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Made a 5C drawbar

Mike DeHart

Aluminum
Joined
Jan 27, 2011
Location
South Jersey, USA
I made two drawbars, actually. One is for my SB 10L, the other for a bud who has a similar 10L. The design is my own, based mostly on what materials I had available.

The tube was purchased online, seamless DOM tube from a place that sells tubing to builders of stock car racing cages. I first made a spider to support the tube as I threaded it inside both ends. I found hard spots where the tube was drawn, which caused me problems with cutting the threads. The solution was to spin the tube while heating it through the colors with a propane torch. After that, it threaded nicely. The pilot cone and main hub was sized based on the thrust bearing I got from McMaster-Carr.

I needed a way to hold the parts together and protect the bearing from dirt. I found what I needed in the auto parts store. I started with a 2-1/2 to 2" muffler pipe reducer. I trimmed the big end to length, cut off the small end, and bored the neck-down area to make a nice retention collar.

The handwheels are different. One was carved from a solid block of aluminum, 6x6x1-1/2". That made a mountain of chips that buried the lathe. I used the taper attachment to put a big draft angle in the ID of the wheel, purely because I thought it would look nice. Then I found that my oily hands couldn't grip the wheel. So I used the little Clausing 8520 mill, a rotary table, and a small fly cutter to cut in the finger grips. The second wheel was made from rock maple. I had a 1x3 that has been in the way for too many years. I cut out 12 segments to glue up two hexagons. Then I glued the hex's together, clocking the joints for good strength. I turned the wood to shape and undercut the back to fit on an aluminum disk for mounting.

The main hub is attached to the tube with red loctite. I made a couple of wood block sleeve clamps to lock in the hub position once I had it threaded into a collet as a test fit. I swabbed loctite on the shaft and in the hub, then slowly rotated the hub onto the shaft to get a full loctite fill in the gap. If that doesn't hold, I'll weld the hub to the shaft.

It seems to work first rate. I gave the aluminum version to my friend, and kept the wood one for myself. The maple handle matches the collet rack I made from an old hunk of maple butcher block. For bearing service, simply remove the three small button head screws and slide the sleeve, cone piece, and bearing off over the long length of the tube.

Drawbar01a.jpg
Drawbar03a.jpg
Drawbar05a.jpg
 

Kevin T

Stainless
Joined
Jan 26, 2019
Exceptional! Thanks for adding in all the details about the process. That really helps add to my skills. I would not have known to add some heat cycles to weird metals to make them behave better!

I made one a while ago and cheated, starting with a purchased threaded section of pipe. I used wood for a handle too but didn't put any finish on the dark walnut so it grips the hands pretty good.

I couldn't figure out, at the time, how to leave a full sized through hole like you have either. I have racked up some good experience with my machine and tools so I could probably re-do mine. I sort of get a mental pass because my lathe is a 16 and I can stick a 2 foot long piece of material in mine as it is. Further justification is that it's cost prohibitive to ship longer stuff! ;-)

....but looking at your work makes me want to revisit my drawbar...really nicely done!
 

SLK001

Stainless
Joined
Feb 8, 2015
Location
Coral Springs, FL USA
Great job! Is the tubing DOM or seamless (DOM isn't seamless)? There shouldn't be any hard spots in a DOM tube. What is the outside diameter of the tube?
 

Mike DeHart

Aluminum
Joined
Jan 27, 2011
Location
South Jersey, USA
Thanks, all, for the positive comments. The DOM/seamless question made me go back to the supplier for a refresher course. They are actually different. True "seamless" tubing is extruded and has absolutely no seam whatsoever. DOM tubing is formed and welded, then Drawn Over a Mandrel to cold work and size it to precise dimensions. The DOM process irons out the weld seam. Because of this, many call DOM "seamless" even though it really is not true seamless. Darn details. Anyway, DOM is a cold working process on top of a weld process, and that can cause work hardening in the material. That was likely why I had hard spots that gave me troubles in my first ID threading attempt. Heating the tube end through the temper colors gave it a stress relieving anneal, and made it behave more uniformly in cutting the thread.

