Boxford lathe help

[slim_boy_fat]

@Dcal Well done! I'd still be crying in my coffee and searching Google for replacement(s).

 

[Dcal]

Thanks slim, I'm nothing if not stubborn.

Managed to get some plaster of paris today so thought I'd put the machine levels back together.
As usual I know I had some but couldn't find it so £2.50 worse off.

Gathered up the bits and cleaned the old plaster out of the level tubes.
Used a paint marker to paint the back of the Chinese vial.

Ordered the vial from here and it came all the way from china in 4 days.

https://www.aliexpress.com/item/HAC...931.html?spm=a2g0s.9042311.0.0.c59c4c4dMZNun4

Not the exact size but fits the level tube fine.



Positioned the vials into the tubes and held them in place with masking tape



Mixed up a bit of plaster, poured it into the ends, assembled the bits and Bobs your uncle



I now have 2 levels and one base. 3 if you count the 6 inch one

Tried them out on the lathe and Pete's level is pretty accurate the Chinese one is stupid accurate, probably too much for my needs (or the level base) but good to have.
Also have this 6 inch one but that doesn't seem to move, when either of the other two would be off the scale.



Can't find a set of feeler gauges to check the resolution but a piece of 80g photocopier paper under one end puts the Chinese vial completely off the scale.



I'll get a set of feelers and do a proper test sometime.

 

[Pete.]

The vial I sent is about a 20 or 30 arc second vial I think. That import one is probably 5 or 10 arc seconds so much more sensitive.

Try putting your Chinese level on the lathe bed then walk around to the other side. It might register the bend in the slab from your body weight.

 

[Dcal]

The vial I sent is about a 20 or 30 arc second vial I think. That import one is probably 5 or 10 arc seconds so much more sensitive.

Try putting your Chinese level on the lathe bed then walk around to the other side. It might register the bend in the slab from your body weight.

Every days a school day.

 

[Seadog]

@Dcal I think you asked about toolpost type. It's this one - https://www.arceurotrade.co.uk/Cata...s/Tool-Posts/Model-111-Quick-Change-Tool-Post

 

[Dcal]

I'm making a couple of chuck back plates for the Boxford. (for practice as much as anything else)

I have some 25mm thick plate (grade 275 or 355 mild steel I think) and I cut a few blanks out with the gas axe.
I cut them them fairly oversize and ground the worst of the gas cutting marks out with a grinder.
I got the first one set up in the small 4 jaw I have(Just) then drilled it out to 25mm (biggest blacksmith drill I have that will fit in the lathe chuck) then took it to size with a boring bar.
I part cut the thread on the lath and finished it off with a 1 1/2 x 8 tap I got on ebay a while ago.
Slow going but it went well I thought, but when I was trying to face off the front of the back plate I get a rough finish towards the middle of the backplate

I'm using the Bangood 12mm insert tools, speed was 570 rpm, really light cuts and fed it by hand.
New tip but just the same as the old tip I was using on earlier cuts.
Overall size is just over 100mm and it starts to cut rough at 65mm dia

Why does this happen at a set point (Tried this a few times and it always the same)
If it's the tool cutting speed, should it not get gradually worse an the speed reduces?

Should I try and cut it at a faster speed (RPM) or increase speed half way in.
Am I way out with my speed (cutting or feed?)
Is it the material, seems strange that it cuts worse where there was the least heat applied.

I don't want to take too much more off as I'm getting close to the spindle threads.

I clocked the face and the edge and there is hardly any run out on it so I'm well pleased with that.

Any advice / comments welcome

 

[Pete.]

The torch has heat-treated the plate, must be some high tensile stuff you got. You get the same effect when turning induction-hardened rod, you get a beautiful finish for the first 3-4mm then it goes rough unless you turn the speed right up.

 

[Seadog]

You're using an insert tool which has produced an excellent finish, so it suggests to me that you need to increase the speed since the surface speed reduces the closer you get to the spindle. Carbide likes high speeds. Do you really need to face it off cleanly all the way to the centre? I know it might look unsightly, but once the chuck is fitted it will not be seen.

 

[Dcal]

Thanks lads,
that was quick.

Pete,
Interesting, I've no idea what grade the plate is (as was just laying about and obviously no mill certs) it could well have come from China.
I was expecting the heat affected zone to be tough but it machined ok (intermittent cut and all)

I have some grade 355 4 inch x 8mm box and I couldn't drill a hole through the seam weld and wrecked a couple of broaches trying and that was supposed to be low alloy, low carbon steel.

Seadog,
Take you point, I can live with the rough finish but I was really curious as to what was going on?
Initial thoughts was the tip speed reducing to the center but the really obvious change from good to bad is interesting (well to me anyway)

Might be a combination of both heat treatment and tip speed.
I'll try a light cut at higher speed just for the hell of it.

I'll report back

 

[Dcal]

Whacked the speed right up (1300 RPM) and tried again.
Light cut, hand fed and much better finish.
Stopped half way to show the difference.

I'll now try and finish it off with the power cross feed.

That line where it all goes off is really odd though.

Thanks for the pointers

 

[Seadog]

I assume yours is a single phased machine. One of the many advantages of having a VFD driven motor is that you can change the speed on the fly, just crank it up as you approach centre.

In general, carbide tips like to be worked hard. That means high surface speed and heavy cut. Watch Abom79 on Youtube, for example. He machines a lot of large spindles and takes some huge cuts, obviously the machine is capable of it. It's worth spending some time experimenting with depth of cut and feed rate to get an idea of what your machine is capable of.

 

[Dcal]

Thanks Seadog,
lots to learn, (one of the reasons I am making chuck backplates) and happy with the results so far.

The motor is single-phase and 1/4hp I think, (which is mad considering it's size) so high up on my list of to do jobs (first is mounting a 3 jaw chuck, then a quick change tool post)
When I replace the motor I will certainly will go 3phase and VFD.
What motor power should I go for?

I changed both drive belts to v belts and no slipping now (a big improvement I think and a lot less noise and viberation but the old belts were scrap) if the belt to the spindle pulling goes I can always go back to the original type if I don't fancy taking the spindle out again But as I don't use it much, should last for ages.

The lathe is underpowered and easy to stall which is no bad thing when.you are learning like me but stops you making a decent cut (especially with power feed)

 

[Seadog]

It really needs to be 3/4hp at least. I fitted a 3-phase 1hp to mine and it can shift a fair bit of metal, with insert tooling.

There's a chap on the Boxford group that has fitted a 2hp with short, direct drive, straight into the head. Now that does chew through steel.

 

[Dcal]

Excellent info Seadog,
when I'm buying a motor I've no problem going bigger as I can always limit the max power on the Vfd

Thanks again for your help

 

[Seadog]

I've removed the countershaft from mine (underdrive model) and replaced the two remaining belts with Nu-T-Link. If you adjust them, according to the manufacturer's spec, then the spindle one is a right bugger to fit. It doesn't often slip, though