topic Re: Drilling and tapping in solid brass. in Tech Help - Software/Hardware etc

Drilling and tapping in solid brass.

shutter — Mon, 31 Jan 2022 15:20:33 GMT

One of my morse keys needs the pivot threads to be re-drilled and tapped to the next size out..

At present, they are 6mm, so the next size up would be 8mm .

Drilling through about 10mm of solid brass. As already drilled and threaded, should not be too difficult to follow through with a bigger drill bit ,

What size drill bit(s) should I use to ensure that the 8mm tap will give a good cut , and not be "slack"

Re: Drilling and tapping in solid brass.

Smith7 — Mon, 31 Jan 2022 16:10:54 GMT

@shutter wrote:

What size drill bit(s) should I use to ensure that the 8mm tap will give a good cut , and not be "slack"

What pitch on the 8mm

1.25 Pitch is a 6.9mm drill

1.00 Pitch is a 7.1mm drill

Are you going to start with a taper tap then a plug or can you drill straight through

I would try on a scrap piece of metal first and use plenty of lubricant and keep it square

If you worried about it being slack use some Loctite or similar

Re: Drilling and tapping in solid brass.

Baldrick1 — Mon, 31 Jan 2022 16:42:26 GMT

@shutter

Start with a taper, then use a plug. Use plenty of lubricant with brass and reverse/clear the tap of swarf regularly. It's very easy to clog the tap and end up over cutting the thread.

Re: Drilling and tapping in solid brass.

shutter — Mon, 31 Jan 2022 16:46:35 GMT

@Baldrick1 Thanks for the reply... haven`t got a taper, only standard HSS drill bits.. and a set of taps and dies.... I was thinking of starting witha 6.5 thne 7 then 7.5 but not sure if that last would be too much, and not leave enough metal for the thread to be strong.

Re: Drilling and tapping in solid brass.

Baldrick1 — Mon, 31 Jan 2022 17:40:56 GMT

@shutter

Not a taper drill, a taper tap. If you start with a small hole you will jam a plug tap.

Re: Drilling and tapping in solid brass.

shutter — Mon, 31 Jan 2022 18:03:15 GMT

@Baldrick1 None of my taps are tapered... only what I think you call plugs... ( parallel tapped thread )

I have a 7mm tap, and an 8mm tap, but can only get 8mm pointed grub screws that I need for the job.

Re: Drilling and tapping in solid brass.

billnotben — Mon, 31 Jan 2022 23:51:14 GMT

Haven't you got the little yellow book? Probably still have mine from my apprentice days.

Re: Drilling and tapping in solid brass.

shutter — Tue, 01 Feb 2022 08:39:02 GMT

@billnotben Huh ? Only little yellow book I know about is/was yellow pages ! ! ..

Re: Drilling and tapping in solid brass.

billnotben — Tue, 01 Feb 2022 10:03:52 GMT

It was a must have book back then that has been well used.

Re: Drilling and tapping in solid brass.

shutter — Tue, 01 Feb 2022 10:09:24 GMT

Hmm. Will copy that and then enlarge it, to be able to read it ! ! ! ! ... cheers

Done ! ... but I still don`t know which size drill bit to use ! ! ! ...

Re: Drilling and tapping in solid brass.

billnotben — Tue, 01 Feb 2022 10:15:11 GMT

Larger.

Which drill? Of course if you're doing it with a hand drill it will depend how steady your hand is. So at the end of the day it will still be a bit of trial and error.

Re: Drilling and tapping in solid brass.

shutter — Tue, 01 Feb 2022 10:37:41 GMT

@billnotben I have a choice... a hand cranked drill, or a 12 v portable drill, or a 240v drill I can use in a pillar drill stand... but it is "slightly off" true vertical to the base.

As the hole and thread are already through the brass shoulders, it`s more a case of just widening the diameter of the hole, leaving sufficient to tap the new 8mm thread into it..

