Advice regarding my worn nuts

[Geoffm]

My late father in law repaired the cross slide screw on his lathe using precision ground acme rod that I mail ordered from MSC. They have right and left hand in various sizes.

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

 

[dieselsamurai]

Yeah they have some interesting stuff in there , could get Acme threaded bar im sure but definitely not in the size i need 23.4mm so would need to machine new nuts or modify the old ones anyway plus i would need to machine either end or the leadscrew thats probably hardened so although new would be nice it would be 10x more work

just a shame nobody makes spares for these machines i think theres a gap in the market there

 

[dieselsamurai]

Progress has been made , mostly producing copious amounts of brass swarf that gets everywhere

well I needed a 27mm threaded bush and having either 25.4mm or 50mm i had to reduce the larger to 5 smaller ones , If figured 2 small practice ones 2 to size and one spare in case i ever need to make one in the future



I thought best to get the most tricky out of the way first 23.4mm Acme 10 tpi lefthand thread , cut a practice one and just slightly over judged it as forgot working off a dial gauge on the tool post it comes of radius not diameter



Just finished the actual bush and fits like a dream just the right hand thread to do now then the fun part mounting and boring the old nuts to fit the bushes

 

[RichardM]

Are you able to put a flange on the bush?
The brass chips can be used for tempering steel.

 

[dieselsamurai]

Are you able to put a flange on the bush?
The brass chips can be used for tempering steel.

I was going to sliver solder it into the old nut once its bored out

 

[dieselsamurai]

X axis leadscrew nut done , brass creates such a mess !



just got to bore out both old nuts ive worked out the centers so hopefully wont need shimming after

Y axis is fairly straightforward in the 4 jaw but X axis will need faceplate probably



How much clearance for silver solder ? are there adhesives that might work not worked with brass that much

 

[RichardM]

https://bbs.homeshopmachinist.net/forum/general/22074-silver-solder-clearance

Centre punch the outside of the insert evenly around both ends to get it to centre prior to soldering.

 

[dieselsamurai]

Nut bored 0.005" oversize for solder , i'll probably do a conversion on the backlash part of it as the system of pinching the top to close the threads is a rubbish idea.



more like this where it is adjustable top and bottom

Mounting the X axis nut will be more of a challenge the only way I can think of at the moment is gripping this angle plate in the 4 jaw with the nut bolted to it , I will run a threaded bar from it to the end of the spindle as a 'hail mary' in case the worse should happen



I need a mill now to drill the angle plate ( this is why you need at least 2 mills ) but of course the the Bridgeport is currently set up to drill and tap a new fixture plate for it , need to crack on with that now

 

[winchman]

York the vice maker in check republic make nuts if it’s any use?

 

[winchman]

Here's a link for nuts

Working on CNC machines, threads, nuts, screw taps, ... | York, spol. s r.o.

www.york.cz

For the people with a Vice fetish

Workshop bench vices - YORK | York, spol. s r.o.

www.york.cz

 

[dieselsamurai]

Useful site , ive already threaded the inserts for the feed screws so gone too far down that path now but my be of use if i wear my nuts out on anything else

 

[E T]

I think you may be misinterpreting the information you have cited.

The Haas reference only tells half the story, as suggested above. We are not in dispute that it is possible, but are discussing the small but crucial details of what is required to make it possible.

The first video screenshot shows a left hand bar (listen at 9:43).

The wisc-online is using ground HSS tooling not inserts. Look at post #18 "this is the insert I think I need". See also Figure 15-3-4 and consider how you achieve both tools shown end-on in a single insert - you cannot so you have to tilt the insert itself.

The Practical Machinist discussion does not address the issue of using an insert nor does it talk about how an HSS tool must be ground differently for the two hands.

As above, every insert manufacturer (Sandvik, Vargus, Iscar, Seco, Kennametal) says the same thing in their technical literature. You can use a right hand insert and right hand bar for the left hand thread but you must change the angle of the insert.

Sandvik Coromant

www.sandvik.coromant.com

"Negative shims are used when turning left-hand threads with right-hand tools and vice versa"

Selecting a Shim for the MMT Series - Technical Info / Cutting Formula | MITSUBISHI MATERIALS CORPORATION

This page is about Mitsubishi Materials Corporation's technical information/calculation formulas. Detailed information on Selecting a Shim for the MMT Series. In addition to an overview of cutting

www.mmc-carbide.com

This one is worth bookmarking. I had not seen the information presented this way before and it is good. Note that in the shim reference table, right hand ones are given a positive value and left hand ones given a negative value.

From a practical and economic point of view, buying an overseas left hand bar and insert is cheaper in money and time than sourcing or making the necessary angle-changing shim.

Interesting stuff this @Agroshield .
I don't want to hijack the thread, but I'm thinking about taking a shot at making a new cross slide leadscrew for my Southbend 9.
That screw is 7/16"-10tpi left hand acme. According to the links you posted I won't be able to cut that pitch on that small diameter with a right hand tool and insert and a negative shim. As I read it the only options are to get a left hand tool and insert and a 4.5° positive shim, or grind a hss tool myself. Is that correct?

