# Home made expanding mandrels?



## Aaron_W (Dec 14, 2017)

One of my main interests in getting a lathe was for making small scale model truck wheels. Looking around and seeing how rings are made, I'm thinking a small expanding mandrel would be very useful. These seem to have a very limited range for holding, but also seem fairly easy to DIY allowing for the exact size I need for a project. I've found a few tutorials for making these, but none seem to give a recommended size for the expansion slits. I'm probably looking at a couple mandrels to cover 5/8"-1" in diameter.

For the price of a set of expanding mandrels I could get myself a slitting saw arbor and a couple sizes of saw. I know I want a 0.01" for another project, but not sure how large I should get for making a mandrel. Sherline carries the 2" saws for their arbor in thicknesses of 0.01" to 0.057" 

Maybe I'm over thinking this, the slots allow the "fingers" to separate so does the slot thickness even matter?

Assume I should do these from an easily worked steel rather than aluminum, any recommendations for material?

Thanks


----------



## Suzuki4evr (Dec 14, 2017)

Hallo Arron.

I did a thread on expansion collets I made and they work very well. I got the idea from the guys of this forum so you can check that out. In my experience,the size of the slit does not matter at all,I would say that the thinner the better 0.7mm or so is fine. Aluminium is good for this application and would machine and cut easily, but 12L14 or EN1A(1112) would work well. I made mine out of EN1A. The main thing is to expand the arbor a bit and machine the outside diameter to the final internal size of your ring or bush so that when you clamp your workpiece it will clamp evenly. Hope this helps.

Michael


----------



## blaser.306 (Dec 14, 2017)

There was just a You tube video done on expanding internal and external arbors, Joe Piesinsky ( SP ) Advanced Innovations is who posted it. Worth taking a look.


----------



## Suzuki4evr (Dec 14, 2017)

There is a good video posted in the Tool junkie section under bushing internal clamping tool, that I posted and,I can't remember who,posted that video and it helped me alot.
Good luck.


----------



## David S (Dec 14, 2017)

Yes I think that Joe's video is a very good one.  He shows how to make them without the conventional slitting, by using O-rings instead.






David


----------



## Suzuki4evr (Dec 14, 2017)

David S said:


> Yes I think that Joe's video is a very good one.  He shows how to make them without the conventional slitting, by using O-rings instead.
> 
> 
> 
> ...


Yes I think that is the one. Very informative.


----------



## Robert LaLonde (Dec 14, 2017)

I was just going to suggest Joe Pi's videos.  I've made a couple.  Its pretty simple.  The real trick for good mandrels I thought was to expand them amd then machine them back to size so they are a more uniform fit with more uniform clamping pressure.  That is something I would not have thought of.


----------



## chips&more (Dec 14, 2017)

I for one can be extremely fussy about wheels, handles and such that wobble when rotated…extremely fussy! And to make a wheel, handle and such to turn true when mounted on its end result is NOT an easy task! Using an expanding mandrel is one way but maybe not the best in all applications. You want to duplicate the mounting exactly from machine making (ie: lathe) to final use…Dave


----------



## westsailpat (Dec 14, 2017)

One thing you might want to consider is the screw . Many life times ago I was told that using a flat head screw was not the best choice . I was instructed to make a screw that had more of a Morse taper on it  and I was given some matching C'sinks to use for the mandrel . I was working in a shop that was building a 35mm motion camera , we were making lots of egg shell thin round parts . Anyhow I made up a few screws that had different lengths and diameters to work in mandrels of various shapes and diameters .


----------



## Suzuki4evr (Dec 14, 2017)

westsailpat said:


> One thing you might want to consider is the screw . Many life times ago I was told that using a flat head screw was not the best choice . I was instructed to make a screw that had more of a Morse taper on it  and I given some matching C'sinks to use . I was working in a shop that was building a 35mm motion camera , we were making lots of egg shell thin round parts . Anyhow I made up a few screws that had different lengths and diameters to work in mandrels of various shapes and diameters .



I used M10 countersink hex screws. Screw lengtes was in accordance to the collet lengths.


