Milling machine feedback

[ahartnet]

I've found a used milling machine that the seller is asking for $3k for. It's an Acra LS-2S (bridgeport knee-milling machine clone). It's got a power feed in the horizontal travel (and Z I think too), and as far as DRO goes, it's wired in the X and Y so it's just missing the DRO display. I also have a contact that will sponsor us with up to $5k in milling machine tooling if I can get a milling machine - which is hugely awesome and I don't know how long that offer will stand.

I was able to get ahold of Acra, and the factory that used to handle this machine is closed. This I imagine would make it difficult to do any repairs, find replacement parts, and difficult to find a manual.

Looking for advice on if this is a good purchase or not. We have a mentor with milling machine experience that I checked it out with. It's in pretty good shape - a little bit of knock when it runs, but not much. Table travels smoothly, handles work well, table is in good shape, etc. He also has one at home that he did a lot of the machining that we needed last year. I'd of course love to get our students that experience though.

[Cory]

Originally Posted by ahartnet

I've found a used milling machine that the seller is asking for $3k for. It's an Acra LS-2S (bridgeport knee-milling machine clone). It's got a power feed in the horizontal travel (and Z I think too), and as far as DRO goes, it's wired in the X and Y so it's just missing the DRO display. I also have a contact that will sponsor us with up to $5k in milling machine tooling if I can get a milling machine - which is hugely awesome and I don't know how long that offer will stand.

I was able to get ahold of Acra, and the factory that used to handle this machine is closed. This I imagine would make it difficult to do any repairs, find replacement parts, and difficult to find a manual.

Looking for advice on if this is a good purchase or not. We have a mentor with milling machine experience that I checked it out with. It's in pretty good shape - a little bit of knock when it runs, but not much. Table travels smoothly, handles work well, table is in good shape, etc. He also has one at home that he did a lot of the machining that we needed last year. I'd of course love to get our students that experience though.

Virtually all the bridgeport clones should have fairly interchangeable parts. Even if the factory is closed, if it closed recently Acra/their dealers may still have access to some spare parts inventory.

Hard to say if it's a good purchase without pictures. If there is minimal backlash and spindle runout and everything sounds OK it will probably do a good job for you.

Before buying you should check and see what DRO scale types it's wired with. It may not actually be a bonus that those are present. Depending on the age they may be considered obsolete by the manufacturer and you may not be able to buy an actual readout for it (though ebay/CL might be an option). We were looking to add a scale to the Y axis on our old mill and due to the age of the scales we'd have been forced to remove the existing X axis scale and buy two new scales plus the readout unit.

[ahartnet]

Originally Posted by Cory

Virtually all the bridgeport clones should have fairly interchangeable parts. Even if the factory is closed, if it closed recently Acra/their dealers may still have access to some spare parts inventory.

Hard to say if it's a good purchase without pictures. If there is minimal backlash and spindle runout and everything sounds OK it will probably do a good job for you.

Before buying you should check and see what DRO scale types it's wired with. It may not actually be a bonus that those are present. Depending on the age they may be considered obsolete by the manufacturer and you may not be able to buy an actual readout for it (though ebay/CL might be an option). We were looking to add a scale to the Y axis on our old mill and due to the age of the scales we'd have been forced to remove the existing X axis scale and buy two new scales plus the readout unit.

Good reminder on the DRO scale types. Meant to snag some information on it when I was leaving but forgot. There's not much backlash on the handles to move the table. Forgive my unfamiliarity with some terminology, but one area of concern I have is that the seller had to go grab a spindle (I believe it's the spindle - whatever drops into the head from above that the collet fits into) and there wasn't a keyway or a key. The collets had a keyway, but the quill and spindle didnt seem to have any sort of key or keyway. I think he was saying he'd provide one for us that did have the key, but English wasn't his first language so I'm not confident that conversation was the same for both of us. Since I have little experience with milling machines, I'm not sure if a friction lock type spindle is something that is common or should be avoided. That said, there wasn't any obvious spindle runout once we went through that process.

I've got some pictures but because I was mostly focused on pictures to help me make sure I figured out who manufactured it, I'm not sure how useful it'll be: http://imgur.com/a/m6oBd

[Cory]

Hard to tell much from those pics. A big one is seeing the ways to see if the original scraping pattern is there or if it's worn down.

The thing he had to grab is called the drawbar. It's just a really really long 7/16-20 bolt. Any mill without a power drawbar is going to have one and you'll need to use a wrench on it to tighten/loosen the collet. The keyway does nothing in terms of clamping the tool. The only purpose it serves is to keep the collet from spinning while you tighten the drawbar. All the clamping force comes from the interaction of the taper on your tool and the mating taper in the spindle.

There is normally a pin inserted in a cross hole in the spindle that matches up with the keyway on the toolholder. It's super common for these to snap off. You can use it just fine without the pin in there, or you can replace it. If you don't replace it you should at least make sure the remains of the snapped off pin are removed so that it doesn't gouge your toolholders.

[ahartnet]

Thanks for the input! Good info for me to move forward with.

