Identifying taps

[RainbowsParticipant @rainbows]

I got a wooden drawer of taps from a boot sale a while ago. Various bunch. Some Presto, some Warrior, some Goliath and some SKF. The older whitworth taps tend to have a nice deep stamp in them declaring them C & H 5/8" WHIT or 3/8" GAS (I assume that is BSP). The newer taps however have had the details etched or lasered in and only under a strong lamp with a lot of squinting is it possible to read out Warrior M12x1.75 HSS. A lot more have straight up no legible marking.

So two questions here.

1. Anyone know how I can test thr thread of the taps in a non destructive way?

2. Anyone know how to mark the tapsin a clear manner? I don't fancy using letter punches on HSS.

[RainbowsParticipant @rainbows]

[Mike LightfootParticipant @mikelightfoot72419]

Hi, I would use a thread gauge ( a bit like a set of feelers but looks like a lot of saws ) match the TPI and Diameter to a thread chart or alternatively if you have a bolt of known size match it to a tap I find if you hold them together and up to the light you can really see if they match, not sure how to mark hem except small boxes to keep them in sets.

[David Clark 13Participant @davidclark13]

You might be able to etch them with a Burgess top etcher. You might need a diamond point.

You might be able to compare one unknown tap with a known one.

[AdrianhParticipant @adrianh95127]

I do this every week in my job, you need a vernier, imperial 55 degree and metric/unified 60deg thread gauges and a thread specification chart/booklet.

The diameter of a tap is always slightly less than the nominal thread diameter. Then using a set of thread gauges you can establish the TPI ( teeth per inch) or metric pitch. Take all your measurement furthest from the end of the tap as a first and second tap are tapered.

If you have a lot of old looking taps you will probably find they are BSW or BSF.

Taps marked GAS are ussually BSP parallel.

Remarking taps is almost impossible as the majority are HSS ( high speed steel) with the markings etched on – a Dremmell may work.

If you need anymore I have draws full especially of the older threads

[RainbowsParticipant @rainbows]

After getting 50 taps and a pair of molegrips for £4 anythng else starts looking pricey in comparison. 😛

At the moment half of them half little masking tape flags on them with their sizes on. I remember buying a thread gauge for finding the thread on a chuck backplate but of course now that I need in again it has disappeared.

Also I have a tap here marked 1/2 Ground thread but no thread form. Despite being 1/2 it came in as ~0.775" give or take some wobble. Would this tap likely be a BSP tap?

[JohnFParticipant @johnf59703]

Rainbows, marking on HSS can be done with an electric arc pencil, tried to add a link but the site will not allow me to ! However Google electric arc etching pencil and you will see plenty of examples and DIY plans.

Marking is easy, legible and permanent regardless of hardness. Don't know your location but if you are in the NW PM me.

Regards John

[Author]

Posts