 

[Agroshield]

According to the links you posted I won't be able to cut that pitch on that small diameter with a right hand tool and insert and a negative shim. As I read it the only options are to get a left hand tool and insert and a 4.5° positive shim, or grind a hss tool myself. Is that correct?

Is that from the Mitsubishi one? I guess they know what they are talking about. To verify what they say, perhaps draw up the thread in CAD and try to find dimensions of an insert and holder (or maybe a 3D model from one of the manufacturers). That would tell you at what angle you need to present the insert in order for it not to rub.

As it is an external tool, you could rotate the tool itself in the toolpost (or mill the base and top at an angle) to gain some extra angle where the shim runs out of steam. Think of a conventional turning tool. If you sat it in a vee block and screwed it back into the holder, its clearance angle has changed by 45 degrees. It would not cut very well like that, but in principle you are doing the same to a lesser degree to the threading tool.

The key point is that you have a lot more options to do things with an external tool (screw) than with an internal one (nut).

If the standard RH shim gives + 4.5 degrees of helix angle, altering the base of the tool by 9 degrees would make it cut at -4.5 degrees helix. An overseas RH tool is cheap enough to modify.

If someone were cutting many LH threads, perhaps altering an external tool's shank from square to round and then clamping it in a split sleeve would allow you to set it to any helix angle at all.

 

[E T]

Is that from the Mitsubishi one? I guess they know what they are talking about. To verify what they say, perhaps draw up the thread in CAD and try to find dimensions of an insert and holder (or maybe a 3D model from one of the manufacturers). That would tell you at what angle you need to present the insert in order for it not to rub.

As it is an external tool, you could rotate the tool itself in the toolpost (or mill the base and top at an angle) to gain some extra angle where the shim runs out of steam. Think of a conventional turning tool. If you sat it in a vee block and screwed it back into the holder, its clearance angle has changed by 45 degrees. It would not cut very well like that, but in principle you are doing the same to a lesser degree to the threading tool.

The key point is that you have a lot more options to do things with an external tool (screw) than with an internal one (nut).

If the standard RH shim gives + 4.5 degrees of helix angle, altering the base of the tool by 9 degrees would make it cut at -4.5 degrees helix. An overseas RH tool is cheap enough to modify.

If someone were cutting many LH threads, perhaps altering an external tool's shank from square to round and then clamping it in a split sleeve would allow you to set it to any helix angle at all.

Yes, that came from the Mitsubishi one (see the screenshots down below). That where I got the +4.5° shim from as well. The standard shims are +1.5° I think.
I don't really need a new screw, but I thought it might make a nice project.
When I bought the Southbend it had a fairly worn metric 7/16"-2.5mm pitch cross slide screw. I then ordered a 7/16-10tpi imperial screw from Australia and a imperial nut from the usa. Those are still in good shape, 0.2mm backlash on the worst part.
The worn metric screw is still on the shelf and yesterday I just thought it would be nice to machine a new imperial acme thread for it.
I ordered some cheap RH acme inserts on amazon and have a bit of a tinker.

 

[dieselsamurai]

So holding the X axis nut for boring produced this contraption but actually was not scary at all even at 500rpm I bolted with a threaded bar through the spindle so wasnt going anywhere

This is set up for centering the only way I could think of doing it was with a MT3 taper stuffed in it centered off the tail stock



Alot of brass chips later and a 0.15 over bore produced , I had to drop it 0.75mm so will need to shim it back up when back on the mill



Now I just need to silver solder these



Not done anything this big before will a propane plumbing torch produce enough heat ?

 

[Seadog]

So holding the X axis nut for boring produced this contraption but actually was not scary at all even at 500rpm I bolted with a threaded bar through the spindle so wasnt going anywhere

This is set up for centering the only way I could think of doing it was with a MT3 taper stuffed in it centered off the tail stock

View attachment 489679

Alot of brass chips later and a 0.15 over bore produced , I had to drop it 0.75mm so will need to shim it back up when back on the mill

View attachment 489678

Now I just need to silver solder these

View attachment 489677

Not done anything this big before will a propane plumbing torch produce enough heat ?

If you surround it with firebrick to concentrate the heat it should be fine.

 

[Agroshield]

What advantages does silver solder offer in this situation over soft solder? The joint area is huge and it is never going to fail.

 

[RichardM]

What advantages does silver solder offer in this situation over soft solder? The joint area is huge and it is never going to fail.

I doubt an, especially if both parts are fully tinned first.

 

[RobCox]

Now I just need to silver solder these

I used green loctite on the y axis feed nut on my mill. No sign of problems after 7+ years so I guess it's ok. A lot easier than soldering or brazing!

 

[dieselsamurai]

I used green loctite on the y axis feed nut on my mill. No sign of problems after 7+ years so I guess it's ok. A lot easier than soldering or brazing!

I am tempted to use that the only reason why im tempted to solder is the narrow split part that is used to adjust backlash do you think it would still hold on that ?

My only reason for silver soldering is because i have some but if i can do it chemically id rather do that as I have a big bottle of green loctite too