Shortening screws

Steve, that looks like a very useful lathe accessory - at least for the things that I do. One thing does puzzle me, it appears from the photos that the individual collets are not threaded, I would have thought that if they were it would give you more control over where the screw sits in the chuck, or am I seeing a problem that isn't really there?

Phil

Hi Philip, I did consider threading the collets and I would have made one if I needed lots of different lengths of screws.

However I needed a couple of dozen of the same length (3.5mm + 4.5mm) so I made collets to suit. I opened the holes with watchmakers broaches so it's a nice snug fit.

The holes in the front plate are witness holes. The plate is made from 1/32 ground flat stock with the centre hole bored (4mm) with the whole thing assembled to ensure it's true. I then hardened and tempered it and the holes make sure it goes back on the same.

The body was made fro an old M4 thumbscrew drilled and M6 tapped and the shaft is a sawn off M6 bolt.

It is a treat to use in the watchmakers lathe. It takes no time to saw to length then round and polish screw ends pre-blueing.

I'll make more collets as I need them - again take minutes to make with a hand graver.

Steve

Use nut plate as described by mechman48 then cut off extended thread section with a cold chisel done properly the nut plate will clear up any slight burr.

Neil

I made a Lantern Chuck, but made the error of making collets with clearance holes. Result? The screws wobbled, and parting off was rather hazardous. Next time, I'll tap the collets.

There have been a number of designs published

If the screws are held in a Lantern Chuck, the ends can be chamfered after shortening.

Unless a neat end is imperative, you can chamfer by hand with a file, while held in the Lantern Chuck or a plate; or even a nut.

Howard

+1 for a simple lantern chuck.

I just got an M10 bolt with plain shank of about 12mm left once the head was cut off . Get a number of M 10 nuts and solder or silver solder them onto a piece of scrap brass sheet to cover over the front of the nuts. Then screw nut on , mount in chuck, trim the brass plate to diameter , drill and tap whatever size you want and there is your lantern chuck. Unscrew the nut to fit your screw of whatever thread you choose. Helps to mark the nuts with whatever thread they have been tapped - dont ask how I know !

I actually drilled down into the M 10 bolt end and fitted a little copper pad to cover the top of the M 10 thread with a spigot on the back to locate it in the hole, this prevents damage to the screwhead.. Also to help with longer screws, I fit a loose piece of copper of brass bar into the same hole , the right length to accommodate the length of the screw I want remaining inside the chuck. When doing this I find it best to also tighten up a nut on the inside of the lantern chuck facing / securing nut.

For shortening studs I use a "stud box " A short length of Hex bar say 8mm drilled and tapped through with the thread e.g 6 BA. leave thread tight , I use second taps only. On one end fit a 6 BA bolt and nut. In the other end place your embryo stud. Adjust the bolt and nut to give the exact length of stud you want and lock the nut. Hex bar in lathe and form the end of your stud. Reverse the stud in the stud box and form the other end. " Ditto repeato" This morning I did 20 6 BA x 1/4 long studs in far less time that its taken to type this !!

Happy workshop time All.

5 sec. on a scotch- brite grinding wheel and you have a burr free thread.

Exactly what I ended up doing. I made the nut plate from gauge plate and hardened it. A spacer ensured that the right length could be cut off with a sharp chisel. 50 8BA x 1/2" reduced to 3/8" plus a few spares done in half an hour!

John

Is there a tool just for de-burring the cut end ? I was thinking along the lines of a hand held tool in a handle and just give a twist on the screw end. I can't find anything on line, do they exist? Any ideas for making one ? I'm thinking a sort of reversed countersink but can't think how to make simply.

Gordon W:

There used to be a tool like the one you envisage for chamfering the ends of wooden dowels. I will try to find a picture.

Gordon W:

This is the sort of thing I had in mind:

**LINK**

One for screws would no doubt be smaller and the cutting element HSS or, perhaps, TC.

I prefer to perform this operation in the lathe using a suitable fixture but it is a time-consuming job.

Gordon W:

Here is an alternative form which could be suitable for shop manufacture:

The picture is from Ernest Joyce's Technique of Furniture Making.

Hi, I think John Wilding did a chamfering tool in one of his books.

This is the sort of thing:

**LINK**

Matt

Thanks for the quick replies! Wildings tool is the sort of thing I was thinking of, looks quite difficult to make tho'. The woodworking tool looks do-able, will think some more. Another idea- was looking at my clutch pencil, some have a lead sharpener at the end. This is just a long blade at an angle, this might be improved, more thinking.

"Is there a tool just for de-burring the cut end ? I was thinking along the lines of a hand held tool in a handle and just give a twist on the screw end. I can't find anything on line, do they exist?"

The answer is yes, but for me the effort involved in making one for each size was why I adopted the 'concave diamond mini drill tool' (q.v.). What you seem to be looking for was published in the M.E. 31/05/2002 p. 394.

(Edit to correct page number)

Edited By Fowlers Fury on 20/03/2018 14:30:12

I think the tool is easy to make by using a triangular or wedge file file end on and then again at right angles.

How about this gadget? **LINK**

Perhaps a bit OTT, but we used air tools similar to these for shaving the ends of aluminium rivets on aircraft. The air tool has a two fluted flat end mill in the 'gun' which is adjusted to fly about 0.001" above the surface of the sheet metal, so I assume if a gauge was made of the required thickness, several holes could be drilled the clearance diameter of the bolt(s), bolts clamped into the plate and shortened. Mind you, you would still have to chamfer the ends !
BobH

Perhaps you should consider the idea of a: PRECISION SCREW AND BOLT CUTTER. Used in the aircraft industry. It is a guillotine for bolts. See: https://www.aircraft-tool.com/shop/detail.aspx?id=SBS1

I don't know how badly damaged the end of the bolt would be after it is guillotined.

Seems a good idea for people who murder Police Officers.

Vive le France.

Vive la liberte!

Vale Colonel Arnaud Beltrame.

Matt posted the following link here earlier:

**LINK**

(Thanks for that Matt). So spent a few happy hours today knocking one up with a 9 BA collet drilled out with a No.49 drill to hold my 9BA screws which are .072” over the threads. Hopefully this “tightish” fit will avoid any Howard Lewis type wobbles.

Shop time for today came to a halt a short while ago when I ran out of “standing up time” ( don’t larf you’ll be like it one day!) so not been able to try it out yet. I’ll have another bash tomorrow.

If it works OK then I’ll go ahead and make some different sized collets but not before I have worked out a method of “mass” production. This is where I miss the ability to go from turning speed to parting speed at the turn of a knob as I could on my now departed wm 250 vf.

One more observation - the 20mm bolt as seen in the photo (of which I have a box full), is the sort commonly found on building sites and used for fixing steelwork. I fully expected it to be as soft as muck but to my surprise it was as tough as a very tough thing. My lathe is a Warco BH600G - big enough to make mincemeat out of something like this. Anyway, two chipped carbide inserts later the job was done. So much for my supply of cheap car boot steel.

Rik

Just in-case anyone is interested- I have come up with an idea for making a hand held de-burrer. Cut 3, or 4, triangular pieces off a cheap "warding" file, cut a conical hole in end of a steel rod. Fix the bits of file into the cone with 2-part epoxy. Have not tried it yet but will as soon as my car stops falling to bits.