Carl Wilson
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Here is part B,
- Thread starter Carl Wilson
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Carl Wilson
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No need to be sad slim, we live and learn, I have a new plan!
When I did the insert nut for my old 4" Abwood vice I cut the internal thread with HSS brazed onto a bar (old carbon steel motorbike head stud) and ground to shape.
details here:
details here:
Abwood Machine Vice Nut Material
I've just bought an old Abwood 4" machine vice, unfortunately it needs a new nut making. Original looks like PB (a bit redder than the brass I have). Could I make the nut out of brass ( I have a bit that would suit) or meehanite (cheaper than PB) instead?
www.mig-welding.co.uk
Carl Wilson
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Thank you for that Richard, massively appreciated.
Carl Wilson
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That's great, I have an Abwood vice for the Harrison mill but I think it is a little far gone. I will post a pic of it soon.
Hi Carl, I had a Harrison like yours and did a partial rebuild of it about 30 years ago. You're doing a much more comprehensive job than I did!
On mine both the spiral gears that raise / lower the table were badly corroded. I think coolant can get into the knee casting and be trapped there.
It might be worth putting a drain hole in if there isn't one.
I replaced both these gears and the table feed screw with a new ones from Harrisons which back then you could still get.
I also bought, but never fitted the worm-wheel/feed nut which I still have somewhere at home.
Mine was an imperial machine and it really ought to go to someone with one of these machines rather than gather dust in a box of bits!
Anyway to get to the point .... I made a new nut for the table Z, just as you're doing. When I took mine off I was glad I did.
The thread was almost worn away to nothing. I reckon a few more jobs and the whole table would have dropped to the base.
Being even less experienced back then I bought a chunk of drawn PB. PB102 I think.
Oh my, not nice at all. Seemed to want to close up on a drill, but boring and plain turning were OKish.
I did successfully screw-cut the thread and the nut was still fine when I sold the machine about 5 years ago.
Cast PB would have been easier to machine.
I have done a few similar internal acme and square threads since and I usually make a boring bar specifically for each job.
Starting with a length of square steel stock that will fit the tool-post I machine the end round to a diameter that will just pass through the core diameter with a toolbit in the end protruding enough to get to full thread depth.
At the and of the bar I cross-drill and ream for a round HSS toolbit. This is then secured with a socket grub screw
The length of the round section is made just long enough for the tool to clear the end of the work.
By doing this the bar is as rigid as it can be without resorting to exotic materials.
I have not watched your U-Tube vids as I'm temporarily away from base and on a s l o w internet connection, but I guess that you're having problems with cutting the thread.
Apologies if this isn't the case!
One final thing I ought to mention. When I ordered spares from Harrisons (Still in Heckmondwyke IIRC), I asked about accessories for the machine.
Apparently there was a slotting head. They were kind enough to send me some of the drawings for it. It's not a full set but I reckon there may be enough for someone that wants a project!!
Good luck.
Martin.
On mine both the spiral gears that raise / lower the table were badly corroded. I think coolant can get into the knee casting and be trapped there.
It might be worth putting a drain hole in if there isn't one.
I replaced both these gears and the table feed screw with a new ones from Harrisons which back then you could still get.
I also bought, but never fitted the worm-wheel/feed nut which I still have somewhere at home.
Mine was an imperial machine and it really ought to go to someone with one of these machines rather than gather dust in a box of bits!
Anyway to get to the point .... I made a new nut for the table Z, just as you're doing. When I took mine off I was glad I did.
The thread was almost worn away to nothing. I reckon a few more jobs and the whole table would have dropped to the base.
Being even less experienced back then I bought a chunk of drawn PB. PB102 I think.
Oh my, not nice at all. Seemed to want to close up on a drill, but boring and plain turning were OKish.
I did successfully screw-cut the thread and the nut was still fine when I sold the machine about 5 years ago.
Cast PB would have been easier to machine.
I have done a few similar internal acme and square threads since and I usually make a boring bar specifically for each job.
Starting with a length of square steel stock that will fit the tool-post I machine the end round to a diameter that will just pass through the core diameter with a toolbit in the end protruding enough to get to full thread depth.
At the and of the bar I cross-drill and ream for a round HSS toolbit. This is then secured with a socket grub screw
The length of the round section is made just long enough for the tool to clear the end of the work.
By doing this the bar is as rigid as it can be without resorting to exotic materials.
I have not watched your U-Tube vids as I'm temporarily away from base and on a s l o w internet connection, but I guess that you're having problems with cutting the thread.
Apologies if this isn't the case!
One final thing I ought to mention. When I ordered spares from Harrisons (Still in Heckmondwyke IIRC), I asked about accessories for the machine.
Apparently there was a slotting head. They were kind enough to send me some of the drawings for it. It's not a full set but I reckon there may be enough for someone that wants a project!!
Good luck.
Martin.
Well here's the old vertical feed nut which was lurking in my odds box.
The problem for these is they have always got the the weight of the knee, table, feed motor plus what ever is on the table pressing down on them.
An example of my typical home made boring/threading bar is behind but it may not have been the actual one I used.
It certainly hasn't got an Acme form toolbit in.
