Split: Dowels – Finding a professional model engineering service

[toptracksParticipant @toptracks]

I have a small workshop which includes a Myford lathe, small CNC router and an old Chinese Milling Machine. I have a requirement to manufacture 400 mild steel slugs, 8mm Diameter (Drawn bar, no turning required) 100 off 10mm length / 100 off 12mm length / 100 off 14mm length / 100 off 16mm length. Can anybody quote me for this work, or put me in contact with a suitable supplier.

Many Thanks

Lawrence

[BazParticipant @baz89810]

Simple parting off job, why can’t you do them on your Myford?

[toptracksParticipant @toptracks]

Hi Baz, I am currently making them on the Myford, however it is very tedious work. Also after these 400 off I think I will need another 1000. Hence its a CNC job, but I cannot find anyone interested.

[JasonBModerator @jasonb]

Unless someone has a bar feeder on their CNC it is going to be almost as tedious due to having to stand there and advance the stock.

Is a parted off end acceptable with the likely resulting pip? Or do you need both ends facing and any form of deburring/chamfer?

What is the length tollerance 0.01mm or 0.1mm?

[Peter Cook 6Participant @petercook6]

Have you looked at Accu.co.uk. They advertise dowel pins in the sizes you want – albeit in stainless. 8mm diameter 10mm long look to be 35pence each, 16mm long go up to 43p each in 100 off.

They also advertise custom made parts so may be willing to do a mild steel special.

[BazParticipant @baz89810]

That is certainly not a job for a CNC, more like a capstan or turret lathe job. I would look for someone with a Britan turret lathe, ideal job for that machine, they have a pneumatic bar feed so it’s just a case of face, feed and part. The killer will be if they have to be second op faced to length which means hand loading to collet with backstop.

[JasonBModerator @jasonb]

Why is it not a job for a CNC?

They have bar feeders and if a full machining ctr would be able to hold the part in the second chuck while it is parted off and face the end of that while the end of the next bit of stock is being faced and chamfered in the first chuck. That is how the likes of ACCU will produce a batch

You can even get a bar feeder for the little Sherline CNC lathes

[baz]

On baz Said:

That is certainly not a job for a CNC, more like a capstan or turret lathe job. I would look for someone with a Britan turret lathe, ideal job for that machine, they have a pneumatic bar feed so it’s just a case of face, feed and part. The killer will be if they have to be second op faced to length which means hand loading to collet with backstop.

Surely the issue isn’t whether it’s done on a CNC or traditional batch machine, but that although the batch size looks huge for a small DIY machine it’s tiny for a commercial job?

[BazParticipant @baz89810]

Yes Jason a CNC lathe with kissing chucks will do exactly as you say but at what cost? It’s far cheaper to run a capstan or turret lathe per hour than it is to run a CNC machine, just look at the size of the power cable going in to the back. I am not saying CNC can’t do the job, it’s what it would cost to do the job.

[John HaineParticipant @johnhaine32865]

What’s the power cable got to do with it?  Apart from the spindle motor (same as a capstan), the electronics are unlikely to use more than 500W.

[Julie AnnParticipant @julieann]

Baz is spot on, it’s all about money not technology. Using an expensive CNC turning centre charged at around £100/hour for a simple job is uneconomic for the machine shop, and for the customer. One machine shop I used professionally had a Britan for exactly that reason.

There are CNC chucking lathes available, essentially a CNC version of a capstan lathe.  But I’ve never seen one in a commercial machine shop.

As it happens I have a Britan, complete with bar feeder, in the workshop. But I don’t have an 8mm collet.

Julie

[baz]

On baz Said:

Yes Jason a CNC lathe with kissing chucks will do exactly as you say but at what cost? It’s far cheaper to run a capstan or turret lathe per hour than it is to run a CNC machine, just look at the size of the power cable going in to the back. I am not saying CNC can’t do the job, it’s what it would cost to do the job.

I doubt if there are many shops with capstan or turret lathes still around? But maybe someone does know of such a shop still running these machines?

Tony

[BazParticipant @baz89810]

Thank you Julie. I also have an Britan, 1 1/4 capacity a later version green one with bar feed, also got their four in a row tool grinder.

John Haine

2 HP motor takes as much as 20 HP spindle motor, don’t think it does, not in my shop.

Tony

Lots for shops have an old capstan or lathe with capstan attachment for cr#p that’s not worth doing on CNC

[Nick HughesParticipant @nickhughes97026]

Hi Lawrence

Try EKP Supplies https://www.ekpscrews.com/

[Nick Hughes]

On Nick Hughes Said:

Hi Lawrence

Try EKP Supplies https://www.ekpscrews.com/

On baz Said:

Thank you Julie. I also have an Britan, 1 1/4 capacity a later version green one with bar feed, also got their four in a row tool grinder.

John Haine

2 HP motor takes as much as 20 HP spindle motor, don’t think it does, not in my shop.

Tony

Lots for shops have an old capstan or lathe with capstan attachment for cr#p that’s not worth doing on CNC

Nobody specified either 2 or 20 hp.  My point was merely that the spindle power on a cnc or capstan could be the same so the only extra power needed like for like is for the controller which is likely to be sub kW.

