Tap/Die sets – BSW/BSF or UNC/UNF?

[Maurice TaylorParticipant @mauricetaylor82093]

Hi , There are plenty of Whitworth ,bsf, cycle thread bolts ,nuts etc on eBay.

Not much difference in price of similar size metric or Whitworth bolts.

Maurice

Edited By Maurice Taylor on 24/10/2020 10:52:42

[Anonymous]

Bother, due to finger trouble I've just lost what I was typing. Just as well though as I was beginning to ramble. I can now start again with a better idea of what to say. On the plus side it's just started raining so I can abandon plans for weeding the garden and hit the workshop instead.

The OP needs to decide what he wants to make before buying taps and dies. I'm building a relatively large (4" scale) engine but the most common threads are 1/4" BSF and 2BA. Smaller engines will most likely be metric, BA or UNC/UNF depending upon where and when they were designed.

I mostly use metric threads for work related design, but my engines are a mix of metric, BA, BSP and BSF and even one part which is 5/8" UNF. Internally on my engines I use metric threads and commercial socket head bolts/screws. But for visible threads I reverted to the original BA and BSF threads after a brief period of aiming to convert everything to metric. I use commercial BA nuts and small BA screws from EKP. I understand that small scale metric fasteners are available from European suppliers. But I use so few that I make my own. I was unimpressed with commercial fasteners for the larger threads so I also make my own; 2BA bolts and M4 nuts:

1/4" and 5/16" BSF studs:

And matching nuts:

Of course it helps that I've got a repetition lathe; once set up it's very quick to turn out multiple parts.

To summarise the ramblings; decide what to make and then buy taps and dies as needed. There are two rules for buying taps and dies, and any type of cutting tool:

Rule 1: Don't buy cheap

Rule 2: See rule 1

I buy from professional tool shops for taps and dies I use a lot. For odd sizes I won't use often I tend to buy from Ebay, but only branded names such as Dormer or LAL and from UK sellers.This is what happens to cheap tools, bought from a UK ME supplier, that were not up to standard:

They get recycled!

Andrew

[Paul KempParticipant @paulkemp46892]

Andrew,

That is some failure on the taps? I don't think I have ever seen a tap break like that, was there a groove in the shank at point of fracture? Were you hand tapping when they broke or under power? I do have one die with a similar appearance to yours lol, I think the problem with mine was less with the die and more with the holder being oversize and allowing me to Jack the die open too far.

Paul.

[Henry BrownParticipant @henrybrown95529]

LOL, I wish all taps broke there if they are going to Andrew!

Another good reason for buying quality taps, it's usually not so bad if a die goes other than the inconvenience of getting another…

[Anonymous]

Posted by Paul Kemp on 24/10/2020 13:00:48:

That is some failure on the taps? I don't think I have ever seen a tap break like that, was there a groove in the shank at point of fracture? Were you hand tapping when they broke or under power?

None of the above. I broke them deliberately (Widlarised is the technical term *) as the threads they produced simply didn't fit together properly whatever I tried. I can't remember the exact details but I got so fed up making, and scrapping, parts that didn't fit that I binned the taps and die. I then bought a 5/8" UNF spiral flute tap from a commercial supplier (probably Cutwel as the brand is YG) and screwcut the external threads. I no longer use the ME supplier from whom I orginally bought the taps and die.

Andrew

* After the legendary analogue integrated circuit designer Bob Widlar. Having found a duff component during debug his advice was to smack it with a hammer, for two reasons. One, it makes you feel better, and two if you leave it lying around someone else will use it and then have to go through the same debug process.

[Jeff DaymanParticipant @jeffdayman43397]

Just my $0.02 worth re fastener systems for ME – if I were starting to gather tooling and fasteners for some ME activity, with a view to cost and global availability of tools / fasteners for next 10-20 years, I would go all metric all HSS tools no question. Most of the world apart from USA and UK have gone metric some time ago. The high volume manufacturing power in the far east means normal commercial metric fasteners and threadmaking tools are reasonably priced and very available.

One thing that is increasingly hard to find (anywhere) is small size steel hex stock under 5 mm a/f for nut making for steam models. If you plan to do any hex fastener making I recommend getting a stock of some small hex now. It may not be available in a few years as commercial screw production goes away from screw machine screw production and into all very high volume cold-headed fastener production of standardized screws per DIN etc. I like to use nuts and studs on steam models because a) that's what the originals used, so they look right b) if you make your own studding and nuts you save a pile of money on scale screws and bolts and nuts c) making a big pile of scale 0.8 mm thread nuts is good for building character, is very "Zen", and good for realigning your chi (life energy) pathways.

[William AyerstParticipant @williamayerst55662]

So no 63 tooth change gear with the lathe but presumably I can buy one if required?

What brand should I be looking for, for taps and dies? Dormer? Presto?

[VicParticipant @vic]

Posted by Jeff Dayman on 24/10/2020 14:42:52:

Most of the world apart from USA and UK have gone metric some time ago.

I don’t know where you got that idea from but the UK went metric decades ago.

**LINK**

It’s a darn sight easier to get metric fasteners over here but you can still get some imperial stuff, likely due to the USA still using them.

