Member postings for old mart

Back nearer the topic, what do you want to reverse the spindle for? I have left hand boring bars and singlepoint threading bars which have justified a lock for the Smart & Brown model A, but the conversion was deemed much too sophisticated for anybody to copy when I posted a thread. 4 three jaw chucks, 1 four jaw and one er25 collet plate can be locked.

I have bought from them and was pleased with the results. well done TT.

Diogenes II has measured the pitch of an imperial measurement chuck. The tooth pitch is 5.08mm, or 0.2", 5 teeth per inch. If your chuck is a metric one the pitch will be 6mm. This is the easiest way to tell the difference between the 100mm chucks.

You need to check the pitch of the teeth with these chucks, some are imperial and some metric.

With care and a file, you could certainly produce one, plus patience. I would make it out of brass.

Myford lathes used to have only the Dewhurst switch, there was no alternative except the switch on the wall.

It would be a good idea for everyone with a Zeus book to run through all the pages, I have used them for many years, and surprised myself finding some info that I didn't know was in the book.

Benzene was used in cleaning aircraft instrument parts up until the early 80's when its carcinogenic properties got it replaced by trichloroethane 111. Carbon tetrachloride went out slightly earlier.

I've never seen one, are you sure it is a holograph and not a diffraction grating?

The camlock replacement studs may have metric or Unified threads,depending where they are made. The complete assembly should be interchangable on the same spindle size whatever threads hold its parts together.

In the case of the drawing shown, the exact radius is not vital,and could vary. I notice that the material is not vital either, (ALU/MS).

I'm surprised that the jig boring coordinates are missing from a Zeus book as the metric revision has been out for a number of years. I have recently bought some copys marked issue 11/19 and the hole spacing page is about 3 pages after the UNF threads.

50mm shell mills with APMT 16 inserts are easy to get hold of and will cut to a shoulder. 50 and 63mm 45 degree shell mills which take SEKT 12 inserts are good for facing and are easier cutting.

Welcome, Jyorge, we are always glad to have new members.

A very useful addition to any workshop would be a Zeus book of engineering formula. There is a page showing how to produce pcd's using X and Y coordinates on mills and jig borers if you don't have the luxury of a rotary table.

I'm not sure if this has come up, but remember that there must be space above the spindle to access the drawbar. Should you decide to use a VFD and belt drive, you could get away with only 2 belt speeds with about a 4:1 ratio. If you then bought a 6 pole three phase motor, running the spindle from1870rpm to 5600rpm in high, and 467rpm to 1868rpm in low gear, if the VFD was set from 25Hz to 75Hz.The easiest way to run that would be with a belt for each speed as mentioned by Pete Rimmer in another post. You can work out the ratios needed simply by the diameters of vee belt pulleys. For instance, a 2:1 ratio would be achieved by running a 3" and a 6" together. For the belt lengths, see my thread "pulley size help required".

One advantage of vee belts verses toothed belts is they can be tensioned to slip before too much damage is done, as already mentioned.

Edited By old mart on 22/06/2021 15:15:04

Ady, that rubber glove on your head must be the cause.

When I decided to change the spindle on the Tom Senior light vertical from MT2 to R8, I bought a 1hp three phase motor to use with a VFD. The motor specs are as follows.

6 pole motor 1 hp@ 50Hz 935rpm.

1 hp@ 75Hz 1402rpm.

0.43 hp@ 25Hz 467rpm

For my purposes the frequency of 25 to 75 Hz is sufficient. Note the drop off in power as the frequency drops. Because of this, the original set of 4 speed pulleys have been kept. The top spindle speed of 3000rpm is fine for the mill and the lowest is 174rpm. To get a decent torque throughout that range both the VFD and the 4 speed pulley system is essential.

I use Peter's method even when the backlash is only 0.002". Always back off a greater distance than your machines backlash and it helps to write down the start and finish figures before each set of moves. Setting stops if they are available also helps. I might machine a test piece rather than risk the actual job if complications look like arising.

The 5 1/4" and 3" pulleys are now joined, I used Loctite 638, but have added four screws for extra security. The screws I had are going to be replaced with better ones which will be secured with Loctite 270. I will be leaving that plain diameter but will remove the centre part to just above the screw heads.