Thread: Having trouble unscrewing chuck from lathe

If the Backgear and or spindle gears are the same dimensions as given they appear to be Module gears.
Seems strange if the Headstock is Module that the Change gears would be DP.

Ironwood, my spindle gears tally with yours: 44 & 74, same diameters. I notice Grizzly give the smaller spindle gear as a 39T. No count given for the bull gear. I can't see a way to find out if their back gears would mesh with our spindles.

Pipeclay is right - it would be odd to have metric and imperial gears on one machine. Though I've found some odd things on mine so anything's possible. Anyway you should try to verify your change gears independently of mine.

Is the Centre distance between your Backgears and Spindle something around 96.456 mm.

Originally Posted by pipeclay

Is the Centre distance between your Backgears and Spindle something around 96.456 mm.

I measure the centre distance on mine at 102.05mm.
The backgear shaft has an eccentric offset of approx. 6mm.

Is that with the Backgear in or out.

Originally Posted by pipeclay

Is that with the Backgear in or out.

My headstock is completely disassembled at the moment.

That is what I measure the distance to be, from the centre's of the bores in the headstock housing.

The way I am seeing it, the 6mm offset on the backgear shaft, gives a possible 12 mm of movement of the backgear.

Pipeclay,

Brian's back gears at 12.26 DP don't sound like standard DP gears, so, as you say, they are probably metric. If metric, they work out consistently to 2.07 mod, which is also an unusual number, though fairly close to 2 mod. However they are very close to 6.5 mm circular pitch. What do you reckon is the likelihood of using metric circular pitch gears on a relatively modern lathe which uses DP change gears? The equivalent circular pitch in inches is 0.256 from Brian's figures, so maybe it is a possibility also, though it is not as close to a conventionally used number as is the metric equivalent. It seems strange to mix Mod and DP or circular pitch gears on the same machine though

Just trying to make some sense of the figures.

Frank.

That being the case you maybe able to replace the spindle gears and backgears with the grizzly spare parts,there centre distance equates to approximately 97.486,1mm bigger than what you have now.
I suppose at the worst you could allways convert to a spur gear headstock drive.

Frank I would take a punt and say they are 2 mod in the Headstock.
After seeing what machine manufacturers do in regards to the gearing they use in the machine tools the gears could be anything.
Hercus is a fine example,they make the machine so they can make the gears or other items to suit there needs.
Even on there Metric machines there Cross slide Screws are not as far as I have found a true Metric size,there dials may be metric and have the correct amount of markings but a complete rotation dosent come out to a full number or even a half.
There change gears and Back gears,bull gears are a similar story.
If you calculate for a certain DP tooth count the OD can and is the same for gears with different tooth counts.
Even there small change gear 16 tooth is not a standard size.
There is no problem with anyone doing this,and there are reasons why with the 16 they would but cant really understand why the change the normal practice on the bigger gears.
At least the keep there 16,18 and 20 DP gears together.

Hello Ironwood,
If You can't buy the gear with the correct tooth count,you could possibly get someone to build up the gear with hard bronze and then with a couple of files and a lot of patience you could file the teeth (assuming you don't have a mill) . With a little inginenuity you could perhaps hold the gear in the chuck and turn your lathe into a shaper by mounting a tool of the correct profile in the toolpost and cut the teeth by winding the saddle towards the chuck.
Russell

What about a large strap wrench around the chuck or cutting a timber lever to wedge in the chuck jaws?
I would not use any jarring forces as you may do more damage.
Sterob

Originally Posted by Sterob

What about a large strap wrench around the chuck or cutting a timber lever to wedge in the chuck jaws?
I would not use any jarring forces as you may do more damage.
Sterob

If this is in regards to the stuck chuck its off.

Russell its a Helical gear.

Oops, That makes it a little more difficult .Russell