Between centres boring of cylinder blocks

[Firebird]

Hi

I think the best way to bore the cylinders for my loco is between centres in the lathe. The bore by the way will be 1 3/16".

Has anyone made a between centres boring bar? one with micro adjustment?

Any help here will be appreciated.

Cheers

Rich

[Jasonb]

I have got several but not bothered with micro adjust, I did see a comment on ME forum about using a boring head in the tail stock to give micro adjust which sounds like it would work OK and saves a lot of time in making a special bar..

[fumopuc]

Hi Rich, these are on my wish list, but never used before.
http://www.hemingwaykits.com/acatalog/_Tidy__Between_Centres_Boring_Bar.html

[Firebird]

Hi

Thanks Jason and Achim 

I like the look of the Hemmingway idea. Should be easy enough to make one along those lines.

Cheers

Rich

[Chipswitheverything]

Hello Rich, there is a good design for a micro adjust boring bar published by Geo. H. Thomas - not sure which of his books it may be in, I got the design from one of his magazine articles years ago.   I made the bar up, the round cutter bit lies at an angle so the micro facility can be incorporated in the bar, and the locking mechanism is a push rod within the bar section.   It is a better design than the Hemingway version, and the cutter adjustment can be read directly with a mike over cutter tip and the bottom of the boring bar.  Doesn't need a separate gadget.   Dave

[mikemill]

Rich

I have always machined cylinders in the 4 Jaw, face the valve surface and use that as your datum, then set up the to bore the cylinder with a piece of packing to protect the valve surface, make sure you have the end of the cylinder facing the motion and forward enough to have some run out of the boreing tool, bore to size and then face the cylinder end all in one set up.

Mike

[steamer]

I usually bore the hole first and then machine the male piece to fit.  That allows a bit of leeway with regards to size.

If you go to my Southbend thread, you can see the set up I used to rebore the tailstock housing dead straight.

Between centers is a great way to do it.

Dave


Actually the first page of the thread has the counter shaft bearing being bored between centers    same deal
http://www.modelenginemaker.com/index.php/topic,369.0.html

[Firebird]

Hi

Thanks Dave, Mike and Dave 

I presume when boring between centres getting the cylinder to the right height on the lathe is a case of trial and error with shims?

Cheers

Rich

[Jasonb]

It is always worth knowing the exact ctr height of the spindle above the cross slide, mine is 3.387" so it is a simple matter for me to pack up items as required rather than trial and error. I stack up a combination of parallels, 1:2:3 blocks and feeler gauges.



Wobbler ctr finder give syou front to back location, or locate an edge and feed in/out with teh cross slide

[kvom]

I prefer to bore cylinder on the lathe, but that wasn't possible on the Joy engine, where there were two cylinders on the same large block of CI.  The weight was so imbalanced when I tried it at first that my 3000lb lathe was shaking.

[Nick_G]

.
Not having a T slotted crosslide is one omission to my lathe I wish it had.

Other than being bigger. 

Nick

[steamer]

.
Not having a T slotted crosslide is one omission to my lathe I wish it had.

Other than being bigger. 

Nick

You can always make a plate up that bolts down with the compound fastenings.    Make is out of Cast Aluminum Jig Plate....sometimes called "Mik-6"   flat to .005/12 so pretty good.    I did that on my Logan to do all the between centers work.

Dave

[Art K]

Hi,
I've been following along and would be interested in more information about the "micro adjust boring bar published by Geo. H. Thomas". Is this in a book or Model Engineers' Workshop article? I could see this being handy for an engine larger than my single cylinder jobs.
Dave I'm with Nick not having a slotted cross slide thanks for the great idea about bolting aluminum to the compound mount.
Art

[Chipswitheverything]

Hello Art, re. the GH Thomas design of boring bar.  I have found the article, in Model Engineer, 1977, and taken a few not very good pictures of my bar made from GHT's design.   George wrote a series of excellent articles covering all aspects of boring in the lathe, they are in the ME mags for 1977, and also in one or other of his two published books on workshop equipment and practice.
 I haven't got the books, as I have most of the original magazine articles, someone may be able to indicate which book is involved here.   Many of GHT's superb designs for practical tooling have featured here and there on builds on this forum. If you are not familiar with GHT's output, which mostly appeared in Model Engineer articles back in the seventies and early eighties, but have all been republished in two books, you may find investigation very rewarding! Dave

[Jasonb]

Andy, is there an angle specified for the adjusting screw, I seem to recall that an angle of about 53 degrees gives 0.020" movement for one turn of the 40tpi (0.025" pitch) screw. Which is more usefull than drilling at 45deg as that gives 0.0177" per turn

[kvom]

It is always worth knowing the exact ctr height of the spindle above the cross slide, mine is 3.387" so it is a simple matter for me to pack up items as required rather than trial and error. I stack up a combination of parallels, 1:2:3 blocks and feeler gauges.

In this photo, did you first use a drill in the spindle to rough it?

[Jasonb]

That one had a cast in core so no need to drill first.

I often use the same method for crankshaft bearings and do drill them first, often apply a little pressure with teh tailstock to reduce risk of pushing the casting out of position

[Chipswitheverything]

Hi Jason, with ref. your query about the angle of the cutting bit in the Geo. Thomas design.  In the text, GHT suggests 40 degrees, to give 16 thou a turn.  Also, when the bar is first made, put it up between centres and lightly skim the area in the vicinity of the cutter, so that the mike readings, bar bottom to cutter tip,  can be made over a true running part of the diameter.
  Great photos of the substantial component set ups, by the way, Jason ....      Dave  ( not Andy! )

[Jasonb]

Sorry Dave I was mixing uou up with CHIPmaster

[sbwhart]

Hi

I think the best way to bore the cylinders for my loco is between centres in the lathe. The bore by the way will be 1 3/16".

Has anyone made a between centres boring bar? one with micro adjustment?

Any help here will be appreciated.

Cheers

Rich

Bit late with this one, No micro adjust but:- I used a clock with a flat stylus on a magnetic base on the bar and zeroed on the tip of the tool to give a reading of tool adjustment worked fine could control cut to 0.05 mm or better.








Cheers
Stew

Hope this helps

[Firebird]

Hi

Thanks to one and all 

Cheers

Rich

[Tennessee Whiskey]

I know I'm a bit late, however, I was watching a Keith Fenner video and saw these sleeves for a tool bit in a boring bar. Maybe a bit pricey, but, unless you can broach a square hole or just want to use a round bit only, these seem to do both with the added feature of pretty precise adjustments .

https://www.mscdirect.com/product/details/82432204

Cletus

[Jasonb]

I just drill a hole to the across corners size of the square tool bit, the grub screw bears on the flat surface of the tool bit so it won't rotate

[Firebird]

Hi

Thanks Cletus and Jason.

I have 2 chunks of cast iron now so I'll be looking into making a boring bar shortly.

Cheers

Rich