meddings

So, I'm finally putting my Meddings MB2/2 , that I found on EBay a couple of years ago, back together. But I found a problem with the tables. A thread has been damaged.( Maybe that's why it was on EBay) .Can anyone suggest where I might find an Acme tap 3/4" x10TPI right hand. To either borrow, rent or buy?

Contact Tracy Tools 01803 328 603 they might be able to help you ?

Best Wishes Martin

Edited By Martin Walsh 1 on 17/04/2014 22:49:16

No Martin, they only have 5tpi. they suggested RDG but no luck there either. I can get one from across the pond but at a cost! About £200 . I am hoping someone has had one in their tool box for the last 40 years and needs the space hehe.

I'll check tomorrow, definitely got a 3/4" one but think it's 8 tpi.

Hi Mike

Another place worth a Try is the tap and die company

www.tapdie.com 0208 888 1865

He is a helpful chap

Best Wishes Martin

They don't list them which given their 'blue sky' prices is probably an advantage

Thanks Martin but it looks like no luck there either. NO acme taps listed at all.

Mike

I am a novice machinist but learn fast. is it possible to clean up an internal Acme thread using a boring bar with a tool ground to suit Acme profile? I could probably turn the chuck by hand as its only one thread that is damaged. What does the team think?

You certainly can clean up with a suitably profiled boring tool. Don't worry about trying to get the width at the bottom dead right. Concetrate on the flank angles and make the tool come out bit narrow. Set up for 10 tpi with your topslide parallel to the lathe bed so you can adjust the tool to trim one side at a time.

Standard machine tool makers practice back in the day to get minimal backlash nuts. Friend John used to do such for CVA.

Clive

Pardon my ignorance but I have some old but good British made 3/4 x 10tpi BSW taps and would sell one or two ...are these what you are looking for ?? Or is acme a different thread. ???

Edited By Loose nut on 21/04/2014 00:06:56

Clive, youre going back a bit - CVA? what, in Portland Road, Hove? My Father worked there during part of the last war until he was head-hunted by the Army to be a civil servant at Preston Barracks, Brighton! CVA site flattened since I was a kid and SEEBOARD had offices built there. EDF now occupy site.

Mike, I did a silly trick once, my chucks wouldnt go on mandrel smoothly so I pushed a bit harder and got one jammed on. Got it off and decided to give mandrel thread minute inspection and found a tiny rough, scabby appearance in one place - squashed swarf. Cure was an old - fashioned thread chaser, 12TPI for Myford, set lathe going in lowest backgear speed and very carefully ran chaser along thread, scraping off the swarf. Worked a treat! Moral; if it dont go, dont force it! Anyway, reason for relating this is so you can see there is another method of thread cleaning. Good luck with your prob.

John

I have often found squashed swarf in a chuck scroll - too hard to remove with a toothbrush and needs winkling up with a scriber or some such.

To remove the scroll I lightly bang the chuck flat down on the bench top.

Loosenut, all "normal" thread forms are triangular but vary by included angle. Acme threads take the form of, for the sake of argument, a square thread with sloping sides, the included angle being a mere 29 degrees. Hope this explains it for the uninitiated.

Rick

If you are thinking of taking the trouble to set up for boring you sound like you have the confidence/experience to just make a tap anyway. It would only need ot be a few turns. The problem being the cost of a big bit of silver steel.

Since Acme is a flat topped thread you could make a hand boring tool. A plain bar turned down to fit the hole in question smoothly. Then cross drill for a tool bit and again for a grub screw. Then you only have to file up a small bit of silver steel to profile as the tool bit. You have a sort of single tooth tap or guided scraper that is guided by the inside edges of the existing thread. Feed by hand and gradually advance the tool for depth of cut.

Edited By Bazyle on 21/04/2014 11:00:16