Opening the gap…

This topic has 22 replies, 11 voices, and was last updated 17 March 2016 at 00:46 by John Stevenson 1.

Viewing 23 posts - 1 through 23 (of 23 total)

Author

Posts
15 March 2016 at 01:43 #229992
Robin Graham
Participant
@robingraham42208
I have what is basically a generic 12×36 import gearhead lathe. When I bought it a forum member helpfuly pointed me to the Grizzly manual for their 'Gunsmith's lathe', which is a (much!) better written guide to the machine than that which came with my machine. That manual says that removal of the gap piece would be a ''modification', ie irreversible.. I didn't give much thought to this because I thought I'd never want to turn anything bigger than 12" anyway, but you know how it goes…

The lathe is running nice and true at the mo – my question is, am I likely to screw things up by taking the gap piece out?

Robin
Advert

15 March 2016 at 01:43 #8053
Robin Graham
Participant
@robingraham42208
15 March 2016 at 07:13 #229998
Michael Gilligan
Participant
@michaelgilligan61133
Very interesting, Robin … and very honest of Grizzly !!

I was intrigued by your reference & downloaded the 2015 manual. Sure enough; there it is, explicitly stated on p74.

They do say [or at least, strongly imply] that it is the insert that may distort, but; in truth, I think you must accept that the bed will also twist or bend to some extent, however slight that may be.

MichaelG.

Edited By Michael Gilligan on 15/03/2016 07:16:49
15 March 2016 at 07:39 #230000
JasonB
Moderator
@jasonb
I have heard that Chester view removing the gap piece in the same way and it makes the warantee void.
15 March 2016 at 07:44 #230002
Danny M2Z
Participant
@dannym2z
Then what is the point of selling a 'gap-bed' lathe?

I'm confused. Are the manufacturers/re-sellers admitting that it don't work?

* Danny M *
15 March 2016 at 07:49 #230004
pgk pgk
Participant
@pgkpgk17461
Posted by JasonB on 15/03/2016 07:39:36:

I have heard that Chester view removing the gap piece in the same way and it makes the warantee void.

I had heard that rumour before i bought mine and asked that specific question at Chester. I was told that the whole point of a gap bed lathe is to be able to remove the gap and it has no effect on their warranty.

Mind you I've had mine over a year and not removed the gap (yet) so I doubt any warranty applies.

My understanding is also that it's more of an issue trying to put the gap piece back afterwards….??
15 March 2016 at 07:51 #230005
Michael Gilligan
Participant
@michaelgilligan61133
Danny ,

It's a fact of life [fact of mechanics] that if the insert was ground in-situ; things will 'never be the same again' if you remove and replace it.

Call it honesty, or call it "mitigation against litigation" …

MichaelG.
15 March 2016 at 07:55 #230007
Michael Gilligan
Participant
@michaelgilligan61133
Posted by pgk pgk on 15/03/2016 07:49:54:

My understanding is also that it's more of an issue trying to put the gap piece back afterwards….??

.

The instructions are on p74 of that Grizzly manual

… It appears to be a fairly snug fit.

MichaelG.
15 March 2016 at 08:42 #230013
Anonymous
I have a friend with a 13×40 import lathe. The manual is quite explicit; if you remove the gap piece and then replace it they do not guarantee that the lathe will still turn parallel where the saddle runs over the gap piece. On my lathe (Harrison M300) that is not the case, although it can be a PITA to get the gap piece back and still have the lathe turning parallel. It's not so much as case of being ground in situ, or not, as of the machined surfaces and dowels to ensure that the gap piece can be put back with the same alignment. The key is ensuring that everything is scrupulously clean and to follow the sequence of fitting dowels and hold down bolts as per the manual.

Andrew
15 March 2016 at 09:01 #230019
Michael Gilligan
Participant
@michaelgilligan61133
Andrew,

I may be wrong, but; I think we are saying much the same thing, in our different ways.

The gap insert on your Harrison was engineered to be readily removeable and replaceable … and all the details are finished accordingly.

The Grizzly [et al] machines have a very tight-fitting insert, which is not designed or built that way …

MichaelG.
15 March 2016 at 09:41 #230030
pgk pgk
Participant
@pgkpgk17461
Posted by Michael Gilligan on 15/03/2016 09:01:32:

Andrew,

I may be wrong, but; I think we are saying much the same thing, in our different ways.

The gap insert on your Harrison was engineered to be readily removeable and replaceable … and all the details are finished accordingly.

The Grizzly [et al] machines have a very tight-fitting insert, which is not designed or built that way …

MichaelG.

..and that's the point. If it's fiddly to get right with the harrison then I'd expect it more so with a clone built to a price. As for close fitting.. well if it wasn't having a structural benefit then there'd be not much point in the gap piece at all. I'm not looking forward to the time i need to remove mine ..mostly because that's where all the chips land so out and in are bound to be a cleaning 'mare
15 March 2016 at 10:06 #230039
colin hawes
Participant
@colinhawes85982
If no great care was taken to ensure good clean finish when originally fitted there is not much chance of the gap piece being accurate after removal and refitting. Some of the imported machinery I've used shows such carelessness in other areas and I suppose that's inevitable at the price. Colin
15 March 2016 at 10:12 #230041
Michael Gilligan
Participant
@michaelgilligan61133
Posted by pgk pgk on 15/03/2016 09:41:56:

As for close fitting.. well if it wasn't having a structural benefit then there'd be not much point in the gap piece at all.

.

May I just elaborate on that ?

There is another good reason for having a [non-structural] gap filler … It lets the saddle get close to the headstock, but also allows the use of big chucks in the gap.

Have a look at a Myford, or similar, and you will see the compromise that otherwise needs to be made.

