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

Milling for beginners

Please use this thread to ask questions of make suggestions about the series in MEW

All Topics | Latest Posts

Search for:  in Thread Title in  

Matthew Sugden27/10/2018 11:22:36
9 forum posts
5 photos
Posted by JasonB on 25/10/2018 13:00:46:

I would do the three full width (of the cutter) passes just clear of the edge to take you down to the 13mm depth then a 13mm high by 1mm deep finishing pass to define one edge of your slot and then a series of 13mm high cuts working your way across the work until you get to the other side.

70x13 groove.jpg

That's brilliant Jason, thank you!

Ron Laden27/10/2018 11:23:45
avatar
2233 forum posts
443 photos

Thanks guys,

Andrew, my rpm limit is 2500 and I,m sure you have a lot more power available than I do with my little mill so I will have to keep within its limits.

Ron

Andrew Johnston27/10/2018 11:48:59
avatar
6213 forum posts
676 photos
Posted by Ron Laden on 27/10/2018 11:23:45:

Thanks guys,

Andrew, my rpm limit is 2500 and I,m sure you have a lot more power available than I do with my little mill

You'd be surprised; both the Bridgeport and my CNC mill are only 1.5hp, ie, about 1100W. While the Bridgeport has constant power across the speed range the CNC mill doesn't as it's driven by a VFD, albeit with a low/high belt driven ratios. I know where the base speeds (at 60Hz) are for both ranges and run low or high to ensure I'm in the constant power regime. I would assume your mill is similar, at least in that maximum power is available at maximum speed.

Andrew

SillyOldDuffer26/11/2018 11:55:29
Moderator
7468 forum posts
1648 photos

In MEW № 275 Jason covers using a slitting saw to cut screw slots, illustrating the method with this photo:

dsc05829.jpg

Normally I don't care much about the appearance of my rough experimental machining but it does grate on the eye when screw slots are cut off centre and/or crudely hacksawed. I occasionally use a slitting saw as shown by Jason to avoid upsetting anyone who might care about good workmanship.

My problem is, what's the best and quickest way of centring the saw accurately? Even slightly off-centre slots offend the eye! The measure/test/repeat method I use to centre the saw is time consuming and not particularly reliable, and I suspect a machinist would have his saw aligned in a flash whilst I was busy faffing towards nearly right.

Dave

JasonB26/11/2018 12:06:04
avatar
Moderator
21279 forum posts
2414 photos
1 articles

The way I tend to do it is to touch the blade onto the top of the work, add a fag paper if you want and zero Z. Then feed down by half diameter or thickness of the work plus half the thickness of the blade for round work. For a cut that is a set distance down then touch off again and zero then feed down half blade plus distance to ctr of slot.

If you get it right you can do things like thiswink

Firefly95

Ron Laden26/11/2018 14:21:08
avatar
2233 forum posts
443 photos

 

Might be a daft question Jason but in the picture of the screw in the collet, what is the collet chuck fitted to, is it a table mounted vertically on the mill..?

Edited By JasonB on 26/11/2018 16:30:34

JasonB26/11/2018 16:30:02
avatar
Moderator
21279 forum posts
2414 photos
1 articles

Ron, you have not been doing your homework and catching up on the Milling for Beginners seriessmile p

Part 3 Photo 31. or one of these

Ron Laden26/11/2018 17:59:26
avatar
2233 forum posts
443 photos
Posted by JasonB on 26/11/2018 16:30:02:

Ron, you have not been doing your homework and catching up on the Milling for Beginners seriessmile p

Part 3 Photo 31. or one of these

Thanks Jason, I have caught up having read all the series so far, I will probably go back and read them all again so it sinks in..smiley

Excellent series by the way.

Ron

SillyOldDuffer26/11/2018 19:55:58
Moderator
7468 forum posts
1648 photos
Posted by JasonB on 26/11/2018 12:06:04:

The way I tend to do it is to touch the blade onto the top of the work, add a fag paper if you want and zero Z. Then feed down by half diameter or thickness of the work plus half the thickness of the blade for round work. For a cut that is a set distance down then touch off again and zero then feed down half blade plus distance to ctr of slot.

If you get it right you can do things like thiswink

Firefly95

Thanks Jason - that's simpler than the way I was trying to achieve the same thing. Fewer chances of making a mistake, I'll give it a try.

If only 'getting it right' were easy I would be doing things like that. As it is I'm a time-served maladroit who deserves sympathy. Fellow members - please send cash until I feel better!

smiley

Dave

Ron Laden05/12/2018 07:31:29
avatar
2233 forum posts
443 photos

I,m guessing that the band on the side of the plate is telling me that a section of the end mill has lost its edge..?

dsc06269.jpg

JasonB05/12/2018 07:46:15
avatar
Moderator
21279 forum posts
2414 photos
1 articles

Or as you seem to be cutting dry you may have some metal stuck to the cutting edge. Try a little paraffin or WD40

Was it the same one you milled the hornplates with as the width of the affected area looks about the same which may have just taken the edge off slightly.

