Cutting large diameter, short lengths of stock- round or square etc.

I made the amateur mistake of trying to save some money using a solid round of 6061 T6 aluminium of 250mm/ 10 inches OD which was longer than I needed rather than buying another piece of the correct length. Big mistake, lesson learnt.

I have machined one end of it to the dimensions required for a 250mm pulley I am making. My 3 jaw cannot hold the part on the OD (as it is not big enough) so I have tried holding the billet on the ID of the pulley part and parting off the remaining stock using a parting tool. The part has slipped twice whilst I was trying to part. I tried using paper shims between the stock and the chuck but it slipped again.
I am currently using about a 9 inch slitting saw blade on the mill to try and cut the stock off which seems a very poor option.


A few question come to mind:

Was I doing something wrong when parting?
I ran a very slow speed and did the chuck up fairly tighty (I didn't want to use a bar as this could damage the scroll if I'm not mistaken?). Feed was slow and I cut 2 grooves side by side to assist with chip removal, kerosene as cutting fluid. I never have trouble on small stock. Seemed more of a case of work-holding trouble than a parting problem? Would the 4 jaw improve my chances or clamping it on a face plate? Or is it too deep a part- I have bored the middle to 124mm (250-124)/2 = 63mm of material on both sides of the bore?



Aside from buying the correct length of stock in the first place, how do/ would most of you cut short lengths (too small to clamp in the horizontal band saw, which I do not have BTW) of large diameter pieces (say round, square etc.)?
I have seen a post about vice extensions for horizontal band saws but one would need a hefty size saw to cut something of this size.


Are large slitting saws say equivalent to a cold saw or is it a bad idea to use this as a cutoff tool?


Looking forward to people's thoughts,
Xavier

Well, the obvious choice here is a horizontal bandsaw with a large enough throat to take a 10" round, Doesn't
require an especially large saw but if you don't have one you could potentially be looking at $1500-$2000 for a
saw in that range. Honestly though, for larger material like that, it's often best to just bite the bullet and buy only
as much material as you need. I've been in this situation too and yeah, the cheap in me tends to resist the need
to buy a small piece from a place like Metal Supermarket but in the end, as you have learned, it's often cheaper in
the long run.

What I do to cut short pieces of round stock is to weld a chunk of angle or tube to the end--when the piece is too
short to grab in the vise you can clamp on the angle. Works great. I think the slitting saw idea is just a disaster
looking for a place to happen...

Thanks for the reply Keith.

According to this thread: Use mill as cold saw - good/bad idea?
milling machines don't have the torque ability, so that idea is dusted.

Looks like a case of starting again with the right length unless I can find a shop to cut it...

Parting 63mm deep should not be too much of a problem. I think parting twice that deep would be a bit hair-raising on more machines. For one thing, where are you going to get a parting tool/blade that long?

I think the 4jaw chuck on the OD would be a better choice than a 3jaw on the ID. The leverage is working against you when you hold on the ID. I.e., the friction on the chuck jaws has to be even greater than the cutting forces.

If your slitting saw is of a respectable width, you shouldn't have any big trouble getting through the 63mm remaining, provided you can keep the work from slipping on the mill. If it moves and jams, you are likely to break that saw. 3mm or 1/8" would be kind of narrow for a 9" saw. I'd prefer 5mm or 3/16" for a deep groove, and a side milling cutter rather than a plain cutter would be great for chip clearing.

As LKeithR said, the obvious tool for this job is a bandsaw. In a complete pinch, you could use a hacksaw (preferably 12" or bigger) to get through the 63mm remaining by hand, in a series of chord cuts around the perimeter. For aluminum, use the coarsest blades you can find.

xavier2089 said:

According to this thread: Use mill as cold saw - good/bad idea?
milling machines don't have the torque ability, so that idea is dusted.

Click to expand...

Depends on your mill! If you're running a Bridgeport or something similar, the statements in that thread are probably valid. If you're running a mill with an NMTB40 or NMTB50 spindle taper, it will absolutely laugh at the claims that "it's only for small cutters and doesn't have any torque". People have used horizontal mills of that character as large faceplate lathes, mounting the work on the spindle and clamping toolholders to the table, so they've got enough grunt torque to rip stumps out of the ground.

I know this sounds really kludgy but I did it once when I had a problem similar to yours. At the time all I had was a 9" SB and a 6" round to cut off. No bandsaw (boy those were the days). I could grip the ID as you are doing but had no way to cut it off using a BXA holder and cutoff blade. I had some reciprocating saw blades nearly a foot long and a good variable speed sawsall. Here comes the kludgy part. I bungie corded the handle of the sawsall to the tool post and laid the blade into the groove previously started with the cutoff tool. Set up the lathe and saw to run as slow as possible and went and did something else. I put a board over the ways to catch the cutoff and the sawsall. It took about 20 minutes but it worked. I just had to sweep it with a flycutter to clean it up.

I would have brought in the tail and parted it running at higher speed to a 1 to 1 1/2 inch core diameter..Then still on the tail would have compass saw, sawsaw or even a high quality wood saw cut through the the last inch or so.

Not a bad idea to fudge up a deep cut hack saw if expecting more of this kind of work, perhaps just over half your lathe swing.

