Boring Head

I needed to make a 13mm hole with a decent finish in an alloy part the other day and failed. I crept up on the final diameter and the finish I was getting using stub drills on my VMC was great but the only 13mm bit I had was a jobber and although sharp it didn’t play ball. I don’t have a reamer that size either. One tool I’ve put off buying not least because of the cost is a Boring Head but I’m wondering if I could have done this particular job using one? I don’t think it’s something I’d use very often but being able to produce holes of virtually any size sounds attractive. I’m wondering if something like this

**LINK**

would have done the job. Do any of you have this particular head or are there any others I should look at? I’ve never used one before so any insights into their use would be much appreciated.

Vic,

It's not the size of the boring head that determines the size of the holes that you can produce, within reason, it's the boring tool itself. If I were you, I'd go for a 50mm boring head, to part future-proof your investment and get a suitable, good quality, boring tool that will cope with small diameters.

John

Thanks John. I picked that one because it has a boring range of 7mm - 52mm. I can’t see me ever needing to bore a hole bigger than that. The 50mm boring head has a good range but only goes down to 10mm which may be less useful to me. Buying mail order I’m not sure how to pick a good one so any particular recommendations would be appreciated.

Edited By Vic on 29/07/2019 10:53:17

How deep was this hole? I always use an end-mill if I want a hole (or holes) straight, with good finish and of predictable size. Drill bits are just rough and ready, as far as I am concerned, when it is precision that is required.

I only drill if I’m going to finish with a reamer - and even then an end mill might be used, just in case the initial pilot hole meandered.

The larger head is also likely to be more rigid.

Vic,

The minimum hole diameter is normally governed by the size of the boring cutter. Yor could possibley go smaller by making your own cutters. Also, the boring head can make much bigger holes by mounting the cutter in the side hole instead of the one at the base. They are very useful and worth the investment. Lots of useful videos on Youtube.

Paul.

The hole was only 14mm deep NDIY but I don’t have a 13mm end mill either! I’m just thinking getting a boring head will save me buying new bits all the time. Sometimes it’s not the money but wanting to get on with the job rather than waiting for the postman!

Vic, the tool size of 6mm for the smaller head is very small I would go for larger head with a more substantial tool size the 38mm or the 50mm head I believe would be better - as ega says more rigid not so much the head itself but the tool.

John

PS you can of course use a small tool in the larger head for small holes

Edited By JohnF on 29/07/2019 11:24:06

How big do you think I need to go? Some of the other heads take 8mm or 10mm shanks. Are both of those sizes freely available if I need new cutters?

I agree with John above.
Just imagine truing to bore a cylinder 30mm dia and 30mm deep (and most steam engines are not 'square' so would be deeper) using a 6mm shank tool. You'd never want to use that length of stick out on a lathe tool of only 6mm dia. Rigidity of tools probably goes up by the square of diameter* or something so big is definitely better.

* hopefully a mechanical engineer can correct me here.

Vic,

To briefly return to your original request - I have had one of the 50mm size boring heads and it has served me well for several years. There are numerous suppliers on the web for these devices and I suspect most are very similar in quality and construction. I can recommend one of this type.

The minimum diameter of bore that you quote from the Arc web site is probably the minimum acheivable with the supplied brazed carbide insert tooling. I have not found these to be very satisfactory, but that's more than likely due to my inexperience. I purchased a Sandvik boring tool off eBay for less than £10 delivered, from a UK source and it is excellent. It has kept its edge and is also used in a dedicated holder in the lathe. It will bore down to 10mm diameter. If your pockets are deep enough, I understand boring tools are available for diameters as small as 0.3mm. That should be small enough for you!

John

The best answer for the original hole would be a D-bit.

Neil

Vic,

As it happens, I needed to bore a recess for a bearing today and so I used the Sandvik boring tool that I referred to above. The recess started as a through hole of 6mm diameter, but could have been smaller, if necessary. Here it's in use in the lathe, but would have been equally at home in the boring head in the mill as well.

John

Thanks for all your thoughts. I’ll perhaps get something bigger as suggested when funds allow.

As an aside I changed the material for the part and this also allowed a redesign. I managed to complete the job using a 13mm “Bullet” drill I had and the finish was very good.

One thing to get your head around if, er, heading for a larger head is the head room the head requires.

The body and standard toolbit of larger boring devices can eat up a lot of your Z-axis space.

Buy a decent one too, the far east import ones can have dials that mean nothing. I have one here and its neither metric or imperial, i should chuck it in the bin ideally. I bought one made in California, Criterion i think and its miles better. You get what you pay for.

I have used a similar boring head for many years, from time to time.

The minimum bore size is determined by the size of the tool that you fit, and by the minimum radius that you select.

the maximum is determined by the greatest radius to which the head can be adjusted.

Mounting the tool in the horizontal hole will allow much larger holes to be bored. But there may well be a gap between the maximum with the tool in a vertical hole, and in the horizontal hole.

Howard

Minimum bore size is dependent upon the size of the tool, as many have already stated, and more importantly by the thickness and rake angle of the HSS or tungsten carbide tip. What will happen trying to bore too small a hole is the bottom of the TC bit will likely hit the workpiece first and scrape the bore and it will get very hot. I've just bored out a hole to 34mm diameter but it wasn't until I got out to near 24mm that it started to cut correctly.

Most boring tools with brazed carbide tips need to be ground before use. It is necessary to grind the correct clearance on the end and on the side. If your tool did not work well on the smaller holes I suspect insufficient side clearance.

The most common boring head in machine shops seems to be 2" diameter with 1/2" holes for the tool. The boring tools themselves are available in solid HSS or solid carbide as well as the brazed carbide tools commonly sold with the boring heads. The sizes range from near microscopic to about 1/2". The smaller tools will require an adapter sleeve for use in a larger boring head.

My favorite boring head for work is a Tenthset 37. It takes 3/8" tools. As the name implies they can be set in increments of .0001". The Tenthset 50 is similar but a bit larger and takes 1/2" tools. The Tenthset heads are often available on flea bay. Shank size is unimportant. The back of the boring head is threaded 5/8-18 so it is quite easy to make a shank to fit it.

Flea bay is a source of the smaller boring tools I mentioned.