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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: Looking for a block of cast iron please
17/04/2021 14:47:58

I would also go for mild steel, unless you can get some SG cast iron. Cast iron is the messiest stuff to machine as the dust gets everywhere. The SG, (spheroidal graphitic, or ductile iron) is easy to machine not brittle and the swarf is nice, too.

Thread: Milling around with bits
16/04/2021 21:13:06

Assuming you have only a small ammount of backlash on the Xaxis, say 0.01", 0.25mm, you can get away with climb milling using shallower depth of cut than conventional and applying a little braking from the locks. This is useful for the finish cut which will be smoother.

Thread: Threaded milling cutters
16/04/2021 21:05:12

Thank you, Jason, for the clarification, I was indeed refering to threaded collets, the er collets have a range of usable sizes, although I would prefer to fit a 12mm shank in an 11-12 rather than a 12-13, for instance.

The screwed shank collets do not have any leeway at all, the difference between 16mm and 5/8" collets sometimes requires measuring the cutter shank to be sure

Thread: Myford Backplate tapered thread size
16/04/2021 15:41:23

The spindle thread shows a lot of wear, but with a new backplate, the joint will be satisfactory. The front of the backplate will have to be trued up by skimming in situ.

Thread: Threaded milling cutters
16/04/2021 15:37:35

If the size on the cutter is metric, you will need metric collets, and with inch/fraction sizes you will need inch size collets, they are NOT interchangable. That holds good for any variety of threaded collet.

Thread: Plumbing mystery
15/04/2021 20:59:07

No, the whole estate was built in the early 70's when a lot of gerry building was going on. It didn't even have an electricity consumer unit, I retrofitted one myself. Even the central heating is only 15mm in a large semi.

15/04/2021 20:28:28

Good thought, Jim, I had forgotten my old Aquavac in the garage, it will make emptying the last water in the cistern and toilet bowl easy.

Dave, I just pulled the bath panel off to check, and my new connection is to a bend that is about 1" above floor level, so I might not have noticed at the time.

Thread: Myford Backplate tapered thread size
15/04/2021 17:53:27

Here's a picture of a myford thread, it is not tapered.

**LINK**

Thread: An odd ball
15/04/2021 17:50:29

I think Jason has the most plausible explanation.

Thread: Gear Change Wheels for a Smart & Brown Model A lathe
15/04/2021 17:41:17
Posted by DG on 14/04/2021 22:18:45:

As a matter of interest, what gear configuration did you have to produce your 8 tpi 2 start thread, because that’s one of my jobs that I need to do on my lathe, is to fit a quick change tool post at some time.

 

I doubled the gear ratio and set 8tpi, which resulted in a 4tpi lead. I have also got 5,(10) and 6,(12) as well as 4,(8).You only want 5,(8), so the single 30 tooth fitted to the output will work perfectly, but to get the 8,(4) you will have to put a 60 tooth gear to fit on the input shaft eventually.

Be aware that these gear ratios are specifically for the Smart & Brown model A which runs input and output shafts at the same speed as standard, and may not work with other makes of lathe.

 

 

DG

 

Edited By old mart on 15/04/2021 17:41:42

Edited By old mart on 15/04/2021 17:45:13

Thread: Help needed with identifying a tool
15/04/2021 17:30:53

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

Thread: Plumbing mystery
15/04/2021 17:21:34

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.

 

_igp2740.jpg

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

14/04/2021 21:42:08

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.

Thread: Gear Change Wheels for a Smart & Brown Model A lathe
14/04/2021 21:28:33

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.

 

 

_igp2500.jpg

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

Thread: Covid
14/04/2021 21:14:07

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.

Thread: Plumbing mystery
14/04/2021 21:03:51

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?_igp2739.jpg

Thread: Gear Change Wheels for a Smart & Brown Model A lathe
14/04/2021 19:52:32
Posted by old mart on 13/04/2021 16:41:37:

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.

As I said earlier, the leadscrew pitch has nothing to do with it.

Thread: Parting Tool Holder
13/04/2021 18:47:54

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

Thread: Gear Change Wheels for a Smart & Brown Model A lathe
13/04/2021 18:45:22

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.

Thread: Citric acid pickle
13/04/2021 18:41:20

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

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