Help ML4 sick!

[JCSteam]

Well I've come in from the shed disheartened tonight, went to turn some steel and a massive amount of chatter, so I reground the tool, same chatter, changed tool, same chatter reground same chatter, so I tried a softer metal, some Ali and new tool, same chatter, tried lighter cuts, ok, but still not right, the pic shows from left to right, 2thou cut, 4thou cut and 10thou cut, I've taken upto 20thou before and not had this issue.*

I moved my top slide so it was better supported, i checked my toolpost and cleaned the mating faces off still the same.i checked all the gibs, and even locked them up and still got chatter.*

After eliminating everything else, gibs, tool, material, flexing of the tool, by bringing it closer to the toolpost. So as little as possible was sticking out.*

I'm only left with one piece of kit, the headstock and it's bearings. I removed the chuck and clocked the register looking for movement, and I found it.

Endfloat was clocked at 6thou, horizontal movement was clocked at 3thou, and vertical was clocked at 2thou. So i assumed I would adjust the bearings again. Which is what I did, with the adjusters for the bearings first.*

I removed the shims that were there to stop the headstock casting been overtightened, and gradually tightened the bolts up until the spindle could just be turned by my hand gripped around the nose, i started at the front then did the rear, then i tightened the endfloat adjuster, again so the spindle could be turned by hand, (with a little resistance).*

Here's a little video of the issue, if anyone can offer me any other advice than just replace the bearings, then I'm willing to give it a go. I knew they were worn, but I think they've had it, unless I am missing something.

https://youtu.be/ZIjRAk-Ch5g

 

[JCSteam]

Another video of me adjusting and to get a measurement of the movement in the spindle, if I go tighter than this, the spindle locks, so I don't think I can adjust out anymore of the movement.

https://youtu.be/nMA1qup1RsQ

 

[michael-au]

How about tool hight, is that correct

 

[Buchanan]

Try with much less radius on the tip of your tool. You don't want a long length of cutting edge peeling a wide thin chip. Also make sure your tool is not above center height and check your jib adjustment. Every little bit helps on a small lathe.

 

[Hopper]

Your tool geometry in the top pic looks a bit out of kilter. Beside the too large radius, there appears to be a flat on the end of the tool, angling away from the corner radius. So cutting would be taking place on that farthest out point, instead on the very corner where your radius is. It would generate a wedging action as it was fed into the work and maybe create the patterns seen on the job in the pic.

 

[bazmak]

I would also say the problem is the tool.Never seen one ground like that before
Do you have other tools the tool needs to be ground at about 80o on plan
with side ,front and top rake.Is it my eyes or is that that tool a LH brazed
carbide tip with you cutting on the wrong side,ie the softer shank. Weird

 

[JCSteam]

How about tool hight, is that correct

Tool height is set with a dead center in the tailstock, so that is correct.

Try with much less radius on the tip of your tool. You don't want a long length of cutting edge peeling a wide thin chip. Also make sure your tool is not above center height and check your jib adjustment. Every little bit helps on a small lathe.

The gibs were adjusted as i said in the videos. Everything from just right to locked tight to eliminate them as the culprit

Your tool geometry in the top pic looks a bit out of kilter. Beside the too large radius, there appears to be a flat on the end of the tool, angling away from the corner radius. So cutting would be taking place on that farthest out point, instead on the very corner where your radius is. It would generate a wedging action as it was fed into the work and maybe create the patterns seen on the job in the pic.

I can see what you mean when I look at it this morning, I'll regrind that and try again, I'm sure it wasn't with that notch when I put it in.

I would also say the problem is the tool.Never seen one ground like that before
Do you have other tools the tool needs to be ground at about 80o on plan
with side ,front and top rake.Is it my eyes or is that that tool a LH brazed
carbide tip with you cutting on the wrong side,ie the softer shank. Weird

The tool is HSS, as said above I'll regrind that, this is the third tool that's been put into the toolpost. The others gave the same results. I've gone from cutting steel which was bad, and went through two different tools, before slipping the one pictured in and also changing to Ali

 

[fcheslop]

Hi Jon, Tool geometry is a wee bit of
just my two bobs worth
I cannot hear the video very well as Im deaf as well as daft
This tip was from Clock it n flog it motor engineers inc

 

[JCSteam]

Sorry it was 11:30pm so I wasn't going to shout for the video.

I will attempt a regrind and see what it looks like after, and how it cuts.

 

[goldstar31]

I have recommended the following MANY times and again suggest that you Google Conrad Hoffman's excellent dissertation on Advanced Tool Grinding.

I'm sure that he must have known me or Frazer as one of the Grumpy Old Farts but I was 'playing about' in my dotage and getting an almost mirror finish on what had been a lump of rusty round steel. The last cut was so fine that the scarf was 'barely perceptible.' It would crumble in my gnarled old set of fingers and not pierce my delicate and long retired skin.

Laughingly, I can do better than that but Hoffman sets off to make a jig that will cut like a razor.