Originally it would have been a British Thread,... being made during the 1930`s, but over the years of abuse by hundreds of different "fists" ( wireless telegraphists ) ... the threads have worn somewhat, and are not fit for purpose... i.e. the "pointy screws" that act as the pivot point can "wobble", slightly, which upsets the way the key works, causing errors in transmission.

Re: Drilling and tapping in solid brass.

shutter — Tue, 01 Feb 2022 11:16:28 GMT

Just to explain the "Pointy pivot screw"

being replaced with this.... https://www.ebay.co.uk/itm/401859514894

M8 A2 Stainless Cone Point Grub Screws Hex Socket Set Screw DIN 914

Note.... Drill Bit Sizes available....6.5mm 7mm 7.5 mm 8mm

Re: Drilling and tapping in solid brass.

RobPN — Tue, 01 Feb 2022 11:35:50 GMT

@shutter wrote:

... causing errors in transmission.

Random extra dots?

Re: Drilling and tapping in solid brass.

Smith7 — Tue, 01 Feb 2022 11:56:24 GMT

@shutter wrote:

only standard HSS drill bits.. and a set of taps and dies.... I was thinking of starting witha 6.5 thne 7 then 7.5 but not sure if that last would be too much, and not leave enough metal for the thread to be strong.

In my book the drill for a 8x1.25 pitch is 6.9 and Baldrick1 chart is slight smaller at 6.8

A easy way to remember is to take the pitch from the size 8-1.25 = 6.75

Therefore if you use your 6.5 drill that's approx 11.8 thousands of an inch or 5.9 each side smaller and brass being quite soft it's negligible not like taping stainless steel

Like I said before try in a spare piece of brass use plenty of lubricant and back off every quarter of a turn and remove the swarf so the tap does not jam

Good luck

Re: Drilling and tapping in solid brass.

Baldrick1 — Tue, 01 Feb 2022 12:12:24 GMT

@shutter

Looking at the photo it looks like the pivot screw has a separate small locking screw entering from the top of the block. Doesn’t this stop any wobble?

Are you sure that this is your problem? Is it not the point on the old screw or the indent in the arm being worn that’s the issue?

Re: Drilling and tapping in solid brass.

shutter — Tue, 01 Feb 2022 13:10:38 GMT

@Baldrick1 All points you have mentioned, do come into the equation,.... and yes, the lock screw, does stop some movement.. however, I have held the pivot screw during operation, and can feel the "wobble" even with the lock screw done up tight.

As for the pointy bit... yes.. that was well worn on the original, and also the pivot hole... I have replaced the rocker arm and re-centred the pivot point holes, used replacement 6mm pointy pivot screws ( new ) which "kinda" lets that area out of the problem... Drilling out to 8mm and replacing the pointy screws with those shown, should eliminate the "wobble" ... hopefully..

Shame that it needs so much replacement.. but it was a key I used in the Navy, and has some sentimental value to me.

Re: Drilling and tapping in solid brass.

Baldrick1 — Tue, 01 Feb 2022 13:36:14 GMT

@shutter

Another thought, if the pointed screw is ok and it's only wobble that you're worried about, have you tried wrapping the thread with PTFE tape as used in plumbing?

Re: Drilling and tapping in solid brass.

shutter — Tue, 01 Feb 2022 13:51:33 GMT

@Baldrick1 Yes... I have tried that... it seems to work for a short while, but anything over 5 minutes, and it seems to come back again... hence the choice of drilling out and re-threading...

The thing is,, A morse key needs some really fine adjustments to get it to work properly, any part of it that becomes worn slightly, can affect it`s performance... e.g my preferred gap setting is 6thou... if I use 5thou it does not work well for me.. using 7thou and it sounds like a machine gun firing away.

Re: Drilling and tapping in solid brass.

Dan_the_Van — Tue, 01 Feb 2022 14:01:53 GMT

@shutter

I get where you're coming from, it's all dots and dashes to some though !

Dan.