Line boring bar diameter advice

[CRS51]

You've got no adjustment in your bearings?

Also you will need to straighten your bar. Especially if doing long sets of bores on a 4 in 1 etc.

Evening Brad, how do you mean adjustment in the bearings ?
The bar is 40mm dia by 3m long bright bar, still have to drill out 12 mm holes for the cutting tool.
Any advice really welcome as not done this before
Cheers Chris

 

[Seadog]

This chap does lots of line boring. Certainly worth watching if you've not seen any of his videos -

 

[CRS51]

Step 2

BORING BAR ALIGNMENT PART 1

An accurate, quality-assured set-up of your line boring machine will result in a better and longer-lasting repair job. It’s crucial to make sure to take your time with the set-up process to ensure the bore is as rigid and accurate as possible.

www.climaxportable.com

Thankyou Brad

 

[pressbrake1]

Cutting edge knows his stuff
I keep meaning to make a line borer as a lot of jobs are a nightmare on a horizontal borer as you have to set a manky old lump of poop to spindle axis and there’s usually no decent datum left where with line boring you set the light easy to handle bore to the job using simple fixtures

 

[CRS51]

Hopefully up to the job of driving the boring bar. Used two universals to allow for any miss alignment of the mag drill.

 

[CRS51]

The mag drill is a Rorabroach Element 100 so is quite substantial

 

[Agroshield]

I hope you will forgive me if you already know this, but paired universal joints work best when they are 'in phase', so maybe mark the two parts with paint to make sure they always go back correctly. See:

Universal Joint Phasing | Belden Universal Joints

Phasing is the process of aligning the universal joint yokes on both ends of the drive shaft in a parallel fashion. Correct joint phasing is crucial for the assembly to operate at sustained velocity, without vibrations, in order to prevent sub-optimal operation and premature joint failure.

www.beldenuniversal.com

 

[CRS51]

First go with the homemade line boring rig yesterday, went well although we did break a few cutting tips.
Also needed bracing reinforcement too.
Never done this stuff before but more than happy with the result.
Cheers Chris
@Kram @Agroshield

 

[Agroshield]

Would you be able to say which boring bar you bought and which inserts please? Thanks.

 

[CRS51]

Would you be able to say which boring bar you bought and which inserts please? Thanks.

Yes I’ll find the exact codes / numbers / description from the paperwork and put it up later
Cheers

 

[Rrobson]

You’ll be better with hss over carbide with that rig, you won’t have the rigidity, speeds or feeds suitable for carbide. Plus you can grind a tool with favourable angles for that application which will not only lower cutting forces but should give a better surface finish. Otherwise a good effort

 

[Newlands]

You’ll be better with hss over carbide with that rig, you won’t have the rigidity, speeds or feeds suitable for carbide. Plus you can grind a tool with favourable angles for that application which will not only lower cutting forces but should give a better surface finish. Otherwise a good effort

I thought the surface finish looked pretty good from the photos. The big advantage of carbide inserts in this sort of setup is that if a tip breaks then it doesn’t need resetting after replacement. But as you say, a damn good effort. Plus a shed load of money saved given the 5k quote!

 

[Lewis_RX8]

This is impressive work well thought out

 

[Tigman]

I'm impressed !

 

[Rrobson]

@Newlands yes the surface finish does look decent. Looking and being are two different things though. I’m certainly not making a negative comment about this job, far from it in fact!
Based on lots of previous experience on similar work hss is mostly far superior. The fact there have been multiple breakages says it all. If your using carbide correctly you will almost never have catastrophic failure of the insert, their breakage all boils down to incorrect use.

If that bore was welded up and machined back with the same tool it would be even worse, you will get horrible chatter, terrible surface finish, regular breakages of inserts and nothing but tears. Hss would result in significantly less tears and a better overall job.

 

[CRS51]

Would you be able to say which boring bar you bought and which inserts please? Thanks.

@Agroshield here are the codes;
Boring bar S12M-SCLCL06
Inserts CCMT060202HMCTP125
I’m still at a loss on how to understand the coding, wish I could find it in a “very simple”
chart so I could read and understand it properly Lol
Chris

 

[8ob]

This is impressive work well thought out

I'm impressed !

Ditto

Bob

 

[Agroshield]

Boring bar S12M-SCLCL06
Inserts CCMT060202HMCTP125
...a “very simple” chart...

These two are good:

Understanding the Boring Bar ISO Code System

Confused by boring bar ISO codes? This quick guide explains what each letter and number means so you can select the right boring bar for your application.

www.cutwel.co.uk

MMC HARDMETAL U.K. LTD

www.mitsubishicarbide.com

For your bar: (S) steel (12) 12mm dia. (M) 150mm long (S) screw mounted insert (C) insert shape (L) lead angle 95 degree (C) relief angle 7 degree (L) left hand (06) insert size 06.

For the insert: (C) insert shape 80 degree rhombus (C) clearance 7 degrees (compare with relief in the bar code) (M) tolerance. M is standard; only other common one is G (for ground) (T) fixing method hole (compare with screw mounted for bar) (06) insert size, same as bar code (02) insert thickness (02) corner radius. The HMCTP125 is likely specific to the insert manufacturer.

One thing to note is that the corner radius has a big bearing on the fragility of the insert. A larger radius (06 inserts can be had in 00, 02, 04 & 08) might help with the type of cut you are doing - maybe the 08 radius for the first pass of the welded bore and then change to an 04 or 02 for finishing. Using an 02 from the start may be one of the reasons for the broken tips you mention.

I could only find one reference to your insert, from protool, and they do not provide a translation of the manufacturer-specific part. If you go for a brand name insert, there will be a data sheet available with this info. on it. One thing to note is that carbide is available in different grades - some are tougher then others, some more wear-resistant than others. For the initial pass of the welded bore, you need an insert with the maximum toughness until you have removed enough material to obtain a uniform bore.

Even if you go for an HSS tool as suggested above, the grind on the roughing tool will be quite different to that of the finishing tool.