How hard is gauge plate?

[pgrbffParticipant @pgrbff]

Posted by Andrew Johnston on 07/03/2022 09:03:21:

Posted by pgrbff on 07/03/2022 07:48:20:

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

A plug tap is the last in the sequence of hand taps to be used. It has a very short taper, 1 to 1.5 times the thread pitch. One might get away using only a plug tap in brass, but not in gauge plate. If only one tap can be purchased buy spiral flute taps. They are machine taps intended to blind holes, but are fine when used by hand.

Andrew

This is described as a machine tap. Would it work? From Germany. Euro 15 each plus 10 for shipping, to tap 4 holes. My mistake for ordering plug taps.

[Tony Pratt 1Participant @tonypratt1]

Yes that would work & looks like a decent German brand.

Tony

[HopperParticipant @hopper]

Do you still have your BSW tap you had before you ordered the expensive UNC plug tap? Is it a taper tap? If so, run the BSW taper tap through the hole first, then finish it off with the UNC plug tap.

[JohnFParticipant @johnf59703]

It maybe worth investigating here **LINK**

or look for OMPS & Noma around the Brescia or Gardone VT area, lots of gunmaking and Engineering in that area, OMPS is very much aligned to that trade but if you ask either company if they can recommend where you can get what you want.

John

[pgrbffParticipant @pgrbff]

Posted by Hopper on 07/03/2022 09:49:00:

Do you still have your BSW tap you had before you ordered the expensive UNC plug tap? Is it a taper tap? If so, run the BSW taper tap through the hole first, then finish it off with the UNC plug tap.

Yes, I still have the BSW taps. Remind me what the difference was, I'm afraid I got a bit lost with all the discussion, is it just the thread lead angle?

[HopperParticipant @hopper]

Posted by pgrbff on 07/03/2022 09:53:16:

Posted by Hopper on 07/03/2022 09:49:00:

Do you still have your BSW tap you had before you ordered the expensive UNC plug tap? Is it a taper tap? If so, run the BSW taper tap through the hole first, then finish it off with the UNC plug tap.

Yes, I still have the BSW taps. Remind me what the difference was, I'm afraid I got a bit lost with all the discussion, is it just the thread lead angle?

Yes, The only difference between 5/16 BSW and 5/16 UNC is the irrelevant (in this instance) angle of the sides of the thread profile. As I told you before I have been using the two interchangeably for years. So has just about everyone else in Australia due to circumstances similar to your own: shortage of local suppliers and extortionate shipping and import costs.

Run your BSW taper tap through the hole first and then finish it off with your UNC plug tap. It really is that simple. May not be world's best practice, but needs must. It will work. I have been doing it for over half a century now and never before heard that "It can't be done."

[Anonymous]

Posted by pgrbff on 07/03/2022 09:26:10:

This is described as a machine tap. Would it work?

Yes, it's a spiral point tap, intended for machine tapping of thru holes; the swarf is pushed ahead of the tap. Like spiral flute taps they work fine when used by hand.

Andrew

[larry phelan 1Participant @larryphelan1]

I buy from China ,without those strange high charges.

[speelwerkParticipant @speelwerk]

Do not know about postage but should be reasonable coming from Germany. "Form A" does have a slightly longer lead but this "form B" should also be OK. Niko.

**LINK**

https://www.gewindebohrer-shop.de/gewindebohrer-schneideisen-maschinengewindebohrer-verstaerktem-schaft/maschinengewindebohrer-durchgangsloechermit-verstaerktem-schaft-form-4022835745105-p-631.html

Edited By speelwerk on 07/03/2022 11:31:56

[pgrbffParticipant @pgrbff]

But I'm guessing you're not in Italy?

All couriers here charge 5% or minimum 18 euro for handling fees. The post office, which is divided up into different businesses, charge a minimum of 9 euro, but SDA, still the post office, are classed as a courier.

VAT is calculated at 22% of the total cost including shipping.

I did look at Amazon.jp as you pay the VAT etc upfront and it's delivered by DHL within 4 days but the costs always came out more or less the same, and most of the taps for sale seemed to be Chinese anyway.

Things are still changing. Everything went mad after Brexit. I'm still waiting for a Parcelforce parcel sent on the 25th November. Tracking stopped early January and I just asked Paypal for my money back.

[pgrbffParticipant @pgrbff]

Posted by speelwerk on 07/03/2022 11:31:21:

Do not know about postage but should be reasonable coming from Germany. "Form A" does have a slightly longer lead but this "form B" should also be OK. Niko.

**LINK**

https://www.gewindebohrer-shop.de/gewindebohrer-schneideisen-maschinengewindebohrer-verstaerktem-schaft/maschinengewindebohrer-durchgangsloechermit-verstaerktem-schaft-form-4022835745105-p-631.html

Edited By speelwerk on 07/03/2022 11:31:56

Thanks for the link.

