Help building radius turning attachment

[Aurelius]

Ohm I doubt a longer one is available. I have reached out to a guy on another forum who machines stuff at a fairly reasonable price to see what he would charge. Depending on his reponse, I may have to revisit alternatives using the short shank.

 

[extropic]

Ohm I doubt a longer one is available. I have reached out to a guy on another forum who machines stuff at a fairly reasonable price to see what he would charge. Depending on his reponse, I may have to revisit alternatives using the short shank.

I recommend getting the shank ~6" long until the design firms up. It's pretty easy to shorten it.

 

[Jimsehr]

This is a super simple radius turner. It works from the bottom of the part instead of the side. But it cuts a radius and is easy to use. I‘ve cut over a hundred balls with it in steel. No bearings no bushings it still cuts a ball within .001 dia. With no chatter.
I’ve made different radius tools that are adjustable. And used boring heads to cut
a radius. So I don’t think bearings are needed to cut pen material and I know it’s much cheaper and easier to swing the radius just using a reamed hole and a bolt.

Plus if you look at my Avatar you can see the 3 different radius in the cube. I used hand ground tools that I made on my bench grinder. So it might be easier to use a form tool then to set up a radius turning tool.
Plus if you want to know a simple way to make swing point for any radius on your lathe Using the compound Ask me.

Jimsehr

 

[Aurelius]

@Jimsehr
Thanks, I was aware of that style tool and know that they can work but I do not think it quite what I am going for. My bench grinder is still in the box so my skills when it comes to hand grinding tools is basically nil and there are other skills I consider higher priority than figuring out grinding.

@extropic
Awesome news. I successfully cancelled the bronze bearing and remembered that, even though I got the shank from Shars, it was actually cheaper to buy from them on Amazon, hence no questions asked return. The icing on the cake is my contact on the other forum can machine me a shank for a surprisingly reasonable cost. Now I just need to finalize the design and get him a drawing. I will be revising my drawing and posting here later this evening (hopefully) to nail down the details.

 

[Aurelius]

OK, so could you guys check my math here?
The stack should look like this:

Back of shank
---
Belleville washer
Washer
Bronze sleeve bearing
AXA boring holder
Bronze sleeve bearing
Washer
Belleville washer
Washer
---
Handle

Is that right? There had been a mention of a thrust bearing, is it worth adding on (or more) in? They don't seem to be that expensive and I would prefer to do it right the first time. If I do add in a thrust bearing, it would go between the washer and the bronze sleeve bearing on the front end, correct?

Once I get the stack right, I have all the specs for the various thicknesses so I'll know the total length I need for the shank and I figure whatever handle I decide to go with can just screw into the tail end of the shank.

Thanks!

 

[extropic]

OK, so could you guys check my math here?
The stack should look like this:

Back of shank
---
Belleville washer
Washer
Bronze sleeve bearing
AXA boring holder
Bronze sleeve bearing
Washer
Belleville washer
Washer
---
Handle

Is that right? There had been a mention of a thrust bearing, is it worth adding on (or more) in? They don't seem to be that expensive and I would prefer to do it right the first time. If I do add in a thrust bearing, it would go between the washer and the bronze sleeve bearing on the front end, correct?

Once I get the stack right, I have all the specs for the various thicknesses so I'll know the total length I need for the shank and I figure whatever handle I decide to go with can just screw into the tail end of the shank.

Thanks!

No Belleville washers at the front (boring bar end) of the straight shank. you would like zero compliance there.

You don't show any room for "stops" in your stack. You don't want stops?

There needs to be an adjustment to control the amount of preload. Assuming that the "handle" bears on the large diameter of the Belleville washer(s), I suggest you tap the back end of the straight shank and use a thick washer and screw to adjust the axial position of the "handle" to achieve a preload the works for you. Additionally, the handle will need a setscrew, or other means, to secure it in rotation to the straight shank.

 

[Aurelius]

@extropic
First up, if the shank is going to be right up against the bronze sleeve bearing, would that be where a thrust bearing should go?

I see a chance for me to learn something. What exactly do you mean by "stops"?

