# Lathe Chuck Backstop



## Blogwitch (Jul 6, 2012)

It is a fair while since this topic has been aired, so for all you new people or beginners, here is a reminder how to do it, one of my older posts from elsewhere.

How many times have you had to make a load of bits on the lathe all to the same length?

PITA isn't it?

What you need is to be able to push the job back into the chuck until it comes to a dead stop, then once tightened, you can use one setting to cut the face, and every one after that will be the same length, within a thou or so.

So this is how I went about making my chuck backstop.

This is about one of the cheapest but best bits of kit you can make for your lathe, and if used correctly can save you hours of machining time, and reduce recycling to zero.


First off, I got a soft end blank morse taper to fit my machine, theses are only a few squid each and I usually have a couple in stock of the two sizes my lathe uses, just in case a job like this comes along. If you want to go the cheapskate and difficult way, and make your own, that is up to you. To me, for the cost of them, they are just not worth making.
The normal sizes used for lathe spindles nowadays is either 2 or 3 morse taper.

A UK example of the type.

http://www.arceurotrade.co.uk/Catalogue/Blank-End-Arbors







If you want to make them yourself, then old large drills with a MT fitting can be utilised very well. The fitting is usually fairly soft anyway, just cut the drill part off. You are not worried about having a hardened MT fitting, or being very accurate, as it isn't doing any driving, just make sure it is cleaned up to a smooth finish. 
Heating to red hot, hold it there for a minute or so, and then letting it cool down slowly should soften it down a lot, allowing you to drill and tap to a good depth.

The soft end needs to be reduced so that it will fit thru the smallest centre of your chuck range into the spindle without having to remove the chuck. The easy way is just to reduce it down to where it meets the taper.

This is a shot of the back end of a 5C collet and a blank arbor.







With the chuck off the machine, mount it into the spindle nose.







Turn down the soft end until it is the same size as the largest part of the taper. As you can see, it will now easily go into the smallest part of my chuck, the centre hole in a 5C collet.







Drill down the centre as far as you can go with a tapping drill of your choice. I am using an 8mm thread, for a 2MT I would suggest 6mm or 1/4" thread.
You will most probably find you can only drill down the length of the softened end, which will give you about 3/4" adjustment on the stop length.








Then tap down as far as you can go.







I used an 8mm coach bolt, but you could use almost anything, even threaded rod if you have it. Screw it as far in as it will go, and tighten up the locknut.







I have removed the chuck jaws to show you what is going on.
All power off the machine, stick a rag into the spindle end and push it all the way thru the spindle with a stick. You do this every time you fit anything into the morse taper in the nose, just to get rid of debris in there that will stop the MT seating properly.
Feed the backstop thru the chuck and get it seated in the spindle.







This is bit of a hoptical dillusion. You need to mark up the screw length just before it would hit the back of the jaws. So if the jaws are tightened up, they won't touch the backstop screw.







Cut the screw to marked length, and face it off.







This shows how the screw fits, it isn't screwed all the way in just so I could get this angled shot. Normally you would take the stop out when not in use, and when you fit it, you adjust it to length to push your part back to, ensuring the locknut has been tightened before mounting it into the spindle..







As mine is, it can only be used with parts that are larger than 8mm and longer than about 25mm (1"), that is because it isn't completely finished.
I will put say a 4mm (5/32") thread in the very end of the 8mm adjusting screw, and make up little adapter noses for smaller material sizes. Just as I have done for the 5C collet backstop in the top of the picture. You soon end up with all sorts of ends that you keep in a little box for almost any occasion.
The bolt at the bottom could be faced off and used for a backstop for material having a hole thru it, say a bored cylinder. You just have to use your imagination a bit.






I will just explain one thing about the commercial stops that fit into the back of 5C collets.

I use a commercial screw in backstop in my 5C collets all the time, because they are so convenient, but they are not super accurate, because the position can be altered by how much you tighten up the collet into the chuck, the tighter you go, the further back the collet sits, and so does the stop in relation to your cutting tool.

This type is spot on, because once it is locked into the spindle, it is going nowhere, and once your saddle is locked, you can just face up to the same length time and again.

If you don't understand anything, just ask.

I can't give any machine specific answers, because unless it is the same as mine, I just won't know. But ask away anyway, because someone on here will know what you are talking about.