I have now watched your u-tube videos and can see that cutting the thread is the issue.
Are you sure you have enough clearance (a) on the sides of the tool - don't forget you have to allow for the helix angle too and (b) underneath the tool - unlike for an external tool the curvature of the job reduces rather than increases front clearance.
I would strongly urge you to use HSS. It's much easier to tweak and for a 'one off' in bronze will be fine.
It's also easy to get a really sharp edge with a slipstone which will help on bronze.
The problem for these is they have always got the the weight of the knee, table, feed motor plus what ever is on the table pressing down on them.
An example of my typical home made boring/threading bar is behind but it may not have been the actual one I used.
It certainly hasn't got an Acme form toolbit in.
I have now watched your u-tube videos and can see that cutting the thread is the issue.
Are you sure you have enough clearance (a) on the sides of the tool - don't forget you have to allow for the helix angle too and (b) underneath the tool - unlike for an external tool the curvature of the job reduces rather than increases front clearance.
I would strongly urge you to use HSS. It's much easier to tweak and for a 'one off' in bronze will be fine.
It's also easy to get a really sharp edge with a slipstone which will help on bronze.
Agroshield
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There was a slotting head. It is shown in the manual as well with a parts list, so the info. there might supplement the drawings. Ostia Tools have the manual online: https://ostiatools.co.uk/machinery-manuals/ (LHS of page near the bottom).
Is is possible to get hold of a copy of the drawings please? Thanks.
@Agroshield - PM your email and I'll send a zip. @Fastdruid had a copy yesterday.
Perhaps you'd better club together and each make some parts.
There are not many of the drawings I'm afraid so a lot would need to be educated guesses....unless someone can lay there hands on one to copy.
FYI I no longer have the mill so I wouldn't be interested.
Perhaps you'd better club together and each make some parts.
There are not many of the drawings I'm afraid so a lot would need to be educated guesses....unless someone can lay there hands on one to copy.
FYI I no longer have the mill so I wouldn't be interested.
Oooh, first copy I've found that has the back page on...Going to have to compare it to "my" manual but that manual is from 1970.
Carl Wilson
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Hello Martin-Sy,
I am sorry it has taken me such a long time to reply to your extremely interesting comments. I am still away at work at the moment, as I mentioned in my last film. I am looking forward to getting home in a few days and having another crack at the 5 tpi acme thread. I suspect that as you mentioned I probably did not leave enough clearance for the helix angle, which would explain some of what I saw when I sectioned the practice thread.
I knew after I had messed around with the modified brazed carbide tool that it was a bridge too far. However by that time I had invested a lot of time in it and I just wanted to give it a go. My initial plan had been to use HSS as you and others have suggested.
Hopefully there will be a video in the near future with a successfully cut thread.
Carl.
I am sorry it has taken me such a long time to reply to your extremely interesting comments. I am still away at work at the moment, as I mentioned in my last film. I am looking forward to getting home in a few days and having another crack at the 5 tpi acme thread. I suspect that as you mentioned I probably did not leave enough clearance for the helix angle, which would explain some of what I saw when I sectioned the practice thread.
I knew after I had messed around with the modified brazed carbide tool that it was a bridge too far. However by that time I had invested a lot of time in it and I just wanted to give it a go. My initial plan had been to use HSS as you and others have suggested.
Hopefully there will be a video in the near future with a successfully cut thread.
Carl.
Carl Wilson
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Hello all, new update,
Interesting to see you are doing differing stop/ramp rates on the lathe VFD. Makes me think I'm being overly cautious with mine and maybe should try something similar.
I wired mine with a push to start, push to stop but after watching your video I've been wondering if an rev/off/run switch might be better as then it would only use two of the programable inputs (rather than 3) and I could also have a jog (which needs two inputs and I only had one left).
Out of curiosity what motor power and what ramp rates are you using (mine is a 2.2Kw)?
I wired mine with a push to start, push to stop but after watching your video I've been wondering if an rev/off/run switch might be better as then it would only use two of the programable inputs (rather than 3) and I could also have a jog (which needs two inputs and I only had one left).
Out of curiosity what motor power and what ramp rates are you using (mine is a 2.2Kw)?
Carl Wilson
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Mine has push on and push off plus jog fwd/rev and the fwd/stop/rev switch. It is 2.2kW. I will have to get back to you regarding the deceleration rates.
Carl Wilson
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Also if you look at my thread on here entitled A vfd for my lathe, you will find more info on how I set up the three position switch.
Carl Wilson
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New update,
Carl Wilson
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Hello people, here is the latest update in the mill saga.
I'm a little perplexed by the use of 63T. This must be an approximation to the imperial pitch.
Presumably it will be out by (2 * 63)/127. Over the length (2.375" ish) of the nut that amounts to a 20 thou error.
That sounds too much to work, but perhaps I'm making some wrong assumptions.
Is there no 127T gear available for the Harrison?
Presumably it will be out by (2 * 63)/127. Over the length (2.375" ish) of the nut that amounts to a 20 thou error.
That sounds too much to work, but perhaps I'm making some wrong assumptions.
Is there no 127T gear available for the Harrison?
