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How would you turn this part on your South Bend Lathe?

Max Weber

Aluminum
Joined
Jun 15, 2017
Material Options:
A513DOM Tube, 6061 Tube, 4130 Tube

Machine: 14 1/2" SBL w/live center & 3 jaw chuck

Total View.jpg
Inner Dimensions.jpg
Exterior.jpg

I currently have a set of indexable carbide cutters (my first set of tools for this new-to-me machine)
https://images-na.ssl-images-amazon.com/images/I/41S9+eEPiYL.jpg

Any help would be appreciated. I'm a novice. Should I even consider doing this project?

Thanks,
Max

Edit: I noticed a couple of the images were resized and made the measurements un-readable...
9 inch overall length
thickness of tube will be roughly .065 (too thin to turn cleanly?)
 
The counter bore and the turning down of the OD you can do in the lathe, but if that's the only machine you have, short answer no. You might be able to drill the radial detail at the end (slot thing), bit you will need a drill press and I am not sure a drill will fit your part, didn't look real close.
 
Good grief...toss that horrible tool set!!! Seriously!

tell me what type and size tool post you have and I'll link some good cutting tools.

What diameter and bore is your tubing before machining?
 
Sharp HSS tools would be fine. As Iwana+ said, cheap carbide tools aren't going to do you any favors in aluminum; where you want truly sharp tools.

As for your part, I'd be inclined to make it in two pieces.

The detailed bit would hold nicely in a collet -- you'll just need a decent small boring bar. It could also be done in your 3jaw - best if it had machinable jaws. If you take my suggestion (below) about two pieces, you'll have to flip the end part to machine a recess and will want to maintain jaw grip location for concentricity. Depending on your chuck and tolerances, that could work.

The long tube might be near enough a stock item to avoid boring the ID and maybe even finishing the OD. Just make a step to join the two pieces and glue, braze, TIG, whatever. If you need to turn the long tube, do it between centers. Boring that length without special tooling would be difficult and it does't appear the ID for the length of the tube (and maybe the OD) is a critical dimension. You could also glue/braze/weld ahead of time and just stuff the long tube into your spindle. Your 3 jaw may or may not keep the tube and end concentric -- you could fiddle with shims or just buy the 4 jaw chuck you ought to have anyhow.

The notch looks to be a secondary milling operation, though it could stay in the lathe if you made a broaching tool, had a Versamil, added a live spindle, etc.
 
Good grief...toss that horrible tool set!!! Seriously!

Amen to that. If the 3/8" in that picture denote the shank size then none of those tools will even fit in the bore the OP wants to make. The
smaller bore is about .285"--it's going to take a pretty small bar to fit in that. I wonder how many beginners get sucked in to buying one of
those cheap and useless kits? Too many I suspect. :eek: I hate to say it because I'm not a fan of HSS but in this case even that would be
a better choice...
 
Need a very sharp and proper rake angle to cut a thin wall long part so likely HSS bit best. Is it a one up or production part? can your 3 jaw get down to needed run out tolerance of the ID bores and steps to OD?
Agree a drill press if the radius detail is a segment of a straight in side bore. Yes a lathe vice can do that but a little tricky . also a little tricky on a drill press.

9" long may need a follow of sorts.. perhaps a nylon brace if not having a steady. Out end might be better served with a centered plug rather than just a live center in the tube bore.

You can make a one-up collect to go into your 3 jaw if your chuck is not true enough..Just a saw-slot slug with a bore made to hold the part. Yes having a steady you can do the big end toward the tail and the small end in the chuck with the centered centered slug in place so tube can't collapse ..
 
The counter bore and the turning down of the OD you can do in the lathe, but if that's the only machine you have, short answer no. You might be able to drill the radial detail at the end (slot thing), bit you will need a drill press and I am not sure a drill will fit your part, didn't look real close.
The radial cut-out doesn't necessarily have to be that exact size, but can be close, so I'll have to see if there's a bit that will fit the job.
Good grief...toss that horrible tool set!!! Seriously!

tell me what type and size tool post you have and I'll link some good cutting tools.

What diameter and bore is your tubing before machining?
I would agree it's a rather junky set! They were like 25 bucks and I purchased them to make sure the machine works before investing more $$ into the machine. This was my grandfather's lathe, which I don't think he used that often, then sat for about 30 years with a heap of junk all around and on top of it. I just got the area cleaned up, the machine cleaned up and oiled. I want to try and use the existing tool holder if possible, I think it might be able to hold 1/2" shanks because the 3/8" shanks need shims to be secured, although 1/2" might not leave enough room for tool height adjustment (unless there is another way to do this?) Anyway here's a picture:
2018-04-24 13.31.56.jpg

Sharp HSS tools would be fine. As Iwana+ said, cheap carbide tools aren't going to do you any favors in aluminum; where you want truly sharp tools.

