By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Jan 24th

Boring heads

All Topics | Latest Posts

Search for:  in Thread Title in  
Andrew Johnston25/10/2018 07:58:34
avatar
5664 forum posts
653 photos
Posted by Simon Williams 3 on 24/10/2018 22:47:47:

Hi Andrew, if that's aimed at me............................................

(I was tempted to answer with something facetious about using a digital Vernier, but I thought I'd better not).

It was actually directed at Ron, but I forebore from saying calipers were the wrong answer! Turns out he's machining to fit an existing part, which is fine, as long as he doesn't get the part stuck. It's quite easy to get a part slightly skew when checking fit wherein it jams and won't come out.

Andrew

not done it yet25/10/2018 07:58:42
5015 forum posts
20 photos

’Posted by ega on 24/10/2018 23:46:07:

Posted by not done it yet on 24/10/2018 22:01:25:

When I have cut out discs for aluminium gears, I have used Starret/Bosch hole saws. Rather cheaper system than rotabroaches. Can get you close to finished size.

Certainly cheaper, and fine when they will do the job. I have often found chip clearance a potential problem with holesaws when used on thick material, often necessitating frequent stops to clear and add lubricant. When, as with gear blanks, the middle rather than the hole is the object, I find it helpful to arrange things so that the kerf runs out at one or more points thus allowing the chips an easier exit.

Apart from the fact that the Rotabroach type of cutter has flutes for chip clearance it has the added advantage that it cuts closer to size and, further, a pilot is not necessary so that the resultant slug has no central hole.

Your reply ignored what I wrote. Read the bit about ‘’getting close”. smiley You pick the size of cutter just below the hole size you require and finish off with a boring head, ther is no problem at all. I think the cutters cut the hole to size, not the piece cut out - well that is what I found when cutting circles for gears. I certainly would not trust a hole saw to give a perfectly finished hole at the nominal size. In my case the slugs needed a hole anyway - gears are like that - and were clearly finished to size on the lathe as the implest way to do it.

It was just an option, a possibility, a choice. If it doesn’t fit ones requirements, there are obviously other options. They are a great deal cheaper than a similar sized rotabroach, too - not just ordinary cheaper - the slug being a secondary consideration, I suspect, if a rotabroach was purchased for a one-off.

Are a few ‘frequent’ stops a problem with one hole? I don’t think so. Using a suitable coolant flow might well alleviate this problem somewhat, but the chips have to go somewhere, with either type of cutter and there will be less with hole saw (I think, anyway). A small hole in the slug could easily be filled, for many uses, if the slug were needed as a solid piece.

Andrew Johnston25/10/2018 08:01:42
avatar
5664 forum posts
653 photos
Posted by JasonB on 25/10/2018 07:18:13:

Well that "cheap" import Soba that is in my picture above manages to cut holes for ball races that are a good fit.

It must be boring being perfect. smile

Assuming 100fpm for HSS in steel the 'correct' speed is around 95rpm. I don't know what the minimum speed is for the SX2.

Andrew

JasonB25/10/2018 08:16:07
avatar
Moderator
18884 forum posts
2080 photos
1 articles

I said good , not perfectsmile p

I've shown before that these machines can be stalled at the low speeds but luckily Ron is looking at Carbide tools and aluminium, add to that light cuts and I think it can be done.

Alan Waddington 225/10/2018 08:36:07
507 forum posts
87 photos
Posted by ega on 24/10/2018 23:46:07:
Posted by not done it yet on 24/10/2018 22:01:25:

Apart from the fact that the Rotabroach type of cutter has flutes for chip clearance it has the added advantage that it cuts closer to size and, further, a pilot is not necessary so that the resultant slug has no central hole.

A pilot isn’t necessary with a hole saw either, if mounted in a drill press or mill, infact you can even use them freehand without the pilot drill if you use some form of jig to centre.

David Standing 125/10/2018 08:54:12
1289 forum posts
48 photos

As the hole required is 100 mm dia and the material 25 mm deep, good luck to anyone using a hole saw for that!

Ron Laden25/10/2018 09:21:50
avatar
2005 forum posts
400 photos
Posted by JasonB on 25/10/2018 07:18:13:

Well that "cheap" import Soba that is in my picture above manages to cut holes for ball races that are a good fit. question

Neil will be better able to comment on the power of an X2 but I'll stick an ARC boring head into the next size up SX2.7 later and see what it can do. SX2 certainly won't have the guts to turn a near 100mm holesaw let alone rotabroach with it's larger kerf but as the boring head allows a much smaller cut the load can be kept down.

Not sure where this 20rpm comes from, more like 130rpm for steel and 170 for aluminium with HSS so 50% or more increase for Carbide tooling.

Ron, is this to fit the "boiler" barrel of your traction engine?

