Member postings for old mart

As already mentioned, your faceplate requires truing up, a difficult job on a lathe without power cross feed. The difficulty is in keeping a constant smooth feed while facing.

I have already mentioned that the register has little or no affect on the repeatability of a screw on chuck.

If the faceplate is trued up, then the backplate could be attached to it, adjusted for concentricity of the female register, and the threads very lightly skimmed. Then before taking anything down, the rear face of the backplate skimmed true. After that is done, the backplate needs to be screwed up tight and backed off several times to settle it down, before checking the runout of the chuck mounting face and the concentricity of the chuck register. Both may require truing up.

Are the guidelines regarding reusing the tape ok with the possibility of it stretching?

Running an inverter from single phase mains usually requires the motor to be setup in delta, so if you can figure out how to set the links it should be fine.

It looks like the motor is 3.7 - 5.5 KW according to the speed selected, you are unlikely to be able to able run from an ordinary socket, it will have to have a dedicated consumer unit, like an electric shower. That 3.7 - 5.5 might be the amps per phase though.

It would help if you tole us what machine the motor is used on.

I have a 6" standard, and a 12" heavy duty Mitutoyo digital, as well as several of the cheap Chinese ones from Lidl.

The Mitutoyos are kept for best, I can measure consistently to 0.001", even bores, which calipers are not particularly good for.

The cheap ones are great value for money, but cannot match the Mits, which doesn't matter for most work. I have noticed that the quality of the Lidl bought ones has dropped in recent years unfortunately.

The angle of an R8 spindle is much too steep to use without a drawbar. I believe that the main reason for the pin is to make sure the tool does not slip round when the drawbar is tightened. It has no other function except, as mentioned, it will ensure that every tool is fitted exactly in the same position each time. This aspect should not matter as the spindle is expected to run true.

Larger spindle tooling such as BT40 are of improved design, having drive lugs, but they can still be installed in two positions.

I am leaning towards omitting the pin for the following reasons:

A. The arguments against are compelling.

B. I save having to drill and tap and make a pin.

C. I think that holding the tooling still during the initial tightening of the drawbar should not be difficult. 

D. I have no plans to run the spindle in reverse.

Edited By old mart on 29/07/2019 14:03:48

Seeing that 160mm chuck, 6.3" on the lathe suggests to me that even a 6" would be too big. The jaws cannot be positioned much past the OD before hitting the bed, so your 5" could probably hold larger diameter stock.

I notice that Pete Rimmer mentions that John Stevenson did not include the pin when he made the custom R8 spindle. It's a great pity that John is no longer with us to explain why, he was a great engineer.

The radius is only about 1/2" greater than the original, so there is a pretty good chance of it being ok. Check how much clearance there is with the jaws on your present chuck extended to simulate the biggest size the chuck is intended for. You may loose a little length with the bigger chuck. The Pratt would be an advantage in capacity and quality, I hope it comes with both sets of hard jaws.

I checked up on suitable alloys and any of the 6000 series are ok, 6063 being the best for colour anodising. It was also mentioned, that for consistent colour, make all your parts out of the same alloy.

There is no way that the pin could prevent slippage, the taper being tight does that. The drill mill at the museum had to have the bottom bearing replaced, and that spindle has two pins, one directly under the inner bearing race. I just set them to allow easy tool fitting. One or two of the R8 tool shanks I bought needed their pin slot relieving slightly before they would fit.

 A spindle lock won't stop the tool being slightly prone to slip while the drawbar is tightened, unless the tool shank has a spanner flat on it. I would hope that smartly seating the tool and holding it while the drawbar is tightened should suffice. The drill mill has no spindle lock, we just hold the top pulley and give the drawbar tool a couple of whacks with the hand. The biggest cutter that is used is 80mm, we have never had a problem, although we refrain from taking big cuts.

The new spindle will project enough to put spanner flats of 32mm without loosing too much wall thickness, there is no other way of holding the spindle due to the design of the mill.

Edited By old mart on 28/07/2019 13:47:20

I am currently converting a Tom Senior light vertical head from MT2 to R8.

