Member postings for Neil Lickfold

Without a DTI, just using the tool, about 0.1 to less than 0.2mm total runout. 0.2mm runout looks quite terrible when it is running. 0.1 looks not too bad, this is TIR . With a DTI and 2 keys, if the bar is round to start with, getting it to about 0.02mm to 0.03mm TIR is actually quite quick. Getting less than 0.01mm takes more time and care. Then every micron takes more time.

Neil

Dick, I sent you a PM.

Neil

John, that flip up threader, how does it go on fine threads in Aluminium? Does it benefit from having some counter balance on the back behind the pivot point ?

Thanks for sharing and taking the time to document the process as well. I'm quite hopeless at documenting what I make. I just do it and take the odd picture of setups that were quite involved or innovative for me at the time.

Neil

We made a hall effect backplate for a 2.5 cc engine for F2A, runs from 39k to 40 k on our test prop and rpm readings from the model. We were really surprised at the RPM variation from shot to shot and the in cycle variation. From 1 rev to the next, can be as much as 400 rpm difference , or effectively a plus and a minus of 200 rpm per rev, Then it can run for a short duration of being within 2 or 3 RPM. What was more interesting was that the model plane flies as fast as it does due to the pulse of power as the engine picks up in rpm at the power pulse. So we could see the model flying in mini jumps. So it pulses every 120 to 140 mm on the circumference. So when compared to a backplate that was made of brass , more fly wheel effect and an Ali one, it was actually faster on the Ali one, but easier to set on the brass one. So in short , it makes more usable power with less flywheel, so it must be actually making more total power. Trying to dyno the power output is very difficult on model engines. I think a brake type dyno is the way to go. For model plane motors, I think that a calibrated propeller is the way to go. So a prop run up on an electric motor and rpm, torque are measured to know it's power absorption. The tachometers sold for model engines take averages of the pulses of light to give a readable average value.

Neil

Getting back to chucks, I tried 3 methods to get the jaws correct on a worn bodied chuck. The video link of grinding a reference through a sleeve and then clamping down onto a spider or plug works for chucks that have a body in good order. The body of this chuck is worn. When I put the jaws from the new chuck into the old one, it would still clamp tighter on the back of the jaws and be loose on the front. When I used the ring with 3 holes in it for the jaws, the end result was the jaws were cut too much on the front. So when I clamped down on my test piece, the front was very tight with the back being loose. So then trimmed with the wood bits and it worked the best on this chuck. The wood is a physically hard wood and is clamped across the grain, not on the end grain. When I bored the jaws, in each case I used a boring bar with an insert capable of hard turning with a 0.2mm nose radius only taking small cuts each time to get a minimum clean up.

Hopefully this may help others who have worn chucks and would like to improve the chucks condition without too much effort with an more than acceptable outcome.

Neil

Yes I deleted it from my album, as I did not want something there that was not effective. The wood can crush quite easily . I tightened the chuck to about the same as holding a part . Then rebored the inner of the jaws and trued the front face.

This is the picture I had in my album. It is a link to http://lathe.com/tips/chuck-jaw.htm

Neil

So I did a minor referb on my old grip tru chuck. I added a grease point that puts grease into the area between the scroll and the chuck body, (main scroll location) and also puts grease into the main body under 1 of the pinions. Time will tell if it is a good idea or not. The other option was to turn off some from the body on the inner loaction and press onto there a sleeve, then retrim and recut the inner of the scroll as well. Here are the pics of the grease fitting and the position of the hole into the body and scroll.

Neil

So I made one of those rings that I had in my album with 3 holes to clamp the jaws with. I was not happy with the result from that method. So then got some jarrah from the left over spa pool surround, and cut it into piece 18mm wide and 5 mm thick. I put these in between the jaws, and turned it all out. Very happy with the result.

Neil

Edited By Neil Lickfold on 17/05/2017 12:04:44

On my S7 there is a Nylock nut on the bottom of the unit like you describe. It is set so that it locks at about 10:30 or 1:30 depending which side you are looking at it. I can't remember that last time it was taken apart and adjusted. The secret is to keep the area under the the bed where it pulls up to clean. I have a leather cover on the front of the saddle and occasionally clean under there with a paper towel. When drilling, I back up the saddle to the tail stock. This leaves almost no gap for stuff to get down there and to be trapped on the under side. I find brass to be the worst for some how making it's way to stick to the underside of the bed .

Neil

Today I added a grease point to the inside of the scroll of my old GripTru chuck. It has a small amount of wear, so instead of recutting and making sleeves etc, I just added the front grease point.

Time will tell if it is a good idea or not.

Neil

Blasting soda is a free flowing baking soda, so it pours quite well. Makes for a very hard compound. Another we use as a wear strip is a combination of blasting soda and carborundum powder. I use it for a landing skid on my model planes.

Neil

Dave, If you have a VFD Variable Frequency Drive, they will stop with in 1 second from 400 rpm aprox. I screw cut at about 200 rpm to 400 rpm.

Neil

You will find that if you use either and extended too bit in a larger block, or use an insert threading tool, you will be further away from the chuck diameter wise.

To not crash into the chuck, when I installed the VFD, I also added a micro switch. This is just set up to trip when the carriage gets to the desired position.The lathe motor stops and so does the carriage. If there is a run out (thread relief area) then retract the tool. Then simple turn the switch to reverse. It goes back and ready for another cut when in the forward position again.