[toptracksParticipant @toptracks]

<p style=”text-align: right;”>Thank you John and Nick, I will try EKP supplies, looks like they have suitable machines and processes.</p>
 

[toptracksParticipant @toptracks]

Just to clarify the part off length tolerance I require is +/- 0 1mm. Some great discussion, thanks to everyone who has contributed

Just to reiterate I need companies who would be interested in manufacturing these items. 8mm Dia (No machining required). Part off / cut to lengths of 10mm, 12mm, 14mm and 16mm. 400 off required.

Thanks Lawrence

[Julie AnnParticipant @julieann]

For a professional machine shop to be interested you will need the following:

• An engineering drawing with tolerances, schedule and material specification
• Any other essential specifications such as no parting off pips and surface finish if important

You will also need to know the answer to the following questions:

• What is the maximum unit cost you are prepared to pay?
• Who supplies the material, customer or machine shop?
• What are your timescales?

You will also need an answer to the following machine shop saying:

You can have the parts fast, accurate, cheap – pick any two.

Good luck in your search.

Julie

[OldironParticipant @oldiron]

Clicking here from the “Latest Posts” tab. I suddenly realised that half of this thread was high jacked.

Started out as a silver soldering enquiry and landed up dealing with CnC/Capstan bulk turning requirements from a totally different author.  Maybe the Moderators can split the 2 threads apart so as not to lose the 2nd half dealing with parting off to posterity.

Maybe a note somewhere to tell ppl not to highjack a thread.

[baz]

On baz Said:

…I also have an Britan, 1 1/4 capacity a later version green one with bar feed, also got their four in a row tool grinder.

My Britan is 1-1/4″ too, but the older, rounded model and it came with a lot of accessories. I was lucky to win a couple of Ebay auctions for Britan accessories soon after getting the lathe. The auctions included some collets for the 3/4″ Britan which I sold to someone with the 3/4″ model who made automata.

Is your four in a row tool grinder the one that was on Ebay for some while?

Julie

[BazParticipant @baz89810]

Julie,

No my grinder came from Steve Holder at Home and Workshop at least 15 years ago, the Britan came from Javelin machine tools at Staines over 30 years ago, quite a bit of tooling included.

[SillyOldDufferModerator @sillyoldduffer]

Lawrence (toptracks) has a nasty problem.

8mm Dia (No machining required). Part off / cut to lengths of 10mm, 12mm, 14mm and 16mm. 400 off required.  Maybe another 1000 later.

Do-able on a Myford or a mini-lathe except the number needed means the job is very tedious.  Making a few thousand would drive me mad.

A capstan, turret lathe or CNC with a bar feeder would do the job, but only if you have one, and they’re not cheap.  I don’t have room for one, and buying in just to make a few thousand slugs is uneconomic.

Outsourcing is nasty too, because a few thousand is low profit for a professional operation, and they may well not be interested.  The customer has to find a firm, explain what’s needed accurately, and not have a heart attack when he gets the quote!  Likely to include a heavy up-front set-up cost, making the first few hundred slugs expensive.   Only after the set-up has been paid for does the per slug cost drop, which it does dramatically as the thousands rise.

There may be a way!  I always recommend everyone buy a copy of LH Sparey’s “The Amateur’s Lathe”; he covers all the basics.   Chapter 16 is “Production Methods in Small Lathes“.   His opening example is rather more complex than toptracks’ slugs, but the way they are made is similar.   Done with stops and a few simply made special tools, nothing complicated, and knocking out slugs that don’t need to be machined accurately to a good finish is simpler.  Stops speed up positioning the material and cutters considerably – they remove the need to measure and reduce the skill required.

The Chapter covers various other production methods that Sparey applied to his Myford, but the techniques can be applied to other lathes.

I think Sparey is a good compromise – Lawrence takes on a mild-tooling up job, and then bangs out slugs.  Still tedious, but much faster than machining each and every one individually, and practical without breaking the bank.

I recently annoyed someone by daring to say that Myford’s aren’t ideal for production work because they are too light.   In this case production only runs into low thousands, so not a problem, but I hope it’s clear that making 100,000 slugs on a Myford would be asking too much.  It will wear out the lathe!  When volume production is needed, outsource or cough up for a hefty capstan or turret lathe that’s designed and accessorized for that type of work.

Dave

 

 

[John HaineParticipant @johnhaine32865]

If making components in a small batch economically is too expensive in time or money, maybe a redesign to eliminate them is called for.

[GreensandsParticipant @greensands]

FAO Jason -This thread has been highjacked. As the originator, could you please take note of Gridiron’s suggestion and do something about separating the two quite distinct lines of enquiry.

[SillyOldDufferModerator @sillyoldduffer]

I’ve split it, but can’t find Greensands original.

Odd.

Apologies if it’s gone wrong.

Dave

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