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Single Pointing Metric Acme Thread

Vancbiker

Diamond
Joined
Jan 5, 2014
Location
Vancouver, WA. USA
If you know the dimensions of the threadform, it shouldn’t be too hard to grind a HSS blank to use if it’s just a part or two. Not everything needs to be cut with an insert.
 

nissan300ztt

Hot Rolled
Joined
Jul 26, 2011
Location
Taylor
If you know the dimensions of the threadform, it shouldn’t be too hard to grind a HSS blank to use if it’s just a part or two. Not everything needs to be cut with an insert.
I agree there. But my shop doesnt keep many HSS blanks around. Last time I needed one I had to hack up another tool.
 

Sandoz

Plastic
Joined
Aug 17, 2021
This comes up regularly on the UK Model Engineer board.

You have to think as if you are the machine tool manufacturer making machines for a world market. Whichever units system you work in, it is more efficient in terms of stock inventory and tool inventory to use the same diameter stock for your leadscrews whether they are imperial or metric and just to vary the pitch of the thread cut on them (keeping the form/thread angle the same).

It also gives you an agile capability - to switch from making an imperial leadscrew to a metric one, just flip a lever to change the gearing of the machine.

No need to change the stock, the workholding for the stock or the cutting tool. No chance of mixing up imperial stock with metric stock. No chance of picking up the wrong toolbit. No need for the tool grinding department to fixture for 29 and 30 degrees.

You can do the same mental exercise for the nut with which the leadscrew works. Same stock, same tapping drill, only the tap itself changes. It might not conform to any conventional standard, but it makes very good economic sense.
Sure it maybe convinient from the manufacturers point but this kind of standard mixing makes me furious.

For example we have a vertical lathe with nearly half of the bearings listed just as non-standard. Not even approx dimensions are given in the sheet, so we'll have to dismantle the whole drivetrain/chuck assembly, measure them, order custom made spares.

And the lathe can't just sit idle the whole time it takes to make the spares, so we'll have reassemble it with the old parts.

And it's not just the bearings on the machine, bolts with metric dimensions but with imperial threats = profit?

So not a fan of this kind of sabotage.
 

winger

Stainless
Joined
Dec 28, 2005
Location
portage county, wisconsin
It was a double start thread and just had to match the existing thread for our own lathe. It could have actually been Acme. Not there anymore to recheck. It worked, sometimes that is what matters,

Dave
 

joecrs

Plastic
Joined
Mar 14, 2013
Location
ohio
Well I tried to use the 29° ACME like I was told to use. And there are clearance issues all over the place. Gage wont go even with making it wider using the workshifts. So I told my company we need either a Tap for these 2 parts or spend the $1000 for 10 inserts and a bar to hold them. Im walking away from this abortion of what should have been a no quote.
hope you got a gorilla working for you to drive that tap, this is probably a thread that may require 2 taps a rough and a finish I have seen ACME threads that require 3 taps unless you have a machine with many ponies on the treadmill
 

nissan300ztt

Hot Rolled
Joined
Jul 26, 2011
Location
Taylor
hope you got a gorilla working for you to drive that tap, this is probably a thread that may require 2 taps a rough and a finish I have seen ACME threads that require 3 taps unless you have a machine with many ponies on the treadmill

Youve got me. Im the Gorilla. 6'3" 360lbs. I would get a slight thread single pointed in first then use the tap to follow it. I wish we had some better machines.
 








 
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