# 5C to R8 adapter



## Blogwitch (Feb 8, 2015)

This little bit of tooling is a follow on from my 5C to morse taper  adapter, which was to allow me to machine blank arbors on my mill so  that I could use them in the tailstock of my lathe, only this time it  will allow me to make my own tooling for the mill, which uses an R8  fitting, not an easy shape to hold for machining.

Unlike the MT  one I made, where I just wacked a reamer up the spout to get what I  wanted, this time it all has to be done with technique.

The first thing was to set my boring bar to the depth, plus a little, of the R8 blank.
I  have measured up the internal diameter of the 5c blank end arbor, and I  will still have plenty of meat left on the arbor once it is bored to  the size required (0.950") of the R8 fitting







What  you have to realise, the blank 5c arbor is in fact made of some sort of  higher carbon steel, so that they can harden the shank, and leave the  main top end unhardened. So this is not an easy exercise, I am boring  thru the softer end, and then taking out some of the hollow hardened  shank. It is for this reason you can never really get a superb finish on  the blank end bits, no matter what type, even though softer, the blank  ends are still some sort of tool steel, that really is designed to be  ground rather than turned.
Anyway, the job was achieved with no major  problems, except the surface finish down inside of the hardened bore  was a tad rough, and was still a little tight for getting the R8 arbor  all the way in.
I would definitely NOT try to use a HSS boring bar, the hard stuff down the bore would flatten it off in no time.







So  out came my bore hone, with just the two stones for smaller bores. I  fitted a hand vice on the end of the flexi shaft so that with the lathe  running at about 500 RPM, I could feed the hone right up and down inside  where I had bored.







After about 15 minutes, the bore was a lot smoother, and both the R8 arbors that I tried slid in nice and smooth, with no slop.







It was now time to cut the taper for the arbor to sit in.
I offset the topslide to somewhere close to the taper required and cut away about half of the required depth.
This  was then lightly smeared with engineers blue NOT marking out blue.  






The  R8 arbor was then pushed into the taper and gently rotated. This  transfers the blue onto the arbor that is touching the taper. I also  marked up with a felt tip how far in the taper had penetrated.
As shown in this pic, only the bottom part of the taper was in contact, showing that the taper sides were too steep.
For  me this is bad news, I always try to start with the taper shallower  than required, then not so much material needs to be removed to reach  the full surface covering required. When cutting tapers, it is very easy  to take too much off, that is why I like to sneak up on it from a  shallower taper.







After  removing about 1/4 of a degree on the topslide setting, I reached the  place where I wanted to start out from, a shallower taper, shown by the  blue being at the top rather than the bottom.






After  slightly slackening the topslide, and gently tapping it with a plastic  handle of a screwdriver, after two attempts, I managed to get the full  covering I wanted, even though very faint, and there was more than  enough meat left in the hole to take it out to full size.






Because I now had the angle spot on, I could just cut down the taper until the arbor sat at the correct depth.
This  pic now shows that the angle is still spot on, although slightly patchy  down the taper. That is caused by surface finish, and was soon put  right by some very fine and slow cutting at high spindle speed.






This is a shot of the back end of the 5c adapter, showing that the bore depth was good with an R8 arbor inserted.






Except for making the draw bolt and washer, as I did with the 5c to MT3 adapter, the job is completed.






All I need to do now is think up what I want to make to fit my mill. I'm sure that I will soon come up with lots.

So that's it for my interchangeable tooling.

I  hope it has given a few of you the insight into how easy it can be  done, and how helpful little bits of tooling like this can help.


John


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## RichD (Feb 9, 2015)

John,
I'm a little behind you in progress, but I've been working on similar interchangeable items between an indexing head with 1-3/8 8TPI threads and my 39mm by 4mm lathe spindle.

I've enjoyed the show and appreciate the shared techniques.

I do have a home made taper attachment that allows for power feeding. That simplifies the machining a little for me.

About a month ago I turned up several MT2 and 3 blank arbors and set them aside for future use. During the process my recently acquired Grandson-in-law came over to try his hand at the lathe. Since I was already set up to turn tapers I had him make up one after a brief lesson on the controls and micrometers and such.

He had a ball and we used the smeared on blue as you did to get a perfect fit. He was so happy and proud.