----------



## Jimsehr (Dec 14, 2017)

Aaron_W said:


> One of my main interests in getting a lathe was for making small scale model truck wheels. Looking around and seeing how rings are made, I'm thinking a small expanding mandrel would be very useful. These seem to have a very limited range for holding, but also seem fairly easy to DIY allowing for the exact size I need for a project. I've found a few tutorials for making these, but none seem to give a recommended size for the expansion slits. I'm probably looking at a couple mandrels to cover 5/8"-1" in diameter.
> 
> For the price of a set of expanding mandrels I could get myself a slitting saw arbor and a couple sizes of saw. I know I want a 0.01" for another project, but not sure how large I should get for making a mandrel. Sherline carries the 2" saws for their arbor in thicknesses of 0.01" to 0.057"
> 
> ...


I did a thread a few weeks ago called   home made ID expanding collets   it has lots of info about what you are trying to do. I don't know if you have ever tried a slitting saw but I can tell you it is not easy. I have been making expanding collets for over 50 years and unless I am making a bunch of them (20 or more) I buy store bought ones from ebay. I now have a bunch of Rovi brand collets  in my collet collection. Also have other brands but I seem to use my own or Rovi brand most of the time. Rovi makes them from very small (around 5/15 dia to 6 in dia in a 5c holder) and they have some videos on you tube showing how to set them up. I also make my own expansion bolts out of shcs. I use leadloy for my homemade ones. And slit them on my band saw. You can turn them smaller and smaller for the size you need.

Pic of some of my Rovi ID collets  

https://photos.app.goo.gl/rOj3NP2KIKOMLStA3


----------



## woodchucker (Dec 14, 2017)

Aaron_W said:


> One of my main interests in getting a lathe was for making small scale model truck wheels. Looking around and seeing how rings are made, I'm thinking a small expanding mandrel would be very useful. These seem to have a very limited range for holding, but also seem fairly easy to DIY allowing for the exact size I need for a project. I've found a few tutorials for making these, but none seem to give a recommended size for the expansion slits. I'm probably looking at a couple mandrels to cover 5/8"-1" in diameter.
> 
> For the price of a set of expanding mandrels I could get myself a slitting saw arbor and a couple sizes of saw. I know I want a 0.01" for another project, but not sure how large I should get for making a mandrel. Sherline carries the 2" saws for their arbor in thicknesses of 0.01" to 0.057"
> 
> ...


I have made mine from Aluminum. I would not buy one, considering they are easy to make.  My only mistake on the first I made was to have the mandrel and screw have the same angle and found this too hard to expand w/o a lot of effort. After that I started making the taper on the srew only and left a slight chamfer on the screw hole. Cut the slits with either a hack saw or slitting saw, and go farther than you think. It makes it easier to expand.  So if you have a sleeve to mount on the expanding arbor go farther than the sleeve's endpoint.  No rule on distance, but farther.


----------



## petertha (Dec 14, 2017)

From my limited experience the tightening force isn't so much a function of the screw head/countersink angle, you can put substantial pressure on that. I found it has a lot to do with the relief cut that allows the segments to expand & length of slits. The Joe.P video shows that detail, how he removed substantial material which I had to figure out by trial & error. He also has makes 3 slits = 6 segments versos 2x90-deg slits = 4 segments which means there is less material at the root of those segments which means less pressure required to deflect them. BTW I id my slitting by putting the part in one of those hex collet blocks & running along the fence of the band saw.

My expanding ID holder 'works' but I find it works best when the OD/ID is very closely matched. If its too many thou different then grip pressure is a narrower band on the tailstock side of part. So its not quite as good for parts with rougher bores or varying ID.

This type of system to my simple mind is more of a unifom increasing diameter. Its more like an ER & similar collet where the slits alternate from one end to another, whereas the above systems originates from a single end so can only expand on that end. But these expansion mandrels are more spendy, more limited range & a bit more fuss to set up many parts. I guess each tool serves its own purpose.
http://www.arceurotrade.co.uk/Catalogue/Expanding-Mandrels


----------



## Aaron_W (Dec 14, 2017)

This is the best video I had found.







