What’s this for…no.5?

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What’s this for…no.5?

This topic has 19 replies, 11 voices, and was last updated 2 March 2025 at 12:12 by Phil P.

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1 March 2025 at 15:45 #786683
beeza650
Participant
@beeza650
Another custom tool. Surely not for grinding again 🙂 ????
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1 March 2025 at 15:53 #786690
Michael Gilligan
Participant
@michaelgilligan61133
Surely is

… or maybe a fixture for checking components that have been ground

MichaelG.
1 March 2025 at 15:58 #786692
Robert Atkinson 2
Participant
@robertatkinson2
A pair of centers on a sine bar. So most likely to be for grinding or measuring tapers.
By putting a slip gauge under one of the round bars you can set an exact angle based on the sine of the distance beween the two round bars and the thickness of the slip.

Robert.
1 March 2025 at 16:10 #786702
Tony Pratt 1
Participant
@tonypratt1
You have some quality kit in your collection! I’ve never seen one of these in the flesh, off the top of my head you could check morse tapers etc without the need of a gauge, super!

Tony
1 March 2025 at 16:20 #786703
Phil P
Participant
@philp
You should find that the distance between the round supports is exactly 10″…….That makes the sine calculations easy.
1 March 2025 at 17:00 #786706
Andrew Crow
Participant
@andrewcrow91475
On 1 March 2025 at 15:58 Robert Atkinson 2 Said:

A pair of centers on a sine bar. So most likely to be for grinding or measuring tapers.
By putting a slip gauge under one of the round bars you can set an exact angle based on the sine of the distance beween the two round bars and the thickness of the slip.

Robert.

I think Robert has got this one exactly right.

Andy.
1 March 2025 at 21:36 #786734
Nigel Graham 2
Participant
@nigelgraham2
Internal and external centres, at that.

When both holders are set correctly and their clamp-screws nipped up, the centres should be exactly co-axial, not slightly misaligned as in your close-up photo.
1 March 2025 at 22:04 #786741
DC31k
Participant
@dc31k
On 1 March 2025 at 16:20 Phil P Said:

You should find that the distance between the round supports is exactly 10″…

It may be an illusion but the tape measure in the picture shows differently.
1 March 2025 at 23:08 #786748
bernard towers
Participant
@bernardtowers37738
surely thats 10.5″ and correct for a sine bar
1 March 2025 at 23:56 #786757
Phil P
Participant
@philp
Where do get the 10.5″ from ?

I have always known sine bars to be usually either 5″ or 10″, or sometimes 100mm

I actually have a 2.5″ one in my toolbox as well.
2 March 2025 at 00:20 #786765
noel shelley
Participant
@noelshelley55608
The sine bar rollers seem to be at an odd dimension though it can still be worked out. Interesting bit of kit. Noel.
2 March 2025 at 08:51 #786778
DC31k
Participant
@dc31k
With something like a Morse taper, the half angle of the taper is kind of a derived quantity or by-product. The taper is specified in inches per foot.

This is complete speculation, but I wonder if the roller centres have been chosen to suit a 1 in ‘x’ taper, where we are interested in the horizontal and vertical legs of the right angle triangle. That does make the item into a one trick pony, but if it is for inspection purposes that would not matter.
2 March 2025 at 10:01 #786798
bernard towers
Participant
@bernardtowers37738
Sorry but having looke again it still looks like 10.5″
2 March 2025 at 10:10 #786801
Tony Pratt 1
Participant
@tonypratt1
The roller centres are irrelevant, you just need to know what they are to work out the slip gauge height.

Tony
2 March 2025 at 10:21 #786803
Michael Gilligan
Participant
@michaelgilligan61133
On 2 March 2025 at 08:51 DC31k Said:

[…] This is complete speculation, but I wonder if the roller centres have been chosen to suit a 1 in ‘x’ taper, where we are interested in the horizontal and vertical legs of the right angle triangle. That does make the item into a one trick pony, but if it is for inspection purposes that would not matter.

Quite so … I was thinking along the same lines, but struggling to express the idea.

If we knew the exact distance between the rollers, then ‘reverse-engineering’ might reveal the convenient choice of Jo Block for the job.

MichaelG.
2 March 2025 at 10:37 #786813
Circlip
Participant
@circlip
Measure from the RH O/D edge of the LH roller to the RH O/D edge of the RH roller instead of guestimating where the centres are.

Regards Ian.
2 March 2025 at 10:48 #786815
DC31k
Participant
@dc31k
On 2 March 2025 at 10:10 Tony Pratt 1 Said:

The roller centres are irrelevant, you just need to know what they are to work out the slip gauge height.

Could you go one small step further and contemplate why someone would make a deliberate, rational and informed choice to deviate from established norms for this type of device.

No-one would just rock up one morning in the toolroom and think “today I’m going to make a sine bar and because it is 29 February 1956, the moon is waxing and Saggitarius is in Uranus, I’m going to make the rollers at 10.3792″ centres. Everyone who uses it subsequently will curse me because the maths is difficult, but I do not care”.
2 March 2025 at 11:10 #786820
Tony Pratt 1
Participant
@tonypratt1
On 2 March 2025 at 10:48 DC31k Said:

On 2 March 2025 at 10:10 Tony Pratt 1 Said:

The roller centres are irrelevant, you just need to know what they are to work out the slip gauge height.

Could you go one small step further and contemplate why someone would make a deliberate, rational and informed choice to deviate from established norms for this type of device.

On 2 March 2025 at 10:48 DC31k Said:

On 2 March 2025 at 10:10 Tony Pratt 1 Said:

The roller centres are irrelevant, you just need to know what they are to work out the slip gauge height.

Could you go one small step further and contemplate why someone would make a deliberate, rational and informed choice to deviate from established norms for this type of device.

No-one would just rock up one morning in the toolroom and think “today I’m going to make a sine bar and because it is 29 February 1956, the moon is waxing and Saggitarius is in Uranus, I’m going to make the rollers at 10.3792″ centres. Everyone who uses it subsequently will curse me because the maths is difficult, but I do not care”.

No I will not go one step further, my statement ‘The roller centres are irrelevant’ is factually correct but ignoring your sarcastic reply I will say that these sine bar related tools are always made with nominal centres to precise limits, I know I’ve made a few.

Tony
2 March 2025 at 11:42 #786833
beeza650
Participant
@beeza650
<p style=”text-align: center;”>It’s 10inches between sine cylinder centres</p>
2 March 2025 at 12:12 #786845
Phil P
Participant
@philp
Thought so………..
Much better to measure it, than guess from a photo.

Phil P
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