Long Bar Holding Option

[MaverickNH]

I planning to replicate a brass cannon I made on our Makerspace Southbend lath on my 7x16 LMS Mini-Lathe. The 1.25" bass rod doesn't fit through the spindle hole. Dimensions aren't critical but I'd like to use best practices as I learn.

The cannon itself is 5" long. What's my best option, turning from centers, a steady rest, other? Thanks!

 

[Charles scozzari]

Make a stepped adapter that slips inside the tube and stops at the step to hold the open end true with a live center in the tailstock

 

[MaverickNH]

Make a stepped adapter that slips inside the tube and stops at the step to hold the open end true with a live center in the tailstock

As a relative beginner, I'm not quite sure what such a design might look like - or if I have the skill to make it. But I'm willing to learn!

 

[Charles scozzari]

As a relative beginner, I'm not quite sure what such a design might look like - or if I have the skill to make it. But I'm willing to learn!

 

[GrifterGuru]

@MaverickNH

Having run long stock on my 7x (full bed length stock at 2"+), here are two things to consider.

1 ) ALWAYS, always ALWAYS run a follower rest to stop stock deflection during initial machining. These mount to the L/H side of the saddle (the bit the cross slide moves across). Be aware, however, that these can cause marring of the surface, so that needs to be considered and planned for.

2 )ALWAYS run a live centre suited to the stock you are turning

3) When running a live centre, you want it as close in to the tailstock housing as possible to limit any possibility for deflection and you will want lock that tailstock down to the bed as much as possible. I often "Tag" my tailstock locking handle with a light mallet to lock the tailstock down to ensure it cannot "skid/slide" backwards or otherwise move during turning procedures. Not recommended, just something I happen to do myself..

4) when the tailsock is in place against the stock, use the hand wheel to apply LIGHT pressure to the stock, then LOCK the tailstock quill in position using the Q/R lever on the top. This both ensures the centre is fully seated and ensures full engagement with the stock.

As for brass, use an aluminium (Example "CCGT / DCGT et-al) insert and remember, brass is very "sticky" and WILL try to "Grab" the tool or climb over the tool if you get greedy on your DOC (Depth of Cut).

Use WD40 as cutting oil.

Most important, ALWAYS make sure the cutting tool is on centre. Brass is more unforgiving than steel since it likes to be Sticky and "grab" at tools or climb over them.

View attachment 505931

@Charles scozzari

Nice idea, but depending on bed length, may not be possible unless extremely short on the outer end that the centre rides.

 

[Charles scozzari]

As a relative beginner, I'm not quite sure what such a design might look like - or if I have the skill to make it. But I'm willing to learn!

@MaverickNH

Having run long stock on my 7x (full bed length stock at 2"+), here are two things to consider.

1 ) ALWAYS, always ALWAYS run a follower rest to stop stock deflection during initial machining. These mount to the L/H side of the saddle (the bit the cross slide moves across). Be aware, however, that these can cause marring of the surface, so that needs to be considered and planned for.

2 )ALWAYS run a live centre suited to the stock you are turning

As for brass, use an aluminium (Example "CCGT / DCGT et-al) insert and remember, brass is very "sticky" and WILL try to "Grab" the tool or climb over the tool if you get greedy on your DOC (Depth of Cut).

Use WD40 as cutting oil.

Most important, ALWAYS make sure the cutting tool is on centre. Brass is more unforgiving than steel since it likes to be Sticky and "grab" at tools or climb over them.



@Charles scozzari

Nice idea, but depending on bed length, may not be possible unless extremely short on the outer end that the centre rides.

Reread the situation. Looking at the photo and thinking it was a tube I gave my option. Your right with what you say, sorry.

 

[GeneT45]

Well, we're all different, but I cut brass dry and like zero-rake tools to do so. Using those "G" tolerance inserts seems like they'd be the reason you had grabbing problems. If I were going at it with a general insert I'd use a CNMT with as little chip breaker as I could find. I usually use HSS for brass though.

GsT

 

[GrifterGuru]

Well, we're all different, but I cut brass dry and like zero-rake tools to do so. Using those "G" tolerance inserts seems like they'd be the reason you had grabbing problems. If I were going at it with a general insert I'd use a CNMT with as little chip breaker as I could find. I usually use HSS for brass though.

GsT

@GeneT45

I have had absolutely ZERO grabbing since I started using ally inserts on brass. The edge is sharp and cuts nicely. CCMT/CNMT always seem to want to grab when I use them, even when on centre.

The WD40? it keeps things cooler and further lessens potential for grabbing.

@MaverickNH

Have you determined your order of operations yet?

Will you be turning the bore first? if so, you will need a fixed steady rest and once bored, you could, indeed, consider @Charles scozzari option of a plug in the bore to centre on with a live tailstock centre.

 

[ChazzC]

@MaverickNH

Have you determined your order of operations yet?

Will you be turning the bore first? if so, you will need a fixed steady rest and once bored, you could, indeed, consider @Charles scozzari option of a plug in the bore to centre on with a live tailstock centre.

Concur with order of operations. However, instead of making a plug for use witch a live center, consider getting a live center with interchangeable tips:

 

[GrifterGuru]

Concur with order of operations. However, instead of making a plug for use witch a live center, consider getting a live center with interchangeable tips:

View attachment 505934

@ChazzC

Since we don't know what equipment he has, particularly as regards centres, I was erring on the side of "I don't have money for that, this is what I have to work with".

I do agree though, the multi-tip live centres are extremely useful. I do actually have one myself and I am looking to expand the capability of it by machining my own, job specific, centres for it..... Once I work out the taper that is.

Short of swinging the compund to the half angle of one of the centre tails, with a centre in a chuck on the lathe, I can only go by taper over run and figure it out from that.

That aside, I also have a small pipe centre and a dual taper centre. I actually use all of them fairly regularly for various different jobs.