By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Forum House Ad Zone

Harrison Lathe cross Slide. unfriendly index dial markings

All Topics | Latest Posts

Search for:  in Thread Title in  
Ian P29/01/2016 19:38:18
avatar
2747 forum posts
123 photos

m250 cross slide index markings .jpg

I have a Harrison M250 and find some of its feature very frustrating. Its a long story, but my machine is imperial but I prefer and mostly live in the metric world.

When I discovered it was an imperial machine, I fitted a DRO with glass and magnetic scales thinking that would totally solve my problems, mostly it does but there are times when the ability to move a slide using the index markings would be useful. A typical example would be when a part is turned to a finished diameter with one cutter and then an 'O' ring groove has to be cut to a certain depth. Changing tools loses the DRO calibration so the obvious method is to use the index wheel referenced to the point where the groove tool makes contact with the part's known diameter. Its simple to convert the depth dimension to inches but the index wheel markings mean I also have to multiply by two.

Two things about the M250 dials annoy me, firstly the markings relate to diameter rather than radius and secondly the digits are too verbose. The feedscrew is 10TPI and Harrison have opted to scale the wheel with 200 increments (.01 .02, .03, etc to .19). In my opinion it just clutters the dial and adds confusion.

Since Harrison offered a T slotted table to fasten to the cross slide it seems odd they chose diameter increments.

Am I alone in finding diameter calibrations on a lathe slide frustrating, I would be interested in how other people get on with this feature?

Ian P

John Haine29/01/2016 19:55:44
5563 forum posts
322 photos

I understand that metric lathes are always calibrated in diameter, odd though that your imperial one is too! All 3 metric lathes I've owned were / are diameter calibrated. Harrison lathes being aimed mainly at a professional market, where a shop is likely to have a milling machine as well, the main use for a tee slotted cross slide would be for boring where you wouldn't use the feed calibrations. So most of the time it would be useful to have diameter calibrations as the main use would be turning perhaps?

Personally I've always been perfectly happy with diameter calibration as I've never had to make the change from imperial to metric.

Spurry29/01/2016 20:52:52
227 forum posts
72 photos

It's probably a case of what you are used to. I have a metric M250 and find the diameter cross-slide fits in with measurements of diameter very well. If I am turning to a specific diameter, a small cut is taken , measure the diameter (not radius) then wind in the reduction required. No halving, doubling or anything else.

In your specific case of wanting a groove at a specific depth, then arithmetic is called for.

When I bought my machine (in 88?) Harrison did make dual reading dials, but I never really liked them and settled to Go Metric only.

Pete

KWIL29/01/2016 21:50:06
3681 forum posts
70 photos

If you want a groove of known depth from a known diameter, just turn to the new diameter required??

Ian P29/01/2016 22:11:21
avatar
2747 forum posts
123 photos

Thats exactly what I do Kwil. Its just made more complicated by the need to convert units (including max/min tolerance dims) when calculating the groove depth (diameter).

I was unaware that the convention for Metric lathes was to read diameter. I did own a Metric Boxford but that had a radius reading index.

Ian P

Clive Foster29/01/2016 22:25:17
3630 forum posts
128 photos

Agree with Spurry that its a case of what you are used to. My big argument against diameter reading dials is that machines so fitted only ever, so far as I've seen, have them on the cross slide. The top side being calibrated directly in travel (i.e. radius) so you have two different scales on the same machine. Problem can get worse if you have more than one lathe tho'.

My Metric Smart & Brown 1024 has direct distance reading dual metric - imperial dials on both cross and topside. Very nice until you read or set the wrong scale. It also has an accurate saddle travel reading dial. Metric only unfortunately. My habit is to set the dials so the final cut is made on zero. Gets all the maths and figuring out of the way before you start cutting. With 2.5 mm and 100 thou per rev on the dials one turn out is easily seen. High end industrial accuracy and repeatability makes life so much easier. Given a sharp tool the cut is what it says to a tenth of a thou or better.