MichaelG.
15 March 2016 at 10:39 #230047
Roderick Jenkins
Participant
@roderickjenkins93242
Posted by Michael Gilligan on 15/03/2016 10:12:44:

Have a look at a Myford, or similar, and you will see the compromise that otherwise needs to be made.

Not usually a problem unless you are using the Myford patent collets, which fit directly in the spindle bore – which is why my swarf guard has become.. er.. "modified"

Rod
15 March 2016 at 10:39 #230048
colin hawes
Participant
@colinhawes85982
Quite right Michael, the gap piece should not be part of the structural strength, my old 7" centre height Drummond has a very usefull removable gap piece for doing bulky work on the faceplate and I've used it many times without problems on vintage car and motorbike repairs. Colin
15 March 2016 at 10:40 #230049
pgk pgk
Participant
@pgkpgk17461
I'm guessing one could design a chuck standoff or a beefier, longer travel cross slide to make up for that..and the compromises that causes.

I was aware of why the gap piece is there and lathes without.

Re the OP's first post… I;m guessing recalibration will be needed after removal of the gap and again when put back. I've just had to redo mine just from use/abuse and I guess it's something that needs checking regularly.. Especially on bench lathes and hobby ones not bolted through the floor.
15 March 2016 at 10:48 #230053
Michael Gilligan
Participant
@michaelgilligan61133
Posted by pgk pgk on 15/03/2016 10:40:52:

I'm guessing one could design a chuck standoff or a beefier, longer travel cross slide to make up for that..and the compromises that causes.

I was aware of why the gap piece is there and lathes without.

.

Clearly, I can contribute nothing further to the discussion.

My first post really said what I wanted to say.

MichaelG.

Edited By Michael Gilligan on 15/03/2016 10:52:36
15 March 2016 at 10:51 #230054
Michael Gilligan
Participant
@michaelgilligan61133
Posted by Roderick Jenkins on 15/03/2016 10:39:12:

Posted by Michael Gilligan on 15/03/2016 10:12:44:

Have a look at a Myford, or similar, and you will see the compromise that otherwise needs to be made.

Not usually a problem unless you are using the Myford patent collets, which fit directly in the spindle bore – which is why my swarf guard has become.. er.. "modified"

Rod

.

Apologies, Rod … perhaps I should have said compromises [plural] … The main limitation, in my mind, is that the Myford gap is necessarily rather narrow.

MichaelG.
15 March 2016 at 10:55 #230055
John Stevenson 1
Participant
@johnstevenson1
Take mine out of the TOS and the Chinese 14 x 30 lathe quite often.

Just need a bit of a clean up [ as expected ] and they go back with no problem.

Sometimes you can over think things. Practical beats theory any day.
15 March 2016 at 12:51 #230078
Bob Rodgerson
Participant
@bobrodgerson97362
I have taken the gap filler out of my lathe (BH 600) a few times without any problems. Just make absolutely certain there is no swarf around that can get in the wrong places.
17 March 2016 at 00:20 #230377
Robin Graham
Participant
@robingraham42208
Well, conflicting views, but it sounds like the importers are just covering their backs by saying that they can't guarantee that that the lathe will still run true if the gap piece is taken out then replaced. Which is entirely reasonable – they are selling mainly to the hobby market I suppose, and there's a wide range of experience ,skill and expectation they have to cater for.

My plan isn't going to work anyway – what I wanted to do was work on a bit of plate mounted on the lathe's faceplate, but the gap is so big I won't be able to get anywhere near it. Doh! I'll find another way to skin this cat, (buy a bigger mill!) but thanks anyway for your replies – if ever I find a sensible reason for taking the gap out I'll do it. In pic below the front of the saddle is lined up with the break in the bed.
17 March 2016 at 00:34 #230380
Nick_G
Participant
@nick_g
Posted by John Stevenson on 15/03/2016 10:55:16:

Take mine out of the TOS and the Chinese 14 x 30 lathe quite often.

Just need a bit of a clean up [ as expected ] and they go back with no problem.

Sometimes you can over think things. Practical beats theory any day.

.

I am willing to make a guess that the problem lies with the 'avarage' end consumer of products that will be in that price bracket of the voided warranty machines.

It's probably simpler for the distributors to make a blanket void than the aftermarket hassle of the 'avarage' end user not being as knowledgeable and adept at putting machines back together properly as John who has had a lifetime of doing such.

I remember seeing a youtube video of somebody putting the gap bed back into situ. – I will see if I can find it.

Edit :- Found it.!

Nick

Edited By Nick_G on 17/03/2016 00:45:37
17 March 2016 at 00:46 #230382
John Stevenson 1
Participant
@johnstevenson1
Posted by Robin Graham on 17/03/2016 00:20:30:

Well, conflicting views, but it sounds like the importers are just covering their backs by saying that they can't guarantee that that the lathe will still run true if the gap piece is taken out then replaced. Which is entirely reasonable – they are selling mainly to the hobby market I suppose, and there's a wide range of experience ,skill and expectation they have to cater for.

My plan isn't going to work anyway – what I wanted to do was work on a bit of plate mounted on the lathe's faceplate, but the gap is so big I won't be able to get anywhere near it. Doh! I'll find another way to skin this cat, (buy a bigger mill!) but thanks anyway for your replies – if ever I find a sensible reason for taking the gap out I'll do it. In pic below the front of the saddle is lined up with the break in the bed.

This is one reason I much prefer the English apron, the handwheel is on the right and still has some travel when the gap is out. True it's unsupported but better than nothing.

The American pattern which is gaining favour as the Chinese sell more in America than the UK has the hand wheel on the left as in the picture. Right in the way of all the red hot crud flying off the work.

I'm sure Capricorn One was for real.
Author

Posts