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Right Angle drive for a Bridgeport style mill.
- Thread starter ducdon
- Start date
Not enough travel. My BP clone has only 5 inches of travel in the down feed function. I've done it but it has to be a very short cylinder.
The knee only travels 5"?
This is the one I have. It works very well. As with anything, the further you hang something out (stack up components), the more rigidity suffers. It does allow for larger parts to be placed on the mill table though.
It is a bit fiddly to get set-up and any out of tram axis of the head will be accentuated because of the long distance away from the center of rotation. It does have a machined surface parallel to the spindle which can be used to indicate the attachment (you can see in the picture).
You don’t have to use the arbor. R8 collets / tooling fit into the horizontal spindle (you probably knew that already).
It is a bit fiddly to get set-up and any out of tram axis of the head will be accentuated because of the long distance away from the center of rotation. It does have a machined surface parallel to the spindle which can be used to indicate the attachment (you can see in the picture).
You don’t have to use the arbor. R8 collets / tooling fit into the horizontal spindle (you probably knew that already).
Getting a consistent and smooth feed while cranking up the knee would be a challenge. Might do for a one of.
That's the one I'm looking at. To do motorcycle ore snowmobile cylinders I would probably need about 8 to 10 inches of travel. Rigidity is the big question. Especially without the outer end support.
A knee power feed would solve that.
Well, if you had access through the cylinder, a special arbor with a table mounted, sliding end support could be made. It would be like line boring then.
YEP. That's kinda the way I was thinking. Do you think it could be rigid enough? Cylinders are usually cast iron lined. I've done experiments on the lathe but its hard to keep out taper just using a boring bar. Setting up a cylinder on the cross slide for a line bore is super fiddley. Wish I could afford a quick way boring bar.
I went looking through my archives but can't find a photo where I bored the spindle holes in my Gingery Lathe.
The basic arrangement is two sets of pillow block bushings holding a long shaft held at both ends. The lathe head stock was installed and connected to the lead screw. The shaft held a cutter that could be adjusted to the size of the bore and then the head stock moved along the bed. The two ends of the shaft were adjusted to be the same height above the bed and relative to the edge.
This made the spindle bore the correct diameter and in line with the bed.
If you can jig up something on the carriage of your lathe to hold the cylinders with the boring bar held between centers you should be able to create parallel holes.
Just an idea.
This made the spindle bore the correct diameter and in line with the bed.
If you can jig up something on the carriage of your lathe to hold the cylinders with the boring bar held between centers you should be able to create parallel holes.
Just an idea.
YES. I would have to make some sort of fixture on the carriage to hold and align cylinders. Ideally it would be adjustable for different size cylinders? I just don't have a good mental picture of what that would look like. Any photo's or illustrations I've seen of that being done include lots of blocking, shimming and hold down. Good for a one time effort but I have a number of cylinders I would like to do. Maybe a fixture plate that would bolt on top of cross slide and replace compound? The mill is appealing because of long travel table, T slots and Y,Z movements. I'll keep thinking about it.
If you have a lot of these to do, my mind drifts toward selling the mill you have and getting a bigger mill.
But also nagging me is to make or buy a new tailstock for your lathe that is basically an x/y holding fixture for your cylinders. It might be easier to adapt a small x/y table to a new 2nd tailstock. In other words, use the existing tailstock to push the new one and modify the new one so slide on the ways in a more controlled fashion like the apron does.
Ya, trading up your mill is the best way to go...... Win-win!
Just some thought starters.
I think so.
If you already tried the boring bar method on the lathe, the right angle attachment on the mill will be worse as you have an even longer unsupported tool.
At least on the lathe, you could use a solid tool post holding a beefy (like 2” or larger) boring bar.
By the sounds of it, a line boring set-up (either on the lathe or the mill) will be the most rigid.
Dabbler
ersatz engineer
Regular boring onto a face plate isn't a bad idea. It does present 2 problems.
1) you have to stop the boring short, or risk hitting the face plate - yes special fixturing can help, however
2) Using a long boring bar is more difficult than line boring, because the flex in line boring is far less than a single ended boring bar, making dialing in to accurate numbers a tad more challenging when using a single ended bar. Not terrible, just more tricky. (for the engineers out there it is order x**3 versus order x**2)
To get tenths tolerances, an single ended boring bar, I'd be going for 2-3 inch diameter boring bar. 1" bar over 8' bore is very bendy, even for light cuts. Normal rule of thumb is 1:4 to 1:5 MAX for diameter versus length of bore for boring bars. I've been using this recommendation for a long time and find it reliable.
1) you have to stop the boring short, or risk hitting the face plate - yes special fixturing can help, however
2) Using a long boring bar is more difficult than line boring, because the flex in line boring is far less than a single ended boring bar, making dialing in to accurate numbers a tad more challenging when using a single ended bar. Not terrible, just more tricky. (for the engineers out there it is order x**3 versus order x**2)
To get tenths tolerances, an single ended boring bar, I'd be going for 2-3 inch diameter boring bar. 1" bar over 8' bore is very bendy, even for light cuts. Normal rule of thumb is 1:4 to 1:5 MAX for diameter versus length of bore for boring bars. I've been using this recommendation for a long time and find it reliable.
Interesting about line boring shaft diameters.
Just to take this off topic just a tad...
I've had to turn pulleys between centers so I can turn them end for end to get access to the various edges without having to dial it in each time in a 4 jaw.
If the hole in the pulley is 19mm then a long 19mm shaft between centers is quite bendy. (Technical term there).
Is it better then, using your rule of thumb to make one side of the shaft quite large and the other end the 19mm as short as possible but still to allow reach for the cutting tool? The shaft is slotted for a key and the pulley blank is also slotted so that's what keeps the pulley from spinning.
I used the same shaft to turn the spindle pulley with a tapered holder keyed to the shaft.
The reason I ask is I find I have a little bit of vibration that I think I shouldn't have. Not sure if the 19mm hole for the motor was just too large and the motor pulley is off center or if somehow the between centers shaft contributed to an out of round pulley.
We can move this to another thread if needed.