Boring bar DIY, has anybody done a boring bar with ER collets for holding the bars.

[Wizard69]

Hi guys;


I happen upon some videos for different boring bar builds and a thought came to mind: why not use ER collets to clamp the boring bars in place. Most boring heads use a single set screw to clamp the bar which seems less than ideal. The thought is ER collets, especially if you already have them, would grip better and easily support a wide array of bar diameters.

Maybe this is one of those wild ideas that will past but I was thinking somebody probably has tried this already.

 

[goldstar31]

I can say 'No' but appreciate the thoughts about singled point fixings. Apart from my inline boring bars, I have two holders. One is the patented but homemade one by Martin Cleeve and the other is the one which George Thomas described in his Model Engineers Workshop Manual. Both can slide to only the required extension before locking down with two or three grub screws.

Having said all this, I've just acquired an Arrand Engineering 2MT boring head which has a series of holes and with a bit of crafty thinking , also do screwcutting and- wait for it-- ball handles. With a sleeve, it will also adorn the mill/drill. With a little more thought, , it can act as a cutter for division strokes and also internal and external slotting.

It will not do tidetables in HongKong harbour but I'll let you know of further uses:hDe:

 

[purpleknif]

I use them all the time in my jig mill at work. Better repeatability .

 

[GLCarlson]

Hi guys;


I happen upon some videos for different boring bar builds and a thought came to mind: why not use ER collets to clamp the boring bars in place. Most boring heads use a single set screw to clamp the bar which seems less than ideal. The thought is ER collets, especially if you already have them, would grip better and easily support a wide array of bar diameters.

Maybe this is one of those wild ideas that will past but I was thinking somebody probably has tried this already.

Different bar diameters, like end mills? Which make adequate boring bars...if it has the reach.

My lathe has a 5C collet holder for the BXA toolpost, which usually has a 3/4 collet in it. I've been known to grab an ER20 straight shank with an EM from the mill and stick it on the lathe.

No, not a wild idea. Works fine.

 

[Wizard69]

Actually guys I was thinking both ways, that is for use on tool posts but also boring heads.

For a tool post holder the idea is that one holder with an ER collet could hold a wide array of bars without the need to make separate sleeves for smaller bars. Of course being ER it could also hold other tooling.

I'm just not sure this is a good idea. As we all know sometimes what we see As a great idea doesn't work out well in practice.

 

[Wizard69]

Different bar diameters, like end mills? Which make adequate boring bars...if it has the reach.

My lathe has a 5C collet holder for the BXA toolpost, which usually has a 3/4 collet in it. I've been known to grab an ER20 straight shank with an EM from the mill and stick it on the lathe.

No, not a wild idea. Works fine.

This is good to hear!

 

[Jasonb]

My only thoughts about using in a boring head would be :

-That you could end up with a heavier moving part to the head which will not do the balance any good.

-You would also probably need to make three "heads" for your boring head, one that has teh ER centrally, one off set to the end and a third when using the bar at right angles to the shank

- A typical 2" dia head can fit down a hole just over 2" dia with the bar in any of the three positions, a ER nut will add extra metal that will mean you can't use it in such a tight space probably 3" minimum without sketching it out.

 

[goldstar31]

The suggested GHT 'design' is cheap and cheerful. The 'collets' are simply bits bored and then split from round bar and the boring bars are from silver/key steel. Mine unashamedly came from the scrap box and the only serious expense was eventually having to buy a new book.
I'd worn the old one away.

I suppose that is the best recommendation. Or is the photograph of the very fancy cup which GHT won in the book more convincing?

Norman

 

[goldstar31]

At much the same time as GHT went to print in 'Model Engineer' another writer called 'Martin Cleeve' emerged.
From what I can glean- and I did a LOT of research, he was not exactly endowed with the World's riches. Somehow, he persuaded the original Myford factory to sell him part of one of their new ML7 lathes. For those who are interested, hard up or whatever, his story is remarkable. Years ago, I attempted to publish much of his stuff at the same time as Bill Bennett did for George Thomas.

Unfortunately, I ran into copyright problems and faced litigation and possible bankruptcy. So I am not going to repeat matters but I can suggest that Cleeve or actually Kenneth C Hart took out a provisional English patent for what became 'a SwingClear Threading and Boring Tool Holder' A revised version appears in Hemingwaykits and a more developed one is published in his posthumous book- Scewcutting in the Lathe. Another article appears in Practical Mechanics for his fabricated version. Another appears in Engineering in Miniature.

However, a Mr Jim Whethren published his version on the net. Suffice to say that I also have a little Myford ML10 similar to his- and when I get over a number of problems, I have an early 'Cleeve' as well to fit on my smaller lathe.

No, I'm not going to run 'foul' again. A Google will reveal what is a most interesting solution for people to follow.

Cheers

Norman

 

[Wizard69]

My only thoughts about using in a boring head would be :

-That you could end up with a heavier moving part to the head which will not do the balance any good.

