Moron The Logan Compound, Advice Needed.

[Xnerd]

Ok its a pretty simple question, but first background:
I have an old logan 1821 that i have been restoring. the major thing wrong with it was that the compound looks like it blown up with dynamite. actually I think that someone gorilla torqued a tool holder or some such device onto it and busted out the tee slot. So at any rate I machined a new one as seen in the image below.
please realze that I understand that my machining is horrifying, but you gotta understand that this is like the 4th thing that I have ever attempted to make on a mill in my life, so I Honestly have no experience at all.

the last operation that I have to do is to bore and thread one end of the compund to receve a guide *see below* for the lead screw. I could either attempt to mound it in my little 10 inch logan 820 which scares the hell 0ut of me lol. Or I can bore it with my mill. The problem is that if i bore it with my mill i will have no way to tap it. The size of the thread is .6800 which is 17/25ths or there abouts. no way someone makes that tap. So im back to using a 10 inch lathe to mount this big chunk of metal in...... if I bore it and thread it on the lathe, it will be fine.... as long as it does not kill me in the process. I mounted it up in the 4 jaw and it felt solid. I found the dimple with a dead center in the tail stock. So I can do this.;

BUT CAN I? Is this too big for a 10 inch lathe?


By the way. the pointy set screw looking deal is a piece of gummy .6800 mild steel that I made to transfer the position of the feature on the original compound. it was some of that crap that you get from the hardware store that turns like frozen bubble gum.......


so do I attempt this or send it out to a buddy to do?

 

[wawoodman]

.680 is pretty darn close to 11/16 (.687) and that is an available tap size, both in fine and coarse. Maybe doublecheck the thread size?

 

[mikey]

First, I think you did a fine job on that compound. It doesn't look like a novice piece at all.

Second, why does the guide thread need to be original? Can you not make a new guide with the original sized guide hole and the external thread something for which a commercial thread is available? Drilling the end of your work piece is a job for a mill, not the lathe.

 

[Xnerd]

First, I think you did a fine job on that compound. It doesn't look like a novice piece at all.

Second, why does the guide thread need to be original? Can you not make a new guide with the original sized guide hole and the external thread something for which a commercial thread is available? Drilling the end of your work piece is a job for a mill, not the lathe.

Thanks.

And I figured that it was more of a job for a mill but I dont know exactly how I would thread it on the lathe once its borned on the mill. Unless I make a morse taper with one side the same size as the bore so that I can perfectly position it... wow.. yeah I could do that easy. I just made a real nice taper attachment and made a couple of morise tapers that came out spot on perfect. The radiuses ???? at the length were right dead nuts on! I was smiling. I made the attachment 26 inches from center of pivot point to tip of a brass needle so the math came out that one degree is equal to .45 inches. but when it was all said and done I indicated a number two and set it up that way lol. not trusting my math and all

So dose that sound like a plan with the tailstock locator? I might see if there is a commercial tap available. first.

 

[Xnerd]

.680 is pretty darn close to 11/16 (.687) and that is an available tap size, both in fine and coarse. Maybe doublecheck the thread size?

yes it is closer to .687 and is 16 tpi. I will have to order that tap asap.

thanks!

 

[mikey]

If you can find the right tap then just drill the hole on your mill, make a generous chamfer at the opening and use a tap guide block to guide the tap. You can make the tap guide by drilling a close tolerance through hole in scrap material. Drive the tap by hand with a tap wrench. Once you get into the thread by 2-3 threads you won't need to tap guide and should be able to cut it straight.

I suggest using a drill 2 sizes larger than the bit normally used for that tap. The guide is not under tension so it needn't be a class 3 fit. A larger hole will tap far easier than using the drill normally called for.

 

[brino]

Yes the part you made looks great. Don't be so hard on yourself.

It's hard to tell the size(length) of the new cross-slide from your pictures. I would not want a big piece swinging around in my face either unless I was sure it was solid. I usually use my own discomfort with an operation as a signal to whether I'm capable to do it or not. I tend to prove things on smaller safer set-ups first until I am comfortable with bigger set-ups.

