Member postings for old mart

Thanks, Jason, Stakesy's has been bookmarked also.

The S & B model L is a specialised lathe intended for small work, it does not have a saddle like common designs. More like an oversize instrument lathe. Bear this in mind when thinking of getting one. If the motor can be changed from star to delta connections, you could run it from an inverter and have variable speeds.

**LINK**

Edited By old mart on 17/04/2022 18:45:59

The trouble is that good taps come in different guises, to optimise different materials. I had to tap a 3mm hole in Densimet which is a Tungsten Cobalt alloy and bought a green ring tap intended for hard material. It did not want to do the job, despite being new and industrial quality. I looked through the box of small metric taps and found one that tapped the hole easily and it looked very second hand. I might have been better off getting a tap intended for aluminium.

For hand tapping, you could make a tap guide that keeps the tap square to the hole, just a piece of metal with a hole drilled using a drill press or mill that the tap can just pass through.

I have bookmarked a Femi distributer, Welding Supplies Direct, the bench model ABS NGS 120 at £819 looks very nice, depends on available funds, though.

Edited By old mart on 17/04/2022 18:11:51

Edited By old mart on 17/04/2022 18:12:42

Edited By old mart on 17/04/2022 18:15:04

When I was working on aircraft parts manufacturing, we used Rotring pens exclusively, partly because the ink was approved for that use. They were easy to use. It would be worth checking their products.

**LINK**

I am in favour of improving any machine if it is within my ability, so would not be put off by small defects. As for the tension meter, they are similar to spoke tension gauges, too expensive to buy, but not difficult to make, that would be a future project.

Edited By old mart on 17/04/2022 16:04:49

In the near future, we will have finished the Atlas 12 x 24 lathe and be able to sell it and some of the proceeds will go towards a metal cutting bandsaw. A floor mounted machine with wheels with between 4" and 5" capacity would be an ideal size for the museum. I would appreciate advise on saws between £400 and £650 their strengths and weaknesses.

I did my application online as soon as the form arrived, but still had to cut the old licence in half and send it back to them. The replacement came within a week.

It is always a good idea to be willing to learn new techniques, but the size to pitch ratio you have chosen would tax the most experienced machinist. The internal threading bar has to be small diameter and is therefore flexible and the coarser the pitch the higher the cutting forces, not a good combination. I have made internal threading bars out of Densimet, a tungsten sintered alloy made the same way as tungsten carbide, but machinable and just threadable with HSS taps. This is stiffer and denser than any steel and helps with the flexibility problem to some extent. I can just manage 3/4" x 8 ACME with one of these with an IR or ER 16 size laydown insert. Those special taps for ACME look like two double length taper taps in tandem, they are expensive.

When I lived in Surrey and walked the dog evenings, one used to fly over from North to South fairly regularly, the noise was unlike any other aircraft I had heard, apart from the unusual shape.

I suppose it could be done with a split die in a lathe or vise as long as the die could be held square. I had one of my apprentices at work many years ago put a thread on some 3/8" rod with a hand diestock. He showed me the 9" of thread and I nearly died laughing, he had made the most drunken thread I had ever seen. From one side it looked like parallel rings and the other looked like a twin start.

Edited By old mart on 14/04/2022 22:49:35

5/8 X 8 ACME internal threads would normally be done with a two stage tap about 10 inches long, as trying it on a lathe with any type of threading bar would be very difficult because there is so little room. I produced nuts in 3/4 X 5 ACME by using an 8 ACME laydown insert in a ground down bar to remove some of the metal, up to its depth limitation and finishing with a tap. This was because I was afraid of snapping the tap if I tried to do it in one go.

With 5/8 x 8 ACME, the starting hole is only 1/2" diameter.

Edited By old mart on 14/04/2022 22:40:28

My current licence is the 5th plastic one I have had, the first had a good colour copy of the photo I had sent to DVLC, and every one since has had a progressivly fading black and white picture. They have really gone to town with the "UK", there are 15 of them that I can see on the license, plus at least 4 "UNITED KINGDOMS". I got my age 73 licence in December, so it has a possible life of three years and four months as it is valid to 3-2025.

You will have no difficulty milling the cast iron with your machine, just listen to the sound of the motor and reduce the feed rate, or use a lower gear if needed. The vise is indeed not really intended for general milling, more those little high precision jobs. You are on a learning curve and as long as you can use common sense and take advice, there is very little you won't be able to accomplish.

The cutter is soft cutting because of the 45 degree edges, although I would have tried an 0.5mm, 0,020" depth of cut. The inserts might not be optimum, they look uncoated in the picture. I was concerned by tool length, but you can only have the quill as short as possible and locked before each pass. Lock the Z axis also. Also, that rod on the front side vise jaw would not be helping the stiffness of the clamping. If the work does not fit well between the jaws of the vise, an old trick is to put some soft aluminium wire between the work and the jaws which gets crushed and fits the uneven gaps. The work could be lower in the vise if the parallel was on its side.

Check the tightness of the SHCS holding the shell mill on its arbor and the insert screws (only use the proper tool to limit the tightness of them).

 Now you have part of the surface flat, could you turn the work the other way up with a couple of thin  parallels under the finished part, it would sit down better then.

If the sides are sloping outwards requiring that rod, it might be worth while squaring up the sides first so the work sits better when you mill the larger sides.

Re reading your first post, did you raise the cutter from the work before or after turning the machine off?

Edited By old mart on 10/04/2022 19:18:01

Edited By old mart on 10/04/2022 19:23:17

Edited By old mart on 10/04/2022 19:26:46

That remounting of the rack suggestion seems a good idea, but as the teeth will tend to accumulate all the falling swarf, some thoughts on how to shield it would be needed prior to cutting metal.

 There is a picture of a Super Zyto in lathes UK showing an inverted rack:

http://www.lathes.co.uk/zyto/index.html

Edited By old mart on 10/04/2022 18:49:01

On this pc, I have both Firefox and edge, Firefox being set to "default" and on another pc, the "default" is set the other way round. Chrome should work just as well, there should not be a reason to uninstall the one you don't use, it can be useful if there is a glitch in one, having a backup. Every time I start up the non default browser, it asks to be made default and I simply ignor that whether from edge or Firefox.

Edited By old mart on 10/04/2022 18:38:15

An electric sewing machine motor with the pedal speed control modified has been used successfully on small lathes. Not as sophisticated as your solution.

Edited By old mart on 10/04/2022 18:28:01

Viton is most easily obtained in 70 shore hardness, but as it is likely to be more resistant to hydraulic fluid, it will not tend to soften and be extruded like the nitrile you are using.

You haven't mentioned the name of the hydraulic fluid you are using.