Author Topic: Continuous slide way oiler  (Read 550 times)

Offline Neil-Lickfold

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Continuous slide way oiler
« on: January 11, 2019, 05:45:50 AM »
So to get the saddle to be repeatable on the slideway, I fitted some oil points, and a gravity oil feed of slideway oil. This keeps plenty of oil on top surface and on the sides as well. I just place the oil put at different levels to control the amount of oil working its way through. Without this, I could not get the consistency required to trim pistons to size, instead of lapping. I also had the top slide rescrapped, and fitted so that it was as true as possible with no measurable wobble in it's movement.
This is required if the top slide is to be used to get very small X movement on the lathe to get to micron trimming for pistons. It also helps if the head stock bearing, in my case a Myford S7 that was new in 1972, is as round as possible, with a then fitted tapered bushing. I have it set very close, and have had it tested to show a 1 micron max runout. The strange part was , a test piece turned, placed in a vee block, and a 0.001mm dti placed on the part and then rotated showed less than the needle width on the DTI. Anyway, this sort of accuracy is needed to trim fast race engines for F2C diesel team race, and for F3D pylon race engines. The power increase due to the better turned piston is very measurable.
Here are some pictures of the basic oiler I use. At some point I need to replace the rear bearing set on my lathe, as it is at it's lifes end for what I am doing with this lathe.
I don't run anymore than 750 rpm for any of my turning.
Neil

Online Jo

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Re: Continuous slide way oiler
« Reply #1 on: January 11, 2019, 07:54:41 AM »
 8) Nice mod to your Myford Neil.

People under estimate the need to have good consistent lubrication on a lathe to be able to consistently turn to very tight measurements. Yours is really simple to make and install as well  :ThumbsUp:

Jo
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Offline derekwarner_decoy

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Re: Continuous slide way oiler
« Reply #2 on: January 11, 2019, 08:22:48 AM »
Nick......my understanding of Myford Super 7 lathes is two [basic] varients were produced.....the first with a pair of white metal axial and singular thrust bearing, and a second with a matched pair of taper roller bearings for the headstock [7007A?]

A number of years ago, I read an article of a reportedly genuine Myford [sourced] set of such taper roller bearings for $1200.00? per pair

With respect to your gravity feed for the saddle [and cross slide?] oil lubrication...... is the question are you using the Myford recommended ISO 68 [ISO VG68] mineral oil?

When we look at this oil, the specific gravity will remain constant within your workshop environment, however the head pressure on the bed & saddle will be dependent on the elevation of the oil feed cup, and a consideration that the actual viscosity of 68 cSt is at 40 degrees C
[this can be considered as an oil drip feed yes, however many other factors determine the actual flow/drip achieved]

When you mention TIR [on small diameters] down to 1 Micron, obviously you are using a clean ER25 collet set & are you using compound instrument makers mechanical indicator or a digital referencing system?

If you require toleranceing to these levels for internal combustion engine components, how do you achieve this on your Myford saddle cross slide?

Derek

« Last Edit: January 11, 2019, 08:39:17 AM by derekwarner_decoy »
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Offline Stuart

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Re: Continuous slide way oiler
« Reply #3 on: January 11, 2019, 08:31:13 AM »
Derek
I believe Neil said he setts his TS to 0.5 deg in another post

But its still a fantastic achievement
My aim is for a accurate part with a good finish

