How can I debur my new leadscrew?
Just got done making a new leadscrew for my 14x54 Hendey lathe, and having trouble figuring out a good way to debur it.
it has about 6 feet of 1 1/8-6 ACME thread with a 3/16 keyway milled down the entire length of it, I have everything pretty well deburred except for down in the roots of the threads where milling the keyway left a small burr, I deburred the rest of it with a deburring brush in the Bridgeport spindle but if I get too much more agressive with it, it will round over the crests of the threads too much.
Try a small file, thats how we did it in the old days. It might take a little time but you should be able to get good results with some care and patience. Good luck
Bust out the jewelers files and go to work, you might do ok with a wire brush on a grinder but that's not a good way to go. You will still need to touch up everything.
Make a pot of coffee and go to work. You might even grind the end of a jewelers file to round off sharp edges you cant file. It cant take that long to do right.
take a sharpy marker and mark each place when done, so you dont lose your place.
This is why Hendeys cost as much a a nice house when they were new. It's worth the effort to get at it with a triangle file and a little tri hone (if you have one). Haven't had to do 6ft, but I sometimes have to make motor shafts for vertical turbine pumps that have keyways cut in them that may have a keyway 2ft long in the thread.
Turn and single point a prehard, (about 30RC) chrome moly nut, snug on it's crests, 50-55° included angle, (loose at root) that engages the burrs in the dedundum of the screw. Hacksaw some shallow slots/teeth in it, plant in vise and run the screw back and forth with a portable drill motor and pipe cutting oil.
The narrow thread will let the small chips wash out.
Haven't tried it but would, unless you report back that it sucked.....
Get a stick of cratex and an assortment of the small discs.
Cratex - Rubberized Abrasives Catalog - Blocks & Sticks
It will save you a bunch of time and results will be A+!
Sounds like I better go get some small files, don't think I have any that will do the job unless I grind one down to fit
Definately don't want to miss a burr either, would ruin my freshly babbited half nuts.
Yeah, I can't believe how expensive the Hendey lathes were, in 1942 mine sold for $4110, what would that be today with inflation?.........$54,363..... That's more than I paid for my house.
Originally Posted by aerodark
Will these conform and get down into the roots of the threads?
Originally Posted by PJRitz
Yes! Cratex is dress-able on a grinding wheel, and will form any profile with some force. I used it in my younger days to deburr the seals we made for turbine engines. It is incredible stuff.
I would be concerned if you have a keyway or other interruption in your screw. It will take chunks out of the stick if you are slowly rotating the leadscrew and the cratex meets an interruption. Maybe a pic of the problematic area would help.
You can cut them, or coarse grind them, to the desired size and shape. So if a stock shape/size doesn't work, you can make a custom size/shape.
Originally Posted by PJRitz
I did the exact same job and tried a few different methods to debur before I finally stopped trying to get out of it and just did it manually with jewelers files. I wish I had an easier answer, but I couldn't come up with anything that would only take metal off where I wanted it taken off and not where I didn't.
Eye loupe, jewelers files, and a some spare time. You get into a rhythm eventually.
As I was deburring, I sat there thinking that there must have been a better way to mill that slot that would minimize that burr. It was too late on that leadscrew, but in case I ever did another one...
I used an endmill in a Bridgeport and "routed" out the slot. Every tooth had the same burr on the downwind side of the cutter spin. I was wondering if a disk cutter in a horizontal maybe would have worked better doing it in multiple passes. Thinking that maybe flipping the cutter over and changing direction every now and then might break the burrs off from the previous pass.
Not sure if it will work for you but I de-bur the inside of box tubing with a wire wheel. If I stay on it it smoothes the edges so they won't cut when handled.
How about a bearing scraper?
Flame deburring might work. An torch set to excess oxygen will burn away the burr and leave the bulk untouched.
Charge some string
Charge some string with compound, wrap the string once around and while turning it in the lathe let it feed up and down until the burr is removed. A light touch and it'll be gone in no time. Seems to me there is a commercially available abrasive sting but I don't recall the name. This has worked a treat for me.
I did this job on a lead screw a few years ago. Just sitting down with a vise at comfortable position, a good light and a feather file made the job easy and even enjoyable. The feather file is just the ticket as it is thin in section(actually a very very shallow vee) and fits into the keyway very nicely. They are usually of good quality and cut cleanly and quickly.
See: Feather File for Japanese Saws
These files are commonly available at woodworking tool stores that stock Japanese saws.
Last edited by dgfoster; 12-08-2011 at 06:28 AM.
The trick to deburring adjactnt precision fitted features is to procede with a plan and gather the apparatus you need.
A keyed lead screw is a PITA. You start with the feature machined last; that most likely is the keyway. Using a 4" mill file find the convex side and using the chisel end of a slat of wood to hold the file flat, use the file to dress the tool marks in the flank of the keyway. Be careful not to roll off the thread crests on either side. This takes care an patience.
Next is dressing the burrs where the thread flanks intersect wiht the keyway. Here use a flat slip stone that can be made to work in the thread root. The object is to dress away the burr so a barely sharp corner appears where the flank intersects with the keyway. This is tediious excruciating work.
When the corners are properly burred, dress with the stone straight across the corner to give a 1/64" flat to prevent the sharp edge from "reaming" the nut.
When the de-burring is complete, scour the keyway and the threads with a soft wire brush to gently round the corners and polish their "agression" off.
As I said this is careful work. If your are the impatient type, it will drive you nuts. . Expect to take several hours and don't forget to take breaks to work the knots from your back and shoulders.
The factory that made the original used an abbreviated file and stone techniquen then turned it over to a man with a selection of fine wire wheels and buffing wheels.
A bad de-burring job will drag in chips, ream or damage the nut, hook your apron and winch you into the lead screw in a "lathe hand's curtsey". A good tidy job may hook a rag or apron but is not aggressive and it adds life to the nut.
50 - 55 deg?.............. on an acme screw (29deg)? - ya lost me Bob
Originally Posted by Robert Campbell Jr.
Originally Posted by Forrest Addy
On my Rockwell 10" lathe (I think it is the same for the Rockwell 11") the sides of the keyway are slightly narrower just below the bottom of the threads. It was done this way so that the key would not raise a burr in to the threads during use. The keys are brazed rigidly in to the power feed/cross feed worm. The difference in width is about 0.015" - 0.020" (not much). Seems to me that such an arrangement would make the deburring process more forgiving as long as the nuts have a clear path along the threads. Naturally one doesn't want bits of lead screw burr flaking off in to the half nuts or other intimate parts of the apron.
I don't know if PJ's lead screw is made the same as mine but to avoid widening the critical part of the slot he could use a protective strip of metal (plastic or wood even) that would lay in the bottom of the keyway while he works on the part where the thread intrudes. The strip will keep the file or stones out of the slot below the minor diameter of the threads.
At 6 TPI and assuming it is threaded the entire 72" that will make for about 864 "corners" that will have to be deburred (ouch!).