Didn't think about that one. This does bring up a question as to why mor thought isn't put into balancing solutions for boring heads.

-You would also probably need to make three "heads" for your boring head, one that has teh ER centrally, one off set to the end and a third when using the bar at right angles to the shank

Actually I was thinking small with this probably an ER 16 sized collet.

- A typical 2" dia head can fit down a hole just over 2" dia with the bar in any of the three positions, a ER nut will add extra metal that will mean you can't use it in such a tight space probably 3" minimum without sketching it out.

At the time I wasn't even thinking about going out the side port.

As it is now, I'm thinking that this might not be a good idea for a large boring head. You guys have pointed out usage considerations that escaped my mind while excited about a new idea. However it might not be that bad of an idea for a small head focused on small diameter bores where the head would never be expected to enter a hole and no side cutting is expected.

I guess the idea needs to go on hold for awhile at least for a boring head.

 

[Wizard69]

The suggested GHT 'design' is cheap and cheerful. The 'collets' are simply bits bored and then split from round bar and the boring bars are from silver/key steel. Mine unashamedly came from the scrap box and the only serious expense was eventually having to buy a new book.
I'd worn the old one away.

I totally forgot about GHT design so I reached for my Red book to look it up again. The use of a cotter is very interesting but I'm not sure if the added bulk of a ER solution would me that much different. This especially if one went the thin nut route.

I suppose that is the best recommendation. Or is the photograph of the very fancy cup which GHT won in the book more convincing?

Norman

I like the simple design that is GHT's boring head, it doesn't bother with an extra rod hole nor the 90° position. It is a little big compared to what I was imagining.

In any event thanks for reminding me of this solution.

 

[goldstar31]

If yo]
u want 'small', why not use a motor cycle spoke? GHT again but a collet drilled to hold a modified one. Saw it done- moons ago.

A spoke is capable of becoming a cutting tool. The bend or angle is ground up and the long end snipped to go into a bored GHT collet.

Mine- I didn't grind it- came with the ML10 is only 1/8th wide- but the guy ground it from a broken drill.

A bit more( pun not intended) and I acquired a squashed nail with the usual blood blister underneath. The nurse had a D Bit ground up from a darning needle.

Digresses- Page 86 Chairman George's little Red Book. Figure 7.5 number 5. Got mine- somewhere

Further digression:hDe: Just cleaned up his Rear Parting tool. I'm making a blade grinding jig from the Eccentric Engineering Acute System.

Hope this all helps

Norman

 

[DJP]

Yes. I just ignore it. If it's important it will be back in a form that I can read.

 

[Nick Hulme]

it will be back in a form that I can read.

It's a SPAM posting that's been replicated across loads of sites

- Nick

 

[Nick Hulme]

I use ER11 collet chucks on 10mm shanks to hold small boring tools, in a conventional 10mm boring bar holder with a clamp screw ;-)

 

[DJP]

There must be some interesting machining challenges if you like jewelry. Perhaps a new thread for discussion?

 

[Nick Hulme]

why not use ER collets to clamp the boring bars in place.

It works for tiny bars, 6mm and under where vibration, full length support and resonance are not issues.

For larger work a longer metal block with a sliding fit hole is far better, even with a single clamping screw, as the issues above are addressed. Add more clamping screws and things, as they say, can only get better.

To use ER collets for larger work would require a double collet system with front and rear clamping, or at least some form of rigid support well behind the collet, eliminating the convenience of the concept.

- Nick

 

[Wizard69]

It works for tiny bars, 6mm and under where vibration, full length support and resonance are not issues.

in this case support wouldn't be an issue as I was only thinking ER16 sized which means shirt boring bars to begin with. However I'm not sure I follow your concern about support as ER collects are used to hold end mills putting the collet under a lot more stress than any boring bar would.

For larger work a longer metal block with a sliding fit hole is far better, even with a single clamping screw, as the issues above are addressed. Add more clamping screws and things, as they say, can only get better.

Having tried using single set screws to hold tooling before I really don't buy this point. Certainly more set screws help, but to imply a single set screw holds better than a collet has me thinking something doesn't jive.

To use ER collets for larger work would require a double collet system with front and rear clamping, or at least some form of rigid support well behind the collet, eliminating the convenience of the concept.



- Nick

Well you have given me something to think about. I'm leaning towards trying this either in a tool holder for a lathe tool post or a boring head. Never hurts to try.

 

[Nick Hulme]

However I'm not sure I follow your concern about support as ER collects are used to hold end mills putting the collet under a lot more stress than any boring bar would.

Yeah, but it's not just about bending moment, for boring you want as much damping as you can get otherwise your bar can ring like a bell, milling cutters are loaded intermittently, not constantly, the requirements for optimal cutting differ for constant and intermittent cuts.
If you don't get chatter or ringing and your finish is good then your holder is good ;-)

Having tried using single set screws to hold tooling before I really don't buy this point.

Close fitting bore was also stated, and it really does make all the difference to have the correct holder size for the boring bar.

Never hurts to try.

Very true!