I just gave up looking and ordered from Germany. The two taps were E25 plus E9.99 shipping.

[HopperParticipant @hopper]

If in doubt, grab any piece of scrap metal and drill and tap a 5/16 or 1./4  or whatever BSW hole  in it and see if your UNC bolt screws into it. Then try the same again with your BSW taper tap followed by your UNC plug tap and see if there is any noticeable difference.

EDIT Just read Michael Gilligan's post. So 5/16 or 1/4 or whatever UNC. They are all the same as BSW except for 1/2" which has a different number of TPI. All interchangeable.

But now i am confused by what is meant by 10 x 24  UNC.

If it is in fact 10-24 UNC, then 3/16 BSW taps will do the job. Same diameter. Same TPI. Job's good.

And BTW, you don't need a plug tap if you are tapping right through 1/4" plate. A taper tap run all the way through will do the job.

Edited By Hopper on 07/03/2022 11:51:17

Edited By Hopper on 07/03/2022 11:54:59

Edited By Hopper on 07/03/2022 11:57:37

Edited By Hopper on 07/03/2022 12:00:30

Edited By Hopper on 07/03/2022 12:03:00

[Michael GilliganParticipant @michaelgilligan61133]

Oops

Having just read Hopper’s post of 10:06:43 __ I realise that I mis-interpreted 10×24 as 10-24, and suggested a supplier on that basis. [… or did I ? … see edit]

How very embarrassing !!

MichaelG.

.

Ref. __ I have to drill and tap 4 through holes in a 1/4" strip, 10×24 UNC and 1/4".

.

Edit: … Having seen Niko’s recommendation … I am now struggling to know for sure.

Edited By Michael Gilligan on 07/03/2022 11:57:29

[pgrbffParticipant @pgrbff]

Posted by Hopper on 07/03/2022 11:50:20:

If in doubt, grab any piece of scrap metal and drill and tap a 5/16 or 1./4 or whatever BSW hole in it and see if your UNC bolt screws into it. Then try the same again with your BSW taper tap followed by your UNC plug tap and see if there is any noticeable difference.

EDIT Just read Michael Gilligan's post. So 5/16 or 1/4 or whatever UNC. They are all the same as BSW except for 1/2" which has a different number of TPI. All interchangeable.

But now i am confused by what is meant by 10 x 24 UNC.

If it is in fact 10-24 UNC, then 3/16 BSW taps will do the job. Same diameter. Same TPI. Job's good.

And BTW, you don't need a plug tap if you are tapping right through 1/4" plate. A taper tap run all the way through will do the job.

Edited By Hopper on 07/03/2022 11:51:17

Edited By Hopper on 07/03/2022 11:54:59

Edited By Hopper on 07/03/2022 11:57:37

Edited By Hopper on 07/03/2022 12:00:30

Edited By Hopper on 07/03/2022 12:03:00

The instructions, which are American say "#10-24" and 1/4”-20. I'm a woodworker so I'm not used to the terminology. I assumed that this meant a size 10 24TPI UNC.

[VicParticipant @vic]

Gauge Plate may be annealed but it can still be tough stuff. I’ve broken an M4 tap in it before. I’ve also stripped the teeth on a hacksaw cutting it due to some kind of hard inclusion.

[HopperParticipant @hopper]

Posted by pgrbff on 07/03/2022 12:11:28:

Posted by Hopper on 07/03/2022 11:50:20:

If in doubt, grab any piece of scrap metal and drill and tap a 5/16 or 1./4 or whatever BSW hole in it and see if your UNC bolt screws into it. Then try the same again with your BSW taper tap followed by your UNC plug tap and see if there is any noticeable difference.

EDIT Just read Michael Gilligan's post. So 5/16 or 1/4 or whatever UNC. They are all the same as BSW except for 1/2" which has a different number of TPI. All interchangeable.

But now i am confused by what is meant by 10 x 24 UNC.

If it is in fact 10-24 UNC, then 3/16 BSW taps will do the job. Same diameter. Same TPI. Job's good.

And BTW, you don't need a plug tap if you are tapping right through 1/4" plate. A taper tap run all the way through will do the job.

Edited By Hopper on 07/03/2022 11:51:17

Edited By Hopper on 07/03/2022 11:54:59

Edited By Hopper on 07/03/2022 11:57:37

Edited By Hopper on 07/03/2022 12:00:30

Edited By Hopper on 07/03/2022 12:03:00

The instructions, which are American say "#10-24" and 1/4”-20. I'm a woodworker so I'm not used to the terminology. I assumed that this meant a size 10 24TPI UNC.

OK. Both of those are the same diameter and TPI as 3/16 and 1/4 BSW.