John


----------



## mzetati (Jul 6, 2012)

I made mine so I could fit and adjust it from the gears end of the spindle.
There's a potential danger in it, if used with the threaded bar protruding more than a small amount from the headstock 
(and that knurled <<so handy, when adjusting the lenght>> knob adds to the risk).
Replacing the threaded bar with a shorter one at need would only take seconds, and they would be spent well.
Here, it is shown with a brass extension made to fit into a 3mm ER32 collet.






Marcello


----------



## Blogwitch (Jul 6, 2012)

Very nice indeed Marcello. 

Anyone else got pictures of how they achieve the same result?

That way, people can choose whichever way they want to go.


John


----------



## mzetati (Jul 6, 2012)

Thank You John,

had to choose that way because my spindle has a MT3 taper, while the chuck bore is somewhere in the 20 / 25mm range.
Either that or I had to dismount the chuck anytime I needed to use/adjust the backstop.

Marcello


----------



## Bluechip (Jul 6, 2012)

Some pics of mine. Fitted to Myford S7

There is a 3/8" tapped hole in the business end to take an extension, as that is only long enough to give some 4 1/2" to the chuck jaw ends.

Brutish but functional, a bit like me.  ..... 'Cept I'm only half way there ...

Dave BC

BTW the gears aren't really chewed up, Moly grease on them ...


----------



## romartin (Jul 7, 2012)

Thank you John for this stimulus; I frequently have the problem but hadn't thought of making a tool. Now I will - after the current heat wave has passed and after I've finished the QCTP I've planned.
I'm in the same situation as Marcello: chuck bore too small to pass an MT3 jig. So I will make one which is inserted from the gear train end of the spindle, following the examples of Marcello and Dave BC. After which I hope to get back to steam engines....


----------



## DICKEYBIRD (Jul 7, 2012)

Just finished one for my Compact 8 clone. The 9x20 chinese lathe design is a direct copy of the C8 so this method should work for them as well.

There's 7 or 8 extra threads on the end of the spindle so I bought an extra preload adjusting collar nut for a 9x20 from Grizzly that fits my spindle for cheap. I mounted a chunk of 2024 alum onto it and drilled/reamed it to fit a length of 3/8" drill rod and added a setscrew with a bit of brass at the end to prevent damaging the rod.











I wanted the hole to be concentric with the spindle center so I made up a drill extension by heat shrinking a piece of 1/2" shaft on the drill. I put a piece of 1/2" ID brass tubing in an ER32 collet, slid the drill shaft through it and drilled the hole, holding the end of the drill in the tailstock. I added a delrin bushing near the drill-end sized for a sliding fit in the spindle to keep the drill from wandering.

It works great and allows fairly long work to be repeatably positioned when needed.





















Only snag I had was the face of cheapy spindle collar wasn't even near to being square to the threaded center hole. Had to do some extra work to get it square and now the stop shaft runs right down the middle of the spindle.


----------



## modeng2000 (Jul 11, 2012)

Here is a picture of my version of a chuck backstop for my Warco WM180, similar to the one posted by Marcello.






The studding is M6 and the thread for tightening the two parts of the spindle clamp is M10, diameter of the split clamp is 21mm. The left knurled knob is for positioning the end of the stop and the next knob is to lock it in position. The 3rd knob tightens the spindle clamp by pulling the two halves together giving a friction fit in the spindle bore.

I'm not sure what end fittings I'll need so I've just left it with a threaded hex spacer. I can make up what is necessary at the time of use.

Hope this is useful.

John


----------



## mzetati (Jul 11, 2012)

I like those knurled knobs!

No more hunting for the correct wrench to break the tightening bolt due to overtorquing. 
Mine has the same dimensions as Yours: M10 bolt to tighten the spindle clamp, and I'm using the 'spare' M6 nut and washer to lock the stop.

Marcello


----------



## chucketn (Jul 11, 2012)

I am lucky enough to have a couple of MT3 tools to make the backstop from, and am capable of turning a MT3 taper if I had to, and had the stock to work from. But, I had a brain cramp and thought "Where would I get a MT3 blank arbor that Bogs described. Found this source:

http://www.victornet.com/cgi-bin/victor/productlist.html?subdepartments=Blank+Morse+Taper+arbors:275

Chuck


----------



## DICKEYBIRD (Jul 11, 2012)

Just curious...do you guys with the MT3 arbors have much trouble getting them back out of the spindle?