Previously I used to do the marker pen thing for internal threading and just looking at the thread relief when external threading. I like to use the angled approach when threading, except when I have some special situations where an angled retraction in internal thread can cause damage to the end face. In these cases, I leave the compound on zero.

Neil

Rod, you can buy the ISO standard for chucks, but no where did I find it free to read. Only references to it. Did find that the 1991 is replaced with 2005. In saying that, class 1 is more accurate than class 2 , I did find a TIR for chucks to 300mm being 35um. I also found that super precision chucks have a repeatibilty to 0.013mm( 1/2 thou I assume) and an adjustment to 0.005mm. These were from the Pratt site about Griptru chucks. In realty if the spindle bearings are very good and the right gear, you can get a Griptru down to less than 2um. It won't repeat to that, so once the part has been removed, it will need dialing in again.

From what I have seem, the repeatibility and the TIR seem to go hand in hand. On chucks over 300mm the TIR goes to 75um so 3 thou in real measurements.

Neil

I pulled apart my newer Griptru chuck. I was surprised to find it had bellville washers under the std washer under the capscrew. I knew the old one had the bellville washers under the capscrews. Anyway, I put it back together without the mini spring washers, and did not like it at all. So I put them back in, but left out the regular washers.

The grease in the chuck had gone to a very thick gunky wax like substance. New thing for me is to make stripping and cleaning more often than 20 years. I was pleased that there was no swarf in the back. Maybe the gunky waxy grease is like that for a reason. In the mean time, I just used Lithium EP grease.

To the OP, 3 thou on an old 3jaw that may have been abused is not too bad really. Considering that a lot of parts are essentially made in 1 operation and the 2nd op is just a facing operation after, it will be fine.

Neil

The truing up of the jaws is a good thing when they have worn a little on the front. I have a couple of Grip True chucks. The older one of the 2 has little bellville washers under the back plate cap screw heads. The newer one does not. Only had ordinary washers under the cap screw heads. Does anyone know if the bellville washers are original or an upgrade from the previous owner.

On the original 3jaw chuck that came with the lathe, I trimmed some off the diameter of the back plate spigot, and then brought some bellville washers. Made the od smaller to fit into the counter bored holes of the chuck. So when I needed to get it close to 0, I can just loosen off the cap screws a little, the pressure from the washers help to hold it in place when when making the small adjustments.

The grip true is quicker than the std chuck and the 4 jaw to dialling in. But a 4 jaw with 2 keys is fairly quick, but not as fast as the Grip True.

With chucks, the 1st thing to assess is if the run out is due to the jaws, or if it is a swash problem. The swash problem is easily solved by turning a bar, closing the chuck onto it and then skimming the back registry face. To assess the swash runout, just close down on a few different sized bars. Then when indicated near the chuck jaws, and then at some amount depending on the length of the bars, like 50mm or so, see if they are in the same direction relative to any reference on the chuck. If it shows a correlation then it is a swash error with that chuck. Some more things to look for anyways.

Neil

We used to do all our own heat treatment years ago. But as the gear got old and required upgrading the decision to have it all done by an outside company happened. The advantage of the inhouse setup was control of the process and saved time for the part being made. The downside was cost and the time being spent to monitor the process. In this regard, the commercial heat treatment company is cheaper, but is a 3 day turn around or sometimes more. Now days most parts are single tempered, but double or triple tempered can be asked for. They do have inert atmosphere ovens which reduces scale etc and leaves the parts looking nice and sharp corners being still sharp.

Neil

I would look at the end float of your spindle. Can you easily move the spindle back and fourth by that amount you are showing as an error? Did you have the saddle in a locked position on the bed? Did you take a skim cut for the final cut if it was running in a swash situation before trimming? Lots of questions I know, but these are all reasons for the error you are seeing. Excessive wear in the cross slide gibs and compound gibs can also allow movement , especially if there was a reasonable amount of an uneven cut thickness while the part is turning. Often excess wear in the cross slide can show as a taper on the face, but that is not obvious in your video.

Neil

Thanks Muzzer,

He under states the importance of holding parts if true roundness is required. The more round you want it, the harder it becomes. Having compounds that cut with little resistance is also understated in his video. The other secret with laps is that they are softer than the material being cut. The sunnen approach for external honing just can't be beat for roundness and the control of the taper. Lapping can take away material in areas that you do not need material removed. A high polish finish on a surface can be easily achieved with balsa wood and fine abrasives. Flexure laps for inside lapping have been around for a very long time and do work very well.

Honing allows you to get to the near very bottom of a hole or upto a shoulder on a shaft. Lapping often does not lend it's self well to blind holes and shafts with shoulders.

Neil

What I want to know, is how did they manage to make something as precise as they did? Where files and forms of lathes common place at that time? What steel tools were available at that time? Did they use forms of ceramic tools back then?

Neil

You could make a poor mans external hone , by making a small vee block, and then using thin double sided tape or glue the fine wet and dry to it , or quite fine stones to it. Then us another sitting almost vertical above and polish away. For the 10mm bearing, if you want a press fit size for size . If you want a light slide fit, it is about 9.992mm and about 9.996 is a very light fit. Hope this helps, Fine is 240 to 320 paper or stones.

Neil