The tube I bought was DOM steel, 1-3/8" outside diameter x 1/8" wall thickness. It took some homework and sketching to lay out the initial bore size and back end relief counterbore for cutting the threads. I found most of that info in a search of this forum. I was just copying the people with the real talent there. Here is a link to the tube supplier. I have no affiliation with them other than buying a couple of feet and being happy with it.
DOM Steel Tube - Steel
I think I paid about $14 for enough to make a pair of drawbars.
 

Kevin T

Stainless
Joined
Jan 26, 2019
Thanks, all, for the positive comments. The DOM/seamless question made me go back to the supplier for a refresher course. They are actually different. True "seamless" tubing is extruded and has absolutely no seam whatsoever. DOM tubing is formed and welded, then Drawn Over a Mandrel to cold work and size it to precise dimensions. The DOM process irons out the weld seam. Because of this, many call DOM "seamless" even though it really is not true seamless. Darn details. Anyway, DOM is a cold working process on top of a weld process, and that can cause work hardening in the material. That was likely why I had hard spots that gave me troubles in my first ID threading attempt. Heating the tube end through the temper colors gave it a stress relieving anneal, and made it behave more uniformly in cutting the thread.

The tube I bought was DOM steel, 1-3/8" outside diameter x 1/8" wall thickness. It took some homework and sketching to lay out the initial bore size and back end relief counterbore for cutting the threads. I found most of that info in a search of this forum. I was just copying the people with the real talent there. Here is a link to the tube supplier. I have no affiliation with them other than buying a couple of feet and being happy with it.
DOM Steel Tube - Steel
I think I paid about $14 for enough to make a pair of drawbars.


Ahh, 14 dollars beats the 90 I paid for a threaded one!
 

Kevin T

Stainless
Joined
Jan 26, 2019
Maybe, but you didn't spend a month of Sundays trying to figure out how to cut custom, fine pitch, internal threads. :-)

True, I was itching to start using the collets I had collected. Working with a collet set up is so nice. I just hit my first tiny thread issue with a broken screw inside an Albrecht chuck collar I just got. I finally back drilled it out and of course it's metric and right around 50 tpi. I think I've got it figured as a M3 x .5 and am tempted to make one. I've never made anything that tiny, and of course my QCGB skips from 48 to 52. I don't need a lot of threads maybe a 1/4 inch worth. We'll see how this plays out...
 

Mike DeHart

Aluminum
Joined
Jan 27, 2011
Location
South Jersey, USA
Kevin, M3 x 0.5 mm is a standard metric thread, according to my tap drill table. That screw should be available to buy. Even if the screw head shape is something oddball that you can't buy, you can still buy the thread die and make the screw blank. Either way, it will fit properly. As threads get finer, it becomes more critical that they are made to proper size. There is less wiggle room. Maybe the best bet is to send a note to Albrecht and ask if they can send you a replacement screw. Good advice from the toolmakers I worked with: Make it when you can't buy it.
 

LFD

Plastic
Joined
Jan 25, 2022
Man those are beautiful, my first post because I truly appreciate your workmanship.
Kevin
 
Joined
Oct 20, 2020
Kevin, M3 x 0.5 mm is a standard metric thread, according to my tap drill table. That screw should be available to buy. Even if the screw head shape is something oddball that you can't buy, you can still buy the thread die and make the screw blank. Either way, it will fit properly. As threads get finer, it becomes more critical that they are made to proper size. There is less wiggle room. Maybe the best bet is to send a note to Albrecht and ask if they can send you a replacement screw. Good advice from the toolmakers I worked with: Make it when you can't buy it.

Also a purchased screw will be rolled ( then possible hardened ) and be stronger than a cut screw. which might make a big difference in the smaller size.
 

