|Chris Evans 6||20/07/2018 16:33:26|
|1288 forum posts|
One of the reasons I made a new cross slide for my lathe (a 14"x40" Taiwanese copy of a Harrison M300) was to add tee slots for a rear tool post as well as the ability to bolt an angle plate or casting on there.
|Alan Jackson||20/07/2018 17:45:31|
143 forum posts
|928 forum posts|
I just come off the cross slide 55 degree dovetails and clamp. Rear tool post fits straight on top for opposite hand tools rarely use it.
Clogs seriously should be able to wazz through most steels even the tougher types, titanium 5, brass real easy. If you can do aluminium 6082 you will part anything to 6" dia listen to the tone coolant or not makes little or no difference. As above i rarely use the rear tool post on a similar M300 except for small scale production.
Having been there and not wanting to fork out severe dosh i had a cnc setter operator give me a load of tools for jobs done for him, what a revelation no more struggling plough straight in.
375 forum posts
I certainly support the purchase of books, I did when I started and I'm still buying and reading them. But you can't remember it all or substitute somebody looking over your shoulder and putting you straight, even though they may have been there 10 mins watching you stuff up.
472 forum posts
I never ever had parting off problems on my two 6" Roundhead Students. My parting off chatter problems only first appeared post Colchester ownership with my current Boxford VSL.
Both lathes ran/run a Dickson style tool post. I always wind the top slide back on the Boxford so the tool holder sits more central over the cross slide which seems to help. This was never neccessary on the Colchester.
Would be interesting to see a photo of your parting off tool holder.
Edited By thaiguzzi on 22/07/2018 06:16:19
1117 forum posts
Mine still being developed.
Works well with aluminium and brass BUT not tried steel yet as overhand may be a bit too much.
Will move the holder further right.
Geoff - if it goes bang on steel I'll know!
Edited By OuBallie on 22/07/2018 11:15:48
2904 forum posts
|Niels Abildgaard||22/07/2018 17:25:47|
|154 forum posts|
A Boxford part of system capable of 125 mm alu and 100 mm mild steel
I never got round to making a rear,upside down version as my crosslide had no T tracks
472 forum posts
Yes, thanx for that, but i'm determined to persevere from the front, using both HSS and tipped tooling. If it worked on a Colchester (yes, i know, mass & rigidity etc), i'll be damned and eventually make sure it will work on a Boxford. No problems on 30-40 mm alloy etc, but the same cannot be said for steel or S/S in the same OD.
I was always under the impression that rear toolposts were designed for Myfords, with their flat ways, and saddle design....
|147 forum posts||
Two experiances that may be related
We had a Colchester Master at work with a rear toolpost carbide insert upside down, reasonable machine but when I tried to part of a load of M24 A4 stainles steel bolts (316) by hand feeding as i worked in design normally but i needed these for a Factory acceptance test the next day, it kept digging in and breaking the tip. This was only cured by using power feed then I did about 50 of them easily.
Now days at home I have a MKII Colchester student, using a front mounted T2 Dickenson toolpost and a Sandvik inserted blade I had digins, changed the toolpost to a create multifix copy now goes through 316L like butter, best on power feed but can do it by hand if you keep cutting.
Couldnt see angy damageon the Dickenson toolpost but the multifix seems far more rigid,
|Clive Foster||23/07/2018 13:07:03|
|1507 forum posts|
In my experience many Dickson problems are due to folk not cleaning the innards. They pop apart very easily so no great issues there. If they have not been done for ages its amazing how much stuff gets inside. Don't for get to brush off the mating surfaces of holder and post before insertion. Its important that the adjuster stud is straight and that the collar is a free fit in locking nut slot.
Brand new or properly scrubbed up clean there is little difference in holding power and rigidity between a Dickson and a Multifix. Factory fresh Multifix will beat well used Dickson set which, almost invariably, have bent adjuster studs due to years of mishandling. Correct technique is to hold the tool carrier up against the post. Pulling into position vial the locking cam eventually bends the stud. However Dickson does have inherently more overhang between tool tip and centre bolt so if not properly bolted down or retrained by the locating pin it is more prone to rotate under cut. Cost me a parting blade to learn that!
2164 forum posts
I have a rear tool post made from a kit & it works fine after a couple of mods; ( see my album; rear tool post ). I also have the x slide tool post wound back along the compound slide to allow more support under the tool point ( rigidity )...It also helps part off under power feed quite easily as it allows the parting tool to locate nearer the centre of the cross slide.
Edited By mechman48 on 23/07/2018 14:03:32
|928 forum posts|
Great price that Murray, Korloy are good tips so is the blade holder a bargain.
|Clive Foster||23/07/2018 21:28:46|
|1507 forum posts|
Last couple of parting blades I broke, one HSS, one tipped, were due to tool post pivoting fractionally on deep jobs forcing the blade to bend. Which tends not to be good thing at 2 or 3 inches or more depth of cut.
Looks like I shall have to either finally make a rear tool post for the 1024 or drill the topside for the Dickson location pin.
Using Rocol synthetic coolant probably doesn't help as the silvery component gets everywhere. Stays too. Too serious scrubbing to get the chuck jaws properly clean and grip back up to what it should be.
3023 forum posts
Not really. I think the idea came originally from many industrial capstan lathes that commonly used a rear parting tool and was picked up by early model engineering types who were exposed to such machinery at their day jobs.
Certainly easier to implement on a Myford with T-slotted cross slide than Boxford's Yankee-style slide.
I've tried both front and rear parting tools on my Drummond and Myford and definitely the rear works best. Whether that is due to the chips falling out of the groove or the spindle forces being directed downward into the more solid half of the headstock bearings is a debate that rivals oil choices and will probably never be solved.
But at work years ago we always used front parting tools, normal way up, but that was on large industrial lathes of top quality (DSG, Monarch etc) in good condition, with plenty of coolant flowing. I don't remember ever trying to part off jobs over 2" diameter, in other words the same size that we are today trying to do on relative tiddlers of machines such as Boxies and Myfords.
As usual, model engineers are forced by necessity to push their machines to ridiculous limits and beyond.
Edited By Hopper on 24/07/2018 02:31:37
472 forum posts
# My Dickson (genuine Bison copy) is dismantled and cleaned a couple of times a year. The first time i did this was prolly after 10 years of ownership - could not believe the crap in there...
# The tool post has a location peg/hole in the top slide.
# i have learnt to have the part off tool over the cross slide - this does help.
# Cross slide is a t slot type with longer dovetails than the stock "Yankee style". It's not on the top of my list of Things To Do, but maybe, one day, i'll get around to making a rear tool post. In the meantime...........
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