Lathe Tool Grinding

[George SwordParticipant @georgesword12072]

I wonder if anyone can supply me with lathe tools ground to shape to enable me to produce the semicircular grooves required for the manufacture of the formers required for the tube bender described in issue No 297 of MEW. I only require the formers for the 1/4" and the 3/16" pipes.

I will recompense for all costs including postage.

Many thanks.

[George SwordParticipant @georgesword12072]

[EmgeeParticipant @emgee]

George

What size tooling does your lathe use ?

Emgee

[not done it yetParticipant @notdoneityet]

Posted by Emgee on 02/11/2020 17:13:46:

George

What size tooling does your lathe use ?

Emgee

Doubt it is less than 1/4”?

[George SwordParticipant @georgesword12072]

Emgee,

I usually use 10 or 12mm tooling. My lathe is a Colchester Student.

[Nigel Graham 2Participant @nigelgraham2]

This is a matter I have in mind to extend the range downwards of a Rothenburg pipe-bending set.

I might also need similar operations to make aluminium or Nylon pulleys for block-and-tackle.

My thought is either to make simple tangential tools from silver-steel or the shanks of worn-out/broken cutters etc, or to use insert button tools.

The latter are metric so 5mm and 6mm but I don't think the diameter error for 3/16" (0.24mm below 5mm) and 1/4" (0.25mm above 6mm) would hurt. Cut the 6mm groove 0.1mm wide each way, testing with a sample of pipe.

[peak4Participant @peak4]

I haven't really thought this through fully, but after turning the blank, how about transferring to mill & rotary table/dividing head, and using the side of a ¼" end mill?

Bill

[EmgeeParticipant @emgee]

Posted by peak4 on 02/11/2020 21:34:36:

I haven't really thought this through fully, but after turning the blank, how about transferring to mill & rotary table/dividing head, and using the side of a ¼" end mill?

Bill

My 1st thought Bill but the poster request was for form tools to use on a lathe, perhaps he doesn't have a mill and rotary table.

Emgee

George, check your mail box on the top menu bar.

 

Edited By Emgee on 02/11/2020 22:22:28

[Howard LewisParticipant @howardlewis46836]

You could make your own tools.

All that you need to do is to make up one or more tool holders, to hold a piece of High Speed Steel toolbit of the desired diameter, at an angle of about 12 degrees from vertical.

You grind the end of the tool bit at an angle of about 20 degrees and install it in the holder so that the ground surface is at centre height, to give a rake angle of about 8 degrees.

You then gently plunge the tool into the work for half the diameter of the toolbit, and you have a semi circular groove ready for pipe bending..

GENTLY to minimise the risk of chatter, at low spindle speed.

HTH

Howard

[EmgeeParticipant @emgee]

Howard, won't grinding at any angle destroy the circular shape on the end of the tool ?

Emgee

[HopperParticipant @hopper]

The traditional method would be to take a piece of 1/4" HSS square blank and grind the required radius on the end freehand on the bench grinder. It's not hard to do. Make a template by drilling a hole in a piece of sheet metal and cut it in half. Grind tool to match template,with 10 degrees or so of clearance all round.Tool is then held in toolpost on top of suitable packing strips to achieve centre height.

It's a skill well worth developing and not terribly difficult.

[Stewart HartParticipant @stewarthart90345]

The best and most accurate way to produce the formers is with an end mill of the desired size. Mount the former in a spin indexer or other similar device on the Mill and with the end mill of the requires size simple advance the end mill into the former and at the same time slowly rotate the indexer keep advancing the end mill until you've got the required depth you'll end up with a perfect radius of the correct size in the former. No messing about grinding forming tools

Stew

[Brian Baker 2Participant @brianbaker2]

Greetings, I used the end of a broken centre dill of the size required, ground at a suitable angle, in a home made holder to cut the radius formers you are looking to make. Quick & easy, if you have any broken centre drills otherwise use round tool steel.

regards

Brian

[Lee RogersParticipant @leerogers95060]

Grinding your own is well worth the time and effort required. A usefull project is to fit a very stable rest on to your bench grinder. Make it larger than the old floppy one and possibly build in a guide system. It doesn't have to be a masterpiece , just functional. One other point, several posters have quoted angles of ''about x degrees'', absolutley right , you don't need to get into 17 1/2 degrees or whatever just get it about there.

[George SwordParticipant @georgesword12072]

Many thanks to everyone for replying. It's all been a great help.

Regards

George

[Howard LewisParticipant @howardlewis46836]

Emgee,

Yes, grinding a circular bit at an angle will produce an ellpse, but for pipe bending the discrepancy probably won't matter all that much..

Recently I used this method to cut a 4 mm pitch semi-circular thread. The "follower" is a ball bearing, snd the end result serves the purpose for which it was intended.

Howard

Wireless keyboard GRRR

Edited By Howard Lewis on 04/11/2020 21:52:23

[Mick B1Participant @mickb1]

Posted by Hopper on 03/11/2020 02:20:59:

The traditional method would be to take a piece of 1/4" HSS square blank and grind the required radius on the end freehand on the bench grinder. It's not hard to do. Make a template by drilling a hole in a piece of sheet metal and cut it in half. Grind tool to match template,with 10 degrees or so of clearance all round.Tool is then held in toolpost on top of suitable packing strips to achieve centre height.

It's a skill well worth developing and not terribly difficult.

Absolutely. It only takes a bit of time and patience, and you can make tools of almost whatever form you can imagine to achieve what you're aiming for.

[Mick B1Participant @mickb1]

Posted by Hopper on 03/11/2020 02:20:59:

The traditional method would be to take a piece of 1/4" HSS square blank and grind the required radius on the end freehand on the bench grinder. It's not hard to do. Make a template by drilling a hole in a piece of sheet metal and cut it in half. Grind tool to match template,with 10 degrees or so of clearance all round.Tool is then held in toolpost on top of suitable packing strips to achieve centre height.

It's a skill well worth developing and not terribly difficult.

Absolutely. It only takes a bit of time and patience, and you can make tools of almost whatever form you can imagine to achieve what you're aiming for.

[Author]

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