Author Topic: Another Inverted parting tool ? (Read 11138 times)

Pelallito · « **on:** March 26, 2009, 07:11:45 AM »

Hello,
I have an inverted parting tool holder for the Aloris that works from the back. You feed it in with the chuck spinning in its normal direction.
I have never really had a lot of luck using it.

It digs in and then raised up over the cut. I have tried many combinations of things and it never cuts well for me. I am using it on a 12" Atlas and am wondering if the lathe is too light weight for this tool. Perhaps I don't have my gibbs set up tight enough? I have the factory gibbs that are made from some sort of plastic. Should I replace them with steel or something else? Would that make my machine a little more rigid?
Thanks for the help.
Fred

Bernd · « **Reply #1 on:** March 26, 2009, 08:20:35 AM »

Quote from: Pelallito on March 26, 2009, 07:11:45 AM

Perhaps I don't have my gibbs set up tight enough?
Thanks for the help.
Fred

Fred,

I have that trouble on my 9 X 19 Grizzly bench lathe. I noticed it was picking up the back of the slide.

I don't know what the remedy would be. Maybe Bogs (John) will make a comment here as to how you can fix that. He's pretty knowledgeable on that. Bogs?

Bernd

Pelallito · « **Reply #2 on:** March 26, 2009, 09:25:03 AM »

Bernd,
Thanks for chiming in on this. I hope that Bogs does get involved. For one thing, besides being very knowledgeable, he had an Atlas that he used for many years.
I bought that particular holder because I had read that it would be better for a light lathe.

Fred

bogstandard · « **Reply #3 on:** March 26, 2009, 12:33:36 PM »

Hi Fred,

I'm here and reading, but don't hold out much hope of helping.

So what you are saying, this holder fits onto your QCTP, with the tooling upside down, sticking out to the rear rather than the front, and is then is fed from the rear of the chucked piece.

If that is how it is done, the mechanics are all wrong.

As long as you are using a QCTP there will be no advantage whether cutting from the front or rear. A QCTP will never be as rigid as a tool bolted straight down onto the cross slide. That is why people make the solid toolholders to bolt straight down onto the cross slide to do rear tool parting. That to me is where the advantage comes from to make the cutting easier.

Bernd also made a comment that might have some bearing on the subject.

Quote

I noticed it was picking up the back of the slide.

On a normal setup you are using the toolpost on an area of the cross slide that has full support of the gibs. Most lathes are the same, and not designed to have the toolpost working on the very rear of the machine, because the dovetails don't reach that far back. So you might be operating in an area where the the underside dovetails aren't supporting the cross slide as much. It is easy to check, put the toolpost in the area you are working in, and feel under the cross slide to check whether you have full length support of the gibs.

Because I don't have any problems with parting off, I have never had to resort to drastic measures, and of course I can only give you maybe cures for your problem.

If none of the above solutions look to be the cause, then maybe you should look at how I get uneventful parting off.

I always set my tooling a few thou high. This allows for the slight downwards flex of the tooling, so when it is at it's maximum 'bend' the tooltip ends up at the right height for cutting. It takes a little to find the 'sweet' spot, but once it is done, no further action is needed.

I would try setting your tool about 5 thou low (opposite to mine), and try a cut, if it still tries to lift over the top, try it a bit lower. If it doesn't want to cut, reduce it to a couple of thou and try again. You will eventually find the spot of maximum bend, and it should then cut thru like a hot knife thru butter.

I do hope these suggestions help you with your problem.

John

Pelallito · « **Reply #4 on:** March 26, 2009, 02:56:29 PM »

John,
Thanks for your advice. I was afraid of what you pointed out. I will try what you recommended, though. Perhaps I should get these for the Atlas-
http://www.statecollegecentral.com/metallathe/A-11.html and
http://www.statecollegecentral.com/metallathe/MLA-6.html and
This one is new to me
http://www.statecollegecentral.com/metallathe/MLA16D.html
I liked that one too!
Thanks again,
Regards,
Fred

Bernd · « **Reply #5 on:** March 26, 2009, 04:11:26 PM »

John,

It was actually picking up the "whole" saddle on the rear flat way of the lathe.

