Member postings for T.B

Looking at the photos , its a Myford ML7 Tri leva

It also looks like a long bed version to me and that would explain the Super 7 type cross and top slide which are far superior and where often fitted to long bed ML7's

Any Myford 7 series tailstock will fit as the bed dimesions are the same on all models , in fact the Super 7 type tailstock was often fitted to long bed ML7's along with the different top and cross slides as mentioned above so its very likely the missing tailstock was a Super 7 type

I must admit I've not read the whole thread , but all the Centec 2B's i've ever seen have the motor mounted on a hinged platform inside the cabinet.

Its a pain to set up and the same as someone else mentioned, I ended up lying on the floor on my back with my head in the cabinet to set it all up , but the drip trays big enough as it is and takes up enough room without having the motor sticking out the back as well !

There are 2 cap head screws on the rear side of the tailstock

The one nearest the headstock end is as you say for clamping the tailstock.

The other one forces the two opposing sides of the tailstock casting apart and needs to be tightened / adjusted  just enough to allow smooth sliding along the bed rail , be careful not to overtighten this screw or you will crack or break the casting.

Edited By T.B on 10/05/2021 13:53:41

Hi Joe

Thats definately a question for Ross as opposed to me , he did the drawings for the ones pictured.

I'll give him a nudge as I don't think he regually reads this forum.

Hi

just to add , the air cylinder is connected to the body at faces 4/5 , as Ross says we did have some problems with the piston binding , but if I remember correctly this turned out to be something causing misallignment in the rear bush and once this was rectified we where able to make this connection.

It works whether connected or not but if not connected the air cylinder could move axially when energised enough to make an annoying knocking noise as it hit the inner face of the main body

Ok , hopefully these will help make things clearer

Some details to the rear , namely the homing disc etc changed and the drawings never got updated

but the piston cartridge details and layout are correct and as we made them.

Why does this forum software seem to randomly place pictures all over the place seemingly no matter what I do !!

Edited By T.B on 22/04/2021 01:25:46

No the piston does not rotate , although if it wasn't for the force of the belleville's pushing against it and the drag of the seals it could.

the centre bore of the piston is sealed to the shaft with a lip or ring seal , I can't remember the proper name but it was only a couple of pounds from the local pneumatic suppliers.

A lot of the hissing sound in the video is the cheap ebay solenoid leaking that was used for testing , I did pressure test the whole cartridge at one point and it held the belleville's in compression for about 20 minutes by which time I got bored !

I've got to go now as I'm due my 1st covid vaccination in an hour or so but i'll try and speak to my mate tonight re some air cylinder details

Hi again

It was actually a joint project between me and a friend , he did most of the design stuff and I did the machining.

I will ask him if he has any drawings I can send to you but in the mean time I will do my best to show / explain the workings. I did in fact show him this thread a while ago as he often talks about wanting to build a machine along similar lines to what you are doing.

You are correct the spindle slides in bronze bushes , these where made to a close sliding fit but again in retrospect I think it would have been easier making them looser with the spindle less constrained as the hirth coupling when pulled into the locking position does all the location work.

Inside the ATC body is a pneumatic cartridge that contains a stack of belleville washers and a piston.

when at rest the belleville's are pulling the hirth coupling closed with some considerable force , the piston when actuated compresses the washers and pushes the spindle forwards , this leaves the hirth coupling disengaged and importantly the spindle is then totally free to rotate so that it can be driven round with a little nema 17 motor.

Behind the rear cover you can see a disc that is keyed to the main spindle but free to slide axially , this plate has a small hole , which along with a sensor is used for homing / referencing tool position on start up.

The little green stickers are covering up additional holes as to start with we where going to add more sensors and use a sort of Gray scale to give tool position feedback after a tool change.

In the end we decided this was making things overly complicated as the rest of the lathe is on open loop steppers anyway ie: with no position feedback.

I did however add a pressure sensor later on to the air line feeding the ATC as forgetting to turn my compressor on was proving to be the most likely fault scenario, if the pressure drops too low to open the hirth coupling the lathe pauses its cycle and throws out an error message.

I should have more photos showing the workings of the pneumatic cartridge but I cant find them at the moment.

hopefully this link will work , showing the ATC in the testing phase

: **LINK**

Hi Joe

I built a small lathe ATC a while ago , after experimenting with a pawl and ratchet for a while I went with a hirth coupling design in the end.

I wouldn't be too daunted about making the couplings , mine where made on a Centec mill so not vastly different in size to your mill, while I'm sure there are inaccuracies in my machining of the couplings , due to the self locating nature of a hirth coupling its seems that its still very repeatable to the point where I struggle to measure any deviation in a closed tool position.

In retrospect I think the whole thing is massively over engineered but on the positive side its extremely rigid , I only wish I had made the toolplate to a better design !

I also often use a 4" bison 5C chuck for the reasons you state but still often wish the nose of the chuck was longer so I didn't have to cut down so many stub drills and boring bars etc.

Funny this should come up , I know nothing about shooting but was given a .22 Parker Hale Dragon a few months ago and keeping meaning to buy a scope for it !

2BA , 1/4" BSF and 7/16" BSF would be a good start.

If you have a late model ML7 with a 3/4" leadscrew theres a good chance this will not even be an issue as myford started standardising parts between the ML7 and S7 , presumably to simplify production

Another thing to think about is the fixings for the rear countershaft bracket they are different between ML7 and S7's , although i'm pretty sure I have seen some beds with tapped holes to take both ML7 and Super 7 countershaft brackets 

Edited By T.B on 16/03/2021 18:14:23

Edited By T.B on 16/03/2021 18:16:36

One of the difference's between beds can be in the cutout in the bed under the headstock casting that allows clearance for the back gear cluster

A super 7 cluster gear is larger ,

i'm not sure how easy it would be to tell though until you start removing headstocks , but on the other hand you could probably add clearance if this was an issue without to much problem

Edited By T.B on 16/03/2021 17:03:34

Edited By T.B on 16/03/2021 16:46:59

I ended up making a new screw and nut for the Y axis when I refurbished my Centec 2B.

I was too tight to make the whole nut from bronze so pressed a piece into a steel body.

From memory the original nut was a light press fit in the knee casting 

Edited By T.B on 03/03/2021 15:51:10

Edited By T.B on 03/03/2021 15:53:08

Edited By T.B on 03/03/2021 17:17:30

That drawing is freely available on ebay alongside the pulleys for sale

If i needed one, at £54 a go i'd probably make it too !

The standard ML7-R uses the same type of dial as the ML7

Unfortunately no. Super 7 dials will not fit an ML7 or ML7-R

Bit late back , but thank you for the heads up on possible suppliers

Collets hopefully now winging there way to me

Yes that would be an obvious solution , unfortunately it won't work for my application

If theres no UK suppliers any info on overseas suppliers would be gratefully received

Hi

Can anyone tell me of a UK supplier for 12mm oversize ER16 collets

Gloster Tools normally sell them but they are sold out and i'm struggling to find another supplier

Thanks in advance