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Chamfering on the lathe

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Hugh Gilhespie23/05/2014 17:21:38
130 forum posts
45 photos

I would be very interested to know how other forumites set up for chamfering on the lathe. I find it a bit of a struggle and it usually takes me a couple of tries until I have a set up that lets me access the edge of the piece I am turning without either hitting the chuck or running out of travel on the cross slide or top slide. I am using a Cochester Student lathe with a QCTP and the method that I usually use is to set the top slide over to 45 degrees with the tool post pointing towards the chuck, fit a tool with a 9 mm circular insert and chamfer on the far side of the piece with the lathe running in reverse, using the top slide to move the tool past the edge of the work and backing the cross slide until the tool starts to contact the work. I can't help feeling there must be an easier way so all suggestions gratefully received.

Hugh

JasonB23/05/2014 18:21:29
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If its a small chamfer say below 2mm long then I have a tool ground with two 45deg faces which will do for both internal and external chamfers. No need to move toolposts ot topslides about just change tool holders and away you go.

imag2583.jpg

If its much wider than that then if I'll move the topslide handle away from me to 45deg and use a right hand tool.

Les Jones 123/05/2014 18:27:31
2255 forum posts
156 photos

Hi Hugh,
Nice to see you back on the forum after a long time. That method of chamfering seems perfectly sensible to me. How is your stepper controller project for driving the cross feed going ?

Les.

Clive Foster23/05/2014 18:58:10
3103 forum posts
107 photos

# 2 for Jasons method. Flat top tool does fine.

I too have a QC post (Dickson) and the tool gets switched from one end of the holder to t'other on a regular basis depending on whether endwise, as in Jasons picture, or straight in does best. On my Smart & Brown 1024 chamfers up to 1/2" long are feasible with such tooling although with the larger ones its better if you have something roughly right cut stepwise or left from a roughing tool to start with so the chamfer tool is cleaning up rather than cutting it all. Coolant / cutting oil helps too. I use a Bjur Spraymist system.

Entierly agree about the difficulties of setting up to cut relatively long chamfers. Big problem I find is the sheer bulk of the QCTP which can seriosuly get in the way.

Clive

Hugh Gilhespie23/05/2014 19:57:30
130 forum posts
45 photos

Jason - I like your method. I have tried this with an old carbide insert with a 90 degree point - i.e. two faces at 45 degrees but it wasn't terribly successful, just not sharp enough away from the tip I think. I am STILL working on the Worden tool grinder I started 4 years ago and hopefully when I finish it I will be able to grind form tools including one like the one you are using.

Les - I moved house in late spring last year and have only just got a workshop back so everything has been on hold for about 18 months. I got as far as completing all the electrical side of my cross slide drive project but stalled on the - in theory - simpler stuff to design and make the mechanical components to drive the cross slide handle. It is on the ever growing Things To Do list and I am motivated by having a lovely new workshop - ex stone barn but now fully insulated and with a new roof, concrete floor, etc that is a pleasure to work in.

Hugh

steamdave23/05/2014 20:09:47
510 forum posts
44 photos

I can't disagree with the short chamfer methods suggested.

For a long internal chamfer, why not use a boring bar with the toolpost set round to the required angle? Just feed in with the topslide. Use the X axis for the depth of feed.

For an outside chamfer, use any toolbit that has a straight edge with the toolpost swung round to the required angle and just feed in. Jason's set up for the external chamfer will avoid hitting the wrong bits of the lathe.

Am I missing something?

Dave
The Emerald Isle

John Haine23/05/2014 20:52:35
4622 forum posts
273 photos

I just dial it in as a short taper at 45 degrees using a cnc wizard in Mach3 and set it off...

jason udall24/05/2014 11:29:10
2031 forum posts
41 photos
It seems that the use of simple form tools is out of favour. ...
jason udall24/05/2014 11:30:17
2031 forum posts
41 photos
Or even gravers
JasonB24/05/2014 11:51:15
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Posted by jason udall on 24/05/2014 11:29:10:
It seems that the use of simple form tools is out of favour. ...

