What materials are you turning?

Some thoughts come to mind:

• The least preload possible to obtain the desired outcome. Larger Øs and heavier cuts (work deflecting) will require more preload.
• Some type of grease (moly/bearing) to interface contact surfaces.
• Slowest speeds possible (reduce heat/friction).

Use a live centre for 95% of the work, finish with a dead centre

edit: you can make your own one, it's an interesting and useful project

Edited By Ady1 on 14/05/2021 06:50:01

As for how deep to drill with a centre drill. I always shorten my centre drills to prevent the end breaking off, not often I use one smaller than number three (1/4&quot to suit the work I do. With a shortened centre drill 3mm or 1/8" is enough to still hold a bit of grease and not let the point of the centre bottom out. A drop of oil during use is a good practice to start.

Edited By Chris Evans 6 on 14/05/2021 08:04:58

You will note that a centre drill has a pilot. Do you fill this pilot hole with lubricant? If not, that might help.

Another way to avoid ‘burning up’ your dead centre is to use a carbide one.🙂

The centre is there to support the part, not squeeze it between the chuck and tailstock in an attempt to distort the part! It’s not likely doing the lathe spindle bearings any good either. Anneal the bolt? A better, sharper cutter?

With a revolving centre I wind it in until it revolves with the work, plus a tiny bit extra but not so much as to heavily load the lathe bearings. You will be cutting axially, not radially, most of the time, so cutting pressure should be towards the chuck. Radial cuts are best carried out closer to the chuck as there is more support at that end.

Plain bearings cannot work at the same high speeds as ball or roller bearings (unless with pressure-fed lubrication think car crankshafts?) and require regular lubrication (think myford spindles), so work more slowly and lubricate more often.

Items are often joined together by ‘friction welding’ where rotation and pressure are applied simultaneously. No need to try to go there!

Another advocate of lubricating with grease, molygrease or tallow, and not to use excess pressure.

As NDIY says, the centre is there to support and locate, so only apply just enough pressure. You are not trying to, launch the Great Eastern, (Which stuck on the ways )!.

If it gets hot, the pressure is too great, back off!

Howard

I'm in the habit of easing then re-tightening the centre at intervals on long turning work, rather than waiting until things start to complain.

Also re-set it after a long interruption in the middle of a lengthy turning task, to compensate for the work-piece having cooled.

Unless you are working to super precision limits, I would say a decent quality live centre will cover most of your work.

You can use it for the heavy cuts, and then swap to the dead centre for the finishing cuts if you wanted to.

The only big downside of a live centre is that it can be quite bulky and get in the way when turning small diameters, I quite often use a "Half dead centre" for those jobs.

When you get a live centre, just test it with a DTI to make sure it has no run out. You get what you pay for as with most tooling.

Phil

Jeremy,

You will find my my Gepy ‘pin- up’ and some other useful info. here : **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=134291

MichaelG.