The few times I've used the MT3 dead center in my lathe I had to whack hard it enough to get it out I was worried about dinging the spindle bearings.


----------



## Blogwitch (Jul 12, 2012)

DB,

Mine is actually 5MT, and I have a length of hex brass bar the just fits down the spindle sitting at the back of the lathe.

All I do is put the bar down the spindle and throw it down the tube, when the bar hits the MT that is in the spindle, it sort of reactions against it and the MT then just falls out of the end, then push the bar back and store it until it is needed again. That is after I have even used a draw bar to hold the MT fitting in the spindle.

No problems getting it out at all, usually a few seconds.


John


----------



## ShopShoe (Jul 12, 2012)

Dickeybird,

What Bogs just said. I have a Mini-Lathe with MT3 in the headstock and I use the same procedure Bogs does and the MT3 comes out easily.

The other thing I will mention is that I clean everything very well before putting the tapered attachment into the headstock and usually this is only an occasional thing I do and it usually is taken apart again as soon as I am done with the required use of the lathe. Usually the 3-jaw stays on the lathe unless I need the taper or one of my other chucks.

--ShopShoe


----------



## DICKEYBIRD (Jul 12, 2012)

OK thanks I'll try the brass drift routine next time. 

I must have a spindle/center taper fit in my lathe that is the same combination of angles the Triumph Spitfires I used to work on had in their rear axle flanges. I swear you could put them together, torque down the big nyloc nut, take the nut off & throw in your toolbox and drive to California & back & never lose the flange! ;D (That's assuming of course something else didn't fall off on the way!) :big:


----------



## chucketn (Jul 12, 2012)

2 each MT3 tools gave their all this afternoon to make the "Bogs Chuck backstop". 

I cut the tapers off a MT3 "Bridge reamer" and a Drill bit. I turned the business end of one to fit through my 4" 4 jaw chuck, and the other to fit the smallest chuck, which is the original 3" 3jaw that came with my Micromark 7 x 14. I drilled and tapped the chuck end of both for a 1/4" x 20 thread. I'm thinking about threading the outer dia. of the chuck end to accept other accessories, but don't yet know what they would be. I like tooling that has multiple applications. Any suggestions?

Thanks to John Bogstandard for suggesting and demonstrating another great tool!

Chuck


----------



## Blogwitch (Jul 13, 2012)

Chuck,

It wasn't just my post that made things interesting in this topic.

You only have to look at all the other peoples solutions to find one that will give you exactly what is needed.

I'm glad yours worked out OK.

John


----------



## V 45 (Jul 18, 2012)

chucketn said:


> 2 each MT3 tools gave their all this afternoon to make the "Bogs Chuck backstop".
> 
> I cut the tapers off a MT3 "Bridge reamer" and a Drill bit. I turned the business end of one to fit through my 4" 4 jaw chuck, and the other to fit the smallest chuck, which is the original 3" 3jaw that came with my Micromark 7 x 14. I drilled and tapped the chuck end of both for a 1/4" x 20 thread. I'm thinking about threading the outer dia. of the chuck end to accept other accessories, but don't yet know what they would be. I like tooling that has multiple applications. Any suggestions?
> 
> ...


 
Hi Chuck...would you post pics of your stop? I have the 7x16 Micro Mark.
Thanx...V 45


----------



## chucketn (Jul 19, 2012)

Here you go.

Shows stops, the tools that I cut off the tapers, and the piece of broomstick I use to remove them from the spindle.

http://s571.photobucket.com/albums/...Chuck Stops/?action=view&current=DSCF1244.jpg

Chuck


----------



## deverett (Jul 19, 2012)

A very simple backstop was detailed in the Myford ML7 Lathe Manual.  Basically it was a piece of bar that was a close fit in the bore of the chuck that rested against the front of the lathe spindle.  There is a screwed bar for length adjustment and different size backing pads can be put on the end.






Shows my version that has served me well for many years.  Pads are made up as required to sit on the left hand side.  I keep meaning to drill a hole for a small diameter rod on the right hand side, but have never got round to it.  the right hand smaller end is 3/8" in my version.

It does have a possible disadvantage an that is if the bore of your chucks are different, you will need one of these for each chuck, but in practice, I have not found them necessary.

Dave
The Emerald Isle


----------

