Startrite Mercury drill

[David GaltParticipant @davidgalt22481]

Feed stop nuts thread specification

[David GaltParticipant @davidgalt22481]

Hi All,

I have a Startrite Mercury floor standing drill. Unfortunately I have lost the knurled two feed stop nuts off the top of the feed stop. Looking to replace them I measured the thread (male part). It was measuring as 14tpi with and approx 15.9mm over thread. From this I assumed it was a 5/8” BSF and ordered a couple of lock nuts. Of course they did not fit!

Can anyone confirm what the thread specification is?

[not done it yetParticipant @notdoneityet]

What thread form is used on the rest of the machine? Could they have used a non-standard thread?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by David Galt on 20/04/2020 20:07:50:

[…]

From this I assumed it was a 5/8” BSF and ordered a couple of lock nuts. Of course they did not fit!

.

That does seem an eminently reasonable assumption

… Have you inspected the new nuts ?

MichaelG.

[Pete.Participant @pete-2]

7/16 14tpi

[Pete.Participant @pete-2]

I just checked mine with a thread gauge, that's what it was on mine.

[David GaltParticipant @davidgalt22481]

On the basis that 7/16 BSW takes a 11.5mm clearance drill, I ruled that out as my thread externally was nearly 16mm

[David GaltParticipant @davidgalt22481]

I have minimally inspected the new nuts with a vernier only, as I don’t have thread gauges. Internal diameter inside the nut is 15.5mm. It’s difficult to measure the tpi

[Michael GilliganParticipant @michaelgilligan61133]

Posted by David Galt on 21/04/2020 06:39:23:

I have minimally inspected the new nuts with a vernier only, as I don’t have thread gauges. Internal diameter inside the nut is 15.5mm. It’s difficult to measure the tpi

.

Just screw the nut onto a wooden dowel, David … Then measure the tpi of the the impression.

MichaelG.

[Clive Brown 1Participant @clivebrown1]

Posted by David Galt on 21/04/2020 06:39:23:

I have minimally inspected the new nuts with a vernier only, as I don’t have thread gauges. Internal diameter inside the nut is 15.5mm. It’s difficult to measure the tpi

The minor dia. for 5/8" BSF is about 14mm, so whatever you have been supplied with doesn't seem to be that.

Nearer to 11/16" BSF in fact.

Edited By Clive Brown 1 on 21/04/2020 08:50:12

[OldironParticipant @oldiron]

Do you have the tools to make a new set of nuts ? Or even a new stop bar.

regards

[Gary WoodingParticipant @garywooding25363]

In the following chart the tapping drill size should indicate the ID of the nut.

[Pete.Participant @pete-2]

Might as well buy a thread gauge, if you don't want a decent one, you can buy a cheap one for a couple quid, it'll pay for itself by dodging one wrong order.

[Martin KyteParticipant @martinkyte99762]

I Have a bench mount Startrite and the nuts on that are 14 TPI 5/8" BSF if that is any help.

regards Martin

[HopperParticipant @hopper]

Posted by David Galt on 21/04/2020 06:33:37:

On the basis that 7/16 BSW takes a 11.5mm clearance drill, I ruled that out as my thread externally was nearly 16mm

BSW is irrelevant to BSF. Different TPI, different thread depth. And clearance drill? Do you mean tapping size drill? Clearance size drill for 7/16 would be 15/32".

Edited By Hopper on 21/04/2020 11:08:38

[not done it yetParticipant @notdoneityet]

I’ll stick with metric, unless the OP confirms the rest are imperial. No age given for this machine and it is a common mistake by the inexperienced to measure the distance between ten crests instead of eleven…

But still only guessing. Initially I thought that maybe they had used a bastard thread, like 16mm x 1.75mm pitch (some manufacturers are known to do this sort of thing), but now I reckon it could be 16mm coarse thread.

[Rod RenshawParticipant @rodrenshaw28584]

My 1970s vintage Mercury bench-top drill appears to be built to Imperial standards and the depth stop thread measures as 5/8 " X 14 TPI and the thread gauge seems to confirm 55 degree angle thread, though I can't find an actual nut to confirm, all my stuff is smaller than that. I wonder if the O P has been sent the wrong size nuts, it does happen, young people now only get taught about metric!

Anyone got a spare 5/8" BSF nut they could send him?

Rod

[Martin KyteParticipant @martinkyte99762]

I concur with that. Thats what mine is.

regards Martin

[FarmboyParticipant @farmboy]

Can't tell you the size as it is completely missing on mine and replaced with a bit of threaded rod and nuts, but spares do seem to be available ( for more than I paid for the whole drill ) from Machine Spares Ltd.

Mine is actually a benchtop model but I believe the head is the same as the floor standing one, although there are several models, I believe.

Mike.

Edited By Farmboy on 21/04/2020 12:39:34

[David GaltParticipant @davidgalt22481]

Metric? Ok, I have just had a look over the drill and there are m8 bolts holding the motor down and m5 holding the cowl on.

M16 x 1.75? Funny you should say that, because I have a standard M16 nut which starts for a couple of threads but then tightens. The 5/8-14 BSF doesn’t even start.

I include the enclosed photo of pitch. I set my vernier to 25.4mm and took the photo. I count 14 pitches.

25.4/1.75 is 14.28 so I think you may be correct.

next question is if it is M16x1.75, then where would I buy a couple of half nuts? Or even better, knurled thumb nuts?

Many thanks for your help so far.

[not done it yetParticipant @notdoneityet]

The standard pitch for 16mm is 1.5mm and 16mm coarse is 2mm. I doubt if 16mm x 1.75mm pitch anything is available – unless to special order. Fingers crossed that the new nuts supplied were metric instead of imperial!

[Michael GilliganParticipant @michaelgilligan61133]

Posted by David Galt on 21/04/2020 12:31:10:

[…]

I include the enclosed photo of pitch.

.

… welcome to the wacky world of posting photos on this forum: **LINK**

https://www.model-engineer.co.uk/forums/postings.asp?th=103028&p=1

MichaelG.

[Keith LongParticipant @keithlong89920]

Posted by not done it yet on 21/04/2020 12:52:43:

The standard pitch for 16mm is 1.5mm and 16mm coarse is 2mm. I doubt if 16mm x 1.75mm pitch anything is available – unless to special order. Fingers crossed that the new nuts supplied were metric instead of imperial!

Actually "standard" metric pitch ie metric coarse and what you'd get over the counter if you just asked for an M16 nut or bolt is 2mm, the 1.5mm pitch is the usual metric FINE value.

16mm x 1.75mm pitch certainly would be an odd ball, even Tracy tools don't do one that matches that, although they do list taps and dies for 16mm dia. in 0.75, 1, 1.25, 1.5 and 2mm pitches.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Rod Renshaw on 21/04/2020 12:26:05:

[…]

I wonder if the O P has been sent the wrong size nuts […]

.

Exactly my thought, Rod … When I asked:

… Have you inspected the new nuts ?

MichaelG.

[Clive Brown 1Participant @clivebrown1]

Posted by Michael Gilligan on 21/04/2020 14:37:29:

Posted by Rod Renshaw on 21/04/2020 12:26:05:

[…]

I wonder if the O P has been sent the wrong size nuts […]

.

Exactly my thought, Rod … When I asked:

… Have you inspected the new nuts ?

MichaelG.

Well, he says that the minor diameter of the nuts he was sent is 15.5mm. That isn't 5/8" BSF which he ordered, it's larger.

That though doesn't really tally with them not even starting on the male thread on the drill.

 

Edited By Clive Brown 1 on 21/04/2020 15:12:49

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