About then my Granddaughter came in and scolded him that they had to get going for dinner. As he was a newly-wed, I told him he better get going and that I wouldn't touch a thing until he returned to finish.

I'll take that as a good sign...

Rich


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## Blogwitch (Feb 9, 2015)

Rich,
I did all these posts about 3 years ago, but put them up again because the original posts had lost their pics.
I am sure, that once you do get your interchangeable stuff completed, you won't regret it. As I said, these are from a while ago, but I still marvel at how easy it is to do certain jobs now that I don't have to set up every time the piece part is moved.
This one was done because R8, and the matching MT3 arbors can be difficult to hold in a vice without damage. Now I can just throw in a blank arbor and make as many special tools that I want.
It all helps to make model engineering more enjoyable.
Of course, there will be many people on here that will never want to do or need to do what I am doing, but if they just read a few of my posts, there are many easy techniques shown that will come in handy for the future when doing other jobs.
Glad your grand son-in-law is taking an interest, I tried with my grandson, but he just didn't get into it, he is more into electrical and electronics, which is what his apprenticeship is all about.

John


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## Mike N (Jan 10, 2022)

I did a search & found this post today.  
I would like to make a 5C to R8 adapter,  like the one you show here.  I just bought a Hardinge Horizontal Milling Machine. It has a 5C spindle, I want to be able to use my R8 shell cutter arbors that are already setup to use in my Bridgeport Milling Machine. I found this drawing to make the R8 ID inside of the 5C blank.


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## Richard Hed (Jan 11, 2022)

Mike N said:


> I did a search & found this post today.
> I would like to make a 5C to R8 adapter,  like the one you show here.  I just bought a Hardinge Horizontal Milling Machine. It has a 5C spindle, I want to be able to use my R8 shell cutter arbors that are already setup to use in my Bridgeport Milling Machine. I found this drawing to make the R8 ID inside of the 5C blank.


I don't believe this is a 5C to R8 adapter.  It looks like an R8 made to place in a lathe tool holder.


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## Jasonb (Jan 11, 2022)

It says he used that drawing to get the dimensions for the internal 5C socket

_"I found this drawing to make the R8 ID inside of the 5C blank._ "


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## Mike N (Jan 11, 2022)

Richard Hed said:


> I don't believe this is a 5C to R8 adapter.  It looks like an R8 made to place in a lathe tool holder.


It is a Lathe R8 collet tool holder!  I just used this to show the dimensions of the R8 features that are going to be machined in the 5C blank arbor.  Bought it on eBay for $27.


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## Mike N (Jan 11, 2022)

This is my progress so far.  I'm going add a key so the R8 won't  spin.  Thanks to Blogwitch for getting me started on this.  It should work great on my Hardinge Milling Machine.


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## Scott_M (Jan 11, 2022)

Hi Mike
Did you need it to be an extension too ?
If not, it might be better to saw off most of the blank end and sink the R8 as deep into the 5C as possible. The less stick out the better. Look how far John has his in. Looks to be only about 3/4-1" of the large diameter left.

Otherwise Looks good !

Scott


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## Mike N (Jan 11, 2022)

Scott_M said:


> Hi Mike
> Did you need it to be an extension too ?
> If not, it might be better to saw off most of the blank end and sink the R8 as deep into the 5C as possible. The less stick out the better. Look how far John has his in. Looks to be only about 3/4-1" of the large diameter left.
> 
> ...


Yes, I wanted the extension also.  I think it could have been a little shorter though.  It seems pretty solid  in my lathe.  I will need to give it a try.  I can fix this one if needed or just start over with a shorter blank.


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## Scott_M (Jan 11, 2022)

Cool !
If you need it, you got it. 

Scott


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## Iampappabear (Jan 11, 2022)

Would love one of those, are you taking orders? 

Colin


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## Mike N (Jan 22, 2022)

Mike N said:


> Yes, I wanted the extension also.  I think it could have been a little shorter though.  It seems pretty solid  in my lathe.  I will need to give it a try.  I can fix this one if needed or just start over with a shorter blank.


I decided to make a new shorter one.  The R8 collet is just short enough to work without sticking out the back end of the 5C blank.


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## Scott_M (Jan 22, 2022)

Nice ! That should prove to be a useful adapter.

Scott


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