R8 spindles were designed with a pin projecting into the bore to stop the tooling from slipping when the drawbar is tightened. There are mixed opinions as to whether the pin is needed, or just a liability. I have the choice at this stage, "to pin, or not to pin, that is the question".

I look forward to your comments.

I did try checking the flatness of the X axis ways, it had to be up on the four 1-2-4 blocks which I bought to mill the top of the bed. The leadscrew nut bosses project above the surface. I got lucky with the 1-2-4 blocks, not only are they an unusual size, but they match well as a quartet.

I will post more pictures when the head is dismantled.

Nothing more than oil and wire wool on the edge, but fine wet and dry paper, say 600 or finer on the rest.

I would worry about all the ferrous swarf sticking to the strip all the time, or are you only going to be turning non magnetic metals?

I forgot to ask what alloy you are using.

We have the mill bolted down on the 4" of wood using 12mm studding glued into 4" holes in the concrete floor. The machine is not being fully repainted, just a good abrading of the paint and a spray of Plastikote lawngreen paint. The colour is a brighter green than the top of the can suggests, so not exactly concours, but it seems to be oil resistant. The tray got sprayed Hammerite satin smooth black, and has a red strip surround intended for car doors.

We were lucky with the Y axis leadscrew nut, which in conjunction with new metric thrust bearings, seems to have only 0.001" backlash, I haven't checked it with a dti yet. The thrust bearing housing had to be bored deeper and larger diameter to accommodate the larger metric bearings, which are much heavier duty than the originals.

I am just starting the conversion to R8 spindle taper. I have an SKF taper roller bearing 35-62-18 for the bottom of the spindle. Also a spindle from ArcEuroTrade intended to fit one of the Chinese mills they sell. The spindle was bought because I didn't feel confident in producing the internal dimensions well enough. The spindle has been checked for accuracy and concentricity and to my relief, there is nothing over 0.0005" tir.

Simon Williams may be interested that prior to disassembling the head, I found that his mill is not the only one that has needle roller bearings in the spindle drive. The machine was made in 1969, has the long bed, the later style quill lock and all the castings have the same assembly number 7 stamped on them. A bit of a mystery.

Use a dental mirror to look for something stuck in the threads, there must be something there. I have chuck backplates with registers varying from 0.0005" to 0.015" clearance. They all repeat perfectly, the tight one can be difficult to get on and off though.

Once you manage to get your chuck screwing on and off more easily, then remove the chuck from the backplate after fitting on to the spindle and check the face and register for the chuck with a DTI. A light skim may be required in one or both planes.

The anodic layer is porous and the pores tend to close up during rinsing, especially in hot water. The dye is trapped in the pores in a heated dye tank.

You may have to run a series of test pieces to find the best method of rinsing before the dye tank, also the optimum time in the dye.

 Maybe your voltage is too low, anodising is a non conductor, and the voltage is normally increased as the coating gets thicker.

Edited By old mart on 27/07/2019 19:45:52

You can certainly hold a hexagon in a four jaw independent if you want to.

Those three jaw scroll chucks with independently adjustable jaws are intended for use with odd shapes which are all the same. Once the chuck is adjusted for the first one, then simply by using the scroll, you can rechuck successive components quickly. Otherwise they are a PITA.

 Most of my three jaw scroll chucks have reduced registers and enough play in the backplate screws to allow a few thousandths of an inch fine adjustment. It is easy to increase the number of bolts/screws holding the chuck to the backplate from three to six for added security. The exception is my Pratt with the serrated jaws, which is normally used with soft jaws, so it always runs true.

Edited By old mart on 27/07/2019 19:31:58

When I was working, we had two polypropylene 30 litre tanks of acetone for first and second rinsing of aircraft sub assemblies which were tested with Skydrol hydraulic fluid. Skydrol in a phosphate ester fluid which is non flammable and used extensively in commercial aircraft. It is not a pleasant substance to work with.

We never had a fire when I worked there, if the stuff had ignited, running away was the only option.