Some old folks still like to buy imperial machines for some reason rather than convert to metric but they seem to be a dying breed. Machine tool dealers don’t help either sometimes, my metric VMC mill was supplied with a Whitworth draw bar that got thrown into a cupboard never to be seen again!

[VicParticipant @vic]

Just out of interest I looked to see what imperial stuff Australia still sell and sure enough, like the UK they still sell 8’ x 4’ sheets of ply – marked in metric sizes of course!

**LINK**

[Bill PhinnParticipant @billphinn90025]

Posted by Mike Poole on 23/10/2020 22:57:01:

Posted by Bill Phinn on 23/10/2020 22:22:57:

Posted by Mike Poole on 23/10/2020 20:41:34:

if you are making them from scratch then you can put whatever head you like on them.

Mike

A genuine question, Mike, if a little off-topic:

A large choice of head shape is clearly something any lathe can offer, but what about the "slot"? A simple line slot will surely look wrong in some situations, but what other realistic choices does the lathe owner making fasteners from scratch have? Hex, Torx, Pozi, Philips et al. are surely not practicable.

I was rather thinking of getting the proportions of a hex head to be pleasing. A rotary broach or wobble broach could probably do hex socket and Torx but cross heads are forged I think so not a practical proposition for most people, the broaching is quite an ambitious method but it has been discussed on the forum and in the magazine. Of course the plain slotted screw is easy to make if they are appropriate for the job. Unless you have some sort of facility to do repetition work I think making more than a few of something will soon tax the will to live.

Mike

Thanks for your answer, Mike. I sensed this was the way things were, though I didn't know you could broach Torx slots.

[Andy CarlsonParticipant @andycarlson18141]

Posted by William Ayerst on 24/10/2020 14:54:21:

What brand should I be looking for, for taps and dies? Dormer? Presto?

Oh lordy. Way to kick of a huge discussion on here

Some brands aren't what they were. No doubt others will chip in.

I went for opportunistically picking up job lots of decent used ones – LAL, Warrior, Herbert. I got a few duff ones but ended up with a set that covers most of my likely needs for not too much money.

BSF/BSW for me because they mostly get used for mucking about with old lathes and other such British made kit. I also have some metric stuff – metric all bought new, mostly Sherwood.

I'm off back to 2FS land now before I cause any more trouble. Welcome to the ME forum BTW.

[Howard LewisParticipant @howardlewis46836]

Purely an aside, but with a 8 tpi Leadscrew, there are many more thread pitches than multiples, or factors of 8 that can be cut.

A correct selection of changewheels will allow many variations.

From time to time you will run across some of the various "standard" threads, as well as "specials" used by certain manufacturers, for their own particular purposes. As instances:

The Myford ML7 Lathe uses a "non standard" thread to carry the chuck. A 1.125" x 12 tpi Whit form.

The predecessor ML1,2, 3 and 4 started by using a 7/8 x 9 tpi (Standard 7/8 BSW ), then moved to a 7/8 x 12 tpi on the Mandrel. (The Leadscrew was 8 tpi, but the Cross and Top Slide Leadscrews were 12 tpi )

10 tpi makes graduating the handwheels with divisions equating to 0.001" so much easier!

Some far eastern lathes use a 2.25" x 8 tpi Whit form thread for the chuck and Mandrel!

"Screwcutting in the Lathe" by Martin Cleeve (No.3 in the Workshop Practice Series ) and

"Gearing of Lathes for Screwcutting" by Brian Wood will show how a variety of pitches can be cut by the correct selection of changewheels.

The changewheels do as their name says, CHANGE the ratio between the Mandrel and the Leadscrew.

As proof, recently, a Lathe with a 3mm pitch Leadscrew was used to cut a 4 mm pitch thread. The same machine has been used to cut 1.5 mm pitch threads (for ER collet holders ).

With suitable selection of wheels, a mini lathe with a 1.5 mm pitch Leadscrew can advance a tool by as little as

0.06 mm for each revolution of the Chuck. (The changewheels, on mini lathes usually cover from 20T to 80T in 5 tooth increments. In this case, there are two 20T and two 80T wheels in the set.

As in many cases, extra gears can be bought, new or secondhand, to duplicate, or triplicate if you so wish.

BUT the gears must be of the same DP and pressure angle, as well as the required tooth count! A 14 DP gear will be coarser and larger than a 20 DP one with the same number of teeth.

A 127T wheel will allow Metric threads to cut with maximum accuracy, but a 63T wheel will produce threads with acceptable error in most cases, on an Lathe with an Imperial pitch Leadscrew.

For most "standard" threads smaller than 1/2" or 12 mm, I use taps and Dies.

If it needs to be said, BSW and BSW are a different thread form from UNC and UNF. In some cases the pitches coincide, but they are not properly interchangeable. Metric threads are the same form, (60 degrees ) as UNC/UNF but are not interchangeable because of differences in diameter and pitch.

Model Engineer threads (40 and 32 tpi ) are Whitworth form, as are British Standard Pipe and British Standard Brass. Cycle threads are 60 degree form although the same 26 tpi as BSB.

BSP and NTP forms differ in both form and pitch.

BA, mostly used on older electrical fittings, as well as by modellers use another different thread form, and are basically Metric in dimensions.

Howard

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