[HopperParticipant @hopper]

 

I just happened to have this same job in the workshop today, which reminded me of questions raised in this thread, while making a cotter clamp for my upgraded carriage stop. (Which is another story, more of which anon.)

1/4" BSW taps.

 

Tapping a 1/4" BSW thread into the brass cotter clamp

 

Screwing in a 1/4" UNC screw by hand. No binding. No slop. No dramas. It always works for me.

 

Sorry about the sideways pics. They were right way up at my end before uploading and there seems to be no facility this end to rotate them. Perhaps some kindly mod will stop by and rectify?

Mod edit: rotated photos.

Edited By SillyOldDuffer on 09/03/2022 10:36:04

[pgrbffParticipant @pgrbff]

The gauge plate arrived. I, naively perhaps, expected 3/4" to be 3/4".

it is in fact oversize and as a woodworker I have no way of machining it.

So I am slowly grinding one side down with a piece of 100 micron lapping film stuck to a piece of plate glass.

[HopperParticipant @hopper]

Posted by pgrbff on 09/03/2022 09:52:18:

The gauge plate arrived. I, naively perhaps, expected 3/4" to be 3/4".

it is in fact oversize and as a woodworker I have no way of machining it.

So I am slowly grinding one side down with a piece of 100 micron lapping film stuck to a piece of plate glass.

That sounds like slow work. How much too big is it? What is it that you are making out of it?

[Anonymous]

Rectangular gauge plate is ground to tolerance on the wider sides (usually a thou or two) but left as sawn on the narrow sides. What size did you order?

Andrew

[pgrbffParticipant @pgrbff]

It's 3/4" x 1/4" bar 18 inches long. It slides in a slot 3/4 wide in a tablesaw cast iron top. It needs to be a tight fit with minimal sideways movement.

The narrow sides are rough sawn and it's about 250 microns too wide.

sorry for the mix of measurements but I never did get used to using an imperial vernier.

[HopperParticipant @hopper]

Posted by pgrbff on 09/03/2022 10:38:38:

It's 3/4" x 1/4" bar 18 inches long. It slides in a slot 3/4 wide in a tablesaw cast iron top. It needs to be a tight fit with minimal sideways movement.

The narrow sides are rough sawn and it's about 250 microns too wide.

sorry for the mix of measurements but I never did get used to using an imperial vernier.

Don't worry, I do the same after growing up with Imperial in Australia, then we converted to Metric, then I went to live in America and had to convert my brain back again to Imperial, and now I am back in Metric Australia I still have to look up what 250 microns is in "thou" before I can think about it.

You might make quicker progress if you file the edge of the gauge plate down using something like a 10-inch (250mm!) flat file applied carefully. For what you are doing, a piece of 3/4 x 1/4 Bright Drawn Mild Steel flat bar might have been closer to size in all directions. Usually within a thou or two of the nominal size. (Or a 0.025mm or two!)

[pgrbffParticipant @pgrbff]

Posted by Hopper on 09/03/2022 10:48:03:

Posted by pgrbff on 09/03/2022 10:38:38:

It's 3/4" x 1/4" bar 18 inches long. It slides in a slot 3/4 wide in a tablesaw cast iron top. It needs to be a tight fit with minimal sideways movement.

The narrow sides are rough sawn and it's about 250 microns too wide.

sorry for the mix of measurements but I never did get used to using an imperial vernier.

Don't worry, I do the same after growing up with Imperial in Australia, then we converted to Metric, then I went to live in America and had to convert my brain back again to Imperial, and now I am back in Metric Australia I still have to look up what 250 microns is in "thou" before I can think about it.

You might make quicker progress if you file the edge of the gauge plate down using something like a 10-inch (250mm!) flat file applied carefully. For what you are doing, a piece of 3/4 x 1/4 Bright Drawn Mild Steel flat bar might have been closer to size in all directions. Usually within a thou or two of the nominal size. (Or a 0.025mm or two!)

I wanted something a bit harder with some resistance to rust and I wasn't sure how accurate mild steel would be.

The cost of the steel was low compared to the cost of sending it to Italy.

[Anonymous]

Posted by pgrbff on 09/03/2022 10:38:38:

It's 3/4" x 1/4" bar…

No problem with the measurements, I'm bilingual.

The gauge plate will be ground on the wide surfaces as standard, so the 1/4" dimension will be accurate but the 3/4" dimension will not be. The only exception is that square section gauge plate is ground on all four sides.

Personally I'd draw file one edge to fit rather than lapping. I use micrometers for accurate measurement, not verniers.

Andrew

[pgrbffParticipant @pgrbff]

I have always wanted a micrometre but can't really justify the cost. My Mitutoyo vernier is good enough for what I do.

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