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Member postings for old mart

Here is a list of all the postings old mart has made in our forums. Click on a thread name to jump to the thread.

Thread: Lathe steady position
30/08/2019 17:22:26

I would try testing what would happen if the front hole in the steady was repositioned. Looking from the chuck side, the steady minus the front screw could be pivoted until the vertical finger is directly above the spindle axis. At this point, the horizontal finger should be checked to see if it is in line with the spindle in the horizontal axis. If those two positions can be achieved, then the front screw position in the steady can be remachined. The new hole at the front of the steady will be further from the edge where there is plenty of meat.

Thread: Tool post project
28/08/2019 20:50:33

Taking your design to extremes, assuming all your tools are the same size, would be to put the round groove directly in the top of each tool. It could be done with solid carbide bullnose cutters, although the ends wouldn't stay sharp very long.

Thread: Home Made "Inserts" -Feelin' Groovy.
28/08/2019 20:40:49

I had the work shift slightly in the chuck when parting off, and it destroyed one end of my Kennametal 26mm blade which holds the 1.6mm inserts. I am very careful with it now, only one end left and 7 new inserts which only fit that exact blade. I try to avoid parting off in a three jaw chuck, four jaw independents are much more secure.

I always lock the saddle when parting or grooving.

Edited By old mart on 28/08/2019 20:44:52

Thread: Start of Tom Senior refurbishment.
28/08/2019 20:17:53

Today, I thought I ought to check whether my conversion to R8 has been up to scratch. With the er25 collet holder nice and tight in the spindle, using Vertex and Cutwel collets and trying 6,10,and 16mm shank endmills, the runout was 0.0003" tir on each size. Then I tried out my Osborn Titanic II, with 16mm, and 1/4" shank endmills and got 0.0005" tir on both. All the careful setting up of the spindle parts and the lower bearing outrigger has paid off. I had been worrying about how the two halves of the spindle would run, especially as the SKF lower taper roller and the Timken upper taper roller ran on different halves of the spindle. One drill chuck runs from 0.002" to 0.004" and the other larger 16mm one runs 0.004" @ 16mm, dropping nicely down to 0.001" at 6mm. The self extraction with the drawbar works very well, just 1/4 turn between pulling and pushing.

Not everything is quite as fortunate as that, however, I found out that my boring out of the motor pulley isn't deep enough, so it has to go back up on its mandrel for another 14mm of bore.

Thread: Home Made "Inserts" -Feelin' Groovy.
27/08/2019 17:34:40

Sorry, I don't understand when you say the cutting part is to the right, (picture 5). As for chuck clearance, what about the SHCS sticking out? I also cannot understand why the steel should go blunt so quickly in brass. Have you tried a file on it after tempering, if the steel is low carbon mild steel, it will still be soft after any heat treatment.

Edited By old mart on 27/08/2019 17:36:18

Thread: 0.300" & 0.400" 28TPI Tap
27/08/2019 15:35:06

At the museum, having had many donations of tools over the years, we have many taps which were made for specific jobs in industry. Many only have factory code numbers and can never be identified, and others which are usable at first glance, have + or - tolerances added, which could be disastrous. My favourites are a set of three 0.7" buttress thread taps, they look wonderful, but I cannot think of a use for them.

Thread: Home Made "Inserts" -Feelin' Groovy.
27/08/2019 15:22:37

If the ground flat stock is gauge plate, it is the equivalent of silver steel. I would try hardening it, polishing it and then heating it very slowly from the other end until the tip area is light straw, before quenching. After tempering, finish hone with a fine diamond lap. If the dimensions allow, grind the end so that the plan view is biased to the right, yours is to the left, which is not so well supported by the groove in the holder. So far, I haven't needed anything narrower than 1.6mm, the width of my smallest carbide inserts for 26mm blades. I'm not sure of the best profile for brass, it is a matter of trial and error.

Thread: Taper Turning using set-over attachment in tailstock
26/08/2019 20:55:24

I'm sure you know that the measuring equipment must touch exactly on the centreline, and this also applies to the tool height, internal and external.

Thread: QCTP problems
26/08/2019 15:18:51

Got it, the first time I looked, the "QC" was black and I ignored it. Now it is blue, must be magic!

26/08/2019 13:55:15

I think you will have to explain what you are talking about, so far it doesn't make sense.

Thread: ACME thread identification question.
25/08/2019 22:34:43

What condition is your spare leadscrew and nut? Could it be used? I recently made a new 3/4" x 5 Acme nut for a mill, and bought a tap from Tracy Tools. When I tried a test thread in aluminium, I realised there was very little chance of tapping the thread without a tap wrench with a 3 foot long handle. The tap was about 8" long with a gradual taper, and I had to shoehorn a smaller acme insert on a special threading tool just to partially produce the thread for the tap to finish, and then it was hard work. This was in leaded bronze (gunmetal).

