acme/trapezoidal threading inserts?

[BrokenBiker]

are these a thing?

i have plenty of HSS blanks i could grind, but a quick ebay search didnt bring anything up so thought id ask...

my tooling takes er16 60ag and ir11 60ag inserts if that makes a difference

 

[m_c]

They exist - https://www.shop-apt.co.uk/threading-inserts.html

 

[BrokenBiker]

They exist - https://www.shop-apt.co.uk/threading-inserts.html

ta much, exaclty what i need

 

[Kram]

If your trying to do smaller internal TR threads the inserts wont fit or unlikely to fit, depending on pitch, for anything suitable on a small machine.

You'd need a boring bar instead.

MIR Mini Carbide Threading Bars 30° TR Trapezoidal Associated Production Tools

MIR Mini Carbide Threading Bars 30° TR Trapezoidal

www.shop-apt.co.uk

However my approach was to chop up a NR22 TR4 into three peices insert and braze it to make a bar for doing TR16x4.

I also had success hard turning a bar of HSS to make a TR12x2 tool. Once the angles were correct, I eyeballed grinding the extra side clearance.

 

[BrokenBiker]

If your trying to do smaller internal TR threads the inserts wont fit or unlikely to fit, depending on pitch, for anything suitable on a small machine.

You'd need a boring bar instead.

MIR Mini Carbide Threading Bars 30° TR Trapezoidal Associated Production Tools

MIR Mini Carbide Threading Bars 30° TR Trapezoidal

www.shop-apt.co.uk

However my approach was to chop up a NR22 TR4 into three peices insert and braze it to make a bar for doing TR16x4.

I also had success hard turning a bar of HSS to make a TR12x2 tool. Once the angles were correct, I eyeballed grinding the extra side clearance.

i am not sure of the sizes required yet, just having a gander to see if inserts were available...ive yet to find an 11ir acme insert but im not opposed to grinding the internal one if needs be, or buying a tap

i have 2 jobs to do, 1 is strip the vice, figure out whether ive damaged the screw or the nut and repair accordingly, the second will be making a lead screw and nut for a heavier duty milling attachment for the lathe as the one that came with it just wasnt suitable...im in the process of modding it to be slightly more suitable, but mostly so i can then make a better one with as little faff as possible. that also ties into my milling cutter post, but the site in the link has centre cutting HSS end mills and carbide end mills, slot drills and indexable end mills so will likely just put a bulk order in for a few sizes of end mill, some acme inserts and some new boring bars as my insert ones are naff and you need ear protection when using them even when theres only 20mm sticking out the tool holder

 

[E T]

Do you need to make a right hand or a left hand thread?
For a left hand thread you'll need a different toolholder and insert than for a right hand thread. And the appropriate shim under the insert with the right angle depending on the tpi and diameter.
You can adapt a right hand tool to cut a left hand thread. I learned a lot from this thread on this forum.

Thread 'Advice regarding my worn nuts'

Feb 26, 2025

I think after 40+ years I thought it a good Idea to have a strip down and check how bad my nuts were on my mill/drill i mean as climb milling has never been on the cards and accuracy was almost within reach

I always planned to sell it when I got my Bridgeport but its always been difficult for me to sell any tool and 1 mill just doesn't seem enough now, Its been really handy for heavy drilling and with the 2 axis dro I'm fitting it will be of more use im sure.

Turns out after a stripdown that the X axis nut was loose hence the large amount of backlash I was hoping that it meant the nut...

• dieselsamurai
• Replies: 67
• forum: Lathes and other Machining Equipment

• 

And the result.

Post in thread 'What are you machining?'

May 11, 2025

I made a start at making a new left hand acme screw for the Southbend cross slide. I had just about enough bearing bronze left to make two new nuts with the 7/6"-10tpi left hand acme tap I bought a couple of years ago.
Then on to the scew. Thanks to the good info from Agroshield in the 'worn nuts' thread. https://www.mig-welding.co.uk/forum/threads/advice-regarding-my-worn-nuts.142278/ I kind of new what to do.
I made two test pieces. The first with the right hand threading tool In its original state and a second with a 5° chamfer milled on the bottom side to get the right helix...

• E T

• 

Here's some good videos from Max Grant on single point threading a left hand trapezoidal thread.

 

[Kram]

some new boring bars as my insert ones are naff and you need ear protection when using them even when theres only 20mm sticking out the tool holder

What do you currently have?

I would highly recommend carbide shank boring bars, they have 3x the stiffness of steel ones. The only sensibly priced place to buy them are used stock on ebay or new ones from ebay china, which in my experience are just as good.