Offline Neil-Lickfold

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Re: Continuous slide way oiler
« Reply #4 on: January 11, 2019, 10:24:31 AM »
SO, I normally set my compound at  0.5 deg angle per side taper, that gives me the very close to 0.1mm top slide movement is 0.001mm on the side movement. When I do the MB40 pistons, I need 0.75 deg compound angle, so to get a 1um diameter movement, I only need about 0.038mm of top slide movement. Another aspect that I forgot to mention, is that I made a M8 X0.5mm pitch cross slide screw, and use the original 100 division imperial dial. So every division on the dial is 0.01mm in diameter. My lathe has  the tapered bronze head stock bearing. SO if the room is at 12 deg C, It will not turn at all. So I have the room heated in winter to 20deg C with a little heater in the shed that costs a measurable amount of money per moth to run. In summer it stays around the 22 to 24C temp so is quite nice. The slide way oil is the normal 68 weight oil, and is slow flowing through the 4mm OD tubing. The tubing lengths are altered so that the flow to the front of the saddle and the rear of the saddle become about the same. Just trial and error  before connected to the fittings that were M5, but I ran I die down them for the BA thread that they are. Cant remember what that is these days. It ment that the fitting for the Myford saddle remained factory and if need be could put the original oiler fittings back in.
I guess the next level  is setting the tools. So I cheat here, and as I know the aprox diameter I am triming the piston to, within 0.03mm diameter, I turn a test piece with normal tools. Then set the compound to the desired angle, either 0.5deg or 0.75deg. I only have 2 choices I use, and my favourite is the 0.5deg. I use a phone ap called smart tools and has a magnifying glass camera tool. Really good to zoom in and see the middle of the markings and get where you want it. It is also really good to look at the insert edge and see of it is still sharp or that the surface finish is what you expect it to be. Anyway, after making the dummy test piece, I set the compound so that the front is lined up with the casting and then has about equal movement forward and back. With the dial in a downward position, I use a piece of 8mm video tape between the tool cutting edge and the test piece to set the tool position with. Gently tighten the screws just enough to hold the tool holder, then I wind out 1 turn, tighten the holder, and then see where the tool zero is. PCD tools can be easily damaged, so extreme care is needed.
Then I am kind of all set. I do have some really nice measuring tools, like a Tesla 0-30mm reference micrometer in 0.001mm increments, and a set of calibrated gauge blocks with their reference certificate which is really handy. The mic comes with a histogram of it's errors, so that is really handy as well. I also have a refernce 0.001mm DTI with its histogram so can allow for errors in the travel etc. And other 0.002mm finger dial indicators etc.  Once you get to levels of smaller that 0.002mm in diameter, really it becomes a mater of making it work with the bore and its taper. Remaking a part to 0.002mm is a lot easier that trying to achieve 0.001mm diameter. But you can try the liner over the piston on the mandrel, and clean with break clean the two parts, wait for it to get back to room temp, then try the fit. On these diesel engines, 1micron is about 0.5mm of movement up the cylinder bore. As they have a taper of about 2micron per mm of travel. But each cylinder needs measuring to check what the actual values are for that particular cylinder.
It is not easy work, and they can take up to 2 hours to fit a piston. Can you turn and lap one is less time, absolutely you can. Will it perfrom as well, No it wont. So that is why we trim to size. The feedrate of the tool with a 0.4mm radius  is about 0.01mm per rev or there abouts. The lowest feedrate on the Myford gearbox
is 2 thou per rev, so is about 1/6th of the lowest feedrate. My chuck of choice is a Burnard Grip true chuck, that I have serviced and looked after. I can use an indiactor and get it set to a very small amount of error. I have set up pistons and trimmed a total of 0.002mm off them for refitting. When trying to bring the tool in, mark with a blue or red sharpy ink pen. Easy contrast for old eyes. Then just run passes untill you take the high of the marker pen off. You will see the blue or red build up on the tool tip. As you get closer, you will see the high shiny spots on the work piece, and the market pen still in the micro grooves at the bottom. Here is a picture of  piston that needed 0.002mm off it and you can see the roundness error in the bottom part of the piston. The total roundness error of the bottom was about 0.015mm or so. I hope this may be of some help to others out there. Just practice and be very patient, and use very sharp tools. You can see the shading of the marker pen. I think it is interesting any way. Often a marker pen is about 0.02 to 0.03mm thick, in that range per side.
Neil

Offline steamer

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Re: Continuous slide way oiler
« Reply #5 on: January 11, 2019, 11:11:53 AM »
PCD is cool....but a bit pricey.
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