When you talk about preload, I thought that having Belleville washers on both ends would create a tension that would be controlled by tightening the handle against the washer. If I remove the from Belleville but had a thrust bearing, wouldn't there still be tension holding everything together? From what you said, I gather that is incorrect, no?

As for the threading/setscrews/etc. I was planning on figuring that out once I picked a handle. That is relatively easy as it just requires me to put it in the drawing I send to get made.

Thanks!

 

[extropic]

@extropic
First up, if the shank is going to be right up against the bronze sleeve bearing, would that be where a thrust bearing should go?

The back of the boring head mount (arbor) goes right up against the flange of the Oilite bearing (NO BELLEVILLE WASHER in there). The flange of the Oilite bearing is the "thrust bearing" in this case. That's why we chose a flanged Oilite bearing rather than an plain (no flange) Oilite sleeve bearing.
That is the simplest way to go and perfectly adequate for your purposes. Using a ball or needle type thrust bearing will add cost (only a few $$) and complexity. We will need to seal that type of bearing from swarf and other contamination. None of using ball or needle type thrust bearing is difficult but it is unnecessary here. You decide and let me know, so we can converge.

I see a chance for me to learn something. What exactly do you mean by "stops"?

In reply #4, @mjks included a link to post about a radius turner that he built. His build incorporated stops that are simple to build can be set to limit the rotation of the boring head. Please take a look at the linked post, which is well explained and has many good photos. If, after digesting that post, you still have questions about stops, ask away.

When you talk about preload, I thought that having Belleville washers on both ends would create a tension that would be controlled by tightening the handle against the washer. If I remove the from Belleville but had a thrust bearing, wouldn't there still be tension holding everything together? From what you said, I gather that is incorrect, no?

I don't understand the question. In reply #16 I thought I explained the parts stack-up and some parts to buy. I did not mention stops in reply #16 but stops (like mjks's) don't change those purchased parts.

As for the threading/setscrews/etc. I was planning on figuring that out once I picked a handle. That is relatively easy as it just requires me to put it in the drawing I send to get made.

Does that statement mean that you are not prepared (skill, tooling, whatever) to shorten and/or drill/tap a "too long" straight shank?
In reply #32 I wrote "I recommend getting the shank ~6" long until the design firms up. It's pretty easy to shorten it". If you're not going to heed my suggestions, please make that clear ("why" would be nice too) in a timely manor. I'm trying to converge and make progress but find I keep having to back up.

I'm getting the sense that you don't want to expand your machining skills/tooling beyond what is necessary for pen making. Does that sum it up or would you prefer to do some machining (which may well require the purchase of some tooling) and expand your experience and skills in the construction of the radius turning attachment? In other words, do you want to make something or do you only want to bolt some parts together? The design and the discussion depend on what your intensions are.

Hypothetical: If I can explain a method for you to make your own arbor, rather than have a third party make a new one for you, which would you prefer? Would you be willing to spend the same $$ on tooling rather than paying someone else to make the arbor?

What type of tool post do you have on your lathe? A picture will do.

 

[Aurelius]

The back of the boring head mount (arbor) goes right up against the flange of the Oilite bearing (NO BELLEVILLE WASHER in there). The flange of the Oilite bearing is the "thrust bearing" in this case. That's why we chose a flanged Oilite bearing rather than an plain (no flange) Oilite sleeve bearing.
That is the simplest way to go and perfectly adequate for your purposes. Using a ball or needle type thrust bearing will add cost (only a few $$) and complexity. We will need to seal that type of bearing from swarf and other contamination. None of using ball or needle type thrust bearing is difficult but it is unnecessary here. You decide and let me know, so we can converge.

Got it, no need for the thrust bearing.

In reply #4, @mjks included a link to post about a radius turner that he built. His build incorporated stops that are simple to build can be set to limit the rotation of the boring head. Please take a look at the linked post, which is well explained and has many good photos. If, after digesting that post, you still have questions about stops, ask away.

Ok, I understand now. For everything I envision using this for, I do not think I need stops.