 

Hi Jason, you dont miss a lot do you..smiley yes, the boiler is 4 inch 10swg alu tube with the firebox made up from 6 inch alu flat bar with a 25mm thick front plate..surprise I can imagine people going into shock and horror now, I know it breaks away from the conventional way but I wont explain my reasons here I will start a thread and explain there. Thinking about it a bit more, I doubt that 4 inch alu tube will be perfectly round so my tolerance of a couple of thou is probably an exaggeration, I would need to measure the tube and work out a size for fit.

Ron

Edited By Ron Laden on 25/10/2018 09:41:50

Edited By Ron Laden on 25/10/2018 09:48:23

Simon Williams 325/10/2018 09:28:05
525 forum posts
80 photos

Morning All,

My suggestion of needing to be able to run at 20 or 30 rpm comes from having done exactly the same job myself, using a Rong Fu drill mill. By the time I got to 75 mm diameter running the cutter at a "proper" speed I'd got all the chatter in the world going on, so reducing the speed significantly is one way of reducing this to give a good enough surface finish to hold that tolerance of a couple of thou. I just wanted the biggest hole I could cut in a steel flywheel as part of a home made wood chipper, I got to 100 mm dia eventually but it was on the absolute limit of my capabilities. I wasn't bothered about hole tolerance, it was a clearance hole for the chips to go through, but I did want it to look pretty. Incidentally I cut two of them, as the flywheel had to balance (approximately!)

The mill drill has its limitations, but it is big and heavy (for the size of machine) and it will run slowly with lots of torque. No offence to the SX machine, but I've got me doubts.

I forgot to note that the boring tool used in the head axially is a right handed tool, but the tool needed for the radial position is a left handed tool, as it cuts on the opposite edge.

I'm afraid I'm responsible for putting Ron off having a go. My apologies for being such a doubting Thomas, by all means have a go but approach with circumspection!

I've also drilled holes in one inch steel plate with a hole saw. They will do it, but we mounted the work on the table of a big vertical mill with flood coolant and went very slowly with frequent withdrawals. That was a 40 mm hole, not sure that much larger is viable as the saw is too flexible.

Best rgds Simon

Ron Laden25/10/2018 09:59:29
avatar
2005 forum posts
400 photos

Dont apologise Simon, I would rather know all the possible pitfalls than to go ahead and possibly damage the mill.

Ron

Alan Waddington 225/10/2018 10:01:00
507 forum posts
87 photos
Posted by David Standing 1 on 25/10/2018 08:54:12:

As the hole required is 100 mm dia and the material 25 mm deep, good luck to anyone using a hole saw for that!

Shouldn’t be a problem with a decent quality holesaw and patience, problem with ally is it clogs the teeth, so needs plenty of lube, parrafin or WD40. Best to peck at it too, or the heat build up nips the blade.

Have done a 75mm hole through the web of an RSJ using a cordless, whilst balancing on a step ladder........now that was interesting cheeky

JasonB25/10/2018 10:08:15
avatar
Moderator
18884 forum posts
2080 photos
1 articles

Ron, as it is a throat plate will it actually be a hole of just a half circle cut out the top edge?

Ron Laden25/10/2018 10:16:36
avatar
2005 forum posts
400 photos
Posted by JasonB on 25/10/2018 10:08:15:

Ron, as it is a throat plate will it actually be a hole of just a half circle cut out the top edge?

Jason, sorry I dont know all the correct terminology and methods yet, I was planning on a hole with the boiler tube fitted the full 25mm depth. Is there a reason for the half circle which I am missing..?

JasonB25/10/2018 10:19:44
avatar
Moderator
18884 forum posts
2080 photos
1 articles

It is just a common way to do it with copper and steel boilers but all bets are off with yours!!

I only asked as I will do a similar cut to what you propose so if it were a half circle then that is what I would have tried.

Ron Laden25/10/2018 10:31:16
avatar
2005 forum posts
400 photos
Posted by JasonB on 25/10/2018 10:19:44:

It is just a common way to do it with copper and steel boilers but all bets are off with yours!!

I only asked as I will do a similar cut to what you propose so if it were a half circle then that is what I would have tried.

Really appreciate this Jason, I will be interested to know the results as if its possible I would like to give it a try.

Ron

Edited By Ron Laden on 25/10/2018 10:31:51

Clive Foster25/10/2018 10:33:37
2374 forum posts
76 photos

Chip problem when going deep with hole saws is greatly alleviated if you drill a couple or four holes slightly overlapping the cut to give the chips somewhere to go. Maybe 1/4" diameter if doing big hole. Need somewhere below for the chips to go too. I've done 3" diameter in 20 mm material. Less than ideal but did the job. Went through halfway and flipped the part over.

Finished off with a boring head in a big Chester Lux style square column mill. VFD drive got the speed down low so it did the job fine but I'd not care to have gone much bigger as I'd have been pushing what the machine could do in normal operation. Really don't like pushing machines beyond their capacity and nursing a job through.

My boring head is a middling range affordable import type. Two gib screws and a central lock screw. Really prefers to operate with the dovetail slide covering both gib screws. Any further out and it all seems bit much for it to behave well. Can still do the job but you have to work at it.

