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Help building radius turning attachment
- Thread starter Aurelius
- Start date
@jwmelvin Yes, thank you! I definitely would like to understand why I'm doing what I'm doing rather than blindly following directions.I think your advice, extropic, was very good (especially the front thrust washer) but I wanted OP to better understand the considerations behind it. He seemed interested in thinking about the design rather than simply following directions.
@extropic
As far as the spring washers, I will admit that I was thinking about the wavy kind only because those are the only ones I have every dealt with. So that I am clear, are you suggesting a Belleville washer and a thrust bearing at both ends? For the Belleville washer, which way do you mount it? I'm assuming flared end towards the thrust bearing, but please correct me if I'm wrong. Also, as I am completely new to these things, if you have any specific recommendations for washers or bearings, that would be terrific.
So you know, this is the bronze bearing I am talking about. It is not Oilite but I think the information is still applicable so thank you. I'll admit, for whatever reason I mentally sped right past the fact that this is 1/16" wall thickness. In the one video I was watching, thewy just tapped the (admittedly larger) bearing in with a soft hammer. I guess I am going to have to be a bit more gentle.
have you seen this video? I have looked at several ball turners for my 1228 and keep coming back to this one. Simple, handle for leverage. adjusting screw on both sides, flat face for truing up and I really want to try his homemade cutting tool. https://www.bing.com/videos/search?...8B00ED7CF7402DF40A3C8B00ED7CF7402DF&FORM=VIRE
@Chewyhave you seen this video? I have looked at several ball turners for my 1228 and keep coming back to this one. Simple, handle for leverage. adjusting screw on both sides, flat face for truing up and I really want to try his homemade cutting tool. https://www.bing.com/videos/search?...8B00ED7CF7402DF40A3C8B00ED7CF7402DF&FORM=VIRE
Yes, that Is one of a handful I was pulling ideas from. The main difference was I was going to use the AXA boring holder instead of machining the body like he did. Not having a mill would make copying that design quite the chore. I realize it could be done but then I start falling into tool-ception - building tools to build the tools I need to build the tool I want when this was intended as more of a smaller project.
You can probably get some one to mill the slot on the side for you. Just ask. The rest can be done on the lathe. Mount the body on tool holder and bore out to fit shaft, turn sideways and end mill flat face. The only other thing is to drill the handle on an angle which you can do on lathe, but a drill press or mill with a solid vise would be easier. On second thought, you could mount on cross slide using compound to line up and then just feed into drill mounted into headstock.
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- Nov 24, 2014
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@Aurelius
It often takes way too long to eek out enough information. Let's see if I understand what you're intending to do.
You have purchased a boring head and a 5/8" straight shank arbor plus an AXA 3/4" boring bar holder. Is that correct?
How long is the straight shank?
How long is the bore in the holder?
Alternatively, what is your plan to attach a wheel or handle to the straight shank?
To adjust and maintain the preload, I think you'll need to use a nut/thread. How can that be implemented?
At this point, assuming the straight shank is longer than the AXA holder (not as pictured) I recommend buying two of these Flanged Sleeve Bearing.
Cancel the bronze bearing you previously referred to.
No need for ball or needle thrust bearings.
Buy one (pack) of these .032 thick Washer.
Buy one (pack) of these Belleville Disc Spring.
At the handwheel end of the arbor, put one .032 thick washer against the flanged sleeve bearing. Orient the ID of the Belleville washer toward the .032 thick washer.
The Belleville washer is 1.5" OD and you'll want it to bear on a steel surface on the handwheel (or handle). A washer will do if the handwheel is aluminum.
Please reply to the five questions above so we can converge.
It often takes way too long to eek out enough information. Let's see if I understand what you're intending to do.
You have purchased a boring head and a 5/8" straight shank arbor plus an AXA 3/4" boring bar holder. Is that correct?
How long is the straight shank?
How long is the bore in the holder?
Alternatively, what is your plan to attach a wheel or handle to the straight shank?
To adjust and maintain the preload, I think you'll need to use a nut/thread. How can that be implemented?
