Form Tool or other way?

Hi Everyone,

Thank you, some more really helpful comments. The machine is this one: **LINK** (Click to play the video). I am replacing the existing old 1425rpm 1/4hp 240v motor, with a 2800rpm, 36v, 250w motor as we are working to make all the electric machines in the studio solar powered (except the weaving looms which are treadle powered!).

To be honest the existing drive pulley is a V profile, but I assumed that this was used simply because that is what the crofter had to hand (the machine is from the Isle of Lewis on northern west coast of Scotland where everything is bit Heath Robinson!). But perhaps not... certainly the driven pulley, which is 7", is also V profile. Perhaps this is my answer?

James

Edited By James Jenkins 1 on 19/05/2016 22:46:51

Edited By James Jenkins 1 on 19/05/2016 22:47:34

Edited By James Jenkins 1 on 19/05/2016 22:47:52

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James,

I agree 100% with Rod's comment

... and I think you have a wonderful project there

Best wishes for its success !!

MichaelG.

Old pre second world war Singer sewing machine heads had v drive pulleys, they were usually driven by round leather belting, this allowed the metal staple used to join them to pass through the V if set correctly. The round belt would slowly form into a rounded top and bottom V. If you can find it the best belting has a little hair on the top surface. It was left there to prove that the belt was cut from the top layer of the hide. A good belt would last for years of daily industrial use.

Regards
John

Thanks everyone, it seems a V profile is the the way to go and will be easier to turn as well. A double win!

I'll revise the drawing and post a pic of the finished item when done.

Thanks again everyone, really, really appreciate it.

James

Here is my revised design, to fit on the 8mm shaft of the motor. Secured by the left handed thread and a grub screw down to the flat. I realise the old hands will think this way over the top for 'a simple bloody pulley', but it does help me to get my head around it!

Why do you have a LH thread? Seems a bit OTT to me. If there's a flat on th shaft anyway that should do the trick. I doubt the motor would come with a LH thread cut, so how would you make it? Also 8mm is 0.315 inches not that the odd thous matter.

Hi John,

Thanks for that. The motor has a LH thread on the end of the shaft... I agree the flat would be enough, but I thought as the thread was there I might as well use it.

Thanks for the heads up on the math - I copied the text from the flange width and forgot to change it - I guess because it looked done. I'll change it now, so new readers won't notice!

James

The change to a V groove is a wise decision. You need the wedging action to keep the belt from slipping. The driven pulley also needs a V groove unless there is a long arc of contact. I suggest 34* to 38* included angle for the groove.

James

A drop or two of threadlock won't go amiss on the M4 screw for additional security. Nice project and it's good to know there are still such people as yourself to keep our heritage working.

Emgee

I would make the groove narrower and not flat bottomed. No pojnt making eth top of the vee more than a smidgin wider than the belt.

Neil

James - can't offer any more advice on the pulley but super-impressed with your machinery restorations.

Dave

How about rotating the workpiece slowly on a rotary table or dividing head while a cylindrical milling cutter nibbles away at the groove? And if the groove needs to be a non-standard diameter, set the cutter at a slight angle.

Not quite an exact 'circular' groove in the latter case, but does that matter?

Cheers, Tim

James,

There is no reason to avoid a flat at the bottom of the groove. Plunge a parting tool at the center of the groove. Take additional plunge cuts with the parting tool to get close to the V contour. Using the compound feed a tool down each side of the V.
Top of the V width can be as narrow ad the belt diameter. Since you are going to be pedaling the lathe don't take off any more metal than necessary.

John

Hi all,

Thanks so much for your advice everyone. Really helpful. Thank you also for your kind words regarding the weaving mill, I do hope that once we get set up you'll come and see them in action if you are ever in Suffolk.

I have been thinking about the operations to make the pulley, watched a couple of videos etc. Most seem to use a mandrel for turning these pulley's between centres, with the piece glued on or fixed on with a press. However, I cannot make a hole larger than 6.8mm and that feels too thin.

So after going through a few options in my mind, this is the draft procedure I currently thinking of:

1) Mount the the 2 1/2" diameter x c4" long bar in the 3 jaw chuck, center drill and mount onto a half centre

2) Working at the tail stock end, size the 2" diameter of the pulley into the bar, with sufficient clearance for further work, and cut the angled faces (Parting tool to depth, a series of straight cuts coming out to decreasing depths and then angled cuts to smooth).

3) Reduce the diameter of the flange to 1" and face the flange and the side of the main section. Break edges

4) Either part off (or hacksaw off) the pulley with 1/4" waste to the left. Mount in to the three jaw chuck, with the flange facing out. .

5) Successively drill up to 6.8mm, finishing inside the waste piece (to protect the rear of the chuck)

6) Turn the piece around in the chuck, using the flange as a mount and bring up the half centre on the tail stock to support the work. Remove the 1/4" and face. Break Edges.

7) Increase the bore to 7.8mm to a depth of 0.625" (end of the thread) and then ream to 8mm.

8) Remove from the lathe to tap the end thread and drill/tap the grub screw hole.

Am I about right or way, way off?

James

Edited By James Jenkins 1 on 23/05/2016 15:17:00

Edited By James Jenkins 1 on 23/05/2016 15:18:11

I would try and do the hole and V at one setting to keep things concentric.

1. cut off a bit of your bar say 1/4" overlength.

2. Hold in 3-jaw face off end and form reduced 1" dia of the boss.

3. Reverse in chuck so now holding by 1" dia. Face to length then form hole as described above.

4. Bring up tailstock support, turn 2" OD of pully

5, Cut Vee as described above.

Out of interest I needed to make a bender for some 1/2" tube yesterday, found a bit of scrap brass and used a 3/8" bull nossed HSS tool that I already had to form the 1/2" concave, just offering up the tube a couple of times and using eyeball and hand co-ordination for the rest.

There is if using a compliant belt that moulds to the shape of the groove, if it 'bottoms out' it will become more likely to slip as the wedging action with increased tension is much reduced.

Neil

Hi Jason, thanks so much for that. Really helpful. Thank you also Neil - helpful advice.

I started to work on sharpening up the tools that came with it. However, they are only tool steel and require quite a bit of work to get them in shape. So I am thinking I should get some HSS ones. In an ideal world I wouldn't buy a whole set now, but the prices for a set of 8 are often the same as 4 individual ones. These are the ones I am thinking of:

 http://www.myford.co.uk/acatalog/1_2__Tooling.html

http://www.chronos.ltd.uk/acatalog/Sets_of_HSS_Lathe_Tools.html (10mm or 12mm? - made by Soba)

Or second hand Myford (doesn't actually say HSS, but presumably is?) http://www.ebay.co.uk/itm/Original-Myford-boat-with-11-tool-cutters-Direct-from-myford-stuff-/182128615827?hash=item2a67b62193:g:YQkAAOSwvU5XNHpG

I wouldn't normal buy new, but I don't really want to spend days regrinding the tools to the correct angle… I am assuming the new ones will come nicely set up.

Any thoughts, ideas, alternative suggestions?

Edited By James Jenkins 1 on 25/05/2016 19:37:11

Edited By James Jenkins 1 on 25/05/2016 19:54:56