Thread/Feed chart and change gears

[SteveG]

Had to do my first bit of thread chasing the other night on my 80's Takisawa lathe (TSL1000-D).
It has a quick change gearbox and I knew it was capable of both metric and imperial threads but hadn't really looked at the chart before, let alone tried to interpret it.

The only change gears I have are the ones currently fitted 50T , 50T, 60T, and 120T.

Trying to get my head around the chart:
   

Here's how I interpret it:


Top left chart - feed pitches (crossfeed is half the value shown)
- Being a Taiwanese lathe and the max feed rate is 3.78 I'm guessing the values are mm (per spindle rev).
- To get very coarse feeds you require 73/80/46 gears
- to get the very fine ones you need 50/85/30/120

Bottom left chart - imperial threading values are TPI
- pretty obvious, but note there's no way of getting 13 TPI (required for 1/2" UNC)

Top right chart - metric threading pitches, and feeds (self explanatory).

Bottom right
- Not sure what the 4mm P means, or the 1.5M
- the long list of numbers is the full list of change gears for all the charts shown.

Does that sound reasonable, and can anyone throw some light on the parts I'm not sure about?

Steve

[f350ca]

Think your on the right track Steve. 11.5 tpi for pipe thread is missing too.
The change gears can be pretty cryptic on some lathes, to get 11.5 tpi on my Summit requires changing out a gear but by the chart and the manual it took me an hour to figure it out.

[SteveG]

(08-23-2017, 09:26 AM)f350ca Wrote: Think your on the right track Steve. 11.5 tpi for pipe thread is missing too.
The change gears can be pretty cryptic on some lathes, to get 11.5 tpi on my Summit requires changing out a gear but by the chart and the manual it took me an hour to figure it out.

Thanks. The only manual I have is suspiciously quiet on the subject. Only chart is the one on the lathe itself.

After a bit more research, I think the "4mm P" is leadscrew pitch (options in the manual are 4mm, 6mm, and 6TPI).
The 1.5M seems to be 1.5 module gears going by an old post I found elsewhere where someone had bought generic 1.5 module gears and they matched.

So if I had some cutters, a dividing head, some material and the skill to do it, it shouldn't be hard to make the extra gears!!
First 3 of those can be solved with $$$, but the 4th might be a challenge for me.
Guess I could always just buy some, but sounds like genuine ones would cost me more than the lathe did, and anyway, whats the point of having tools if you don't use them to make more tools.....

Steve

[f350ca]

I've cut a couple of gears Steve, its not that difficult. Aluminum would probably work fine for the amount of use we give these machines.

[SteveG]

Good point. And aluminium gears would likely run quieter too.
Along the same lines, I've got a large sprocket in the shed that I salvaged. It's made from some engineering plastic (Delrin or similar)and about 25mm thick and 1m in diameter. Wonder if that would be a suitable material to make some gears from.

Steve

[f350ca]

Probably would work fine, you may need to insert a metal hub to carry the keyway load.

[Mayhem]

That might be bakelite. It is often used for 'sacrificial' gears.

[Vinny]

Been there, done that. Don't use plastic for gears. ABS works ok but only for light duty lathes. I used a special plastic resin made for gears, the first time there was stress on it, it became toothless.

If you have a number of gears of the same module to make, consider a hob. I got one from a Chinese vendor/manufacturer on ebay that worked like a dream when I had to do some gear cleanup on my logan. I had it for about a year and could no longer read the numbers on the side of the box. A quick email to the guy and a few hours later he sent me all the info I needed. Then when I was setting it up on the mill I noticed the numbers were engraved on the opposite side I was looking at. DOH!

[jocat54]

I made gears out of delrin for my SB9A for cutting metric threads and they worked well. Don't think there is much pressure on them when cutting threads with a small cutting depth (also made a set out of aluminum) I still have them forgot to give them to the guy that bought it last year and don't have any way of contacting him.

[SteveG]

I'm not 100% sure what this plastic is, so think I will give it a miss. Probably no point putting the effort into an unknown material that's may fail.

My local metal supplier usually has a bunch of different size flame cut steel circles leftover from where they've cut holes out of plate for custom jobs. If they've got some that are thick enough they'll be a cheap source of steel stock.

Vinny - I hadn't considered a hob as I thought they needed the gear blank to be rotated at a specific speed to match the hob. If that's right it would be out of my capabilities and tooling at present.
Also, it looks like I can get the 3 involute cutters I'd need to do all the missing gears for AUD$30 total, whereas a hob is about 6 times that price. I guess the cost difference narrows significantly if you need to buy the full set of cutters.

I started looking around for ideas on how I could index them without having a dividing head etc.
Came across this simple idea of using a indexing disc made out of cardboard. The guy then made it even easier by using a USB microscope to line up the indexing lines.

Gear Indexing Video

So that gets me around indexing without a proper indexing head.
Should then be a simple case of making up some sort of spindle to mount the gear on, clamping it into a v-block or similar and cutting it.

Steve