I like to draw my compound back / or turn angle so my parting tool is more centered to the saddle...

luckily you only have to go 63mm in, which this will just do. This is a versatile tool anyway for sawing up bar and plate for future projects.

8" Metal Cutting Saw

Any circular saw with carbide tip blade can cut aluminum but the Milwaukee can cut steel and is quite heavy duty.

Don't forget to buy a big stick of wax lube.

I’ve used a woodworking chop saw with a negative rake carbide blade to cut blanks off a 6” 6061 round. Need to rotate the stock to two or three positions to get through. Lots of WD40.

Jon

So you made the pulley part on a mill? (Makes sense...)

As noted above, "milling machine" covers junk you get with breakfast cereal to machines with 100hp spindles using HSK100 tooling - and I've seen the robot club folks in my shop use slitting saws in steel on a little deckel fp1 with success.

But as a short term measure, make sure the part has some extra stock and cut it off with hacksaw or the like - seems to me I've seen hacksaws that will span 250mm - and of course you only cut the narrow part. Then you clean the end up in your lathe.

Also, when you have a decent bandsaw, buying stock in long lengths to cut to size DOES make a lot of sense - it can take days or weeks out of the project schedule. It doesn't have to be a very big bandsaw to have this effect.

Sorry, I should have specified- my mill is about the size of a Bridgeport but an import. Apparently it is not as rigid as a Bridgeport and cannot take as big a cut in comparison. It struggles too much with the slitting saw which is about 3mm think so I stopped trying to prevent possible damage to the mill.

I did the bore on the lathe using a bolt as an arbor and worked around it slowly to create the bore, thinking that it would be a good idea as I could then finish the OD without adjusting it. As it turned out, boring it on the mill would have been a far better option. This has been a case of learning valuable lessons the hard way (I have had very little machining experience). Thorough job planning and correct sequencing can save a lot of time and money haha.


Was using a 1/8 x 3/4 x 6 parting tool which should be long enough. My 4 jaw is too small to grab the part on the OD unfortunately. Another factor which may have slightly come into play was that when the part heats up, it expands and because it was being held on the ID, it would continually loose holding power/ pressure the warmer it got.

OK - been there done that have the scars.

First, parting off is one of the most finicky and difficult aspects of any lathe project, and doing it with a workpiece you cannot really hold on to, AND which is pretty large for the lathe at hand, strikes me as a way to get hurt.

Several suggestions above about what to do.

Second, the "turn it on the lathe or with a boring bar on the mill " is hugely complicated question with about 50 "it depends on" issues. (Strong mill but weak lathe? Strong lathe but weak mill? Deep bore? Shallow bore? Undercut? Grooving? What boring heads, boring bars, holders, are available? ) So, don't feel bad about that one.

And yes, order of operations matters a lot, and opening your mind to see new orders is a big part of improving as a machinist.

Third - OK, that parting tool may be "long enough" in some sense, but whether it's "stout enough for the length is what matters" - and while I'm NOT a great lathe worker, I use a 1/4x1 parting tool for things like you are describing. (But that's on a 14x40 lathe could hold your part in the chuck normally too.)

If this is Correct a 250 OD, a 63 ID. You did not say how much you need to remove in length to be finished. Say it is less than 100 mm, leave it on mill and turn it into chips. A lesson learned.

Or you could make a 63mm arbor with a very small taper at at the long end, press the pulley on to the shaft. now part off the excess.

You may need to add a hole for a 8mm bolt in the pulley, and add a dog to drive the pulley, to avoid slipping on the shaft.

So I got through it with a fine toothed tenon saw. I wouldn't have predicted it to cut so well because when turning the material (6061 T6), it felt reasonably hard and tough (probably because it was mounted poorly on a small arbor so I couldn't put much pressure on it). Obviously not preferable as the blade will dull quickly but it got the job done.

One day when I have enough room, a large used horizontal band-saw will be the next big item on the list. I bought a small home made power hack saw a while ago but it is fairly useless. A reciprocating motion is no comparison to the continuous cutting style of a band saw.

Thank's for the replies,
Xavier

Toms Wheels said:

If this is Correct a 250 OD, a 63 ID. You did not say how much you need to remove in length to be finished. Say it is less than 100 mm, leave it on mill and turn it into chips. A lesson learned.

Or you could make a 63mm arbor with a very small taper at at the long end, press the pulley on to the shaft. now part off the excess.

You may need to add a hole for a 8mm bolt in the pulley, and add a dog to drive the pulley, to avoid slipping on the shaft.

Click to expand...

ID is 124mm.
That drive dog is a good idea. I haven't seen it done on an arbor before but I'll consider it for future projects. In this situation, I think bryan_machine was right though in that I just couldn't hold onto it rigidly enough to safely perform the cut. With a bigger lathe though it probably wouldn't have been an issue.

Turning it into chips did cross my mind as well as it was well under 100mm. My concern with that was that it would take a very long time and my lathe, although not tiny (390 x 1250mm), does not like large cuts. I really regret buying a new import lathe and mill. In hindsight I would have bought older brand name equipment in reasonable condition.

Facing the waste off in the mill or lathe would be my suggestion. On my CNC lathe, I've got some parts where I turn 2" off. The 2" wasted is cheaper than more advanced work holding.