Which indexable thread cutting tools and chuck to buy?

[M J AliParticipant @mjali]

Hi everybody

I'm new to this forum and to thread cutting and looking for some advice.

I'm a design student at the royal college of art and I'm trying to make some parts for a machine I'm making.

I'd like to thread some parts, mostly with an ID around 20mm. I'm considering indexable because I can replace the tips easily (although more expensive) when I break them(!) and don't trust my ability to sharpen a carbide tip to 60 degrees.

My buying options at the moment are 6 or 8mm shank sized kits from rdgtools (http://www.rdgtools.co.uk/acatalog/Indexable-Screw-Cutting-Sets.html) or individual tools. I was thinking the kits because they have both internal and external tools and a number of spare tips.

Chronos have separate int and ext kits but in a 16mm shank, too big for what I need to do, I think? (http://www.chronos.ltd.uk/acatalog/Sets_of_16_mm_Square_Indexable_Threading_Tools.html)

I can't afford to wait for 12mm shank kits to come back in at rdg, arceurotrade or chronos and at the moment would obviously rather spend a bit less.

Is it a false economy to buy a set rather than individual tools?
Does the shank of the tool holder (8mm vs 10 or 12mm) make such a big difference?
Does the type of tip make a huge difference? Generic A60, G60 vs pitch specific tips?

Unfortunately I can't really afford to make a mistake in terms of time or money just now, with the final exam and show rushing towards me.

I have a 1964 Boxford AUD, which I bought from the college a couple of months ago. It was being scrapped because laterly it had been in the wood workshop for 10-15 years where they just hadn't had the time to maintain it. It was still just about working but needed a lot of tlc because it was totally clogged up with wood dust. I stripped it down, cleaned, oiled, unseized it, changed belt etc and it now seems to be working fine. Well enough for what I need to do at the moment.

So this leads to my second question. The lathe came with a burnerd 3 inch chuck with only the external jaws. I'm finding now that it's a bit small for what I need to do. Chronos has a vertex 100mm chuck but would prefer bigger.

Does anybody have any experience mounting a 130mm chuck on an AUDII for instance? Does it actually go on?
Do I have to take the weight of the chuck into consideration and how will this affect the spindle and bearings? Will it wear them out, or mean that I have to do even smaller cuts?
Would it be better to got the 100mm vertex chuck or even one of the other ones: Sharp, Soba, Turntech, generic?

I'm fairly new to this so apologies for so many questions and if I've left out a ton of information.

Many thanks in advance

Mo

[M J AliParticipant @mjali]

[Ian S CParticipant @iansc]

Mo, someone else will let you know about the chuck. I would go to HSS for your thread cutting. You can use bits of HSS from broken centre drills, end mill, a use for broken taps. A steel bar, drill through the diameter near one end to the size of the HSS tool (if you are really enthusiastic you can file it square), either drill and tap for a grub screwat right angles to the tool hole, or into the end of the bar on the centre. Its much easier on the wallet if nothing else to make your own, and it doesn't take long. Ian S C

[Bob Brown 1Participant @bobbrown1]

Choice of tool to cut threads depends on the material you are looking to thread, e.g. aluminium, steel, brass etc, some are easier than others. Hard materials like stainless steel and some of the tougher steels are better cut with a carbide tool but aluminium is fine with cobalt HSS

Have you considered using taps and dies? you can still machine the threads on the lathe and the Boxford should be able to handle those sorts of sizes.

 

As far as the chuck is concerned the choice is yours but a larger chuck (125mm) is probably more useful, do not forget unless specified the chuck will not come with a back plate to enable it to be screwed to the lathe, RDG do supply them with the back plate so plug and play.

I have swung a large (200mm) 4 jaw independent on my 5" Mk 3 AUD Boxford but find I tend to use the 125mm 3 jaw self centring more than the others. Weight is not a problem as far as headstock bearings etc. It is worth noting that if you run a larger work piece at higher speeds then you can have problems with belt slip due to inertia and not having a brake on the machine means they take a little while to stop. DO NOT be tempted to use your hand as a brake!

Bob

 

 

 

Edited By Bob Brown 1 on 16/04/2014 17:32:34

[BazyleParticipant @bazyle]

Snap! My Boxford came out of a woodshop too.

