Dore Boring Bar set

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello, I am just about to start this Hemingway kit, which I must have had under the bench for perhaps 45 years!

Reading the instructions, there appears to be a gap. I suspect that there is a missing page. The kit is one of the very original ones from, I think, Rochdale. There is an introductory first page and then several more pages giving info on the construction of these boring bars, I suspect that I am missing the second page of the instructions.

If anyone can supply me with a copy of the missing page, I would be most grateful. I suspect that an enquiry to Reeves would elicit a dusty reply!

Regards,

Andrew.

[Nigel Graham 2Participant @nigelgraham2]

Is this the between-centres bars, a set of three of different diameters?

If so it’s likely the same as the set I made, and if I can find the drawings I can probably copy the relevant page.

[DC31kParticipant @dc31k]

If you are unable to obtain a set of third party instructions, is there a chance that the design was previously written up in Model Engineer magazine?

If so, the online, searchable index might find a reference to it. You know the subject; you know the author.

Having issue and page numbers would be a first step to obtain a paper copy.

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello Nigel,

I am afraid it isn’t the between centres boring bar set. It is a set of 3 small boring bars that are held in the Myford tool post. The design is by Arnold Throp, but thanks for taking the trouble to reply.

DC31K,I am fairly sure it was never published in ME. It was originally available as a kit from DORE and has that name cast into the 3 blocks. It was one of the kits that were originally marketed by Arnold Throp. However I will take a look in the ME archives, just in case!

Thanks,

Andrew.

[Andrew Tinsley]

On Andrew Tinsley Said:

It is a set of 3 small boring bars that are held in the Myford tool post.

There are a couple of past forum threads on these in connection with the pre-tensioning (or pre-compressing) idea.

In one of them, there is an external link (found by Michael Gilligan) that may be of use.

[peak4Participant @peak4]

I’ve no idea as to whether these are the threads referred to by DC31k, but it might be a start for those who struggle to search this forum.
Effect of Tensioning a Boring Bar

A Mystery Project

This was the format of my Google search; the first item is a thread about the DW boring head.
Try substituting other keywords for possible alternatives.

This is another by a different work search
Dore small boring bars

Bill

[PeteParticipant @pete41194]

Fwiw Andrew, GHT had a fair bit about making boring bars in his M.E. Workshop Manual book that might be of help.

[bernard towersParticipant @bernardtowers37738]

I have some boring bars that take 1/8 and 3/16 round HSS bits that you grind yourself and the bits are secured by a pushrod thru the length by a grubscrew would this this stiffen the bar?

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello Bernard,

Your boring bars sound very much like the Dore set. There has been a huge thread in the past as to whether the compressed bar stiffens the bar or not. I think the consensus was that it did stiffen the bar, but not by much!

Thanks everyone for your inputs, looks like no one has the page I am missing from the instructions. Not a very big problem as I am sure that I can interpolate the missing bits.

My Myford ML7 is in bits , so I am unable to measure a critical dimension needed in the construction. The dimension I require, is centre height of the lathe to the base where the cutting tool is placed. I would be grateful if someone could give me this dimension. It will be some time before I get the headstock and saddle back in place.

Thanks again,

Andrew.

[Charles LamontParticipant @charleslamont71117]

The top surface of the topslide is nominally 5/8″ below centre, but this varies from machine to machine. Presumably you would bore the holder in-situ.

Looking (very) briefly at the 2017 thread, I am pretty sure that the theory of superposition of forces tells us that putting the bar in axial tension should make no difference whatever to its stiffness in bending. However, it has occurred to me that the tension might alter the bar’s natural frequency. If so, a different theory would be required to explain that.

[egaParticipant @ega]

Another advantage of the tensioned format is that it obviates the need for a pinch screw at the cutting end thus making  more room for chips.

[Andrew TinsleyParticipant @andrewtinsley63637]

Hello Charles,

Thanks for the 5/8″ dimension. Unfortunately, I can’t bore the blocks in situ as my ML7 is in bits at the moment. Perhaps it is safer to wait until I have it all back together, if the 5/8″ dimension varies from lathe to lathe.

Having said that, I suppose it depends how you grind the replaceable tool bit to get the tip on lathe centre!

Thanks,

Andrew.

[Charles LamontParticipant @charleslamont71117]

As it happens, I made a 5/8″ diameter boring bar this week. The hole for the 1/4″ diameter tool bit is drilled 1/16″ below the centre of the bar, and the bar is mounted in an eccentric sleeve to provide height adjustment. This allows considerable variation in the grinding of the tool bit.

Here it is today, boring the Quorn spindle housing.

My Heavy Duty Boring Toolpost casting was supposed to be a tailstock for a Versatile Dividing Head, but the friend who made the patterns, and got the castings done, did not bother to look at the drawings and used most of the dimensions from the main body. It has sat about looking guilty for a number of years until I had a rare flash of inspiration.

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