Is that not what I have shown and several other members shown a preferance for. Also same thing as JS posted on his sharpning thread.

Just as quick to put the above tool in the QCTP than set up a rest and use a graver though I do have a fine file that I keep on the lathe for knocking off corners/burrs and have the end ground like a scraper that tidies internal holes.

J

Ian S C24/05/2014 12:04:32
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7468 forum posts
230 photos

For the work I do on agricultural machinery, I use a long angle lathe file(no one mentions those things), it works well whether it's a small chamfer, or even if quite a bit of metal has to come off, ie., a radius on the end of a shaft.

Ian S C

JasonB24/05/2014 12:11:41
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Ian, have you a picture of said file not heard of a "long angle lathe file" before.

J

julian atkins24/05/2014 12:29:19
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1252 forum posts
353 photos

files and clockmaker's gravel for me too!

cheers,

julian

colin hawes24/05/2014 13:14:54
557 forum posts
18 photos

You need to make sure the tool has enough rake to avoid rubbing on its lower edge when chamfering a bore or for unimportant work set it well above centre height. Colin

Neil Wyatt24/05/2014 15:11:55
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I often use a parting tool with the toolpost turned at 45 degrees. Unlike many tool shapes the cutting edge is flat so you get a true surface. It's much quicker than turning the topslide.

Neil

Clive Foster24/05/2014 15:46:01
3103 forum posts
107 photos
Posted by Neil Wyatt on 24/05/2014 15:11:55:

I often use a parting tool with the toolpost turned at 45 degrees. Unlike many tool shapes the cutting edge is flat so you get a true surface. It's much quicker than turning the topslide.

Neil

Although this can work well turning the tool post and, for that matter the top slide, is a thing to be avoided if at all possible. Yes it does help you get more use out of a tool by pressing it into service to do jobs it wasn't specifically designed for but at the cost of needing to reset back to for normal afterwards. Possibly an acceptable process if you use a rear toolpost for parting or if you have a good indexing base for your four way or QC set-up so as to get things back to parallel automatically. Setting things exactly at 90° for parting off is essentially impossible mid-job with work in progress mounted up unless you have some clever way of gauging things.

Accurate angles belong on the tool not the mounting. The extra cost and mostly one time trouble of arranging a set of tools such that you don't have to routinely shift top slide and/or tool post angles is well repaid by the time saved and better cutting performance got from optimising around one set of working conditions. Shop time is a precious, limited, resource not to be wasted by repeated resetting.

Clive

jason udall24/05/2014 16:55:19
2031 forum posts
41 photos
Jason B..indeed..never said it wasn't. I am trying to agree with you..

It just seemed after your initial post others seemed to "look" for complex ways of doing what if normaly a simple job.

To machine a specific camfer feature or even a large/long one ..yes a different approach but simple corner breaks or radi.....
Well you get the picture..

Colin Heseltine24/05/2014 17:09:56
654 forum posts
227 photos

Hugh,

I cant help with your chamfering issue but am interested in which QCTP you are using. I also have a Colchester Student lathe (squarehead) and am looking to obtain a QCTP for this lathe rather than use the not very nice 4 way toolpost.

Thanks,

Colin

Neil Wyatt24/05/2014 19:27:03
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> if you have a good indexing base

I do, it's as repeatable as swapping toolholders and changing back again.

Neil

Hugh Gilhespie24/05/2014 19:28:08
130 forum posts
45 photos

Colin,

The QCTP came with the lathe when I bought it. It is a Dickson type and I believe it is size T2. It is a pleasure to use and particularly as I was lucky enough to buy a goodly number of tool holders from an ex-employee of Colchester lathes along with some other goodies, including the reat tool post that I use for parting off with an upside down tool.

I will try and post a picture of the QCTP.

Regards, Hugh

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