Acme Threads

[Desab]

Hi Guys
took my cross slide apart to make new nuts im not sure of the tap size the screw is 18mm 5 TPI or .700 +- 5 TPI left hand
My compound is is the same but right hand
Any idea were I can get these taps? I may have found a tap its a TR18 5 left hand tap on ebay

thanks

 

[Brent H]

If it is a metric thread it will be a "trapezoidal" thread and will be something like 18-2.0 or 18-4.0 where the 2.0 or 4.0 is the pitch of thread or the distance in mm between threads. If there are roughly 5 threads in about an inch 25.4/5 = 5.08 pitch - however, 18-2 or 18-4 is more the common metric trapezoidal thread.

 

[Rotaxxx]

McMaster Carr has some, but they aren't cheap!

 

[Chipper5783]

What are the graduations on the hand wheel (i.e. if it is an even value for the inch advance - then it is imperial). Remember, the advance shown on the dial could be movement of the tool (radius) or change in diameter of the part.

 

[TOBARApprentice]

Check out Canadian Threadall Limited in Cambridge Ontario. I replaced the lead and cross slide screws on my Atlas 10F and they (affordably) fabricated both acme threaded rods for me. I’m guessing that they would be able to meet your requirements. My best friend had priced a guy on eBay and McMaster Carr and it was far better to use these guys. Their number is 1 877 777 2612.

Cheers,

Derek.


Sent from my iPad using Tapatalk

 

[TOBARApprentice]

Here is some contact info....

 

[Desab]

Wow lots of feedback. my dials are imp. i will snap some pics today and post them
thanks

 

[Desab]

McMastercarr has some but they want the price gold for one. I replace the one in the tailstock a few years ago but manage to make the cutting tool but these are a bit smaller in dia.

 

[YYCHM]

Are you sure it's 5 TPI? That sounds awfully course for a cross slide screw. What make and model lathe is it?

 

[Brent H]

@Desab : measure your screw diameter again. 18 mm is 0.708". If the screw is 11/16 it would measure 0.6875" and 3/4 is 0.750". ACME threads for those sizes would be 3/4-6 tpi and 11/16th is an odd ball but they do have an 8 TPI thread - so each dial turn is 125 thou

https://www.ebay.com/itm/1pc-ACME-11-16-8-HSS-Left-Hand-ACME-Thread-tap-/254625990325

 

[Desab]

attached photos
definitely 5 TPI dia oddball size