I don't understand the question. In reply #16 I thought I explained the parts stack-up and some parts to buy. I did not mention stops in reply #16 but stops (like mjks's) don't change those purchased parts.

My apologies, I was trying to reconcile my original (incorrect) thinking with what you said. I have the parts you suggested already in my cart at McMaster-Carr and just wanted to make sure I didn't overlook anything before placing the order.

I'm getting the sense that you don't want to expand your machining skills/tooling beyond what is necessary for pen making. Does that sum it up or would you prefer to do some machining (which may well require the purchase of some tooling) and expand your experience and skills in the construction of the radius turning attachment? In other words, do you want to make something or do you only want to bolt some parts together? The design and the discussion depend on what your intensions are.

Hypothetical: If I can explain a method for you to make your own arbor, rather than have a third party make a new one for you, which would you prefer? Would you be willing to spend the same $$ on tooling rather than paying someone else to make the arbor?

In this particular case, I am more concerned with the functionality. My priority is putting my efforts into expanding my skills as it relates to the pen making, this is a side project. I am not averse to spending money on tooling or time on learning new things but, in this case, I feel that the return is just not there. As I understand it, the only skill I am currently lacking for this project would be single point threading the 1 1/2 x 18 threads to attach the boring head. That would require a toolholder plus insert and I am assuming I would need a tap for the tail of the arbor.

The person I have contacted told me that, for around $50, he will machine me exactly what I need with whatever threading or other features I ask for. Given that the tooling alone would be about twice that, for this project, I would be perfectly happy understanding the thinking behind the design, sourcing the correct components to make a quality tool, and ending up with something well made and functional.

What type of tool post do you have on your lathe? A picture will do.

It's the standard PM wedge type AXA qctp.

 

[extropic]

Got it, no need for the thrust bearing.

Ok, I understand now. For everything I envision using this for, I do not think I need stops.

My apologies, I was trying to reconcile my original (incorrect) thinking with what you said. I have the parts you suggested already in my cart at McMaster-Carr and just wanted to make sure I didn't overlook anything before placing the order.

In this particular case, I am more concerned with the functionality. My priority is putting my efforts into expanding my skills as it relates to the pen making, this is a side project. I am not averse to spending money on tooling or time on learning new things but, in this case, I feel that the return is just not there. As I understand it, the only skill I am currently lacking for this project would be single point threading the 1 1/2 x 18 threads to attach the boring head. That would require a toolholder plus insert and I am assuming I would need a tap for the tail of the arbor.

The person I have contacted told me that, for around $50, he will machine me exactly what I need with whatever threading or other features I ask for. Given that the tooling alone would be about twice that, for this project, I would be perfectly happy understanding the thinking behind the design, sourcing the correct components to make a quality tool, and ending up with something well made and functional.

It's the standard PM wedge type AXA qctp.

OK. The fact is, at this point, the other fellow, maker of the arbor, is in control the tool build.

I don't know anything about that fellow (except that he has proposed a low price) so, from where I sit, he represents a high risk. You seem convinced that using his services is the best way to go so I'll give you my best advise within the constraints I understand.

You and I don't know the precise diameter of the "3/4 inch" hole. Therefore, we can't understand the installation of the Oilite bearings. Therefore, we don't know what diameter to specify for the straight shank of the new arbor.

I recommend that you prepare a graphic, with notes, describing the stack of parts and your intensions.
Since his skills will control the outcome, I recommend you send him all the purchased parts, including the boring head.
Also provide him the information I gave you in reply # 11.
He will fit the bearings to the holder and size the straight shank to fit the installed ID of the bearings.
Have him set shank length to achieve .061" working height of the Belleville washer.
I'm not sure where you are on "handle vs wheel, but have him do any requires machining. All I can add (repeat) is that the hub diameter needs to be greater than 1.25" to support the Belleville washer(s). The handle need an anti-rotation feature so a setscrew is probably the easiest to implement. The setscrew should bear on a flat machined on the straight shank.
I would tap the back end of the shank, 1/4-28 x 3/4" deep and use a SHCS w/washer to pull the handle in (compress the Bellville).