You can also buy carbide bar which I did, one day I might make my own. 12mm bar is relatively cheap.


You can also buy premade TR bar and nuts.

 

[BrokenBiker]

only a cheapy that i bought for my chinese lathe but was too big for it...12mm bar with cnmg inserts...its around 100mm long with about 60mm max depth with it inserted properly into the tool holder...i did have to turn the bar down a bit as it only had relief for about 12mm of depth when cutting then the bar would rub on the part but it rang like a bell from the day it was first used

i do have a few brazed carbide bars, 2 that came in a set off here, a few that have been ground from other brazed carbide tools and ive got a few hss tht were ground byt the previous owner that i alternate between depending on what im trying to cut

 

[striker]

I made a longer leadscrew for my mill after fitting the riser block. If I recall correctly, it was trapezoid16 left hand thread. It was my first ever attempt at lathe screw cutting. I got confused by the inserts and riser pads etc. so I ground a piece of quality hss to 60° then eyeballed some clearance. I didn't offset the compound just straight in at 90°. I used the travelling steady. It worked perfectly.
It was trapezoid 24mm.
Post in thread 'Stuff you have made today' https://www.mig-welding.co.uk/forum/threads/stuff-you-have-made-today.67127/post-2140553

 

[striker]

Finished job
Post in thread 'Stuff you have made today' https://www.mig-welding.co.uk/forum/threads/stuff-you-have-made-today.67127/post-2141691

 

[Kram]

only a cheapy that i bought for my chinese lathe but was too big for it...12mm bar with cnmg inserts...its around 100mm long with about 60mm max depth with it inserted properly into the tool holder...i did have to turn the bar down a bit as it only had relief for about 12mm of depth when cutting then the bar would rub on the part but it rang like a bell from the day it was first used

i do have a few brazed carbide bars, 2 that came in a set off here, a few that have been ground from other brazed carbide tools and ive got a few hss tht were ground byt the previous owner that i alternate between depending on what im trying to cut

Cabide shank insert bars can have much longer stickouts and still be quiet. I have a 6, 8, 10, 12 and the 20. In total they cost a bit but were one of my best lathe purchases.
From about 20 seconds..

 

[BrokenBiker]

I made a longer leadscrew for my mill after fitting the riser block. If I recall correctly, it was trapezoid16 left hand thread. It was my first ever attempt at lathe screw cutting. I got confused by the inserts and riser pads etc. so I ground a piece of quality hss to 60° then eyeballed some clearance. I didn't offset the compound just straight in at 90°. I used the travelling steady. It worked perfectly.
It was trapezoid 24mm.
Post in thread 'Stuff you have made today' https://www.mig-welding.co.uk/forum/threads/stuff-you-have-made-today.67127/post-2140553

i will likely go with metric trapezoidal for my milling attachment as i wold like the dial to read in metric, it will be the only axis without a DRO (when i get round to fitting the DRO) so it being metric would be beneficial even though the rest of the lathe is imperial.

as for the vice, ill just make which ever bit is broken to match whats already there, given the age id assume its imperial acme but i may be wrong

 

[BrokenBiker]

Cabide shank insert bars can have much longer stickouts and still be quiet. I have a 6, 8, 10, 12 and the 20. In total they cost a bit but were one of my best lathe purchases.
From about 20 seconds..

definitely need to invest in one of those...mine screams at me every time its used, but the brazed tooling with the same stick out is silent

 

[Martin Hocking]

“….However my approach was to chop up a NR22 TR4 into three peices insert and braze it to make a bar for doing TR16x4.”

What did you chop it with @Kram ? I’d like to do this to cut a new nut for my mill.

 

[Kram]

A mini die grinder/rotary tool thing, fitted with a 22 ir 50mm diamond wheel

Some pics here, I also needed to grind it thinner so it could fit in the hole at centre hieght

Post in thread 'Stuff you have made today'

Jul 11, 2021

Brazed a damaged insert onto 10mm hex key. 600g diamond wheel to light sharpen

Then as I had grinder out, I have a 22IR TR4 insert, too big for a 12mm bore, for a 16x4 nut. Ages ago I chopped into 3 parts. 4.8mm thick, so need to take some off the bottom while preserving flatness for brazing. Brazed onto some key steel so I dont burn my fingers, and for a parallel reference to scribe from.

Dimond wheel to just over 2mm thick

Next to unbraze, grind a 15 degree seat on a bar and stick it on.

• Kram

• 

I cant find any of my other posts on the subject.

 

[Agroshield]

Download the Posithread catalogue for a good overview of what is available in laydown style:

Catalogues | Posithread UK

posithread.co.uk

Chinese sources can offer a few options outside this range but you have to look hard.