However, user @savarin always amazes me with what he does in his lathe. See for instance:
http://www.hobby-machinist.com/threads/a-vertical-slide-for-a-9x20-lathe.49724/
http://www.hobby-machinist.com/threads/a-vertical-slide-for-a-9x20-lathe.49724/#post-426949
http://www.hobby-machinist.com/threads/80mm-long-focal-length-refractor.26212/#post-275479
http://www.hobby-machinist.com/threads/80mm-long-focal-length-refractor.26212/page-3#post-334440

You could still bore it in the lathe, but think about it backwards! Put the boring tool in the spindle(chuck or collet) and mount the new cross-slide on the carriage.

If you do bore in the mill, I would actually start the tap in the mill too if you can. Unplug it, put in neutral, remove belts, whatever you need to do to turn it by hand. I agree that once started a few turn the tapping can be done in a vice.

I agree with drilling slightly larger than the recommended tap drill size, but go by measurements. The phrase "two sizes larger" is a little ambiguous unless we know exactly what drill bit set you have.

By the way, for centering parts on the lathe like the bore you mention above, it is typical to use a dial test indicator either held in the tool-post, or in a magnetic holder attached to the carriage. Measure directly in the bore. With this arrangement, you should be able to centre a part very accurately. Ideally if you can also check again some distance into the bore you can also be sure it's aligned parallel to the lathe centre line. Alternately, you could put a pin gauge in the bore and measure against that.

Have fun and play safe!
-brino

 

[Xnerd]

If you can find the right tap then just drill the hole on your mill, make a generous chamfer at the opening and use a tap guide block to guide the tap. You can make the tap guide by drilling a close tolerance through hole in scrap material. Drive the tap by hand with a tap wrench. Once you get into the thread by 2-3 threads you won't need to tap guide and should be able to cut it straight.

I suggest using a drill 2 sizes larger than the bit normally used for that tap. The guide is not under tension so it needn't be a class 3 fit. A larger hole will tap far easier than using the drill normally called for.

I was thinking that very thing i'm convinced that this is 44 40 steel that was mismarked at the supplier. Its very hard for cold rolled and no way its 10 18.
I often use a larger bit than indicated when the job is not critical. I often bore a guid a few threads deep directly into the piece that i'm working on sacrificing a couple of threads.

 

[Xnerd]

Yes the part you made looks great. Don't be so hard on yourself.

It's hard to tell the size(length) of the new cross-slide from your pictures. I would not want a big piece swinging around in my face either unless I was sure it was solid. I usually use my own discomfort with an operation as a signal to whether I'm capable to do it or not. I tend to prove things on smaller safer set-ups first until I am comfortable with bigger set-ups.

However, user @savarin always amazes me with what he does in his lathe. See for instance:
http://www.hobby-machinist.com/threads/a-vertical-slide-for-a-9x20-lathe.49724/
http://www.hobby-machinist.com/threads/a-vertical-slide-for-a-9x20-lathe.49724/#post-426949
http://www.hobby-machinist.com/threads/80mm-long-focal-length-refractor.26212/#post-275479
http://www.hobby-machinist.com/threads/80mm-long-focal-length-refractor.26212/page-3#post-334440

You could bore it in the lathe, but think about it backwards! Put the boring tool in the spindle(chuck or collet) and mount the new cross-slide on the carriage.

If you do bore in the mill, I would actually start the tap in the mill too if you can. Unplug it, put in neutral, remove belts, whatever you need to do to turn it by hand. I agree that once started a few turn the tapping can be done in a vice.

I agree with drilling slightly larger than the recommended tap drill size, but go by measurements. The phrase "two sizes larger" is a little ambiguous unless we know exactly what drill bit set you have.

By the way, for centering parts on the lathe like the bore you mention above, it is typical to use a dial test indicator either held in the tool-post, or in a magnetic holder attached to the carriage. Measure directly in the bore. With this arrangement, you should be able to centre a part very accurately. Ideally if you can also check again some distance into the bore you can also be sure it's aligned parallel to the lathe centre line. Alternately, you could put a pin gauge in the bore and measure against that.

Have fun and play safe!
-brino

lol its funny you mention the dial indicator as my Last Word just arrived today!! Im not used to being able to do that so I never thought of it.
But yes that would be the best way for certain.