N

 

[JCSteam]

Norm, i can understand previous frustrations with me in not having the kit to measure movements in the spindle previously, the videos I've posted should hopefully put that to bed, and the lathe has been working fine up until the last few months over winter where it was mothballed.

I have spent winter reading a lot of material but will add that to the list shortly.

I did debate wether to trouble you all with this as I had been previously advised and hopefully as you can see have taken note of what was said regards the head, and working through a problem one step at a time. As for tool grinding I already know it's an acquired skill. But practice makes perfect (eventually). I have looked at the Harold Halls website and the tool rest for grinding HSS which I think may be getting made. I ain't the luxury of Stent tool grinders and such, plus they cost the same as the lathe did, if not more.

 

[goldstar31]

Norm, As for tool grinding I already know it's an acquired skill. But practice makes perfect (eventually). I have looked at the Harold Halls website and the tool rest for grinding HSS which I think may be getting made. I ain't the luxury of Stent tool grinders and such, plus they cost the same as the lathe did, if not more.

As for tool grinding being an acquired skill, I simply don't agree. Hoffman and gadget builder.com to which you have been repeatedly referred do not require either skill or a Stent. Hoffman writes to refute the old twerps like me saying it is a skill.

Again, a Stent or perhaps a Brooks Stent can be made on a simple lathe- and mine- if you must know was all of a ton--- £100!

All that one needs is a cheap double ended grinder and a few bits of packing- perhaps plywood and the ability to multiply 0.0088 times the degrees required( perhaps 7) times the diameter of the wheel. The answer comes out in thous and with a bit more guesswork(?) you can tell just how much packing is needed .

Have I suggested that you need even rests? All I have suggested is a very simple multiplication sum that any school child should be able to grasp.

OK, I'm a Mensa case with an IQ well in excess of 130 but most of the time, I count on my fingers or if it gets really complicated, I take my sox off!





N

 

[bazmak]

Nobody needs a tool and cutter grinder for std lathe tools.If you know the basic geometry then anybody can do with a bench grinder.The finish your getting
shows the tool is not cutting at all.Buy a cheap set of RCT tools ,you will have to eventually. Your problems are not with the lathe but simple tool geometry
Keep going dont get disheartened

 

[DJP]

I get chatter when parting off using an old 1940s lathe. I agree that your cutting tool surface is too wide and probably above centre line. A little below centre line so that there is a tiny '***' remaining when end facing seems to work best for me. A fresh new set of carbide bits are not expensive to ensure that lathe is OK and worst case use a live centre to support the end of the work piece for another test of the lathe.

I 'm sure that if your lathe was cutting well before storage it hasn't changed. The problem is that the cutter is dull, too wide or poorly supported.

 

[JCSteam]

Well thank you all. Sometimes it's best to go back to basics.

Adjusted the bearings fully and then reconnected the belt up, and put the 3jaw on. Tightening the same slug of Ali that showed so much chatter yesterday.

I reset my grinding rest so it was around 8° ish and dressed the wheel. Then ground the surfaces as described. The nose been finished with an oil stone.

Packed upto tailstock center height using a dead center.

The results...... well.... great actually, and no vibrations whatso ever.

 

[JCSteam]

In the fourth pic you can see where the Ali cold welded itself, I've nicked this off now, and next time I'll spray with WD40 which seems to work well on Ali.
The chips also wound up nice and tight too.
The line in the work is where I slipped up and didn't have my hand ready to take over and turn the apron handle.

 

[Buchanan]

You have pretty much got it. A small tip radius and straight sides to the tool and enough clearance below and almost any thing will machine properly. Top rake of a few degrees helps on ferrous metals and some sort of lube also helps. One important thing is that the edge must be sharp. when working on light lathes. The edge facing the chuck should do most of the cutting for normal turning and the front face when facing. Loverly improvement.

 

[bazmak]

Here endeth the first lesson.Look for the simple things rather than the complicated. Now you know the tool is the problem try grinding a few
to different shapes etc.Looking on plan your regrind looks about 90o
on the cutting corner.It should be about 80o so you get front and side rake
If your cutting alum then rake angle should be increased INCLUDING the top rake. Try grinding the 3 main rake angles (f,s and t) some more and the 2 clearance angles. Grind a bit more off gradually and keep trying.Its all a
learning curve and you just keep getting better. You will start to look back in amazement at why did i do that. Post a few more photos as you grind tools
to get comments

 

[JCSteam]

I did take a photo looking down onto the tool, and it's more that 90°, how much more I wouldn't like to comment....
Thank you for lesson one.
Now lesson two once everything is adjusted, and the pulley decides to spin on the layshaft...... lol.
Imperial Allen keys on order, don't panic.....

 

[Hopper]

That's good that you found the problem. I have found on these chattery little old lathes that doubling the angle of the side rake on the top surface of the tool, or even more, gives a very sharp "knife tool" a la Sparey and co, drastically reducingcutting forces, and vastly improving finish. As per drawing below.