I like the method used in the Joe Pi video posted above, I had not seen that one. He also offers a few variations I had not seen.

Glad to hear aluminum is acceptable material, I've made a few parts from aluminum, but haven't cut any steel so far.


This seems like a relatively easy project, it justifies buying another tool, allows me to make a tool exactly size to my needs and will provide me some practice turning cutting and threading. 



chips&more said:


> I for one can be extremely fussy about wheels, handles and such that wobble when rotated…extremely fussy! And to make a wheel, handle and such to turn true when mounted on its end result is NOT an easy task! Using an expanding mandrel is one way but maybe not the best in all applications. You want to duplicate the mounting exactly from machine making (ie: lathe) to final use…Dave



The wheels are for static models so they just need to look good, they won't be rolling and often are fixed in place during construction. Rolling wheels on a static display model is kind of like parking your car in neutral and not setting the brake.  




westsailpat said:


> One thing you might want to consider is the screw . Many life times ago I was told that using a flat head screw was not the best choice . I was instructed to make a screw that had more of a Morse taper on it  and I given some matching C'sinks to use . I was working in a shop that was building a 35mm motion camera , we were making lots of egg shell thin round parts . Anyhow I made up a few screws that had different lengths and diameters to work in mandrels of various shapes and diameters .



The video I was basing my ideas around, made a plug that the screw goes through so he could set his own pitch. It makes sense to me that a steeper angle would put more force outward with less effort. I saw another video that went with 60 degrees, just following the bevel made by a center drill which seems easy enough. 




woodchucker said:


> I have made mine from Aluminum. I would not buy one, considering they are easy to make.  My only mistake on the first I made was to have the mandrel and screw have the same angle and found this too hard to expand w/o a lot of effort. After that I started making the taper on the srew only and left a slight chamfer on the screw hole. Cut the slits with either a hack saw or slitting saw, and go farther than you think. It makes it easier to expand.  So if you have a sleeve to mount on the expanding arbor go farther than the sleeve's endpoint.  No rule on distance, but farther.



Again this makes sense to me and makes fabrication easier. The video I posted made a point of matching the angle exactly, but as long as both are perfectly round, I don't see that different angles would make a difference. Many expanding screws are just a cone inside a slotted tube and those seem to work well.


----------



## Aaron_W (Dec 14, 2017)

Suzuki4evr said:


> Hallo Arron.
> 
> I did a thread on expansion collets I made and they work very well. I got the idea from the guys of this forum so you can check that out. In my experience,the size of the slit does not matter at all,I would say that the thinner the better 0.7mm or so is fine. Aluminium is good for this application and would machine and cut easily, but 12L14 or EN1A(1112) would work well. I made mine out of EN1A. *The main thing is to expand the arbor a bit and machine the outside diameter to the final internal size of your ring or bush so that when you clamp your workpiece it will clamp evenly. *Hope this helps.
> 
> Michael



He mentioned this in the video as well but didn't show it. Is this to account for the potential of uneven expansion?

I expected that the slots would be the last step, wouldn't turning the part after the slots are cut cause a lot of chatter as the tool crosses between metal and open space?


----------



## cathead (Dec 15, 2017)

A couple years ago, I made a tapered mandrel that went from slightly over an inch to slightly under an inch using
a taper attachment.  Gear blanks with a one inch diameter hole can be press fitted on the taper quite easily.  I have made many a gear
using this method and found it quite effective.  The taper went from .998 inch to slightly over an inch over 15 inches or so.       
When forming gear teeth, I would run the involute cutter toward the wider end to be sure the gear blank would not work loose.


----------



## petertha (Dec 15, 2017)

markba633csi said:


> I expected that the slots would be the last step, wouldn't turning the part after the slots are cut cause a lot of chatter as the tool crosses between metal and open space?



Probably multiple ways to skin the cat, but in my particular case I left .010" to finish the OD with the slots cut & end screw slightly tightened. That way the diameter is perfectly concentric. If you finish it to size, then slot, then return to chuck & your chuck/part body is out .002", that run-out is reflected on your part. yes Yes the cut was a bit interrupted by the slits but it was just aluminum & didn't seem that bad for the intended purpose. Nothing stopping you from finishing with abrasive stick or light file. The commercial brass body ones work the same way.