Tell you that's quite a frighting sight to see that happen.

The problem was that the screws holding the gib on were a bit loose. Tighting them only let the saddle bounce up and down on what ever clearence there is between the gib clamp and way.

I think the lathe is to light for the kind of parting I want to do.

Like I said in your post on fixing Darrens lathe, I need to go through mine sometime and give it a good tune up.

Bernd

Pelallito · « **Reply #6 on:** March 26, 2009, 04:28:22 PM »

Bernd,
What kind of gib does your lathe have? On mine, they are plastic and, to my way of thinking, can't be too strong. Mine also lifts everything and the parting tool ends up on top of the started cut. As you said, it is a frightening sight.
Fred

Darren · « **Reply #7 on:** March 26, 2009, 04:41:15 PM »

I used to have quite a few parts made at a fully fledged machine shop.

I once asked the owner about rear toolpost parting, is reply was something like.

"if you can't do it from the front correctly then you shouldn't be thinking about going around the back"

Apparently, his words, rear parting is for bigger machines that can handle the extra stress, keeps one tool permanently positioned thus saving time in a working shop. But it's still not ideal.

Bernd · « **Reply #8 on:** March 26, 2009, 08:45:19 PM »

Fred,

The Grizzly has cast iron for the gib in back. At least I didn't see any plastic when I took it off to clean one time.

Bernd

Pelallito · « **Reply #9 on:** March 27, 2009, 07:11:34 PM »

Bernd,
Mine are a sort of white colored plastic. I always Assumed they were the factory gibs. Who knows if I was right, the Bogs knows. So much for my Shadow impersonation.

Since he had a 12" Atlas that he tweaked a little, he must have looked at them a time or two.
Darren,
Thanks for that quote and explanation. I bought that particular tool holder after reading somewhere, who remembers where, that the rear mounted parting tool was better for a small lathe.

Thanks for the help and advice.
I will be doing something about it soon.
Regards,
Fred

bogstandard · « **Reply #10 on:** March 27, 2009, 09:35:20 PM »

Sorry Fred, I had forgotten about your original question about the gib strips. That question must have been in the brain cells I lost a few days ago.

I actually had an Atlas 10F, which used a lot of common parts with other sized models.

When I purchased my lathe as a pile of broken bits, there were in the boxes some white plastic type gib strips. I assumed they must have been a later upgrade to the machine, as they seemed to be made of PTFE. There were no sign of any metal ones, so I made new metal ones myself, which worked very well. I never did put the 'plastic' ones in.
I used to have all the literature for the Atlas, but no longer, so I can't check the spares list to see if they are original or not.

I would suspect they are original specced parts from the factory. As I can't see two individual idiots, doing the same thing, continents apart.

They are rather easy to make, just BMS strip with an angle on each edge and a few dimples where the grub screws locate.

Bogs

Pelallito · « **Reply #11 on:** March 28, 2009, 09:41:46 AM »

John,
Thanks for the reply. I looked through my Atlas parts book and they identify the two gibs as
part #28- 345-077-gib, combination
That doesn't give much information, does it.

The compound and cross slide gibs share the same number.
Those of us on the wrong side of the pond need a dictionary. What is BMS? Sounds like it could be something contagious.

Regards,
Fred

bogstandard · « **Reply #12 on:** March 28, 2009, 09:56:16 AM »

Fred,

BMS is bright mild steel. I think you call it cold rolled steel, CRS. It is basically, a rather softish easy to machine steel.

