Member postings for old mart

I don't recall you mentioning having that milling attachment in your original thread.

Jaws do come up for sale frequently on ebay, but you have to be careful that they are the same size as yours. We had two PB 4" chucks with the same type of damage and I found that the jaws were not interchangeable. It is always the same teeth broken by ham fisted people who must fit work that is too big for the chuck. There is a possibility that these might be suitable:

https://www.ebay.co.uk/itm/Lathe-3-Jaw-Scroll-Chuck-Jaws-Very-Good-Condition-Hard-Internal/133429444822?hash=item1f1103c0d6:g:RHcAAOSwb7te2MHg

Edited By old mart on 06/06/2020 14:17:27

I suppose it depends how wide a speed range you intend to run them at. 30-70Hz would be a fairly safe range, but very slow and the cooling fan does not work very well. There are supplementary fan units which are independently powered, but they are expensive. They would need to be convertible to delta to suit the most common 230V VFD's. The modern motors have different dimensions to the old ones. I had to change the mounts and the pulley bore for the new one I recently fitted.

As long as plenty of thread goes into the end of the tooling, it will withstand the shock of breaking the taper very well. If you later decide to reduce the diameter by a few thousandths of an inch, it could best be done in three or four stages in the lathe. Start by putting a centre in the hex end for tailstock support and it won't matter if the overlaps show.

 Steel for drawbars can be made from en16t or en24t they both machine quite well.

Edited By old mart on 05/06/2020 20:20:50

I made a similar one with a long socket with a brass head pressed into the square end of the socket. The handle had several layers of large bore heat shrink tubing on it. It is for the R8 drawbar of the drill mill.

No CAD was involved, however.

Edited By old mart on 05/06/2020 20:05:44

There are lots of variations in threading, I always use threading tools with the laydown triangular inserts. For internal threading I have the choice of normal right handed bars and left handed. The lefthanded are useful as they cut right hand threads away from the chuck with the spindle reversed. The last thread I produced was an Atlas 1 1/2 X 8 chuck backplate, which is similar to a Boxford one. There is a difference in the register and the threads are 60 degrees. I cut that away from the chuck which is easier as there is plenty of time to stop.

The more practice you get in, the easier and more enjoyable it gets. As already recommended, plastic is excellent as its very forgiving of mistakes.

I went the other way and got a six pole motor. It runs at a similar speed to a four pole native speed at 75Hz and retains a bit more power at 25Hz than the four pole one would. It is mechanically safe at 100Hz, but I haven't needed that speed, reprogramming the VFD would be easy if the need arose. Be sure to get a 6", or more likely 160mm chuck which is rated above the maximum spindle speed that you lathe will be capable of.

Spend some of your money on a lever indicator and stand and you will get to appreciate how good the four jaw independent is. The er32 on a plate does give you the deeper through hole than any other collet system, but you will have to buy the full set of collets to go with it which will cost more. Assuming your old three jaw is on a backplate, a new one of the same size would be cheaper than the collets and easy to set up.

Looking at the illustration in the lathes UK website, your three door stand may have room above the motor for the VFD, or in the middle if the coolant is not used. If you buy from the I D S, make sure whichever VFD you get includes their quick start guide. You can download and print the pdf to have a good read first.

That link I posted for the 1hp motor had a set of expected power outputs at different frequencies, and the figures don't match the advice given to you by the I D S guy. This is the box I put the VFD for the mill in, it is ventilated top and bottom and gives plenty of protection. A similar setup could be used with a lathe.

As for belts, just get some link type belting and custom make your length. The width of the vee in the pulleys in MM will give you the size of belt. Usually the belt comes in metre lengths.

A 0.75Kw (1hp) would be plenty in three phase with an inverter, or a single phase one would be ok.

Edited By old mart on 05/06/2020 16:12:28

The I D S prices do not include VAT or postage, but the quick start guide is well worth the extra. The instructions which come with VFD's are fine for electrical engineers but pretty much mumbo jumbo to everyone else. So many people just go out and buy the cheapest and then whine about not being able to get the stuff to work.

Your present motor is on a mounting plate, whats wrong with that? If it cannot be modified, then you will have to make one.

Edited By old mart on 05/06/2020 15:59:39

I use a sturdy strap wrench to unscrew the Smart & Brown 1 3/4 x 8 spindle thread, it is much safer than chuck keys and hammers. The Pratt 6" lightweight four jaw independent jaw screws are particularly easy to split using this method to unscrew the chuck. The threads on both parts should be dead clean and be lightly oiled before mounting the chuck or plate.

I bought one of these to power a 0.75Kw motor from the same people and took advantage of their quick start guide which makes all of the wiring and programming easy. You won't ever need to be one of the people trying to get help on forums when the instructions turn out to be incomprehensible.

**LINK**

A 0.75Kw 80 frame B3 foot 4 pole motor from The inverter drive supermarket is recommended or the same size is available in the next power range at higher cost.

**LINK**

I have seen them on ebay when I was looking for a knob for a VFD speed control, there are hundreds of variations.

That is bad, I bought a cheap er25 on an R8 shank and it had 0.002" runout, but kept it. Later I bought another cheapie from another ebay source and it is better than 0.0004". Of course, R8 shank ones are much easier to get than MT4, but you could try your luck with another vendor, I notice ARC have all the sizes except MT4, but there are two on ebay for drawbars. RDG Tools have them.

Edited By old mart on 03/06/2020 22:12:05

Edited By old mart on 03/06/2020 22:15:35

It would be worth taking the collet plate off the backplate and check the running of the backplate.

Welcome, Steven, you've come to the right place to get advice on how to spend all your money.

They only seem to be freely available in up to 7mm bore. That size would be a better starting dimension to use a diamond burr to enlarge.