At this point, assuming the straight shank is longer than the AXA holder (not as pictured) I recommend buying two of these Flanged Sleeve Bearing.
Cancel the bronze bearing you previously referred to.
No need for ball or needle thrust bearings.
Buy one (pack) of these .032 thick Washer.
Buy one (pack) of these Belleville Disc Spring.
At the handwheel end of the arbor, put one .032 thick washer against the flanged sleeve bearing. Orient the ID of the Belleville washer toward the .032 thick washer.
The Belleville washer is 1.5" OD and you'll want it to bear on a steel surface on the handwheel (or handle). A washer will do if the handwheel is aluminum.
Please reply to the five questions above so we can converge.
- Joined
- Nov 14, 2016
- Messages
- 3,285
I don't know how well it would work scaled up, but the Sherline radius cutting attachment works well on my Sherline.
It is a fairly simple design so I wouldn't think too hard to enlarge and make one for a bigger lathe.
Sherline radius cutting attachment
It is a fairly simple design so I wouldn't think too hard to enlarge and make one for a bigger lathe.
Sherline radius cutting attachment
CorrectYou have purchased a boring head and a 5/8" straight shank arbor plus an AXA 3/4" boring bar holder. Is that correct?
This is the shank I purchased. The shank portion is 70mm.How long is the straight shank?
77 mmHow long is the bore in the holder?
I had originally planned on utilizing the drawbar threads on the tail end of the boring shank. I believe that they are 3/8".Alternatively, what is your plan to attach a wheel or handle to the straight shank?
I'm not sure if that's the same as what I just said, but I Was thinking that by screwing into the drawbar threads, it would effectively pull everything together. All of the handles/handwheels I have been looking at would either thread on the same bolt of had a ID that would allow the bolt to pass through. I thought that, with the bolt tightened, friction would be enough to hold the wheel to the shaft and that all that would be needed was possibly some kind of washer at either end to keep it all held in place. That was also why I had originally asked about some kind of spring washer(s).To adjust and maintain the preload, I think you'll need to use a nut/thread. How can that be implemented?
I think it will work well to use a shoulder bolt of sorts to pull the back end of the arbor into the boring-bar holder. Use extropic’s suggested design: thrust washer in front (could be needle bearing but plain bearings will be fine), a plain-bearing thrust washer in back, loaded by a Belleville washer. You can design a shoulder bolt to apply the desired preload. The advantage of a Belleville washer (or generally a spring washer) is to make the assembly less sensitive to the compressed length. Without the washer, the length of the shoulder bold is critical; by using compliance; the structure is less sensitive to length so you can get the desired preload with less precision in the part you make (the shoulder bolt).
The preload really isn’t that necessary here, but could help manage chatter. The cutting loads are against the front-side thrust washer. Applying a preload with a back-side spring means that the spindle (the boring head) will handle loads in both directions up to the preload force. Stated otherwise, it takes the play out of the system as long as you don’t apply a load that moves the boring head away from the holder.
Edit: the reason you don’t want a spring washer in front is because you want the front in close contact for the high spring rate of that position (the thrust washer, whether rolling element or plain). The spring washer in back just holds things in the desired position, as described above.
The preload really isn’t that necessary here, but could help manage chatter. The cutting loads are against the front-side thrust washer. Applying a preload with a back-side spring means that the spindle (the boring head) will handle loads in both directions up to the preload force. Stated otherwise, it takes the play out of the system as long as you don’t apply a load that moves the boring head away from the holder.
Edit: the reason you don’t want a spring washer in front is because you want the front in close contact for the high spring rate of that position (the thrust washer, whether rolling element or plain). The spring washer in back just holds things in the desired position, as described above.
- Joined
- Nov 24, 2014
- Messages
- 3,591
@Aurelius
OK. The AXA holder is 77mm long, plus two flanges (.125" x 2 ~= 6.5mm). 77+7 = 84mm + the Belleville/washers + handwheel = ???
It looks like things would be much simpler if the straight shank was at least 100mm long. Can you buy a new arbor with a 100mm long shank?