When I had an 6" hole to do I popped it on a rotary table, chain drilled it and milled round using a normal cutter. Much better way of going about things once you have a rotary table. I left the centre piece in holding it with screws into the sacrificial base between job and table. Knocking out would have meant taking the job off and re-centering.

Clive.

Edited By Clive Foster on 25/10/2018 10:34:24

JasonB25/10/2018 11:48:32
avatar
Moderator
18884 forum posts
2080 photos
1 articles

Rather than waste a nice bit of 6082 25mm plate I found an old fingerplate which is some soft gummy ali but it will do for the purpose and it also made it easy to bandsaw out the waste before butting the two bits together.

Quick rough and ready free hand regrind of one of the tools supplied in this ARC set, it's the same head I'm using too and we are good to go.

As I have said before these variable speed benchtop mills and the vari speed lathes for that matter are better off run a bit faster with a slightly shallower cut than a big old industrial machine would typically use. So being aluminium and with a carbide tip I dialed up 500rpm. Cuts are 1mm off dia (0,5mm DOC) not the smoothest of feeds as I was only able to use one hand and could only add a drop of paraffin at the start. I have set the gibs as I do on my SOBA which is firm then I don't have to faff about loosening and then retightening each time a cut is put on.

 
 
Now the SX2.7 is a bit more rigid and has 750w rather than Rons SX2 at 500w so if he took off half that DOC it would not take too many passes to clean up the last 4mm of material left by stitch drilling with a 6mm drill 1mm inside finished diameter, could probably use quill lever to feed on the initial rough cuts.
 
 
Not much sign of chatter on the cut edge
 
dsc03277.jpg

 

Edited By JasonB on 25/10/2018 11:54:13

ega25/10/2018 12:39:40
1812 forum posts
153 photos

On the theme of hand-held hole saws:

Paul Kemp25/10/2018 13:05:13
560 forum posts
18 photos

Jason,

Doesn't look a lot wrong with that for Ron's purpose!

Ron,

Don't be put off by the nay sayers! Amuses me greatly sometimes when responses to a question prompt a sharp intake of breath and Nay lad, you'll not be doing that! There is usually a way of achieving what you need when you don't need an accuracy of 2/10 of a thou. It's nice to have the all singing all dancing professional kit but for the purposes of back yard engineering perfectly acceptable results can be achieved with less. As someone once said to me, "you can only wee with the willy you've got".

Paul.

Ron Laden25/10/2018 13:09:18
avatar
2005 forum posts
400 photos
Posted by JasonB on 25/10/2018 11:48:32:

Rather than waste a nice bit of 6082 25mm plate I found an old fingerplate which is some soft gummy ali but it will do for the purpose and it also made it easy to bandsaw out the waste before butting the two bits together.

Quick rough and ready free hand regrind of one of the tools supplied in this ARC set, it's the same head I'm using too and we are good to go.

As I have said before these variable speed benchtop mills and the vari speed lathes for that matter are better off run a bit faster with a slightly shallower cut than a big old industrial machine would typically use. So being aluminium and with a carbide tip I dialed up 500rpm. Cuts are 1mm off dia (0,5mm DOC) not the smoothest of feeds as I was only able to use one hand and could only add a drop of paraffin at the start. I have set the gibs as I do on my SOBA which is firm then I don't have to faff about loosening and then retightening each time a cut is put on.

Now the SX2.7 is a bit more rigid and has 750w rather than Rons SX2 at 500w so if he took off half that DOC it would not take too many passes to clean up the last 4mm of material left by stitch drilling with a 6mm drill 1mm inside finished diameter, could probably use quill lever to feed on the initial rough cuts.
Not much sign of chatter on the cut edge
dsc03277.jpg

Edited By JasonB on 25/10/2018 11:54:13

Thanks Jason for taking the time and effort to do this trial it certainly looked like a success. I will order the tooling from ARC and give it a go. Like you suggest if I take light cuts it should be ok, I wont rush it and it will be good to be able to do it myself plus I will have a boring head set for other jobs. I will start a thread later on the traction engine and post a sketch of how I am considering the boiler/firebox.

Thanks again, really appreciated

Ron

Alan Vos25/10/2018 18:31:41
159 forum posts
7 photos
Posted by Ron Laden on 24/10/2018 19:19:20:
I hope ******* is not what I think it may be Alan, but I will assume it isnt.

What I had in mind is described by Channel 4 as "relatively inoffensive and its inclusion, even in a programme watched by large numbers of children, would be unlikely to offend most viewers."

Regarding the original subject, if needed, I would have a go at boring 100mm in aluminium on my SX2P. Nice sharp HSS tool, small cuts, WD40. And, as noted by others, being cautious about the duty cycle to protect the motor. Assuming a chain drilled starter hole, the bulk of the lumps that would cause an interrupted cut could be knocked off using a normal milling cutter and manual X-Y manipulation, or even a large round file.

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

Support Our Partners
ChesterUK
EngineDIY
emcomachinetools
Warco
Eccentric July 5 2018
cowells
Eccentric Engineering
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