Machining Requirements!?

[Welderpaul]

I need a few of these making, not sure if they can be done on a lathe or not?

Tolerance is not critical, +/- 0.5mm on the dia of the 16mm section, the rest +/- 1mm.

Thoughts/price anyone?

 

[penfold]

That's a pretty awkward machining job, would be easier if the 16mm bit could be made separately and inserted into a hole drilled in the 30mm bit; it could be done on a CNC but you'd pay a lot for the code to be knocked up.

Could the design be modified to allow easier turning of the 16mm diameter like this? This would be a lot easier to do on a manual lathe.

 

[Kent]

Yes, the Tollerance is easy the set up of the first slow. If it's a good size batch won't be massive money but a small batch your paying for the set up. I don't know much about full cnc I trained in earlier days

 

[Pete.]

I could make them manually easily enough, except for the angle of the flat where the angled stub sprouts from the 30mm diameter. It would have to be on the axis of the angled bit not the stock.

 

[nickk]

how critical is the squareness of the shoulder/neck ,could be machined on a parallel axis, then forge the crank.

 

[Welderpaul]

Unfortunately the shoulder needs to be square with the 30mm dia section

 

[Pete.]

You could have the outside 4mm square with a 3mm wide undercut 2mm deep?

 

[scott0031]

Paul, knowing a bit about your work do you need to weld onto these? If you do, best to specify material grade and most will pick up en1a or or en1a leaded and you wont be able to weld to either of those successfully.

If it was allowed i would make this in two parts and bolt through with a cap head. Drill c/bore in the 30 Diam to suit M8 or m10, face the 16 diam at the correct angle drill and tap to suit, as long as a cap in the head of the part wont affect anything. No dimensional accuracy is really required and should be adequate in that sense. There are other ways of doing it but i think this would prove the quickest solution without over thinking it.

 

[Pete.]

Hell if they are just handrail stubs or similar just cut the 16mm off at 7 degrees and weld it to the 30.

 

[nickk]

Hell if they are just handrail stubs or similar just cut the 16mm off at 7 degrees and weld it to the 30.

but the weld would have to be counterbored in the head for a square shoulder.

 

[Pete.]

but the weld would have to be counterbored in the head for a square shoulder.

Not if it was tigged you'd just have a radius, which you'd want anyway on a machined part.

 

[J.B. Welding]

For something like that I recon I'd make it all square and straight in the lathe. I'd then drill into the end of a 30-40mm round bar with a 16.5mm bit, plenty deep enough, and then cut the end off of the drilled bar at the 7 degrees.
The straight rivets would get wazzed into the forge, then inserted into the jig hot and a dunt with a hammer would set the head angle. If neatness is required an upper die could be made to take the 30mm head and keep it all tikkety sweet.
30 off in m/s gonna take one heat each so an hour forging max including warm-up time and a few hours on my manual lathe.
Could possibly get you them by November?

 

[nickk]

Not if it was tigged you'd just have a radius, which you'd want anyway on a machined part.

but for adequate strength that rad' will be too big for op.

 

[gaz1]

the only way i see it being done is start of larger but where the red is on the right would it be exceptable for paul to have it designed like that

the back end could just be cut off when finished but the piece would have to bigger to start off with

 

[scott0031]

For something like that I recon I'd make it all square and straight in the lathe. I'd then drill into the end of a 30-40mm round bar with a 16.5mm bit, plenty deep enough, and then cut the end off of the drilled bar at the 7 degrees.

I'm not sure if I'm misunderstanding what you are trying to explain or you are missing a few points. The 16.5 mm hole you want to use will be square with the 30mm Diam head, you can the face off the head at 'whatever the angle is' but you wont put the 16 mm spigot at an angle to the head doing this because your drilled hole is still square which you will insert the spigot into. All you will get is a part that is all square and on a single axis and the shoulder will be at an angle. Or am i misunderstanding what you are saying?

 

[scott0031]

A quick example.

 

[Welderpaul]

Thanks for your input chaps, much appreciated. Scott - you know us too well

I'll do another sketch when I get home to show a bit more information and the bigger picture of what these are to be used for.

 

[J.B. Welding]

I'm not sure if I'm misunderstanding what you are trying to explain or you are missing a few points. The 16.5 mm hole you want to use will be square with the 30mm Diam head, you can the face off the head at 'whatever the angle is' but you wont put the 16 mm spigot at an angle to the head doing this because your drilled hole is still square which you will insert the spigot into. All you will get is a part that is all square and on a single axis and the shoulder will be at an angle. Or am i misunderstanding what you are saying?

Yea kinda misunderstanding me mate-easy done! The drilled out bar with the angled face forms a bottom die. The lathed 'rivet' goes into this. Once heated and hammered the cranked angle on the head will easily form.
Precision engineering it aint but hey ho if it does the job. Without serious cnc gear and a crap load of programming I can't see it being machined. Just needs a hit with a hammer!

 

[MCKDAVID]

make it straight, and a sleeve to suit (to slide over the angled diameter) to give you some decent purchase with a long bar. Heat to red, and bend accordingly?

 

[drjim]

Make the heads and drill hole in it at the right angle then screw a threaded bit in to make the sticky out bit??

What's it for?