My other lathe is a Pratt & Whitney Model B 12 x 30. That has a diameter reading dial calibrated 0-250 in thousandths of an inch on the cross slide and direct travel ( i.e. radius) reading dial calibrated 0-200 in thousandths of an inch on the top-slide. So you have to keep your brain engaged when using both slides. Not a great lover of the diameter reading cross-slide dial for normal turning but had a job this week involving facing out to a diameter leaving a ridge which sowed the direct reading to a advantage. Quite relaxing to watch the dial tool smoothly down to the designated zero for 5" diameter with the wartime built machine purring away at around 100 rpm. P&W gears are quiet. Colchester it aint. Being a four shaft lathe it was easy to drop the drive with less than a thou error using the apron controls for either the forward / reverse single tooth dog clutch or the main drive clutch. With conventional gears for speed setting and screwed star wheel engaged clutches for the power feeds too its had to imagine a bigger contrast to the clutchless, two shaft, 1024 VSL with its motor driven push button infinitely variable speed drive. Anyone used to a typical model engineers lathe could get straight on with the 1024. The P&W would take more of an adjustment.

200 increments on a diameter reading imperial dial is fine. Lets you work to a thou easily. But calibration by decimals of an inch is an abomination. Thous and no decimal points is far nicer. I know there is no escaping decimals with a metric dial but I still don't approve.

Edited By Clive Foster on 29/01/2016 22:26:47

Bazyle29/01/2016 22:40:22
avatar
6956 forum posts
229 photos

Just make a brass band that covers the numbers you don't like and engrave with numbers you do like.

Andrew Johnston29/01/2016 22:49:41
avatar
7061 forum posts
719 photos
Posted by Ian Phillips on 29/01/2016 19:38:18:

Am I alone in finding diameter calibrations on a lathe slide frustrating, I would be interested in how other people get on with this feature?

My imperial lathe (Harrison M300) is as described; diameter reading on the cross slide and direct reading on the top slide. It seems logical to me and I've never had a problem with it.

While my engine build is mostly imperial all of my commercial work is metric. For metric work I use metric micrometers and do the 40 thou equals 1mm conversion in my head. If I need accurate metric dimensions off a given diameter I touch off the tool on the work (with a fag paper) and zero the cross slide dial. I then work out the change in diameter and do the conversion to imperial.

Like the meerkat says - simples.

Andrew

John Stevenson29/01/2016 23:50:26
avatar
5068 forum posts
3 photos
Posted by Andrew Johnston on 29/01/2016 22:49:41:
Posted by Ian Phillips on 29/01/2016 19:38:18:

Am I alone in finding diameter calibrations on a lathe slide frustrating, I would be interested in how other people get on with this feature?

My imperial lathe (Harrison M300) is as described; diameter reading on the cross slide and direct reading on the top slide. It seems logical to me and I've never had a problem with it.

Andrew

.

Seems logical to me as well both dials are direct reading.

If the cross slide was in radius then you would be doubling the cross slide and accepting the top slide ?

You want weird dials then look at some of the bigger Chinese lathes, they go 0.4, 0.8, 1.2 etc

That's weird.

Kettrinboy30/01/2016 08:40:30
94 forum posts
49 photos

My 63 L5 is metric and has a radius reading crosslide dial , ive had it 30 yrs but if i had the choice i would have preferred a dia reading dial as it makes things a bit simpler i suppose at some point i could make a dia dial , i have made my own tailstock dial and though the thread in that is imperial but its still great for drilling to exact depthsharrison l5 tailstock dial.jpg

Kettrinboy30/01/2016 08:40:36
94 forum posts
49 photos

My 63 L5 is metric and has a radius reading crosslide dial , ive had it 30 yrs but if i had the choice i would have preferred a dia reading dial as it makes things a bit simpler i suppose at some point i could make a dia dial , i have made my own tailstock dial and though the thread in that is imperial but its still great for drilling to exact depthsharrison l5 tailstock dial.jpg

JasonB30/01/2016 10:12:52
avatar
25215 forum posts
3105 photos
1 articles

As you have a DRO why don't you just set that to read in radius rather than diameter.

