Thread: Trying to make a QCTP anchor bolt

I'm having a go at turning a bolt down to anchor a Model 000 QCTP to my Sieg SC4/510 lathe.

When I bought the QCTP, I didn't realise that I'd have to make the bthing fit, which is a bit annoying, but I've come up with a cunning plan to hack an ordinary M12 bolt into the right shape (see attached pic...I can't seem to put it inline anymore). The problem I need to solve is that the compound slide has an M12 threaded hole but the QTCP has an M10 bore, so I need the anchor bolt to have M12 on one end and M10 on the other.

I'm trying to hack a Pinnacle brand M12 x 90 mm Class 8.8 high tensile yellow zinc plated steel bolt.

I've done a few trial runs of beheading bolts (failed to part off on the lathe and ended up using a hacksaw), turning it down to 10 mm and trying to single-point a thread...but the finish is awful (even from my beginners point of view).

I guess the finish is not that important but I would like to be able to put the 10mm flange nut onto a decent thread.

Should I persevere with this idea or should I use some other type of steel? or is it just me

Cheers,
Andrew

Hi simplicio,
It sounds a bit like you are trying to run before you can walk.

Lets back it up a bit. I can only assume you pretty new to maching and lathe work.
Some details, lots of them please will aid the mob in sorting your problem if you are making basic errors or not

Parting off the bolt head
Spindle speed. Cutting tool SS of carbide. Size and stickout of cutting tool. Rigidity of cutting tool and holder.Is the parting tool square to the cut off?

If you can supply as much detail as you can of what you did ,it makes it easier to get you back on track.

You say a zinc plated hi tensile steel bolt. I seem to recall that zinc plating places diffusable hydrogen in the metal it is coated to and root cracking at the vee of the threads can occur.

As a test ,why not try a black hi tensile bolt?

Grahame

Hi Grahame,

Yes, I'm very new to this...the plan is to make it one of my retirement activities. Most of my current understanding comes from watching hundreds of YouTube videos

I tried so many variations it's hard to say exactly what I did, but in general I kept the spindle speed between 600 and 800 RPM and hand fed the cutters (see pics) as slowly as I could - sometimes faster, but it didn't seem to improve things.

The cutter holders are 10mm and the cutters themselves (parting and cutting) were both "blue nano" carbide ones from Banggood. I tried to keep the overhang as short as possible. I also tried cutting fluid called "SuttonTools Venom Endurance+ Cutting Spray" but it didn't seem to improve the finish. Oh, and I don't have any HSS cutters yet - maybe I should get some. I set up the parting off bit square to the work and tried to keep the level of both cutters at the centre of rotation. Setting the right height was complicated by the so-called quick change tool post that I am using at the moment seems to raise the height as I tighten it - it's not so quick in practice which is why I want to get this Aloris style wedge QCTP in place.

I used that bolt because it was available locally at Bunnings. I'll hunt around for a black high tensile bolt and see how that goes.

Cheers,
Andrew

When doing the threading are you supporting the work with a live center, how much is sticking out beyond the chuck, can you give us a photo of the work set up in the lathe. I think your idea could work but its the execution thats letting you down (although once you have screwcutting down id just single point both threads for better alignment).

Best of luck!

Hi Andrew, Guys,

Why use a high tensile bolt at all ? They are horrible to machine, and as you have discovered not easy to thread ! In fact the manufacturers don't cut threads on them, they are rolled ! This process deforms the metal causing it to flow, producing a smooth, formed thread.

I would try and get a hold of some nice 12 mm diameter mild steel rod of free cutting variety.

Put it in the three jaw after cutting to the length you want and put a centre in each end.
Using a centre in the tailstock, preferably a live centre, fit between centre and chuck turn down to 10 mm for the length you want.

If you clamp the length of the M12 bit of the bar in the chuck, that will set the limit of travel. Don't make a sharp corner where the M12 and 10 mm diameters meet use a curved surface. This is so you don't introduce a stress fracture at this point.
Once you have your piece of 10 mm rod, you can loosen the chuck and slide the bar into the chuck to cut the M10 thread. I'm assuming that the bore in the spindle will accommodate the 12 mm bar.