The standard 3 jaw for a Boxford is 5 in and the 4 jaw is 6 in. If you get a new backplate with or without the chuck it may be a little tight and need easing. The last one I got from RDG wouldn't go on at first so I put it on backwards after which it went on correctly so must have moved a burr out.

[Neil WyattModerator @neilwyatt]

> I have a 1964 Boxford AUD, which I bought from the college a couple of months ago. It was being scrapped because laterly it had been in the wood workshop for 10-15 years where they just hadn't had the time to maintain it.

You earned the Order of Merit, for saving what is a very nice machine.

I would say 6mm shank is a bit small if you have that much space. 10mm would probably be ideal balance between rigidity and enough room to see what's going on.

Neil

[Bob Brown 1Participant @bobbrown1]

I hope your Boxford has the thread-dial indicator without it you will have problems cutting threads, they can be cut without one but it's tricky! Do not forget the chuck is threaded on to the spindle and running the machine in reverse can and most probably will cause the chuck to come off.

I remember from years ago a lecturer was trying to demonstrate parting off in reverse on a lathe and did not take into account the lathe had a screw on chuck, he found out when the chuck went off down the workshop having broken free, fortunately no one was hurt, just a very red faced lecturer.

[Tony RayParticipant @tonyray65007]

Hi,

I had an HBM 125mm on my AUD not the best in the world but OK. the AUD like all Boxford has taper roller bearings and will hanfle the chuck with no issues ( provided they are not already worn out) A Vertex should be better quality but you really need a 125mm imho. You know you can buy pre ground HSS & carbide tools @ 60 degress for thread cutting. If you really want to go down the insert route try JB cutting tools on ebay. They have been around for years at shows but have only recently started on ebay. I'd use a 12mm shank tool but if you email them and tell them what you want to thread they'll sort you out. I do have one of their tools and it works perfectly.

You could pick up a 4 jaw on ebay for about £40 – 50 with the backplate – 4 jaws don't get the same amount of use and tend to be in good condtion – they take a bit of setting up but that's good practice for you anyway – but you will need a DTI – 'clock' dia test indicator & stand and the chuck will do everything the 3 jaw will and a lot more as well.

Have fun withthe Boxford you have done well

[M J AliParticipant @mjali]

Thank you all, for the encouraging posts and amazing information!

Sorry I haven't got back sooner, I've been burning the midnight oil at college trying to get as much done as I can before college closed for the Easter break. No workshop access now till Wednesday!

Ian, that's a great idea. I have a piece of quarter inch square hss tooling that I found amongst the debris in the lathe. I'll give it a try when I get back.

Bob, I'm going to be cutting threads into aluminium so it should be a bit easier. I did consider using regular taps and dies, but I need a finer thread than a M20 (a tap and die size I don't unfortunately have either).

It's reassuring to know that you've run a 200mm chuck before. I think I might need to take another link out of the belt at some point, as I do get slippage occasionally.

Bazyle. You're right those are the two chucks that came with the lathe and both came with internal jaws only. I guess that's why I thought the 3 jaw was a 3 inch as that seems to be the capacity it can grip around a rod.

The serial number on the jaws also don't match those on the body. Is this normal? I can't seem to find any information about it online. I was also told by one of the technicians that you had to be careful with things flying out of the chuck making me think it might need lapping?

Thank you Neil, I'm discovering what a great machine the AUD is. Even though it hasn't had the attention it needed, it has come back to life surprisingly well. 10mm seems to be a good size for the internal.

Would an 8mm with light cuts do the job as well, do you think? I'm thinking I'll be able to do a bigger range of internal diameters with it, or is it better just to get a the right tip holder for the job?

Bob and Tony. Unfortunately, there's no thread dial indicator. I did get a pair of old Baty dial indicators with a a stand from ebay. I have to honest, they're not great. Very sticky and one of them has a damaged gear which only allows half the travel. Still, they've been very useful. I didn't think to use them for screw cutting but it makes total sense to be able to clock up the travel.

Unless I can get a set of external jaws (if the serial numbering isn't relevant), I'll practice figuring out how to set up the 4 jaw chuck.