As for the groove just bring your parting tool upto the work as its rotating, when it touches simply zero the DRO and then feed in the required amount. You can use incremental if you don't want to loose the absolute.

I have a 10tpi screw and same divisions as you on my 280 and have no issues with it reading dia.

KWIL30/01/2016 10:24:06
3681 forum posts
70 photos

Completely agree with Jason, more straight forward with a DRO fitted, but not a problem if not.

If I am being very particular I can fit my DRO equiped topslide as wellsmiley. With more than one lathe? just need to remember which one you are using!

Ian P30/01/2016 10:37:48
avatar
2747 forum posts
123 photos

Thanks for all the replies. I think the 'user friendliness' aspect is a matter of what one is used to. I did not have a DRO on the Boxford and direct readings dials became second nature. Because of the M250 DRO, I rarely use the cross slide graduations so when I do, I have to take extra time and adjust my way of thinking to avoid errors.

I'm tempted to print a new set of index wheel graduations on white drafting film, wrap/glue it round the existing scale and put thin clear heat shrink sleeving over the top. Might need a couple of attempts to get the strip length exact but it would be an easy fix.

Probably should be the subject of another post, but the M250 spindle speed gear selectors are far more complicated to use than they could be, but even that though is nothing to the confusing setting arrangement of the screwcutting gearbox!

Ian P

John Stevenson30/01/2016 10:40:12
avatar
5068 forum posts
3 photos

If it's a glass scaled DRO then most of them have a 200 tool memory.

When you start the job do a test cut and set this with your normal turning tool as no 1, then swap to the parting tool, light cut measure and set this diameter as No 2.

Then turn the work to size, swap tools, swap from 1 to 2 in memory and you are now back on size for the parting tool.

Simples.

If you run out of the 200 tool memory then I'm afraid it's time to take your shoes and socks off.

Ian P30/01/2016 11:27:26
avatar
2747 forum posts
123 photos
Posted by John Stevenson on 30/01/2016 10:40:12:

If it's a glass scaled DRO then most of them have a 200 tool memory.

When you start the job do a test cut and set this with your normal turning tool as no 1, then swap to the parting tool, light cut measure and set this diameter as No 2.

Then turn the work to size, swap tools, swap from 1 to 2 in memory and you are now back on size for the parting tool.

Simples.

If you run out of the 200 tool memory then I'm afraid it's time to take your shoes and socks off.

John

Mine is a SINO display and it does have umpteen tool memories etc. My problem is that the manual/instructions defeat me!

Just realised there seems to be a common theme to the cause of my whinges,,,, lack of my skills!

Ian P

Ian S C30/01/2016 12:05:10
avatar
7468 forum posts
230 photos

My 13 x 26 Taiwanese lathe is calibrated in diameter cuts, I thought all the larger lathes were. I got trapped when a mate got a second hand Myford S7, and he asked me to do a job or two, just to see if it was OK, first go oops, took off twice what I intended to (silly damn lathe, mutter, mutter), then carry on. The old Harrisons that we had at school were diametric reading, and they dated back to at least 1920.

Ian S C

Cabbage Stack23/07/2016 17:34:00
5 forum posts

I can't see how it would be a problem to turn a diameter using the DRO, then change the tool to a groove tool, "touch off"" on the OD, reset the DRO x value to zero, then cut your groove to the required dia. It's standard practice everywhere I have seen.

"Changing tools loses the DRO calibration " Well it does BUT,

as I mentioned above, that's why you "touch off", meaning you touch the new tool to the spinning work so as to take off nearly nothing, you'll see it when it happens, and then set your DRO accordingly. Same thing on a milling machine. It's been done this way for ages. The real advantage is the fact that with glass scales, backlash in the screws a non-issue because the glass scales read the absolute position.

Many DROs (such as my Shumatech, have diameter and radius mode)

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Sign up to our Newsletter

Sign up to our newsletter and get a free digital issue.

You can unsubscribe at anytime. View our privacy policy at www.mortons.co.uk/privacy

Latest Forum Posts
Support Our Partners
cowells
Sarik
MERIDIENNE EXHIBITIONS LTD
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest

 

Donate

donate