oldneweng]

I am the owner of a Quantum 210 X 400 mm Metric lathe.

The Leadscrew is 2.0 mm metric pith and I can cut a wide range of both metric and imperial threads.

The lathe is designed to cut an reverse, forward (cut) and reverse. There is no Thread dial.

I would like to make a thread dial, but I have now idea how it works. I am referring to the marks on the top of the dial and how many teeth the gear must have that runs on the lead screw.

I have seen some thread dials with 4 marks and even one with 12 marks (numbered 1 - 12).

Where can I get the info how to make one or the theory behind it for me to work from.

I also see that the thread dial is normally situated on the right side of the saddle. My one has got 3 screws standing out on this place, but they are meant for the gib of the half nut. However I am sure I will be able to make use of them without having to influence the grip on the gib.

I will really appreciate any help.

There have been a number of mentions about this on the forum. I believe there was a mention in one of my threads this year. Maybe "New Lathe". My lathe has a dial on the left side. I thought this was normal although until I got this lathe a few years ago I had not had much to do with them since 1984. My mate had one similar to yours in size. No dial I think.

My new lathe which is sitting up at trailer height on massive wooden blocks in my implement shed (weighs about 1.5 tonne) waiting for the needed preparations (long story), has a dial that attaches on the right side. I think it is currently sitting on my work bench in pieces. It was one of the many bits in the tray of the lathe when I got it. I could get some pics if that would help, and check the gearing ratio for you.

Dean

ps. I was wrong. It mounts on the left side as well although it is ambidextrous the lathe is not. Due to different models having reversed apron design.

[pipeclay]

Unless you particularly need/want a Thread Chasing Dial (maybe multi start threads,but you can work around it) you wont need it for cutting threads.

Seeing you have reverse that will be fine,you will need to reverse the lathe to cut Imperial threads anyway.

This method will require the Half Nuts to be permanately engaged.it will incur a little more wear on the Half Nuts and Leadscrew .

If you decide to cut your own gears for the Chasing Dial they would need to be Trapezoidal thread form,although you probably are already aware of that.

For best results when cutting your gears if you don't have a milling machine capable of cutting a Helical profile you would be best to look for a Spiral fluted Trapezoidal tap of the correct pitch.

If you have a Mill you can make a mandrel up for your gears,this should allow the gear blank being cut to be held firmly on its faces but able to rotate as the Tap cuts the blank (the Trapezoidal Tap becomes the gear cutter.

If you haven't a Mill you could make up something similar for the Lathe using the Tap mounted in your spindle.

Brass or Bronze will give best results (Brass is softer/easier).

Calculations will need to be made to make sure the gear teeth will allow for the available pitches.

[Oldneweng]

Pictures as mentioned. 16 tooth gear. The pointer is missing. The hollow in middle picture curves over the lead screw which is 6mm pitch. This was not attached when I got the lathe and had not been for some time. There is a small amount of wear so it has been used. I have not fitted it back on myself and at this point I had no intention to as it has been discussed before that it is not really needed. I noticed some posts here saying the same thing but have not fully read them.

Dean

[cba_melbourne]

The Leadscrew is 2.0 mm metric pith and I can cut a wide range of both metric and imperial threads.

Hi Johan,

I think that you do not need a thread dial. Thread dials are most useful for lathes with imperial leadscrews when cutting imperial threads. In all other instances the benefits you may get from a thread dial are in my opinion quite limited and not worth the effort. Thread dials on a metric leadscrew are a bit a pain to use, sometime you even need to change thread dial gears. That is why most small lathes with a metric leadscrew do not come with a thread dial.

Your leadscrew is 2mm pitch. That means that you can open and close your half nuts anytime (and as often as you like) when cutting threads that are contained as a whole number in 2mm. Unfortunately there are only three such pitches on a 2mm leadscrew:

2mm (this is also the standard pitch for M16 and M14)
1mm (this is also the standard pitch for M6 and M7)
0.5mm (this is also the standard pitch for M3)

For all other pitches, be they metric or imperial or module, you must leave the half nuts closed during the whole thread cutting operation. Chris