Member postings for old mart

There's usually a way to get over problems, I'm glad it worked out for you ok.

I had to measure the distance between the ground floor ceiling and the underside of the floorboards hoping there was a section of boarding, but it measured 8", confirmed by direct measuring from the stairwell. Those pipes must rise up when they pass through the lavatory. Next week I will be in a position to remove the toilet which will give me plenty of room to work. I already know where the waste pipes run in the bathroom, a few years ago, I refitted it with all new stuff and also the toilet. Removing the bath panel confirms that the floorboards run at right angles from the wall and the waste pipes run parallel to the wall just below floor level. There is no sign of wet anywhere except lower down on the line of the vertical 4", 110mm main waste.

Edited By old mart on 15/04/2021 17:27:45

I looked using an 8mm USB snake and my laptop through some 1/2" holes I have drilled. There is about 8" between the upstairs floorboards and the ceiling downstairs. Fortunately, the leak is from the bath/basin, not the lavatory.

Keep us posted with the results. I have cut a few double starts, and I finish the first and then move the compound to do the second. In your case you would move the compound 1/10". Take care of the runout for the second cut. The first one I did was the double start toolpost spindle for the fixed four way toolpost on the model A (not the type which slots into the compound). I think it was 1/2" x 8 ACME doubled, and to get it to screw in, I had to cut both starts deeper than expected. That involved removing the job from the chuck, but as the thread is so coarse, it is easy to pick back up with reasonable accuracy. It was for a special toolpost that I made. The toolpost is for 26mm parting blades and 12mm solid carbide boring bars.

Edited By old mart on 14/04/2021 21:34:51

I get my second dose of Pfizer next week, I was happy to get any brand going, they are all better than the possible alternative.

Our house has been built with separate WC and bathroom, they are adjacent to one another. The waste from the bath and washbasin run underneath the floor. The WC waste is above floor level and is boxed in. The connections to the main vertical soil pipe are boxed in the far wall of the WC. There is a slight leak running down the vertical soil pipe. I assumed that if I drilled a hole in the ceiling below, I would be able to see the bath/basin waste pipe. The pipes run within 6" of the outer wall so I drilled where the X marks are. There is no sign of the pipe. Surely, it doesn't rise up as it passes the lavatory?

The less overhang the better, that is why I avoid QCTP's.

Don't forget, always make the first cut very light, so you can double check the pitch is right. I made that mistake with the model A once when I set a thread pitch in the wrong position and had to puzzle out why the nut would not screw on.

Just in case you didn't know, citric acid solution can also be used for passivating stainless steel.

If you want to set 8tpi and get a 5tpi cut, the leadscrew speed must be increased by a factor of 1.6. If you buy a 30 tooth gear to use as secondary, that will work with the primary 48 tooth to give the correct ratio. 48-120-30. This would be the cheapest way to go.

Don't worry about the 6tpi leadscrew, it will only make the calculations more difficult. The standard gears are 48-120-48 so adjusting the gearing to double the output speed will simply double the original pitches from 8-72, to 4-36. I'm sure you would have looked in the righthand door, that is where the change gears would have been originally stored, although the gears were an optional extra.

I have had no trouble using lesser known brands of threadlock and bearing fit. Just be sure you can assemble the joint quickly if using 638, the 620 gives you much more time

I had to check my Lenovo ideapad 310 and it has got one, the pc is young enough to use DDR4. I simply stick the SD cards in a USB adaptor and bung them in the top of the desktop case.

Thats an interesting thought, Chris, the model A could easily have a QD handle at the end of the leadscrew, like some Myfords. Even easier for me, as I bought a spare Norton box together with leadscrew and feedscrew, plus the end bracket, cheap, no one else was interested.

Edited By old mart on 12/04/2021 19:07:12

The teeth count is not vital, 32/64, or 34/68, or anything that will fit. You can check the DP of your gears with one of the online calculators, the diameter of the 120 teeth idler is all you need.

https://www.technobotsonline.com/gear-size-calculator.html

Edited By old mart on 11/04/2021 17:18:15

If you have a rotary table on a mill, you can produce the knurling, it just takes time. Washers with the knurling in association with nuts would be better, then the knurling will grip, but not be rotating when the nut is tightened.

Edited By old mart on 11/04/2021 15:47:35

There would be some noticable marking on a new ship, but the indentations do get more pronounced as the ship gets older. Destroyers and similar do have thin hull plating, and the indentations are normally much more pronounced near the bows rather than towards the stern.

You could bore 0.002" out of the register of the backplate without any bother, just check the running of the backplate and skim if necessary. There has to be some clearance to fit, but as already mentioned, make sure there is absolutely no trace of swarf in the mating parts first.

Edited By old mart on 11/04/2021 15:20:09

I have cut 6 and 5 tpi threads on the Model A by doubling the leadscrew speed. With the speed doubled, for 5 tpi, the settings are for 10 tpi. Normally the input and output shafts rotate at the same speed, I believe the gears are 48 teeth each. I made some major modifications when I got hold of a metric MOD1 gear with 125/127 teeth. All of the gears were changed for metric ones so the complete original imperial pitches were still available, plus some coarser pitches, and all the common metric pitches as well.

You will need to get a couple of gears with, say, 30 and 60 teeth to use to double the speed. The Model A uses 24DP, 20PA, 3/8 TO 1/2" wide, with a 3/4 bore and 1/8" keyway. Some machining will be needed. I was concerned with the link pin in the input shaft breaking with the additional stress of the coarser pitch and substituted a solid pin temporarily and was extremely carefull not to lose concentration and have a pile up.