Bogs

Pelallito · « **Reply #13 on:** March 28, 2009, 10:15:05 AM »

Bogs,
Thanks again for your help. I had guessed at the MS part of the initials, but the B had me puzzled. I will look around my shop to see if I have anything of the right size, if not, the hardware store is just down the street. I will make them today.
Regards,
Fred

Pelallito · « **Reply #14 on:** March 31, 2009, 07:26:02 PM »

John,
I am not sure if I should post this here or start another thread because this doesn't really have anything to do with the inverted tool.

I spent Sunday working on the Atlas. I had made a steel frame some months ago that I finally mounted to the floor behind my lathe. I bolted a 2' by 4' piece of plywood to it. I took apart my control switch from where it was located under the pan( a long story from long ago), and bolted it to the plywood. Then I had to run new wires to the switch. I cut some almost too short, and had a heck of a time connecting them. I really don't like the looks of what I did and will probably reroute it this weekend.
Then I plugged it in and did not get this

The lathe actually worked and no sparks.

The only 1/8th" by 3/8th" steel I could find in my stash was a piece of O1. I made the first gib and it looked so good that I made the second one.
I don;t have a mill, so I cut the angles with my surface grinder. I put them in a precision vise that I had elevated to a 30* angle and clamped it to an angle plate. After making them, I clamped each one to the correct assembly using a 1/4 inch piece of drill rod and marked them with my transfer punch. I them used a combination center drill to make the divots for the adjusting screws. I mounted a shelf on the plywood and am making holes for my always lost chuck keys and allen wrench. I am going to put a strip of wood all the way around so that things can't roll off. I am trying to get organized.

It made a huge difference in the lathe. It feels much better when I took some cuts. I have not been able to do anything more with it this week.
Thanks for the help.
Regards,
Fred

bogstandard · « **Reply #15 on:** March 31, 2009, 08:06:48 PM »

Fred,

I'm glad the gibs worked out OK for you. I think that over the next few hours use, they will start to bed in and run a lot smoother, then you will be able to make your final tweaks.

A lot of people put the Atlas down, saying it was cheap, badly built and no good. But in all the time I had mine, it never gave me any cause for concern. In fact, it was with the Atlas that I produced some of my most accurate and best work.

The Atlas model I had was much copied by UK manufacturers after WW2, because it proved it's worth during the war years, even in the hands of unskilled people. Being reliable, easy to use, and v-e-r-y versatile.

John

Pelallito · « **Reply #16 on:** March 31, 2009, 08:15:19 PM »

john,
After I get some hours on it I will post again. Maybe I will actually make something on it!

Thanks again for the help.
Regards,
Fred

sbwhart · « **Reply #17 on:** April 01, 2009, 05:08:05 AM »

Hi Fred pleased you got your Atlas sorted and it sounds like your getting your shop up to speed a few pics would be nice

Have fun

Stew

Pelallito · « **Reply #18 on:** April 01, 2009, 06:02:21 AM »

Hi Stew,
I did not think to take the camera with me into the shop. If I can, I will take photos. My shop right now looks like a tornado ripped through it. I don't have a clear horizontal surface on any bench.
Thanks for the banner.

Fred

sbwhart · « **Reply #19 on:** April 01, 2009, 06:16:11 AM »

Fred

Your shop sounds like mine after a few hours, I find that as I go along I use a tool put it down someware:- repeat, repeat, repeat, after a couple of hours I've tools everyware, I've gotten into the habit of tidying the shop up when I first go in, that way I've got the decks stripped for action.

Since joining this forum my camera (ell cheepo kodac digital) has become an every day shop tool, a bit like a spanner.

Have fun

Stew

Pelallito · « **Reply #20 on:** April 04, 2009, 08:21:02 AM »

Stew,

That's basically how I operate. It is mystifying to me how I can put so many tools down while doing a job. Some of which I will put down and lose them on the bench.

Then I have to waste more time trying to find them. I feel like doing this

to myself!
I was finishing some of the lathe work and cleaned up a little yesterday.
Fred

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Author Topic: Another Inverted parting tool ? (Read 11138 times)

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