[sanddrag]

I just bought a very similar machine, although ours is a late 1980's and has a different brand name plate stuck on it, and a bit of a different variable speed drive on the head. As indicated by the big letter "M", it has "Meehanite" castings, which I've read is preferred for Taiwan mills. The OEM may be "Gain Shin" in Taiwan. Aside from the head, the machine appears very similar to their GS15V model, which shows up under Enco "Turn-Pro" Part Numbers 307-3678, 890-9987 and 890-9988. Be aware though, the Enco web page is showing a picture of a machine with box ways, whereas my GS15V has dovetail ways. It could just be a generic picture on the Enco site. The machine is very similar to Precision Matthews and all the other Taiwan mills of the era, and of today. It's not a Bridgeport, but it's also not $15k+ new. I'll take a good condition Taiwan mill over a worn out Bridgeport no problem. Although I haven't milled anything on ours yet, I'm very happy with it so far, for what we paid. The base is rather banged up, but all the important parts are in good shape. The only think I wish it had was hand scraped ways, but beggers can't be choosers.

I'd take a dial test indicator and mag base over to the machine, and thoroughly check it out: Check spindle runout, quill play, perpendicularity of the table to the column, flattness of the table, etc. If you can, take a few decent flat screwdrivers with you to tighten up the gibs. If you can't just snug the axis locks slightly before jogging it. A worn out machine will be free moving in the middle of travel, and tight at the ends of travel, and that type of wear is not something that can be fixed with adjustment. Go over all the ways and sliding surfaces. They should be coated with oil, and there should be no rust present.

A knock in the head sounds concerning. Could be a broken gear tooth or something. You probably don't want to get into a head rebuild.

I don't know what the market in your area is like, but I wouldn't go more than absolute $2k tops for that mill, and hopefully that's with a 6" vise on it. You should also consider the cost and convenience (or lack thereof) of moving it to your location. It's about 2400 lbs. Ours came on a pallet, and cost me only $60 to move, since I was able to do it myself with a hydraulic drop deck trailer.

For reference, at machine tool auctions, I have seen:
Step-pulley 1980s Taiwan mills in good condition go for $800-$900
1980s variable speed head Bridgeports with working 2-axis DRO go for $1600-$2250
Year 2013 "Clark" brand Taiwan mill with DRO and variable speed head in like-new condition go for $4,000 with a 6" machine vise.
*To all prices, add 15% buyer's premium and 9% tax.

The equivalent of that mill new is about $6500-$7000 brand new, with DRO, all day long. Also, there's a bunch of different Jet brand mills in the price range available with free residential lift gate delivery from Southern Tool, so you definitely have to look at the total acquisition cost, including moving it.

[ahartnet]

OK, thanks for the help so far. One final question (I finally got all my approvals necessary to purchase it and have it moved into the school): It has a mitutoyo AT715-350 linear scale on it now. It looks like I can get a 2-axis DRO (174 model) for around $600 pretty easily (http://www.mscdirect.com/product/details/85012953) and that it's not an outdated scale. But since I'm not real familiar with manufacturers in this field, I thought I'd ask for feedback on the quality of mitutoyo parts if anyone has experience with them.

Thanks!

[frcguy]

Originally Posted by ahartnet

OK, thanks for the help so far. One final question (I finally got all my approvals necessary to purchase it and have it moved into the school): It has a mitutoyo AT715-350 linear scale on it now. It looks like I can get a 2-axis DRO (174 model) for around $600 pretty easily (http://www.mscdirect.com/product/details/85012953) and that it's not an outdated scale. But since I'm not real familiar with manufacturers in this field, I thought I'd ask for feedback on the quality of mitutoyo parts if anyone has experience with them.

Thanks!

Mitutoyo is one of the most well known and quality brands in the measuring tool field. While I've only had experience with their calipers (my Mitutoyo dial calipers from the 1970s still work great), I would assume that their scales are good as well.

[asid61]

Originally Posted by frcguy

Mitutoyo is one of the most well known and quality brands in the measuring tool field. While I've only had experience with their calipers (my Mitutoyo dial calipers from the 1970s still work great), I would assume that their scales are good as well.

Ditto on this. I love Mitutoyo everything. Quality-wise they are matched or above Starret (depending on who you ask) but below Tesa/Brown and Sharpe. Their scales should be great.
If the scalres are compatible. I would say go for it. Shop around for the price though; MSC is a lot (1.5-5x) more expensive than other places IME.

[RoboChair]

Originally Posted by asid61

Ditto on this. I love Mitutoyo everything. Quality-wise they are matched or above Starret (depending on who you ask) but below Tesa/Brown and Sharpe. Their scales should be great.
If the scales are compatible. I would say go for it. Shop around for the price though; MSC is a lot (1.5-5x) more expensive than other places IME.

Would highly suggest DRO Pros for a new DRO. We bought 3 sets(2 mill, 1 lathe) from them and have been very happy with them.

If you need additional scales for your Mitutoyo read out you can find reasonably priced replacement scales on eBay. You will need to know what model, size, and PLUG you need. Do not buy a replacement scale unless you are SURE it is the right plug and type. You may also want to buy new rubber guard strips if they are looking beat up and old.

[RoboChair]

Originally Posted by ahartnet

OK, thanks for the help so far. One final question (I finally got all my approvals necessary to purchase it and have it moved into the school): It has a mitutoyo AT715-350 linear scale on it now. It looks like I can get a 2-axis DRO (174 model) for around $600 pretty easily (http://www.mscdirect.com/product/details/85012953) and that it's not an outdated scale. But since I'm not real familiar with manufacturers in this field, I thought I'd ask for feedback on the quality of mitutoyo parts if anyone has experience with them.

Thanks!

THE top names in measuring tools of almost ANY kind are as follows.

Mitutoyo
Starret
Brown&Sharp

all others are typically compared to those.

Mitutoyo is Quality, period. Even old Mitutoyo is Quality so long as it was not heavily abused.

[ahartnet]

Thanks everyone!