Member postings for old mart

I have just got my 12V Team angle grinder out of the garage for a look, and it is the same as yours, with the + and C- contacts in the charger which connect with the + and T on the battery, which also has a - connection. Confusing isn't it. Take the end off the battery and the circuit board is exposed.

That is a very sensible solution to get a job done rather than risk making a hash of it yourself. There will still be the uneven wear on the leadscrew itself to contend with, do you feel rich enough to ask for a quote from him?

If somebody posts a picture of the other side of the mandrill, it will be just as colourful.

Leaving a bit of play in the register and the screw holes gives you the option of getting everything running perfectly, even if one of the collets is less than perfect. With an eccentric collet, you would have to re align every time it was used as there is no way of indexing the collets in the holder.

I have just looked at my Parkside 20V Team charger and it has three contacts. These lithium ion batteries have some sophisticated electronics in the battery, so I have no idea what the third contact is for.

My very old Makita charger for ni-cads had a third contact which was connected to a thermistor, I believe that the heat increase when fully charged caused the thermistor to switch off the charging.

The chances of anybody noticing that the end rad did not match the shank are very small. The need to fit two parts together with such a good match is a very demanding and rare thing. Ball ends are usually used for rads in corners or channels which don't matter so much.

That handle will make all the other Myford people green with envy. You will never get me to post a photo of the one I made.

I'm surprised that the rules are so strict that a shorter mast would be banned, I can see how a longer one might be frowned upon as it might add some speed. Drilling a number of holes lengthwise near the edge would tend to loosen the grip a little. Careful cutting of the bottom of the nylon would expose the end of the carbon fibre to find out exactly how thick it is.

For non critical work, you could use a metric insert to produce a unified thread and vise versa. They are both 60 degree form and the other differences are relatively minor. You could also get away with Whitworth and BSP threads.

As mentioned by Martin Connelly, you must back off the tooling each time you reverse to the start point. Earlier I mentioned zeroing the cross slide dial before starting. Because this is a bore you are threading after practicing on external threads, you should just touch the bore first and then dial in the total depth of cut expected (0.080". Remember, you are cutting backwards like when boring. So you should return each time to 80, or a bit more or the insert will probably break. Having the intended cuts written on a sheet of paper and crossing them off as you go is a help also. So the cuts would be as follows:

80, 68, 58, 48, 40, 32, 25, 19, 14, 10, 7, 5, 4, 3, 2, 1 until the first marks show on the register.

By hand has another advantage, it will be obvious when you run off the end of the thread at each cut. You will feel and probably hear the cut in progress, and if you count the turns from first contact to running out of thread, you can then reverse a couple of turns more backing out. This will take care of any backlash when going into the cut.

Making a practice dummy out of aluminium first before committing to the backplate would be a good idea, but you must use AC90, or WD40 to lubricate it when you are machining it. And it should be set in the chuck with the same gap between it and the face of the chuck as the real thing would have.

The winding handle I made to do the first 1 3/4 8 W backing plate thread was super crude. Whatever materials came to hand. The end in the spindle had a simple expander and the winding handle was just a bit of scrap iron, nothing like those very nice Myford winders.

I made a much cruder vee block out of a foot of 3" channel section steel. I wanted to section a Skeeter gearbox rotor shaft for display. It was good enough to hold it while milling out an 15" by 4" bit to see the innards. The tube was much harder than anticipated and used up about 5 solid carbide end mills.

At the museum, we are fortunate to have at least a dozen, some in pairs which have been donated over the years. I have bought a couple of really big ones on ebay, most people don't want a foot long one so they go for low prices, the channel has been pensioned off after only one job.

Edited By old mart on 22/05/2020 18:16:15

An even simpler way would be to shorten the mast by 40mm, just cut it off.

That Chronos 6" plate was the only one that I could see that had a decent diameter boss for increasing the thread diameter, and the price increase over an unmachined blank is well worth the reduction of CI mess. The 160mm od could be reduced to 5" if that was the size required using the boss to chuck up on normally, and then the four jaw could hold it easily boss to the right. The advantage of using the four jaw is that the plate will then stand off the chuck face, giving a little runout when threading. Boring the register and the thread bore and threading should be done together to ensure perfect concentricity. To check the thread, which will be fine, the cheat is to unscrew the chuck, and try out the thread on the spindle without taking the plate out of the chuck. Screw it back on only if the backplate needs another pass or two of threading.

Edited By old mart on 22/05/2020 17:03:49

I've just read 50 Famous British Locomotives by Peter Herring and your crab is in there. I see that it is the angle of the cylinders that is responsible for the nickname. What ever would Stevenson's Rocket be called at that rate?

What you need is about half a dozen helpers to hold the mast while you use the slide hammer. I would bet on the thread in the nylon stripping before the plug comes out, a larger thread would be better.

Remember to mark the alignment of the old plug with felt tip before removing it. 

The nylon is very unlikely to be glued, as it involves quite a lot of bother. We used to glue a nylon block onto an aircraft part for Westland Helicopters. The nylon was immersed in a very nasty hydrofluoric acid mix, which etched the surface about 0.001" deep. The etched surface lost all of the normal low friction and glue adhered very well.

Edited By old mart on 22/05/2020 16:25:54

Edited By old mart on 22/05/2020 16:34:54

As you don't have a faceplate, holding a blank will be difficult. Therefore, I would tend to go for a part machined, one with a 1 1/2" Boxford thread. It will be easier for you to hold and there is enough meat in the bore to go to 1 3/4" S&B. Being machined will enable you to attach it to one of your chuck backing plates by drilling and tapping it. A four jaw independent chuck can be used as a faceplate if tee nuts are made to fit in the jaw slots. You could also drill and tap the four jaw between the jaws, I have done this mod on both the chucks at the museum to attach balance weights. Chronos have a 6" one that would suit.

**LINK**

By all means use lubricant on steel when you cut threads, I always use a little CT90 spray. When you cut cast iron, do it dry, and a vacuum cleaner and magnets help to reduce the mess of CI powder, and take care to remove all the dust from the lathe afterwards. I made a dummy spindle nose for the Model A, the difficulty is getting it exactly the same size. As I mentioned before, when your insert just makes a mark on the 1.750"/1.751" register, the thread size is exactly right. These large 8 tpi threads have a lot of leeway in the size, going a bit loose is much preferable to tight.

You haven't mentioned how you intend to hold the plate as you machine it.

I fully agree with Jason's method of keeping a firm control on the feed, it stops the drill from getting out of control, and should drill straighter. Try and find a new drill rather than a hand sharpened one.

The only other similar thread is 1/8 NPT which is 27tpi. Using something to seal the threads when you assemble the joint will even work well if there are mismatched threads.

The price of the insert is the highest I have seen. Check out APT.