Mike DeHart

Aluminum
Joined
Jan 27, 2011
Location
South Jersey, USA
Man those are beautiful, my first post because I truly appreciate your workmanship.
Kevin

Thank you for this compliment, and welcome to the forum. While my skills are improving, I am not a machinist by trade and I have a looooong way to go until I can ride with the toolmakers I learned from. Read through the threads "What have you made (with/for) your South Bend" and you will see the wealth of real talent here. That talent is shared freely. I can't thank the participants enough for that.
 

Jaylude

Plastic
Joined
Feb 1, 2020
May I ask what you ended up using for the ID bore prior to threading, the back relief size, and finished thread depth? Did the collet fitment come out to your satisfaction? Did you "sneak up" on the thread depth based on threading a collet in/out, or shoot for a specific number? Curious.
 

Mike DeHart

Aluminum
Joined
Jan 27, 2011
Location
South Jersey, USA
I started with the thread spec for the collets. The 5C uses a external thread of Ø1.238"-20TPI, according to info I pulled from the net. After some research in forums and Machinery Handbook, I worked out a bore size of Ø1.184 inches for the tube. I decided on a thread length of 0.750" from the end of the tube and a clearance counterbore 3/16" beyond that. For the counterbore diameter, I took the OD of the collet thread and added a little clearance, ending with Ø1.245/1.250. I also used that clearance diameter to cut a small lead in the end of the tube 1/16" long.

To cut the bore and c'bore, I ground a cutter that looked like a threading cutter, but with a nose radius for a clean bore. I bored the tube the full length(3/4 +3/16) and zeroed the dial on the crossfeed after the final pass. I was working to the carriage stop to get my length to a good shoulder Then I ran the boring bar all the way in to the stop. I put the drill chuck in the tailstock and locked a piece of short rod in the chuck. I extended the tail ram a bit then slid the tailstock right up to touching the tail end of the boring bar. From there, I backed off the tailstock ram the 3/16 I needed for my c'bore. This gave me two hard stops to work between. I trusted the dial on my crossfeed to give me the right finish diameter. Back out the cross feed a few thou, bounce the carriage back and forth between the stops, and repeat until the dial hit the number. It worked. Pull the tailstock back, reset the carriage stop to cut the lead in bore, then set up for threading. I ran in back gear, nice and slow. I could hear when the cutter broke into the clearance c'bore and was able to pull out the half nuts with time to spare. I took light cuts and gauged it with a random selection of three collets from my rack. When the collets just threaded in cleanly with minimal slack, I called it good.

One word of caution on setting up to thread. My mentors always taught me to turn the compound to 29.5° when threading. This makes sure most of the cut comes from one face of the tool, but the other face takes a very slight shave to keep that face of the thread clean and smooth. I buggared up a thread once by using the 29.5° spec as an absolute rule. The proper use of this trick is to set the compound 1/2° from 30° TOWARD the work. Straight thread tuning means turning that 1/2° clockwise, while internal thread turning means turning it counterclockwise. If you turn that 1/2° AWAY from the work, your back face on the thread looks like a tiny little staircase, and that is scrap. I learned this lesson when I discovered that the degree numbers on my South Bend run the opposite direction from the degree numbers on my older little AMT lathe. I turned the extra away from the work, without even realizing it, and scrapped a nice drill chuck shank I was making.
 

Kevin T

Stainless
Joined
Jan 26, 2019
May I ask what you ended up using for the ID bore prior to threading, the back relief size, and finished thread depth? Did the collet fitment come out to your satisfaction? Did you "sneak up" on the thread depth based on threading a collet in/out, or shoot for a specific number? Curious.

Just for ref. My purchased pre-threaded tube section from ebay is 1.375 OD. Measured with a caliper the inside is about 1.19 (threaded ID)So probably the same as the OP. They opened up the bore of the tube for threading to a depth of about 1.5 and then threaded about 1.25 deep.
 








 
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