I suppose it would be possible to lengthen the existing arbor (now that we know it is threaded for a drawbar). I don't think I've ever seen a straight shank arbor threaded for a drawbar. I also don't know exactly what your skill level is of what skills and equipment you have access to. I'll make some (many) assumptions and here we go. I'll assume the straight shank is soft enough for you to turn.
One idea is to turn a .500" x .1" long diameter on the end of the arbor. Make a new extension, long enough to extend the arbor through the handwheel and leave it .700" OD for now. Drill and tap the new extension through, to match the drawbar thread. Turn a counterbore on the end of the extension .08" deep and ID to closely fit the reduced OD you added to the existing arbor. Attach the two using an alloy steel setscrew (1" long) and your best epoxy. Tight as you can/dare and let it cure completely. If you have access to quality TIG welding, the extension (without counterbore) could be attached by the setscrew and welded.
When it's ready to finish machine, put the boring head end of the arbor in a 4 jaw chuck (on your lathe) and adjust/indicate all of the unmodified portion of the straight shank to run precisely true. Use a steady rest to support the original diameter of the straight shank. Turn a 60° center around the end of the threaded hole in the extension. Remove the steady rest and use a live center in your tailstock to support the workpiece. Turn and polish the extension to match the diameter of the straight shank. Whew!
An alternative is to make a new (long enough) arbor from scratch.
Another alternative is to buy a piece of precision 5/8" shaft, tap one end and silver solder the "big end" of the existing arbor onto it. Again, the existing arbor must be soft enough for you to modify.
I haven't described the remainder of the design concept. However, if you can buy or make a "long enough" arbor, things get pretty simple.
What say you?
IMO, continuing with a "too short" arbor is unattractive in the extreme (how's that for friendly language?). That's not to say it's not possible. Different people have different ideas of what constitutes a nice piece of tooling. Trying to continue using a "too short" arbor isn't attractive to me.
OK. The AXA holder is 77mm long, plus two flanges (.125" x 2 ~= 6.5mm). 77+7 = 84mm + the Belleville/washers + handwheel = ???
It looks like things would be much simpler if the straight shank was at least 100mm long. Can you buy a new arbor with a 100mm long shank?
I suppose it would be possible to lengthen the existing arbor (now that we know it is threaded for a drawbar). I don't think I've ever seen a straight shank arbor threaded for a drawbar. I also don't know exactly what your skill level is of what skills and equipment you have access to. I'll make some (many) assumptions and here we go. I'll assume the straight shank is soft enough for you to turn.
One idea is to turn a .500" x .1" long diameter on the end of the arbor. Make a new extension, long enough to extend the arbor through the handwheel and leave it .700" OD for now. Drill and tap the new extension through, to match the drawbar thread. Turn a counterbore on the end of the extension .08" deep and ID to closely fit the reduced OD you added to the existing arbor. Attach the two using an alloy steel setscrew (1" long) and your best epoxy. Tight as you can/dare and let it cure completely. If you have access to quality TIG welding, the extension (without counterbore) could be attached by the setscrew and welded.
When it's ready to finish machine, put the boring head end of the arbor in a 4 jaw chuck (on your lathe) and adjust/indicate all of the unmodified portion of the straight shank to run precisely true. Use a steady rest to support the original diameter of the straight shank. Turn a 60° center around the end of the threaded hole in the extension. Remove the steady rest and use a live center in your tailstock to support the workpiece. Turn and polish the extension to match the diameter of the straight shank. Whew!
An alternative is to make a new (long enough) arbor from scratch.
Another alternative is to buy a piece of precision 5/8" shaft, tap one end and silver solder the "big end" of the existing arbor onto it. Again, the existing arbor must be soft enough for you to modify.
I haven't described the remainder of the design concept. However, if you can buy or make a "long enough" arbor, things get pretty simple.
What say you?
IMO, continuing with a "too short" arbor is unattractive in the extreme (how's that for friendly language?). That's not to say it's not possible. Different people have different ideas of what constitutes a nice piece of tooling. Trying to continue using a "too short" arbor isn't attractive to me.