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No lathe...tooling and approach recommendations?

martin_05

Hot Rolled
Joined
Mar 11, 2009
Location
Valencia, CA, USA
I don't have a lathe but need to make a part like this.

It's a 1.5 to 2 in diameter cable drum for small diameter cable --less than 1/8 in:

pulley.jpg

I don't have any of the tooling I would need to cut the inside of this pulley.

T-slot cutters seem to be an option but you have to drop a kidney to get one large enough for this:

https://www.mscdirect.com/browse/tn...ters?navid=12106241#navid=12106241+4288178679

The other option is to hog out the inside with an appropriately large end mill and then surface what's left with a ball-end. Flip it over and do it again. Frankly, the finish of the inner OD isn't important, the cable will ride on it. It doesn't matter.

The other, similar option is to do the same while the stock is cubic (for easy clamping and indexing) and hog out the slot similarly to the above but now in four operations. I could then 45 degree the corners and turn the inside drum into an octagon. Frankly, an octagonal shape for the inside would likely be just fine too..or I could ball-end it into something resembling a cylinder.

After that I could round out the end-plates through conventional means.

Would that be a good approach? I don't want to buy an expensive tool if I don't need to.

The other alternative (which is stupid and dangerous...but I've done it before) is to mount the stock (after drilling and blind taping it) on the spindle of my Bridgeport using a partially threaded 1/2 shaft, stick a lathe grooving tool on one of the vices and carefully pretend the thing is a lathe. Please don't yell at me for having done this...I've only done it to grove shafts or otherwise cut simple features on them, never something this large. Probably a terrible idea.


Thanks.
 
PAY A MACHINIST TO BUILD IT FOR YOU THAT does HAVE A LATHE, JUST A THOUGHT....Phil

I would if this was a production part. It's a prototype and it is likely to change many times, even within the same day. I mean, I have a VF2, I think I can make it happen without having to buy specialized tooling or a 4th. axis.
 
I've used my CNC mills as lathes plenty of times, it's NBD as long as you don't get too aggressive with the RPM or depth of cut.

I'd rough the insides out to remove most of the material just clamping in a vise, then mount it on an 1" arbor in a toolholder and use a sideways clamped parting tool for the inside finish profiling. I'd just do it in the Haas, not the BP.
 
...Would that be a good approach?

This...

PAY A MACHINIST TO BUILD IT FOR YOU THAT does HAVE A LATHE...

...I think I can make it happen without having to buy specialized tooling...

Over the years as I've grown my machine shop I've looked at jobs like this as opportunities to acquire new and
different tooling with at least some cost recovery. Most tooling is a long-term acquisition so once you buy it you
have it for future work as well. Sometimes having a particular specialty tool tucked away on the corner of a shelf
can make the next job a whole lot easier...
 
Can you separate the part into two? That would make the job much easier on your mill.

That's very true. One of those "I should have thought of that moments". I blame not enough coffee.

Yeah, I can. Super simple.

I can actually machine the entire thing minus one of the flanges and then make the second flange press-fit/pinned/screwed-on/thread-on/whatever.


This discussion can serve to learn about other ideas for doing it as a single piece.
 
I once had to run some glue gun nozzles that would have been an easy lathe job, but the shop lathe was down or they just didn't have one.. so I made a form shape lathe bit.. ran the stock through the Mill spindle head. put a parting blade on the other side and ran the Bridgeport as a lathe.
 
How about trying to find a PM member close by with a lathe who subs out mill work? You could do a work swap. I have CNC Lathes and just a manual mill. I have a job soon that needs hexes cut I will do on a manual mill with an indexing head. I am sure I am not the only one here in that situation. Of course I am 2600 miles away so that won't work.
 
This...





Over the years as I've grown my machine shop I've looked at jobs like this as opportunities to acquire new and
different tooling with at least some cost recovery. Most tooling is a long-term acquisition so once you buy it you
have it for future work as well. Sometimes having a particular specialty tool tucked away on the corner of a shelf
can make the next job a whole lot easier...

I started out as a manual shop 25 years ago. I can remember many a one off job that all it did was pay for tooling or fixturing equipment.
 
How about trying to find a PM member close by with a lathe who subs out mill work? You could do a work swap. I have CNC Lathes and just a manual mill. I have a job soon that needs hexes cut I will do on a manual mill with an indexing head. I am sure I am not the only one here in that situation. Of course I am 2600 miles away so that won't work.

I would, however, as I said before, this is a prototype part. I will likely cut it, test it, go back to the shop, modify it, test again, etc., All in the span ofa few hours. I might even scrap it a few times and start over within the same day. Not the kind of thing that is conducive to working with another shop. A one or two day optimization process can quickly turn into a week or more.

This, in fact, is the reason I went out and bought my first VF3-SS over ten years ago. I spent $27K getting a set of fancy heatsinks cut. A few days after we got them it was obvious we needed to make a bunch of changes. It didn't take a genius to figure out that a few sets of those would pay for a VF3. So I called Haas, got a machine and started to learn.

When all you do is prototype a few parts a month you don't learn as fast as someone who is doing this every day with a varied range of parts, problems and materials. I think I'm doing OK though. There are lots of holes in my knowledge. For example, I haven't had the need to machine much outside of steel and aluminum or optimize everything for cycle time, cost, finish, etc.
 
I did something similar in 303SS. It was a dual sprocket. I used a robbjack
.15" thick saw in multiple depths and stepovers to do all the undercuts. The followed with a radius slot cutter to finish the curved surface on the edges. Was painfully slow. I like the two piece method if possible.
 
I would sure spend much time looking over existing science to get all the design bugs away first ..then shape it into your needs.
Justhow to hold the cable is a start problem..
Seems that part needs a lathe to make it easy.

mill work could make the part..and what looking at $400.00 cutters that will leave all those Swirls ..
Run on a lathe it would be prrrrety .

OH, What material?
 
I think you will spend more than a few hours making even a rough prototype on a mill. I think just to make one on a CNC lathe without any mill work would take a couple hours, of course part #2 could come in another 10 minutes or less out of stainless steel.
 
Sounds like you have it figured out. If I was in your shoes in the future id probably just make my own T-slot cutter. Just make it from 4140 and use positive insert lathe inserts. Staggered ccmt inserts or maybe even triangle inserts. I make custom cutters like this all the time and they work great.
 
Sounds like you have it figured out. If I was in your shoes in the future id probably just make my own T-slot cutter. Just make it from 4140 and use positive insert lathe inserts. Staggered ccmt inserts or maybe even triangle inserts. I make custom cutters like this all the time and they work great.

If you have one handy, I'd love to see a picture as well as any notes you might be able to offer on design choices you made.
 
How about a side milling cutter on an arbor instead of a T-slot cutter? Interpolate the undercut and use the same cutter to mil the flat.

Absolutely nothing wrong with mounting the part to the spindle and clamping a lathe tool in a vise. Done that a jillion times over the years.
 








 
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