Once you have cut your M10 thread. Turn the bar around and skim the end down to get it round so that you can thread it M12.

Job done.

Don't forget the pictures...

simplico,
Why make life so hard trying to cut threads on class 8 bolts on your small lathe. A couple of suggestions. 1- Drill the QCTP out to 12 mm and buy a suitable length class 8 bolt that is long enough to do the job. Or 2
buy a suitable length class 8 10mm bolt then drill and tap a short length of 12 mm thread to 10mm ID and loctite this in place after you have tested it to ensure it works. I would go for option one as it is easier and stronger.
Bob

Hi Bob,
I thought about option 1, but on closer inspection the 10 mm bore is in a tube which itself is screwed into the QCTP. I can't really verify that until I can get it apart which is proving problematic at the moment because I don't have the right tool (I never seem to have the right tool). The worm gear that drives the wedges is around that tube, so if I bored it out to 12 mm there would be no tube left. I'll look into option 2 though thanks! BTW, I see you're from Ballina - I grew up there
Cheers,
Andrew.

Hi Grahame, (reposting this: it disappeared into the ether)

Yes, I'm very new to this...the plan is to make it one of my retirement activities. Most of my current understanding comes from watching hundreds of YouTube videos

I tried so many variations it's hard to say exactly what I did, but in general I kept the spindle speed between 600 and 800 RPM and hand fed the cutters (see pics) as slowly as I could - sometimes faster, but it didn't seem to improve things.

The cutter holders are 10mm and the cutters themselves (parting and cutting) were both "blue nano" carbide ones from Banggood. I tried to keep the overhang as short as possible. I also tried cutting fluid called "SuttonTools Venom Endurance+ Cutting Spray" but it didn't seem to improve the finish. Oh, and I don't have any HSS cutters yet - maybe I should get some. I set up the parting off bit square to the work and tried to keep the level of both cutters at the centre of rotation. Setting the right height was complicated by the so-called quick change tool post that I am using at the moment seems to raise the height as I tighten it - it's not so quick in practice which is why I want to get this Aloris style wedge QCTP in place.

I used that bolt because it was available locally at Bunnings. I'll hunt around for a black high tensile bolt and see how that goes.

Cheers,
Andrew

Originally Posted by BaronJ

Hi Andrew, Guys,

Why use a high tensile bolt at all ? They are horrible to machine, and as you have discovered not easy to thread ! In fact the manufacturers don't cut threads on them, they are rolled ! This process deforms the metal causing it to flow, producing a smooth, formed thread.

I would try and get a hold of some nice 12 mm diameter mild steel rod of free cutting variety.

Thanks BaronJ,

If high tensile steel is the problem then I'll try a different steel - I was just trying to reduce the amount of threading I'd have to do and thought that modifying a bolt would be the way to go. Maybe not

Cheers,
Andrew

Hi Andrew
I would have to be very desperate to buy ANY bolt from Bunnings.

Roger

Have you thought about a helicoil to reduce the M12 to M10

Pretty sure that would almost be an impossibility, even threading a 10mm nut to 12mm would be borderline.
What I'd do is tap it 14mm and thread a piece of metal 10mm to accept the bolt.
Kryn

Hi Andrew.

Have you seen this thread ?

//metalworkforums.com/f303/t202306-norman-toolpost

A lot more work than modifying a bolt, but far more satisfying.
Anyway you might get some ideas from it.

Hi Andrew,
It sounds like the design of your tool post has eliminated option 1.The suggestion by Dave J of using a helicoil would work out easy for you on option 2. Ballina is a very nice place to live, we have a spot right on the Richmond River.
Bob

I would go with BaronJ’s suggestion and make it from scratch out of free machining steel. It’s a delight to turn and thread compared to using a HT bolt. It will give you the nice finish on the threads you said you want.

You are going to need free machining steel for this hobby anyway, so you might as well grab a few lengths now. 12L14 should be plenty strong enough for this application.