Member postings for frank brown

nah, mate its a sort of plastic me misses tells me to put in the green bin.

(Polyethylene terephthalate)

Frank

This like a lathe with a tracer on it except the pattern is wrapped around the chuck. so you make a band (16SWG MS) equal in length to the circumference of the chuck with a width of , say chuck depth and 2". Along one edge you plot out and cut one cycle of a sine wave with the maximum value of your peak displacement from the vertical of the groove (in both directions).

Securely fix the pattern to the chuck edge. Set up a roller on an arm to engage on the edge of the pattern. Use a spring between the saddle and the tailstock to keep the saddle and its roller against the pattern. Set the lathe going at the minimum speed , or hand crank the spindle if nervous., the saddle should follow the pattern, feed in the tool .0001" at a time. Or replace the tool with a dremel type driven ball end cutter if you just want an oil groove.

Frank

Further to my problems with a spot welding transformer, tried a 100 ohm fire element in series, now not enough current. I reckon it was about 65A. So tomorrow, its going to be 50 ohms.

Frank

Second thoughts :- switching the motors to reverse could (will) cause all sorts of problems as the run down of an unpowered pair of motors with different mechanical loading would result in them becoming mechanically out of synchronisation, even if the electrical drives pulses are still synced up. Or just switch off the spindle drive and hope that the leadscrew drive remains in sync. right down to zero speed (so it stops) and will remain in sync when the spindle is restarted in the opposite direction. This sounds like a problem that can not be 100% solved, and disengaging the half nuts is the way to go.

Frank

.003% sounds very accurate, so I wondered what this would mean in real life. So lets take the spindle as the reference, not disengaging the half nuts and cutting 2" of 40 TPI thread. If the leadscrew is running slow by the .003%, then after the first cut the linear position of the tool would be .003% short of where it should be. i.e. towards the tailstock if cutting towards the chuck. Then running the lathe backwards to get back to the starting position, would also mean that the carriage would run 2" - .003% towards the tailstock which neatly coincides with its starting position. So the error is non accumulative. So the thread will compress by .00006" over 2" this would be extremely accurate!

If the lathe could not reverse, so the half nuts have to be disengaged, then the error is accumulative, both on the cut and the number of spindle rotations for winding the carriage back. So if you can wind the carriage back four times faster then the cutting speed and you need 5 cuts to complete the thread then the total error would be 5 times 1.2 times 2" times .003% , still not a lot. But if the spindle was left running half way through the thread cutting exercise while you have a cup of tea, the errors would become gross.

Frank

Over here we have "Celcon" blockss. These are light grey aeriated concrete blocks that are extremely light and are used fro the inner skin of houses for their insulating properties. They also can be cut with an old wood saw. They are cheap and degrade slowly with hearth temperatures, though I would not recommend them to line a Bessemer converter.

Frank

I got an old spot welding transformer from a mate decades ago and decided to use now. The reason was to connect to stainless steel tabs on rechargeable ni-cad batteries in order to re-use them.

The transformer is about 7" square and 9" long with the output being a couple of 1/2" copper bars about 15" long.It is all painted light green. The mains connection are on a paxolin panel. four terminals, "C" which I took for common (neutral), then .16 ohms to "H", or .255 ohms to "M", or .265 ohms to "L" .

Using the C to L connections , I got 3.5V out and enough current to heat red hot and remove a fair section of a .005" X .25" stainless steel tab.. Despite this I think i might have a good joint.

So C to L , highest primary resistance, highest number of turns, so lowest output voltage. But still an excessive current. Anny suggestions for reducing the output current?

As the kit did not blow the 13A mains fuse during my brief experiment, I presume the transformer has got a bit of leakage inductance built it to limit the current.

All suggestions welcome.

Frank

if you buy a Triton, make sure that you run cold water through it after a shower to remove the residual heat from the element. I did not when I bought one in 1981, changed the boiler in 1983 because it was totally blocked with scale. Replacement, after its cooling down periods was still working in 2009.

Frank

Yes you are right KWIL, I changed a boiler with its internal element which was tripping the RCD in about 1/4 of an hour. To replace the rusted screw in a broken out plastic bush in the case which also carried the main boiler earthing strap took about 3 hours and was definitely non-trivial. ( 28 year old "sportsman" shower). That was three years ago.

Frank

"Buying a new one" will involve, moving the water feed and the mains feed and repairing the wall and re-tiling with obsolete tiles. Repair it or remove it and take it to any electrical/electronic repair person, its a trivial fault.

Frank

You are using some cutting oil/3 in 1 /WD40? Just find the optimum blade speed/ feed pressure and it might come right. In theory the blade should be doing 200 Ft/min (milling cutters). So at .5"/rev this works out to 4800 RPM, seems too high. On the other hand manual hacksawing is 50 strokes per min of a 10" blade , is 500 ins/min or 40 Ft/min, which would be 4800/5 = 1000RPM.

Frank

Felt of various grades is used for the dampers in pianos, try a piano repairers. I am sure that there is one on your high street!.

Frank

You have a choice of start and run capacitors. Are the switches set for your motor HP ? there is an ammeter measuring your single phase current does this show any thing? It should show a huge current when the inverter is powered (30A+?) then settle back to the running current (10-15A?).

here is a circuit diagram of it if its not in your documentation :- www.clarkeservice.co.uk/manuals2/pc20_60.pdf

Frank

Tried a jigsaw with a metal cutting blade? Good for Ali and steel 16 SWG but noisy, never really tried thickerl. I have trimmed down a 5' long black slate mantlepiece with one, the original depth was too big and it appeared to be top heavy.

Frank

BH22

Frank

More power Igor!

Frank

I bought a similar screwdriver from "Home Radio" in Micham in 1964, lost it about ten years ago.

It might turn up again

Frank

I would get 4 round headed coach bolts with nuts and big thick square washers. Drill a tight clearance hole for the coach bolt up through the plywood into the end of each leg of the side frames. Screw nut well down on coach bolt, say within 1/2" of its head, put washer on, push into hole. repeat fro the other three, Now holding the square under the heads and turning the nuts, the stand can be made to stand firmly on your concrete.

Frank

Sorry Brian, I have only just joined your party. I looked at the pictures of your first attempt at parting off and came to the conclusion that the reason for the non flat surface was because the saddle was not locked down to the bed. As the tool you used has an angle on its cutting edge as it cuts it puts a side pressure on the saddle which then moves until it has taken out all the slack in the lead screw/rack. If the tool was put in at this angle it would have squealed so loudly, your neighbours would have complained.

frank

Have you calculated the gearing ratio between one turn of the hand wheel and the distance the saddle should move. On industrial lathes there is actually gearing, trouble is , I can't remember if its geared up or down.

Many cheap lathes have a single sided apron, its OK if the bearing is thick (and lubricated). I think the first thing to do is to make sure that the handle/wheel has a little slop in it, this proves that the pinion and rack teeth are not binding vertically. Running a sheet of thin paper through them will give enough clearance. If this is OK, then its time to see how sticky the saddle is on the bed. On my lathe the amount of push is a bit more then require to shove a 1kG of sugar along on a bit of A4 with a second bag of sugar laying on top of the standing one. So a little shove. If your saddle is roughly in line with this, then the rack/pinion teeth must be interfering.

Frank