----------



## Aaron_W (Dec 15, 2017)

petertha said:


> Probably multiple ways to skin the cat, but in my particular case I left .010" to finish the OD with the slots cut & end screw slightly tightened. That way the diameter is perfectly concentric. If you finish it to size, then slot, then return to chuck & your chuck/part body is out .002", that run-out is reflected on your part. yes Yes the cut was a bit interrupted by the slits but it was just aluminum & didn't seem that bad for the intended purpose. Nothing stopping you from finishing with abrasive stick or light file. The commercial brass body ones work the same way.



It sounds like the final finishing you are talking about is a disposable mandrel to ensure everything is aligned, chuck, the expansion screw didn't move anything etc? 

The added accuracy of this final finishing would be lost the first time it was removed / replaced into the chuck / collet correct? 

Just trying to understand if there is a benefit to this last step if I'm intending to use the mandrel multiple times.


----------



## petertha (Dec 15, 2017)

That's true, but it doesn't make it disposable. In either case when you remove & re-install an expanding arbor you might be faced with runout as a function of your tooling. How you deal with that (or don't) depends on the target accuracy at stake. A 4-jaw independent chuck could dial it in for sure. Other options might be collet based. There are ready to size expanding arbors with integral 5C body. Or alternatively if you had a nice accurate shank on your homemade tool & trusted your collet chuck more than typical 3 jaw, that would reduce runout with repeated in/out re-installation. The choice is really yours suited to the application & tooling you have.


----------



## Aaron_W (Dec 16, 2017)

Ok, makes sense. If I need to eliminate any run out caused by the insertion into the chuck / collet, I need to turn it each time and remove a small quantity of material to true it up. If the run out is within the acceptable tolerance I can just set it up and go without that step.

Thanks


----------



## petertha (Dec 17, 2017)

Ebay store with USA made 5C expanding arbors for purchase or ideas. I've used this & its quite repeatable in a good collet chuck.
https://www.ebay.com/itm/5C-Expandi...275647?hash=item25e71dbc7f:g:skwAAOSwYc5Z9ABs

Off topic but the collet stop is dang handy item.


----------



## 4GSR (Dec 24, 2017)

Here's a picture of one I made many moons ago for holding a 1/2" ID part.  It uses a tapered pin as the expander to hold the part while machining on it.  Didn't have slitting saw capability at the time.  Had to use a hack saw to cut the slots.  Worked like a charm!


----------



## Chipper5783 (Dec 24, 2017)

Another option, depending on how many pieces you are making - consider a heat shrink mandrel.  This is very simple to make and the accuracy matches the capability of the machine.  The main challenge is you need to be able to machine ID / OD to within a few tenths.  Once you sort that out, and it is not a big deal - then you are set.

Generally you would want to select a material for the mandrel that has a significantly different coefficient of thermal expansion than what your work piece has, whether the mandrel is OD gripping or ID gripping and what your heating / cooling options are.

Just the other day I needed a couple plastic 3" diameter rings.  I was using that regular white 3" drain pipe - with a finished wall thickness of 1/16".  I didn't need to take very much out of the bore - obviously the difficulty was how to hold it without distorting the ring.  I simply skimmed a piece of scrap metal for a 1/2" long fit, leaving a land for the back face to butt up to.  I simply warmed the plastic with a hot air gun, tapped it onto the mandrel and trued the outer end with a roller bearing tool.  I took my time boring the sleeve, just 0.015" passes to open out the 1" long sleeve.  To remove the 1/2" long scrap piece I just machined it away at 0.002" over the size of the mandrel, then the little skim peeled off easy.

Another option is to make a slip fit mandrel, then Loctite the wheel into place.  Then use a hot air gun to release the Loctite.

The trick is to sort out the machining steps so that you don't need to remove the "mandrel" until you are finished using it.

Usually this will not be a strong work holding method, but for finish work on delicate parts it can be a very useful technique.


----------