Do try a test piece before the actual nut, you may have to tap into a slightly oversize hole. Keeping the tap straight could be made easier using a dead centre in the end of the tap, with the nut in the chuck, preferably a 4 jaw independent.

Thread: Start of Tom Senior refurbishment.
25/08/2019 18:41:03

I have decided to make a totally new motor mounting plate out of a 1/2" thick piece of 6086 aluminium, 250 x 153mm, as the modern mounts on the motors are quite different from the original ones. This is slightly thinner than the old one, but stronger as it is not a casting. The alternative was a 6mm thick plate as an adaptor, which was not thick enough for threading. The drawbar is fitted which is self extracting with its bronze bottom nut, and brass washer, half nut, main long nut and a second half nut at the top. Because the drawbar nut is a larger spanner size, the hole in the pulley housing which the chrome drawbar cover fitted has had to be bored out in the mill. I will have to look for something to make a cover out of, some nylon bar might do.

Thread: ACME thread identification question.
25/08/2019 18:19:55

Not quite the exact topic, but worth bookmarking:

**LINK**  

Thanks for the the instructions on how to post links, I will try to remember how.

Edited By old mart on 25/08/2019 18:21:30

Thread: Current leakage om CNC
25/08/2019 16:33:34

I have just bought a VFD made by Schneider for the rebuild of the Tom Senior mill. Reading the full manual, there is a mention of an earth leakage caused by the filters fitted to it. I don't know what the value is.

Thread: ACME thread identification question.
25/08/2019 16:25:20

I needed a crosslide leadscrew and nut for the Smart & Brown model A at the museum, and bought a new leadscrew with two nuts which was long enough to modify for the lathe. It was advertised as 8tpi, but turned out to be 3mm pitch. I told the vendor, who immediately refunded my money and said keep it. It was one of those times when hard choices have to be made. Keep looking for a hard to get item, or make the most of what you have got. I used the leadscrew, and also used both nuts for an adjustable backlash feature. On an old imperial lathe, a metric leadscrew is not a good idea, so I used the rotary table on the mill to make a scale for the crosslide with 118 divisions instead of 125. The actual error is tiny, especially if you creep up on the last bit of the size required. The backlash is set at 0.001", which makes for smooth running.

25/08/2019 15:02:56

I have looked up the thread calculator, and the standard bore through an ACME nut of 7/16" by 10tpi, is 0.343". The tip of your tap should be this diameter or a little less. To verify your pitch measurements, the scale on the leadscrew handle should be 0-100 in thousandths of an inch. Holding the two leadscrews alongside each other will confirm whether the pitches match.

https://www.engineersedge.com/hardware/acme-threads-calculator.htm

I don't know how to get a link to work on this forum.

Edited By old mart on 25/08/2019 15:04:46

Thread: Lathe tool holder
25/08/2019 14:24:22

You could hold the shims with a couple of 2mm countersunk screws, if you are up to tapping small holes.

Thread: ACME thread identification question.
25/08/2019 14:11:06

When the exact pitch is in question, then using a longer reference length will give more accurate results. For instance, the difference between 8tpi and 3mm pitch is only about 0.007", which would not be easy to measure over one pitch. Not so difficult if measured over 300mm, (100 X 3mm), or 12", (96 X 8tpi).

25/08/2019 13:20:05

Are you sure that the leadscrew is left hand? If it is left hand, looking at it, the threads will tilt slightly clockwise from vertical. Measuring the pitch can also catch beginners out, measure an inch of thread. There should be ten pitches from the start of the first to the start of the tenth. I would think that Boxford would either use 10tpi or 8tpi, assuming the lathe is imperial and not metric.

 Don't worry about the ACME being 29 degrees and the Trapezoidal being 30 degrees, you will not be able to tell the difference.  

Edited By old mart on 25/08/2019 13:25:02

Thread: Start of Tom Senior refurbishment.
24/08/2019 21:48:21

The head is looking nice now that it is finished except for the motor mounting. Mike fitted the bearings back in the pulley housing and fitted a grease nipple in place on the original button oiler. We don't want anyone oiling the needle rollers. I milled a second flat on the splined pulley holder, so that both of the grub screws in the pulley have something to grip on. I do wonder at the design, the whole pulley and motor assembly is held onto the head with four 2BA screws. The quill spindle drive splines are lubricated with a sparing amount of moly grease applied using a toothbrush. Otherwise, ordinary lithium grease is used for taper rollers and needle rollers. Everything else has slideway oil, except for the leadscrews, which have spray motorcycle chain gease. The quill spring causes a clang if it is let go, so I am getting some 7mm diameter o ring material to make a soft stop. I had put a step in the outrigger where it screws into the quill, for no particular reason when I turned it, and the bump stop will sit there.

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