Parting 3/8' ACME threaded rod

Ddowns46 · Mar 30, 2018

I have a job coming up where i need to cut about 800 3/8' ACME threaded rods to length (material is mild steel). I picked up an affordable but good running hardinge DV59 to do this work. It has a lever cross slide and collet closer.

I am wondering what type of parting tool i should go with? I'd like to use carbide but i'm not sure how the insert would hold up when initiating the cut over threads. A parting tool .090" wide would also ensure that at least part of the insert is in the cut, so maybe it would be ok?

Would high speed steel work better for this application?

For whats is worth, the lathe has a working pump system for continuous application of cutting oil.

Finegrain · Mar 30, 2018

Insert carbide WAD. The insert will be fine. Cutting threaded rod isn't very "interrupted".

Regards.

Mike

L Vanice · Mar 30, 2018

If you need a chamfer, use the front tool holder with a 3/8" 90 degree vee cutter (brazed carbide or HS) first, then cut off with the back cut off tool.

If you need Hardinge tool holders, front or back cut off with carbide blade, I have them for sale.

Larry

Limy Sami · Mar 30, 2018

L Vanice said:
If you need a chamfer, use the front tool holder with a 3/8" 90 degree vee cutter (brazed carbide or HS) first, then cut off with the back cut off tool.

Larry

That is how I would do the job, ........a tip, if you make the vee tool with a flat ''a little'' narrower than the part off blade it will make life easier for that tool.

Ddowns46 · Mar 30, 2018

Limy Sami said:
That is how I would do the job, ........a tip, if you make the vee tool with a flat ''a little'' narrower than the part off blade it will make life easier for that tool.

I think I am going to take this advice. Do you think the 90* chamfer tool will leave clean threads? Ideally the nuts will screw on without any cleanup.

Limy Sami · Mar 30, 2018

Ddowns46 said:
I think I am going to take this advice. Do you think the 90* chamfer tool will leave clean threads? Ideally the nuts will screw on without any cleanup.

IF it's really sharp and fed gently - as I was told when a lad ''give it time to cut'' ......you should be lucky.

L Vanice · Mar 30, 2018

Ddowns46 said:
I think I am going to take this advice. Do you think the 90* chamfer tool will leave clean threads? Ideally the nuts will screw on without any cleanup.

If you are cutting something like 1018 with rolled threads, keep in mind that the machinability rating is rotten. That steel is meant to be cheap and formable, so it has no alloys to make it machine with ease. It likes to bend better than it likes to be cut. In other words, use sharp carbide tools, run fast and feed slow and maybe the burrs on the last threads will not be too bad. Cutting oil may be helpful with the burrs, but makes a mess. Once you try a bar of 12L14, you will appreciate just what can be done with a little alloying.

With regard to running fast, watch out for the skinny bar sticking out of the left end of the spindle. It needs a good solid support suited to the length and diameter of the stock that sticks out. Disaster is waiting for those who forget, or who are getting their first lesson. There was a horrible Youtube video that demonstrates what I mean that was posted on PM recently.

Larry

DDoug · Mar 30, 2018

L Vanice said:
If you need a chamfer, use the front tool holder with a 3/8" 90 degree vee cutter (brazed carbide or HS) first, then cut off with the back cut off tool.

Larry, why not use the pull down cutoff if so equipped ?

I have one to put on my turret lathe, and it's gonna take some machining to do so,
just want to hear the pros/cons from you.

lucky7 · Mar 30, 2018

I've done similar work with a small horizontal mill and a 3/16" thick cutter. Worked fine with little burr. Would a cold saw work, or too much blade wobble?

L7

L Vanice · Mar 30, 2018

digger doug said:
Larry, why not use the pull down cutoff if so equipped ?

I have one to put on my turret lathe, and it's gonna take some machining to do so,
just want to hear the pros/cons from you.

The vertical cutoff works fine, but it is expensive to buy. I bought my vertical cutoff only when I had a complex part that needed front cutting tools and a rear skiving tool. I was forced to buy the expensive new (this was long before eBay) vertical cutoff and skiving tool and priced the parts to pay for the new tooling. A chamfer and cutoff job can be done as I said, and the front tool holder and a rear cutoff tool will be the most economical solution. Plus, you only use the cross slide lever to do all the cutting, saving time.

Larry

DDoug · Mar 30, 2018

L Vanice said:
The vertical cutoff works fine, but it is expensive to buy. I bought my vertical cutoff only when I had a complex part that needed front cutting tools and a rear skiving tool. I was forced to buy the expensive new (this was long before eBay) vertical cutoff and skiving tool and priced the parts to pay for the new tooling. A chamfer and cutoff job can be done as I said, and the front tool holder and a rear cutoff tool will be the most economical solution. Plus, you only use the cross slide lever to do all the cutting, saving time.

Larry

Thank you for that write up Larry.

I currently only have the set up you describe, with the cut off on the back,
and have not had the opportunity to use the pull down type.

Ddowns46 · Mar 30, 2018

What is the advantage of having the parting tool on the back? I unfortunately dont have the back side cutoff tool holder so was planning to have a conventional parting tool on the front and an upside down chamfer tool on the back.

i plan on supporting the rod in a 1” OD 1/2” ID DOM tube on a set of fabricated stands. Im going to build a set of custom steady rests to clamp down on the dovetail bed to support the roughly 36” long cut to length screw. The screw will be supported by 3/8” ID bearings mounted in each steady rest.

L Vanice · Mar 30, 2018

I have to shorten some 1/4-20 SHCS, so I set up the Hardinge to do it. The front tool bit is 3/8" 90 degree vee brazed carbide and the rear is a P2 3/32" brazed carbide T-bit.

The D10 cutoff holder in the pictures works on either the front or rear position. The single 3/8" tool holders come in two heights, one for the front and one for the rear with the bit upside down. Either way works.

As you see, using a cutoff tool works best if the bit is very close to the chuck or collet. Are you saying your finished length is 36 inches? How long are the uncut bars? In my shop, I would band saw to near net length and just face and chamfer the ends in the Hardinge lathe. You can grind a single 3/8" tool bit to both face and chamfer in one stroke of the lever cross slide.

Larry

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