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1925 McDougall Lathe refurbish

Duncan K

Duncan K

Active Member
I had been looking to replace my little Southbend 9" with something a little bigger and with a few more features like power cross feed and a quick change gear box. This 18" McDougall lathe was quite a bit bigger than what I was looking for but had everything I wanted and the price was right. I had already restored the Southbend so I thought this would be a good project. It came with a 12" 3 jaw, a 16" 4 jaw, and steady rest. It currently has a crappy 1 HP motor feeding a 4 speed gear box and then a belt to the spindle pulleys. The power cross feed wasn't working and it was stuck in back gear. I managed to get it out of back gear but now the 1 HP motor will barely spin the chuck. Plans are to swap out the motor and gear box for a 5 HP 3 phase and VFD. I want to get it functioning and then I'll tear it down, clean it all up and paint it.

I took the cross feed and compound off. At some point something heavy crashed into the cross feed dial. The threaded piece that hold the cross feed screw in was broken and the screw is bent.
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There was just enough of it sticking out to tap it around with a punch and back it out.

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I started my first attempt at making a new one. I am ready to start the threads but it turns out I don't have a 1-2" mic so I can measure over the wires to measure these threads. I will have to pick one up before I can continue.

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The cross feed screw is bent pretty good behind the gear. I am thinking about cutting it off behind the gear, then face , drill, and tap for a stud, and thread on a new piece turned to match the old shaft. Not sure if that makes sense, or if there is a better way to fix it

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Nice big WWI vintage lathe - almost 100 years old! If in good condition these can still make accurate parts.

Your fix makes sense - I would probably cut it off, drill and tapped a hole and when it was in I would tig weld it in place and then finished off welds on a lathe.

I would not worry so much about thread depth - threads there are not precision made - I don't even know whatever they had same grades as today as to thread fit. Besides you can find "book" value of thread depth online or probably in Machinery Handbook.

Make sure you keep your small lathe - you need a lathe to fix a lathe. Also making small parts is more comfortable on a small machine then large one.

5hp motor would work. Same as 7.5hp and 10hp. 3hp may work as max speed is probably low & you probably don't plan to use lathe full capability.
 
Duncan K said:
Not sure if that makes sense, or if there is a better way to fix it
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that makes a lot of sense. If it were me, i would try and straighten it first. It is already bent, you can’t make it any worse...

if you have a shop press, straighten it should work relatively easily as I think this shaft material is not that hard. You can put it between centers to mark where the bend is. Then support it accordingly and press it. I use wood blocking to protect the parts. With some patients and only small steps, you might be surprised how straight you can get it. Just a thought...

Keith Fenner has some videos about straightening shafts, both with heat and without.
 
Took 2 attempts but I got this part made.

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I removed the old motor and gear box assembly. Had to use my engine hoist to lift it off. Started to mock up for the new motor and pulley.

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Got the new 5 HP motor mounted and turned a pulley for it. Decided to make it 50% of the spindle pulley size. Now I just have to figure out how to machine a keyway into it. Most of the broach sets I have looked at only cut up to 2 1/2". The key way in the shaft is only 2" long so maybe it will work.

I was looking at this set. https://www.amazon.ca/Accusize-Standard-Keyway-Broach-5100-0010/dp/B00HK0YG0S/ref=sr_1_1_sspa?crid=2O8WLUOW0DA75&keywords=keyway+broach+set&qid=1580325661&sprefix=keyway+,aps,222&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzSjUxV0IxVE9MNTI3JmVuY3J5cHRlZElkPUEwMjI2NTY2MVRVVzFXRUtSUEUyVyZlbmNyeXB0ZWRBZElkPUEwMDQ3MzQzMkpXS01QUFQ4MFNHQyZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU=

Can anyone tell me if this will work?

I was also looking at some videos on YouTube where a boring bar with a HSS bit was used kinda like a shaper using the cross slide to push it through the work piece mounted in the chuck.
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If the metal is soft you should slowly be able to cut a kayway into it with very sharp HSS tool utilizing the cross slide as a ram in a hand powered shaper.

I have a shaper but no tool for making keyways (you need to lock the clapper and make special tool to go into the hole). I as well as many other pp have keyway broaches in sizes needed but usually you need to make your own insert as well as small shims that advance the broach.
 
I was taught to use a HSS bit in the milling machine and using the quill like a shaper. For single keyways, it doesn't take too long. You have more leverage on the mill quill than you do on the lathe handwheel, so it takes less effor and is a little quicker...
 
Sure you can use milling machine as well or even a drill press.

I guess if you like to waste a lot of time you could file it out as well - it may actually be quite fast in aluminium.

You could use long end mill to remove most of the material and then cut with HSS to size or file to size.
 
I had thought about that too. I need to find a boring bar that takes 1/4 HSS. Busy Bee is the only place local that lists them but they are out of that size. I might try to make one. VFD comes in on monday so I'd like to have this pulley mounted and ready to go
 
I ended up just making a boring bar to hold a 1/4" HSS. I set it up in the mill and it worked really well.
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I tries to straighten the crossed screw in the press but I think it ended up worse. I will have to cut the end off and make a new one.

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I don't know if you had time to check out Keith Fenner's videos on shaft straightening but as Peter mentioned he has posted a couple of good ones. This one is an example.

 
I believe I once saw a video straightening a shaft in the lathe using a bearing to run it true.
 
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