As for your part, I'd be inclined to make it in two pieces.

The detailed bit would hold nicely in a collet -- you'll just need a decent small boring bar. It could also be done in your 3jaw - best if it had machinable jaws. If you take my suggestion (below) about two pieces, you'll have to flip the end part to machine a recess and will want to maintain jaw grip location for concentricity. Depending on your chuck and tolerances, that could work.

The long tube might be near enough a stock item to avoid boring the ID and maybe even finishing the OD. Just make a step to join the two pieces and glue, braze, TIG, whatever. If you need to turn the long tube, do it between centers. Boring that length without special tooling would be difficult and it does't appear the ID for the length of the tube (and maybe the OD) is a critical dimension. You could also glue/braze/weld ahead of time and just stuff the long tube into your spindle. Your 3 jaw may or may not keep the tube and end concentric -- you could fiddle with shims or just buy the 4 jaw chuck you ought to have anyhow.

The notch looks to be a secondary milling operation, though it could stay in the lathe if you made a broaching tool, had a Versamil, added a live spindle, etc.
It looks like I will be able to get tube stock with the exact bore size I need, although I might need to lap or do some kind of polishing or reaming to get it cleaned up (I've had to ream other stock from prior batches and its a nightmare lol) Please link me to some tools that will give either the DOM tubing, aluminum tubing, or 4130 tubing a smooth finish.

Amen to that. If the 3/8" in that picture denote the shank size then none of those tools will even fit in the bore the OP wants to make. The
smaller bore is about .285"--it's going to take a pretty small bar to fit in that. I wonder how many beginners get sucked in to buying one of
those cheap and useless kits? Too many I suspect. :eek: I hate to say it because I'm not a fan of HSS but in this case even that would be
a better choice...
I'm getting samples from a potential tubing supplier soon, hopefully the bore will be within the required tolerance and I won't have to mess with the inside dimension. I would love to see some HSS recommendations (I haven't learned how to grind tools yet, but I hope to learn in the future)

Need a very sharp and proper rake angle to cut a thin wall long part so likely HSS bit best. Is it a one up or production part? can your 3 jaw get down to needed run out tolerance of the ID bores and steps to OD?
Agree a drill press if the radius detail is a segment of a straight in side bore. Yes a lathe vice can do that but a little tricky . also a little tricky on a drill press.

9" long may need a follow of sorts.. perhaps a nylon brace if not having a steady. Out end might be better served with a centered plug rather than just a live center in the tube bore.

You can make a one-up collect to go into your 3 jaw if your chuck is not true enough..Just a saw-slot slug with a bore made to hold the part. Yes having a steady you can do the big end toward the tail and the small end in the chuck with the centered centered slug in place so tube can't collapse ..
This is going to be a production part, I'm going to make at least a few hundred in the near term, maybe even more down the road. Hopefully I wont have to mess with the bore (I think I can get the correct tolerance ID from a supplier). I like the idea of plugging or filling the inside of the tube with something to stabilize the work better (thanks!).

Are there any tolerances? That could make a big difference in how you set it up or if you even want to attempt it.
The tolerances can vary +/- about .3mm for the detailed work on the end. I can do the counterbores with a 5/16 and 9/32 drill bit and stay within tolerances (hopefully) I'm assuming I can do that on the lathe with the bits placed in the tailstock, although the critical part will be getting correct (and repeatable) depth of cut. It might be better to do it on a drill press in a collet block.

The main thing I'm worried about is getting a clean cut on the OD.
 
Off the shelf this is the kind of boring tool you need..it is absolutley CRITICAL you ge the tool DEAD ON center...its carbide so it's fragile and expensive...Be worth it to get some HSS blanks....here it is anyway...strongly suggest getting some blanks and grinding them yourself though..
Accupro .23" Min Diam, 1" Max Depth, 5/16" Shank Diam, 2-1/2" OAL, Boring Ba... | eBay

As for turning same deal...HSS blanks...but if you need something then here it is...
tools tooling for hobby lathes

As for holding the work while machining,well, collets are the way to go...but if you only have a 3 jaw chuck you can chuck up a short piece of scrap and bore it to a tight slip fit for your DOM, then just stick the DOM in and tighten the chuck a bit more...the scrap piece will serve as an impromptu collet of sorts with comparable accuracy.believe it or not it will flex enough to grab the tubing.
 
I'm surprised no one has mentioned it yet but, get the SB how to run a lathe book ! Info on HSS tool grinding just for a start.
 