[Bob Brown 1Participant @bobbrown1]

The thread-dial indicator is a part on the saddle and connects to the lead screw so you can pick the thread up in the same place see **LINK**

If you want a fine thread in aluminium then you could go to M20 x 1.5 or 1.0 rather than the standard 2.5 for which taps and dies should be available and in aluminium a far easier job more so if you use a tailstock die holder.

It is more common to use course threads with aluminium.

Paraffin or WD40 as lubricant.

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Bob Brown 1 on 17/04/2014 16:12:27:

If you want a fine thread in aluminium then you could go to M20 x 1.5 or 1.0 rather than the standard 2.5 for which taps and dies should be available and in aluminium a far easier job more so if you use a tailstock die holder.

Tracy Tools list taps and dies M20 x 1, 1.5, 2, 2.5 – one of those should do.

I have a thread dial indicator on my lathe but rarely use it. I find it easier to just reverse the motor to wind the tool out without disengaging the leadscrew. If your lathe has an imperial leadscrew and you are cutting metric threads you need to do that anyway.

Russell.

[Tim StevensParticipant @timstevens64731]

One factor to remember regarding the size of tooling –

In general, the bigger tools are stiffer, so less springy, which can help with vibration and chatter. But the main concern must be the tool holder(s) you have. The tool tip needs to be central to the work, and if the tool shank is too big you will not be able to get it low enough. This is worse with carbide tips as you cannot grind a bit off as you might with HSS. So, put a centre in the headstock, and measure vertically between the end of the centre and the base of the tool-holder platform. This will give you a maximum for conventional straight tools. If the tool shank is too small, you can raise it with packing – mild steel strip or shim.

Of course, some fancy toolposts have an up and down adjustment, but I am assuming you have the standard arrangement.

Cheers, Tim

Edited By Tim Stevens on 17/04/2014 17:11:24

[M J AliParticipant @mjali]

Unfortunately, it has an imperial leadscrew, but as I'm only making visual prototypes at the moment, I figured that the pitch isn't critical at the moment. If I use taps and dies, then I'd be doing it manually with a tailstock die holder, I guess.

I'll keep an eye out for an imperial thread dial indicator as the leadscrew pitch is going to different afaik.

That's a really good point about being able to grind an hss bit down to enable it to fit into a tight hole for the internal threads. I think I'll have a go at grinding down the quarter inch hss stock next week and give it a try.

I bought a new toolpost as the supplied one was in pretty poor shape. No screws and worn out threads from generations of overtightening. I also figured it would be important to be able to do multiple operations without having to stop and adjust the height every time, so I plumped for the T1 quick change number from rdg. It seemed to be most similar to the ones on the three colchesters in the college workshop. It made sense to spend money on that as tooling is relatively replaceable by comparison.

Ultimately, I need to find a 127/100 changewheel to cut metric threads properly. Although I'm considering making one on the cnc machine at college. I have a slot booked for the beginning of May so I have a bit of time to do some research.

[Tony RayParticipant @tonyray65007]

Yes you could use a 127/100 but there are more compact alternatives. I'd encourage you to join the Boxford user group on Yahoo . Members are friendly and knowledgeable & you can find details on the 73/65 ( I think – I no longer have a Boxford) ratio there is a spreadsheet that shows the change wheels you need and the gearbox selections needed in the files section.

[Russell EberhardtParticipant @russelleberhardt48058]

You don't need to use the 127/100 combination.

There are two programs available to download from the lathes.co.uk website. These will enable you to enter the changewheels you have and calculate the combinations required for cutting metric threads using just those. They will give you the best combination to use and give you the error in the pitch.

The first is NthreadsP which uses the changewheels alone. The second, BoxfthreadP gives you the combination to use using the Boxford gearbox as well.

Russell.

[M J AliParticipant @mjali]

Brilliant!! I don't have to design a 127/100 changewheel in solidworks now, and hope the material I choose won't disintegrate in use. Hopefully I also have the full set of gears as well. And I can cut the correct pitch straight away too.

[Gary WoodingParticipant @garywooding25363]

The real problem with HSS bits for threading, is the grinding and shaping to the correct angles. Take a look at the article "Really Simple Threading Tools" in MEW issue 159, page 44. It describes simple holders for internal and external threading, together with a very simple and easy method of grinding correct angles with a normal grinding wheel.

Gary

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