ER32 Boxford – what steel to use?

This topic has 17 replies, 6 voices, and was last updated 25 January 2021 at 20:41 by Andrew Tinsley.

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21 January 2021 at 14:02 #521505
Aled Dafis
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@aleddafis55847
Hi, I'm planning to make an ER32 chuck for my Boxford, would EN8 be a good grade of steel to use? EN3 would be even easier for me to machine but my feeling is that EN8 would result in a better product.

I'm a weekend hobbyist, so it's not going to be used for any kind of production work, just the odd job here and there.

Thanks

Aled
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21 January 2021 at 14:02 #27911
Aled Dafis
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@aleddafis55847
21 January 2021 at 14:05 #521506
Clive Brown 1
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@clivebrown1
All my similar attachments for my Boxford are mild steel, En1A or En3, with no apparent problems I think that you'd really only benefit from En8 only if it was heat-treated. For hobby use that would seem unnecessary.

Edited By Clive Brown 1 on 21/01/2021 14:09:26
21 January 2021 at 14:35 #521512
Aled Dafis
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@aleddafis55847
Posted by Clive Brown 1 on 21/01/2021 14:05:56:

All my similar attachments for my Boxford are mild steel, En1A or En3, with no apparent problems I think that you'd really only benefit from En8 only if it was heat-treated. For hobby use that would seem unnecessary.

Edited By Clive Brown 1 on 21/01/2021 14:09:26

Thanks Clive, that helps a lot to hear that you've had no issues with using EN1A or EN3

Regards

Aled
21 January 2021 at 15:11 #521520
old mart
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@oldmart
That steel will be perfectly good for hobby use, get a nut and use it for gauging the thread. The nut would not be easy to make due to the eccentric collet holder. There are plenty of drawings on line for the er range of holders.
21 January 2021 at 15:49 #521538
Aled Dafis
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@aleddafis55847
Posted by old mart on 21/01/2021 15:11:51:

That steel will be perfectly good for hobby use, get a nut and use it for gauging the thread. The nut would not be easy to make due to the eccentric collet holder. There are plenty of drawings on line for the er range of holders.

Thanks, yes that was my plan, I may as well get the bearing type nut as they're only a few pounds more expensive than the standard version.

Regards

Aled
21 January 2021 at 16:11 #521543
old mart
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@oldmart
I got one of the bearing type er25 nuts from Rotagrip and it is very nice to use.
22 January 2021 at 11:23 #521698
Howard Lewis
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@howardlewis46836
Being Idle / Cowardly Choose as you see fit, I buy my Clamp nuts. The ball bearing ones are easier to use, especially in the larger sizes.

The 40 x 1.5 mm thread is straightforward to produce. So is the 16 degree internal taper (8 degree Top Slide offset ).

To finish the taper, I wrap oiled emery tape around a collet and VERY carefully finish the taper., while the lathe runs at lowest speed.

DON'T press hard in case it grabs!

DON'T tell HSE!

So far, I have survived doing this six times!

Howard
22 January 2021 at 23:24 #521912
Aled Dafis
Participant
@aleddafis55847
Thanks Howard, I'm planning to be equally idle as regards the nut.

Thanks for the finishing tip, I'll keep that in mind.

Are yours EN1a or EN3? Are they holding up fine?

Aled
23 January 2021 at 12:03 #522003
Howard Lewis
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@howardlewis46836
Shouild I say Bore da? Mother was Welsh, but I know nothing!

SHOCK HORROR!

My Collet holders have all been made from dog ends from the Toolroom, when I was at work, so grade unknown, but BMS of some sort..

My guilty secret is out.

All of the holders seem to be standing up to use quite well.

The stable, so far is: ER 25 Tailstock Sliding Tap Holder, ER 20 Drill holder for the Cutter Grinder, ER 25 and ER32 Square and Hexagon work holders for Milling (Like Stevenson Blocks, but less refined ), ER 25 and ER 32 Floating Reamer Holders.

The ER32 Floating Reamer Holder uses home made collets, slit from only one end with 1, 2 and 3 MT internal tapers.

The ones seeing most use are the Tap Holder and the Drill Holder.

The only part seeing much relative movement is the thread. The taper bore sees only the slight movement of the collets as they are clamped or unclamped.

HTH

Howard
23 January 2021 at 15:32 #522068
old mart
Participant
@oldmart
Don't forget, when you bore the taper in the chuck, be sure to set the tool height exactly on the centre line.
25 January 2021 at 15:12 #522538
Aled Dafis
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@aleddafis55847
Howard and Old Mart, thank you both, your advice is much appreciated.

Aled
25 January 2021 at 16:29 #522554
Andrew Tinsley
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@andrewtinsley63637
I seem to remember that G H Thomas experimented with varying tool heights when turning Morse Tapers. I think his conclusion was "take the proverbial pinch of salt" about getting the tool height dead centre. .

Having the tool off centre by a few thou, didn't alter the taper within his measurement capability.. I think he said that it was a bit of an old wives tale, passed down from one book / article, to the next.

Andrew
25 January 2021 at 17:00 #522561
Tony Pratt 1
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@tonypratt1
Posted by Andrew Tinsley on 25/01/2021 16:29:10:

I seem to remember that G H Thomas experimented with varying tool heights when turning Morse Tapers. I think his conclusion was "take the proverbial pinch of salt" about getting the tool height dead centre. .

Having the tool off centre by a few thou, didn't alter the taper within his measurement capability.. I think he said that it was a bit of an old wives tale, passed down from one book / article, to the next.

Andrew

+1 on the reply above quoting G H Thomas, Iv'e got all his excellent books.

Tony
25 January 2021 at 18:21 #522582
old mart
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@oldmart
I have posted this part of the Smart & Brown model A manual before.
25 January 2021 at 19:01 #522589
Andrew Tinsley
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@andrewtinsley63637
Hello Old Mart,

What is quoted above is quite correct. What your Smart and Brown extract doesn't say, is how big the convex error is.

GHT did the measurements and showed conclusively that the errors are minute, even if the tool height is out by a fair amount. The Smart and Brown manual is an example of this old chestnut being repeated down the ages with no body bothering to check it in practice.

After reading GHT's comment a few years ago, I repeated his experiment and could not measure any difference in the taper for a tool height error of I think +- 5 thou. It was a long time ago!

Andrew.
25 January 2021 at 20:00 #522611
old mart
Participant
@oldmart
The height errors when taper turning have a lot to do with the relative diameters of the ends of the taper. If you were turning a taper of 45 degrees from 2" diameter to a point with the tool on centre, the result would be different if the taper was repeated with the tool below, or above the centreline. The error would get bigger as the point was approached. The model A is a high end toolmaking lathe and their recomendations have some meaning.
25 January 2021 at 20:41 #522625
Andrew Tinsley
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@andrewtinsley63637
I suggest that you do the experiment yourself, you might well be surprised at what you find! No point in arguing the toss when you can actually do the taper turning and measure the result,. I did and was very surprised I could not measure any meaningful convex shape. This was on an MT2 taper.

Andrew.
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