Off the shelf this is the kind of boring tool you need..it is absolutley CRITICAL you ge the tool DEAD ON center...its carbide so it's fragile and expensive...Be worth it to get some HSS blanks....here it is anyway...strongly suggest getting some blanks and grinding them yourself though..
Accupro .23" Min Diam, 1" Max Depth, 5/16" Shank Diam, 2-1/2" OAL, Boring Ba... | eBay

As for turning same deal...HSS blanks...but if you need something then here it is...
tools tooling for hobby lathes

As for holding the work while machining,well, collets are the way to go...but if you only have a 3 jaw chuck you can chuck up a short piece of scrap and bore it to a tight slip fit for your DOM, then just stick the DOM in and tighten the chuck a bit more...the scrap piece will serve as an impromptu collet of sorts with comparable accuracy.believe it or not it will flex enough to grab the tubing.
I found some old (what I assume to be HSS) bits that are mostly worn out, I'll see if I can get them sharpened and set up.
 
If you can't get the tube Bore dead right, and don't want to ream ir, you could consider forcing a steel ball through as a first operation.
The larger bore can be cut from the tail stock using an endmill in the drill chuck
I would then make up a steel expanding mandrel to go inside the bore and use that to turn the OD. The mandrel could be overlength to allow you to use a steady on the tail stock end.
A job like this is best done with each operation done as a batch, i.e. The same operation on all the parts before moving onto the next.
With HSS a tools ground with a good toprake and a reasonable nose radius and lapped to a good sharp edge with lots of suitable lubricant should be able to do the job ok.
The cutout is beat done on amill or driller, but you can make a fixture to hold the part on the lathe apron and use and endmill in the lathe chuck.
 
qt:[at least a few hundred in the near term, maybe even more down the road.]
You might price a step reamer.. I used to make them out of a standard reamer...5/16 is .312..looks like you are at about .315 for 8mm.

No idea of the price of a one-up or few-up special step reamer today..and no I don't wist to make one.
8mm reamer about $40 and HSS reamer about $10.

9/32 reamer about the smaller bore. (.281) about the same price as above.
Yes a turret would make good the use of reamers.
 
1- does the part have to be aluminum?
2- what diameter is the though hole? And does it have a size tolerance?

It needs a tensile strength over 40,000PSI and the tubing can't be more than $15 per 9 inch tube. I've only been able to find 6061 T6 aluminum tubing and 4130 Steel tubing that meets the strength, cost, and machinability requirements. Previously these were made from 304 stainless with a rough undersized bore which was a nightmare to ream.

The bore has to be at least .249"-.252"
 
QT:[The bore has to be at least .249"-.252"]..?
is that the hi/low limits or the smallest allowed?

Perhaps the long bore done with one end in the steady and the other in a collect (if your 3jaw run-out is too much)

Having OD turn stock the chuck run-out may not be a factor, perhaps it runs good.

With devoting a drill press and making a good holding jig you might run the 8mm and 7.25 mm IDs there.

The lathe made long Id would set the center and the two reamers would follow that center.

That scalp feature could be done with the part held in a jig in the lathe vise using an end mill held in the lathe spindle.

For a one size job and a run out 3jaw sometimes you can mark one jaw and then use a shim to make better the center..

3jaw holding a thin wall part can have problems with the holding pressure distorting the area of the bore held in the chuck..

Yes I have no idea what your size and concentric limits might be.
 
QT:[The bore has to be at least .249"-.252"]..?
is that the hi/low limits or the smallest allowed?

Perhaps the long bore done with one end in the steady and the other in a collect (if your 3jaw run-out is too much)

Having OD turn stock the chuck run-out may not be a factor, perhaps it runs good.

With devoting a drill press and making a good holding jig you might run the 8mm and 7.25 mm IDs there.

The lathe made long Id would set the center and the two reamers would follow that center.

That scalp feature could be done with the part held in a jig in the lathe vise using an end mill held in the lathe spindle.

For a one size job and a run out 3jaw sometimes you can mark one jaw and then use a shim to make better the center..

3jaw holding a thin wall part can have problems with the holding pressure distorting the area of the bore held in the chuck..

Yes I have no idea what your size and concentric limits might be.

.249"-.252" is the high low limits for the bore
I've found tubing that is .249 and .25 respectively.. but I don't believe the supplier measurements until I measure them. I've gotten tubing from other suppliers that arrive bent, incorrect size etc

The size and concentric limits can be super loose. the longest portion of outer diameter (that I need to turn) just has to be under 8.4mm. Ideally, I need to keep as much thickness as possible, so the closer to 8.4 the better. I'm getting the tubing from my supplier in a day or two and should be able to make some test cuts to see what issues I run into. I'll post more info once that happens.

This Old Tony (youtube) has a good video on tool grinding I'll follow to see if I can get some HSS set up:
 








 
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