Ron Laden05/12/2018 07:57:26
avatar
2233 forum posts
443 photos

Thats its Jason you dont miss much, yes thinking about it, it is the tool I used on the hornplates which were sandwiched together and the width of the band fits.

Oxymoron21/12/2018 16:56:02
46 forum posts
18 photos

Jason, thanks for your brilliant articles and videos, I have found them very informative.

I have the SX2.7 mill which I collected from ARC a couple of weeks ago. My question: In article 6 in MEW 271 you mentioned Tapping mode. Is there a minimum size would you suggest Tapping mode could be used for please?

I have several 7BA holes to tap in cast iron but don't feel confident to go this small (at least to start with). M6 perhaps, also have a couple of 1/4" x 40 ME holes to Tap. Do you have any thoughts if courser or finer threads are better with tapping mode?

Many thanks

Dave

JasonB21/12/2018 17:21:33
avatar
Moderator
21279 forum posts
2414 photos
1 articles

A lot will depend on material, thickness and whether it is a through hole or blind as well as the type of tap being used

The softer and easier cutting the material the less strain will be put on the tap, you can also adjust the tapping drill size to some extent to make life easier for the tap. Finer threads will be easier than coarse.

Again if only tapping thin sheet which may only need a couple of turns of thread you will find that lest likely to load up the tap than doing a deep hole.

Unlike a tapping head the function on the mill relies on the reaction of the user to stop and reverse the spindle, if you can drill the tapping hole to a good depth so there is less risk of bottoming out before you get the number of turns cut then so much the better but if you are doing shallow blind holes there is more risk of a problem.

One of the main things that makes a difference is the type of tap. A traditional taper tap can soon clog up with swarf in a blind hole so as well as the usual backing off will require withdrawing and cleaning before going deeper. If it is a through hole then a spiral point tap will help a lot as these can be driven straight in without the need to back off and the swarf will be pushed out of the bottom of the hole. In a similar way a spiral flute tap when used in a blind hole will lift the swarf out so are better suited to use under power.

The two spiral type taps also have a smaller diameter shank above the "threaded" part so if you do run deep they won't get stuck unlike a traditional tap that often has the shank the same size as the thread's OD or even larger.

7BA with a traditional tap would be pushing your luck particularly if they are blind holes. M6 into say a 5.1mm hole and 1/4 x 40 ME should not be such an issue provided you can stop fast enough before getting to the bottom if they are blind.

 

Edited By JasonB on 21/12/2018 17:22:56

Oxymoron21/12/2018 17:40:47
46 forum posts
18 photos

Jason, that's great information. A lot more to consider than just diameter of the tap. I think I'll try a larger tap in a through hole before I'll feel confident to try tapping any blind holes in a 'prize' casting.

Thanks again.

JasonB21/12/2018 17:45:23
avatar
Moderator
21279 forum posts
2414 photos
1 articles

I don't think I'd risk it if you are asking about that Stuart cylinder, at least not the 7BA blind stud holes. Could have a try on the inlet as the valve chest means it is a through hole.

Oxymoron21/12/2018 17:52:43
46 forum posts
18 photos

You worked out exactly what I'm doing. I broke a 7BA in the base casting and had to drill it out and put a plug in so I'll not take the risk. Thanks for the advice, I'm very grateful.

Dave

Andrew Johnston22/12/2018 14:35:08
avatar
6213 forum posts
676 photos

What distinguishes tapping mode from simply running at a slow spindle speed?

I've done the slow speed, stop, reverse direction and back out once on my mill, with an M12 tap I think. But in general I prefer to use a proper tapping head. There's much less chance of breaking a tap and it's way quicker; with 7BA I'd be running at 800rpm. Tapping is much quicker than drilling the hole in the first place.

Proper tapping heads are expensive but they do appear now and again on Ebay. My small one was bought new for a specific job, 800+ 8BA holes blind and thru, but the larger one was a few pounds on Ebay.

Andrew

JasonB22/12/2018 16:11:11
avatar
Moderator
21279 forum posts
2414 photos
1 articles

Tapping mode really only allows the 3 buttons on the quill spider to use used as fwd/rev switches. So basically start the mill running and bring the quill down until the tap bites and then it will start to draw itself in. When you get to the point you want to stop press the green button on the quill handle and it will ramp down, stop and then run in reverse, which will wind the tap out

There is a speed limit of 400rpm hough at those sort of speeds you would need quick reaction times. I'm waiting for ARC to get something in stock before I cover tapping which will include using the tapping mode but may have a play over xmas and will post a little video if I do

Edited By JasonB on 22/12/2018 17:01:34

Oxymoron22/12/2018 16:24:48
46 forum posts
18 photos

Andrew, I've been out all day so Jason explained tapping function before me and probably better than me anyway! I've not come across Tapping heads before. I'll have a Google.

Jason, I'll await your video/ article with great interest. Thanks

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

Latest Forum Posts
Support Our Partners
Warco
rapid Direct
Dreweatts
cowells
walker midge
emcomachinetools
Eccentric July 5 2018
JD Metals
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