Surface finish when turning Mild Steel Bar.

[LesT]

Hello,
I would like to ask for some advice from the experts on here...
I just bought a set of Indexable tip tools from Myford and they are fine for me.
I can get a good finish on stainless and a good finish on Brass.
On Mild steel the finish looks like an old Vinyl LP, if you can remember those things.
I've cranked the speed up high, and am using a bit of oil. (Advice from reading old posts on another forum)
I tried putting a clock gauge on the job (25mm diameter steel bar), if I lean on the chuck I can deflect it .001 or .002" to the rear and similarly to the front.
My questions are:
Do I need to have a look at the headshaft bearings ?
Is this deflection amount typical of bearings in good condition or is it excessive ?
How easy are the bearings to change ?
Regards,
Les.T.

[rpwilson]

Hello,
I would like to ask for some advice from the experts on here...
I just bought a set of Indexable tip tools from Myford and they are fine for me.
I can get a good finish on stainless and a good finish on Brass.
On Mild steel the finish looks like an old Vinyl LP, if you can remember those things.
I've cranked the speed up high, and am using a bit of oil. (Advice from reading old posts on another forum)
I tried putting a clock gauge on the job (25mm diameter steel bar), if I lean on the chuck I can deflect it .001 or .002" to the rear and similarly to the front.
My questions are:
Do I need to have a look at the headshaft bearings ?
Is this deflection amount typical of bearings in good condition or is it excessive ?
How easy are the bearings to change ?
Regards,
Les.T.

Les
You need to clarify a few things first.
1) What type of steel are you using?

2) What speed are you actually using?

3) What oil are you using to cut with?

4) How much of the 1" bar is projecting from the chuck?

5) Are you using tailstock support, if so are you using a revolving centre or a solid one?

6) Before you start tearing the headstock apart to get at the bearings (most probably unnecessarily), its worth checking the bearing preload. Denford's recommendations are a bit vague, and it depends on the model of 'old Viceroy' which you have. For the Educators with the preload adjuster behind the back bearing, they say (with all gears out of mesh and the belt disconnected), tighten the lock nut until a slight resistance is felt, then wrap a piece of twine round the faceplate and attach a spring balance. Tighten the nut until the resistance is 10-15lb/inches. (If the radius of the faceplate is 4 1/2", then the pull should be around 21/2lbs - 3 lbs).
For the later lathes with the adjuster inside the headstock, behind the front bearings, slack off the lock nut Its left hand thread) and tighten the inner nut, making sure the preload 'is not excessive' The test of this is if the machine can run for an hour at top speed, and you can then place your hand on the spindle nose without discomfort.
If you can feel little or no resistance now, then the bearings do need adjusting. Tweak up the adjuster until you can feel some resistance, then try running the lathe at high speed for a while and see how hot it gets. If the spindle feels rough or noisy when you turn it, then you probably do need to strip it down for inspection, but don't do this unless you absolutely have to.

[LesT]

Hello,
I would like to ask for some advice from the experts on here...
I just bought a set of Indexable tip tools from Myford and they are fine for me.
I can get a good finish on stainless and a good finish on Brass.
On Mild steel the finish looks like an old Vinyl LP, if you can remember those things.
I've cranked the speed up high, and am using a bit of oil. (Advice from reading old posts on another forum)
I tried putting a clock gauge on the job (25mm diameter steel bar), if I lean on the chuck I can deflect it .001 or .002" to the rear and similarly to the front.
My questions are:
Do I need to have a look at the headshaft bearings ?
Is this deflection amount typical of bearings in good condition or is it excessive ?
How easy are the bearings to change ?
Regards,
Les.T.

Les
You need to clarify a few things first.
1) What type of steel are you using?

2) What speed are you actually using?

3) What oil are you using to cut with?

4) How much of the 1" bar is projecting from the chuck?

5) Are you using tailstock support, if so are you using a revolving centre or a solid one?

6) Before you start tearing the headstock apart to get at the bearings (most probably unnecessarily), its worth checking the bearing preload. Denford's recommendations are a bit vague, and it depends on the model of 'old Viceroy' which you have. For the Educators with the preload adjuster behind the back bearing, they say (with all gears out of mesh and the belt disconnected), tighten the lock nut until a slight resistance is felt, then wrap a piece of twine round the faceplate and attach a spring balance. Tighten the nut until the resistance is 10-15lb/inches. (If the radius of the faceplate is 4 1/2", then the pull should be around 21/2lbs - 3 lbs).
For the later lathes with the adjuster inside the headstock, behind the front bearings, slack off the lock nut Its left hand thread) and tighten the inner nut, making sure the preload 'is not excessive' The test of this is if the machine can run for an hour at top speed, and you can then place your hand on the spindle nose without discomfort.
If you can feel little or no resistance now, then the bearings do need adjusting. Tweak up the adjuster until you can feel some resistance, then try running the lathe at high speed for a while and see how hot it gets. If the spindle feels rough or noisy when you turn it, then you probably do need to strip it down for inspection, but don't do this unless you absolutely have to.

Thanks for the answer,

The steel was / is a bit of ordinary "Bright" mild steel bar (rusty). About 3" exposed from chuck.
I ran the lathe at top speed (1350), very small cut (.001).
I used some slideway oil because it was going so fast, nothing would stick.
I tried with no centre (poor finish) and with a live centre (better finish).
Tool was brand new CCMT06 insert

It may just be the quality of the mild steel I suppose.
I'll try some better stuff !

Thanks for the information on the bearing preload and set up, that doesn't sound too difficult to have a go at.
Les.T.

[rpwilson]

One thing I've read about insert tooling (I don't use them much myself) is that they don't like very small cuts. Very good at high speed, high feed and heavy cut, but old Viceroys weren't designed to use insert tooling. High Speed Steel and possibly carbide tipped for cast iron was the order of the day. You might get better results with a really sharp, old fashioned High Speed Steel tool at about 5-600 rpm. I don't want to be rude about Myford (New Myford that is, AKA RDG) but some of their tooling is rubbish.

[dazz]

Hi
Based on similar early experiences I had, I suggest two things.

1. Buy a length of good known grade steel.
2. Run the carbide fast and deep. If it isn't scary, your not doing it right.

If you look up the data sheet for the particular inserts you are using, you will find that a "fine" cut translates to a heavy cut for a Denford.

If you take a look at my projects, you will see what finish you can get from these machines with both HSS and carbide.