How hard is gauge plate?

I'm waiting for some gauge plate to arrive from the UK.

I have to drill and tap 4 through holes in a 1/4" strip, 10x24 UNC and 1/4".

I only have plug taps and hope they will be OK, but having never heard of gauge plate I have no idea how hard it is. Like stainless steel? Less hard?

It's delivered soft in annealed condition and is easily machined.

Gauge plate is usually hardened after being machined into a part. Typical instructions here. The plate is O1 or something very like it. Being a tool-steel, it can be made hard enough to bounce a file off.

Dave

Drill your holes oversized to reduce load on the tap, use new, sharp taps. Use cutting oil and you should be OK.

Nice sharp drills and you will be OK. Nowhere near as bad as stainless.

Thanks for the replies.

In the fully tempered state gauge plate is between 15 and 20Rc, so not particularly hard. However, you will struggle with plug taps only, unless you go for a shallow thread engagement. I expect you will need rather less than 50%. It would be sensible to use a taper tap. New ones, from Drill Service, are around a fiver.

Andrew

They may only cost a fiver but I'm in Italy and it cost me nearly £20 in taxes and charges and postage to buy 2 £6 taps from the UK. Total cost £32

surely there are tool suppliers in Italy/?

You will struggle to make a thread with only plug taps ! If you use a larger drill you will reduce the engagement to a point the thread may well strip with little load. Good luck. Noel.

Isn’t there anyone in Italy who could grind a lead on one of your taps for you?

For the next project, it might be worth getting taper or second cut taps. They'll do a full thread in a through hole if the tap can use its whole length and they can be converted into second or plug taps by grinding part of the end off.

Note also:- UK has taper, second and plug taps, US has taper, plug and bottoming tapse.

For what are typically American sizes at a reasonable cost?

There doesn't seem to be a hobby market here. I recently tried to buy a spare for a Mitutoyo gauge, which cost 2 euro. The supplier didn't take orders less than 50 euro and I had to have a VAT number.

I'm sure there is somewhere. Finding them is the problem and feeling confident they know what they are doing.

I've been trying to get a piece of cast iron repaired for the last year. Everyone says they can do it, mostly tractor repair workshops, but I'm not convinced and none of them gives me the confidence they will succeed. They just say they will try.

What exactly is a tap plug? I understand it has a more agressive longer taper?

In the past, I would have bought a full set but it is just not economical to do so anymore and I hate buying cheaper unknown quality from China.

I tried to err on the slight oversize with the drills. 3.85mm and 5.1mm.

.

This ebay Seller looks promising : **LINK**

https://www.ebay.co.uk/str/milancentral

… I have given the U.K. ‘Shop’ but presumably they also list on ebay.it

[ despite actually being based in Hong Kong ]

MichaelG.

Edited By Michael Gilligan on 07/03/2022 08:03:15

I have seen them before. Hong Kong based.

Sometimes you just have to go with the market:

**LINK**

https://www.ebay.co.uk/itm/363635079100?

MichaelG.

I did find them when I was searching.

Normally I'll buy used UK manufactured as I probably will only use them once. But buying from China is the same as buying from the UK. I still have to pay extortionate handling charges, often 18 euro or £15, plus VAT.

The 2 taps I bought from the UK which weigh a few grams, cost £10 standard airmail. I know businesses have to make money but the postage cost was probably close to a fiver.

Sorry for wasting your time … I will stop trying to help you.

MichaelG.