# Turning a 5MT to 5C Adapter Questions



## Luminast (Jan 19, 2015)

Greetings All,

Enthusiastic beginner here.

I recently acquired a nice set of 5C collets.  I also have an old 5C draw bar that I acquired cheap.  (It will need to be extended to fit my headstock.)   

I don't have a collet chuck.  I have more time than money and would like to try turning my own adapter to fit the 5MT headstock from a non-hardened 5MT to 3MT adapter that I already have.  I'm a real rooky when it comes to boring.  Can anyone take time to review the sequential steps in the process?

I have a bunch of questions in mind.  Should I drill then bore, or start right out boring?  How close should the fit be to the straight portion of the collet?  Should I polish the straight section of the bore?  How best to assure that the taper section is a properly fit?  Should I polish the taper section?  When I shorten the 5MT adapter enough to expose the outside threads of the collet, will the adapter still be long enough to properly center in the spindle?  Sorry for the silly questions, but I've never even SEEN a 5C collet holder, except in pictures.

I read that you can buy these adapters from Grizzly, but I'd rather try making my own superior version.


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## Luminast (Jan 23, 2015)

No responses at all?? 

 Any encouragement, cautions, or hints to "set me right" on my idea would be appreciated


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## Bill Gruby (Jan 23, 2015)

Start with the Dimensions here and ask your questions again. Your first one was easy, you always drill first ans bore second. My question, "Are you trying to change the Spindle Taper?"

 "Billy G" 

http://www.loganact.com/tips/collet.htm


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## Vladymere (Jan 24, 2015)

Luminast,

What brand and model of lathe are you working with?  What is the headstock through hole diameter?  Is the collet drawbar long enough for your lathe headstock?

I would like to do the same but have determined that my headstock through hole would not leave enough "meat" in the collet adapter to work well.

Vlad


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## ozzie (Jan 24, 2015)

Luminast said:


> Greetings All,
> 
> Enthusiastic beginner here.
> 
> ...



My 1st reply ever! Newbie
It's a bit tricky knowing what you are trying to ask.
 When you shorten the tail end of the 5MT adaptor it needs to still have enough length to engage the spindle taper of at least one diameter , preferably 2 diameters of length, maybe 3" long?
 I would bore the plain diameter 1st & polish it if reqd to get no more than a thou clearance on the 5C tail diam.
To get the taper angle on your compound rest correct, I would fit one of your 5C collets in the 3jaw chuck or 4jaw, Fit a dowel in the collet mouth  and a hose clamp to hold its sprung open shape  onto  the dowel, then clock up the taper angle. To get good tapers you need absolute minimal slop on the compound rest feather gibs so the boring bar doesnt waggle around while you hand feed. You could hone stone & polish the taper but it may work OK as machined.
I hope this helps???


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## JimDawson (Jan 24, 2015)

A 5MT to 3MT adapter is a good place to start.  Half the work is already done.  

First set your compound angle, and leave it there through the entire operation.  To set your compound to the taper angle, chuck up a 5C collet and dial it in.  Then put the indicator on the tapered portion and run the compound in and out as you adjust the angle to get a 0 reading.  Ideally the taper portion of the holder should be ground, but a nice smooth turned finish should work fine.

 Put a witness mark on your spindle and the collet holder in this operation so you can always put the holder back into the spindle in the same orientation.

Since you already have a pretty big hole through the adapter I would just start boring unless you have a drill bit just under the OD of the 5C collet.

Make sure your spindle bore will accept the collet drawbar.  Once bored, I might hone the straight part of the bore just to take off the high spots.  The fit needs to be pretty good on the collet body, I'm guessing 1.250 to 1.2505 would be good.  Bore both the straight section and the taper in the same setup so you make sure they're concentric.

Once you have the straight portion of the bore completed, then you can start turning the taper.  Once you have it well underway, you can test the fit by inserting a collet to see how deep to go.  Ideally you wind up with the collet clamped on the part and the outside edge is flush with the face of the holder.  If you go a little deep, you can always face the holder a bit to compensate.

I'm pretty sure the adapter will center just fine after shortening.


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## Luminast (Jan 26, 2015)

Thanks very much for all of the replies. 

Jim, I really appreciate the advice of how to set the compound angle.  That makes good sense and I wouldn't have thought of that method in a hundred years.   I appreciate your other tips as well, and I will act on all of them.  It's good to know that I can just start boring the 5MT to 3MT adapter, because my largest drill bit isn't nearly large enough.  Glad to hear that I don't need to buy one.

For the other questions, my headstock is 5MT taper, and I don't intend to touch that.
The lathe is a Webb-Whacheon WL-435 17"x40".  The spindle through-hole is 2-inches diameter.  
The old draw bar assembly that I have is not long quite enough, but I think fabricating an extension is no problem.

Thanks again.   I feel like I can approach the project with more confidence now that y'all have given me some good tips.  I think this is a good project for me to get some valuable experience while making something useful.  About the most I can screw up is a $20 5MT adapter and perhaps a cutting bit or two.


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